Underground Cables

Underground Cable

INDEX UNDERGROUND CABLES SERIAL NUMBER

TOPIC

PAGE NUMBER

1 2 3 4

INTRODUCTION TO UNDERGROUND CABLES CABLE LAYING CABLE JOINTING CABLE TERMINATION

2 to 21 22 to 38 39 to 70 71 to 81

5

POWER TELECOMMUNICATION CO-ORDINATION COMMITTEE AND PROTECTIVE DEVICES

82 to 96

6 7 8 9

10 11 12

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PREVENTIVE MAINTENANCE &CABLE RECORDS COMPUTERISATION OF CABLE RECORDS FAULT REPAIR SERVICE, TRAI PARAMETERS UPGRADATION & REHABILITATION OF EXTERNAL PLANT, POLELESS SCHEME INSPECTION PROCEDURE TESTING OF CABLES, CABLE FAULTS & LOCALISATION QUESTION BANK FOR UNDERGROUND TELECOM CABLE

97 to 111 112 To 114 115 To 135 136 To 150 151 To 160 161 To 172 173 TO 185

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Underground Cable CHA PT ER

I

INTRODUCTION TO UNDERGROUND CABLES Objective of the lesson:: This chapter provides the insight into the basic requirements of any underground cable to survive the expected life period and needs. The chapter also deals extensively with the different types of cables in use in telecommunication networks and the parameters offered for various utilities.

1.0

BROAD CONSTRUCTION OF ANY TELECOMMUNICATION CABLE

•

Core

::

All the insulated conductors compactly arranged in pairs, units and super units constitute core of the cable •

Moisture Barrier : As the presence of moisture deteriorate the quality of insulation of the telecom cables, moisture barrier protects entry moisture into the core of the cable.

•

Protection

::

Telecom cables require Protection o from probable mechanical damages o from water and chemicals or soil conditions o from Induction due to Electrical lines o from diggings by different agencies and individuals o from damages while handling 1.1. THE CLASSIFICATION OF UNDERGROUND CABLES WITH REGARD TO DESIGN FEATURES ARE :: 

Place where it is used

- Underground / overhead / submarine



Insulation material used

- Paper / polythene cables



The filling compound

- Dry core / jelly filled cables



Mechanical protection

- Armoured / unarmoured cables



Place of utilization

- Primary / Distribution / Junction cable.

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Underground Cable 

System for which used

- Co-axial / PCM



Type of conductor

- Copper cable / Optical fibre cable



Gauge of the conductor

- 0.40 mm / 0.50 mm 0.63 mm / 0.90mm



Pressurization of core

- Pressurized / unpressurised cables

1.2 DESIGN FEATURES :: Before discussing the above classifications in a nutshell let us know what are the purposes of the above Design features in a underground cables. Sheath LSDC / PVC

Insulating material PVC / PAPER

C O R

2nd pair B Limb

Annealed Copper Conductors

1st pair A limb st

1 pair B Limb 3rd pair A Limb

E Filling material Dry air / Jelly MECHANICAL PROTECTION 2 LAYERS OF GI STRIPS

Diagram 2

1.3 PURPOSE OF INSULATION UNDERGROUND CABLES :: (1) The insulation is used to separate the conductors bunched in a unit to prevent short circuit between two conductors in a pair or between conductor of one pair with the conductor any other pair in the unit or core in the cable. (2) The insulation is used as SHEATH to separate the insulated conductors from being corroded or eroded in soil. (3) The insulation is being used for marking / identifying the pair or conductor in the unit and in the cable as a whole for that matter. (4) The insulating material is used for preventing the grounding or earthing of the conductors. (5) The insulating material is used for preventing the corrosion of armouring . RTTC, NAGPUR

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Underground Cable (6) Transmission characteristics of the cable In the primitive stage paper insulation chosen as it has good di-electric properties and low specific inductive capacity which is about 1.5. Its physical properties also enable large proportion of air as dielectric. The ideal dielectric for telecom cable is air which has specific inductive capacity of 1.0. The thickness, width and number of wraps per meter of insulating paper is selected to achieve the required mutual capacitance of cables. The Polythene insulation is easy to apply and have desired electrical characteristic such as low dielectric constant, lo dissipation factor (loss) and high dielectric strength. Mechanically it is tougher than paper and has abrasion resistant with ample tensile strength and elongation. The insulating resistance measurement shall be measured with a DC voltage of magnitude not less than 500V after steady electrification for one minute. The insulation resistance values between each conductor in the cable and all the other conductors connected together and to the screen and earth shall not be less than 5000 Mega ohms / km at Room temperature. ( Cable length in Km x observed insulation in Mega ohms ). 1.4 Pairing and Overlay :: Two insulated conductors shall be twisted together with uniform lay to form a pair. The length of the lay of any pair shall be different from that of adjacent pairs. The lay of various pairs shall be so chosen as to satisfy the capacitance unbalance requirements and cross-task requirement. 1.5 Unit Formation :: The pairs are then assembled into units with different length of unit twists assigned to different units. These units are then assembled into a completed cable core. 1.6 Core wrappings are applied to the completed cable core to hold the units together and provide high di-electric strength from core to shield and to protect the conductor insulation from damage due to the heat of sheathing operation. In PIJF cables non-hygroscopic and nonwicking polyester tape is used as core wrapping. 1.7 Filling compound :: The cable should be filled with suitable water resistant compound which shall be compatible with the insulation, binders and tapes used in the cable. It shall be homogenous and uniformly mixed material containing an anti-oxidant. It shall not contain dirt, metallic particles or other foreign matter. Paper insulated cables :: Dry air only Polythene insulated cables :: Jelly compound. 1.8 SCREEN :: An aluminum tape coated with polythene / copolymer on both sides shall be applied over the cable core with a minimum overlap of 6 mm for all sizes of cables. The nominal thickness of the aluminum tape shall be 0.2 mm and that of polythene / copolymer coating on each side 0.05 mm. The aluminum tape shall be sealed at the overlap and bonded to the inner surface of polythene sheath extruded over it. The tape shall be electrically continuous throughout the length of cable. RTTC, NAGPUR Page 4 of 185

Underground Cable

1.9 SHEATH :: A moisture resistant , gas tight sheath must be applied to all the paper insulated cable other wise relative humidity conditions throughout will increase and insulation resistance will decrease. The sheath also protects the cable form damage during installation and service. The sheath shall be reasonably circular and free from pinholes and other defects. The variation between maximum and the minimum diameter at any cross section shall not exceed 5mm. Paper insulated cables

::

Lead sheath or Polythene sheath

Polythene insulated cables

::

Polythene sheath only.

1.10 CONDUCTOR:: Each conductor is a solid round wire made of annealed high conductivity copper of diameter 0.32 mm, 0.40 mm, 0.50mm, 0.63mm and 0.90 mm. 1.11 ARMOURING :: In the armoured cables bedding and armour are provided over the sheath to be followed by jacket. Then the cables are called Armoured cables. If this arrangement is not done then we call them as un armoured cables. BEDDING two close helical lapping of polythene or polypropylene tape is applied over the sheath to provide sufficient mechanical protection during armouring. Each take is applied with a minimum 5% overlap. The second tape will cover the overlap of the first tape evenly. Nominal thickness of the Galvanised steel Tape armouring Diameter of cable over Polythene sheath Upto 40 mm Above 40 mm

Thickness of Steel tape 0.5 mm 0.8 mm

Armouring is the application of two layers of galvanized steel tape both applied helically in the same direction with a gap in the first tape of 25% +/- 10 % of the nominal width of the tape, the second tape evenly covering the gap of the first tape. The overlap of the second over the first shall not be les than 15% of the nominal width of the tape on either side. The standard armouring types are  Aerial tape armour  Jute protection  Burried tape armour  Modified tape armour  Steel armouring and polyjacketing RTTC, NAGPUR

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Underground Cable  Corrugated steel armouring and jacketing. 1.12 Jacket :: Most cables serve their lives with a basic sheath but after armouring the armouring is to be protected from getting rusty and corrosion and jacket is the protection which does the job. It should be reasonably circular, free from pinholes and other defects. Nominal thickness of the Jacket Diameter of cable over Polythene Jacket Upto 46 mm Above 46 mm up to 64 mm Above 64 mm

Thickness of Polythene Jacket 1.4 mm 1.8 mm 2.2 mm

1.13 Identification and Length markings on a Cable To enable proper identification of Telecom cables the following markings shall be embossed, engraved or printed on the polythene jacket in case of armoured cable and on the sheath for unarmoured cables. These markings are at an interval of one meter throughout the length and are distinct and visible to the naked eye from a distance of about 1 meter.  Telephone handset emblem  Name of the Manufacturer  Year of Manufacture  Capacity of the cable in pairs  Size of the conductor  Length marking 1.14 Sealing of the Ends:: The cables will be sealed with thermo shrinkable end caps of adequate thickness after completion of all tests in factory before dispatching to various stores and workplaces directly. 2.0 POLYTHENE INSULATED JELLY FILLED CABLES :: These are popularly known as PIJF cables and consist of twisted pairs of polyethylene insulated copper conductors. Paper insulated cables (LSDC, PCUT, PCQT, PCQL & PCQL ) are the primitive underground cables that are used in the Telecommunications network. These cables are available up to 1800 pairs. Later on due to various factors like escalation in the cost of Lead and more incidence of faults due to paper insulation the Polythene insulated Jelly filled cables ( Popularly known as PIJF ) are used extensively now a days in the telecommunication networks. The PIJF cables are available up to 3600 pairs.

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Underground Cable Some constructional features of Paper insulated cables are dealt in Job Aid – I, for academic interest and as still a few number of these cables are still serving some of the telecommunication networks. The Pressurization of dry core paper insulated cables is now a avoidable feature as the replacement of paper-insulated cables with PIJF cables is nearing completion. As the PIJF cables are filled with Jelly as filling compound which takes care of prevention of entry of moisture / water into the core of the cable. 2.1

POLYTHENE INSULATED JELLY FILLED POLYTHENE SHEATHED UNDER GROUND CABLE (VIDE ITD S/WT -129 DT. 2.3.83 & ITD SPECIFICATION NO S/WT - 143 DT. 30.7.88 ) (a)

Number of Pairs The cables shall be in sizes 5, 10, 20, 50, 100, 200, 400, 800, 2000, 2400, 2800, 3200 and 3600 pairs.

(b)

Conductors Each conductor shall be insulated with polyethylene of insulating grade. Different gauges of conductors 0.32mm, 0.40mm, 0.50mm, 0.63mm, and 0.90 mm are used in the cables. Each conductor shall consist of a solid wire of annealed high conductivity copper smoothly drawn & circular in section, uniform in quality, resistance and free from all defects. The average resistance of all the conductors in the cable shall not exceed the values shown in Table given below.

Nominal diameter of conductor

Resistance per km per conductor at 20 0 C

in mm ohms/km 0.32 223 0.40 135 0.50 86 0.63 58 0.90 28 2.1.1 The Percentage calculated as follows::

Tolerance on conductor Resistance

Minimum elongation of conductor

Min % conductor Attenuation at Resistance 20 deg C unbalance

Ohms /km percentage Average Db/km 15 1.5 +/- 4 15 1.5 12.0 +/- 3 15 1.0 8.25 +/- 2 18 1.0 6.30 +/- 1 18 1.0 4.40 of Resistance Unbalance of any individual pair tested shall be ( R1 - R2 )

Percentage of Resistance Unbalance =

x 100

R1 + R2 Where R1& R2 are the resistances of individual conductors of pair under test and R1 > R2

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Underground Cable 2.1.2

The temperature correction for attenuation is: Attenuation at t degrees C 0

Attenuation at 20 C =

1 + 0.0018 (t-20)

2.1.3 CORRECTION FACTOR FOR CONDUCTOR RESISTANCE :: Temperature in deg C at which 10 conductor Resistance is measured Multiplier constant for conversion to 1.041 20 deg C 9 (c)

20

30

40

50

1.000 0

0.962 2

0.927 1

0.8945

Insulation Each conductor shall be insulated with solid medium density polythene of density 0.926 to 0.94 to a thickness. The insulation should be uniform, smooth and free from all defects. The insulation will have following color for identifying pairs /conductors under normal lighting conditions.

2.1.4 CODE FOR WIRE IDENTIFICATION Primary colors

Secondary colors For 2nd wire in a pair and binder tape of unit in 50pr/100pr unit Blue Orange Green Brown Slate / Gray

For 1st wire in a pair White Red Black Yellow

(c)

2.1.5

Unit A number of twisted pairs laid up to form a group shall constitute the unit. The color scheme of pairs and wires in a unit shall be read as below. CODE FOR TAPE OR BINDER FOR UNIT IDENTIFICATION Unit number Color of Binder

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1 Blue

2 Orange

3 Green

4 Brown

5 Slate / Gray

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Underground Cable 2.1.6 CODE FOR CONDUCTOR INSULATION Pair No 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Color First Wire White White White White White Red Red Red Red Red Black Black Black Black Black Yellow Yellow yellow Yellow Yellow Natural Natural

Second Wire Blue Orange Green Brown Slate / gray Blue Orange Green Brown Slate / gray Blue Orange Green Brown Slate / gray Blue Orange Green Brown Slate / gray Blue Orange

A

B

C

Note: (a) In 5 pair cable, color code specified for pairs 1 to 5 above is used. (b) In 10 pairs cables and 10 pairs units of 50 pair cables, color code specified for pairs 1 to 10 is used. (c) In 20 pair cables and 20 pairs units of 100 pair cables, color code specified for pairs 1 to 20 shall be used. (d)

The number of the pairs with respect to the color scheme is only for the purpose of identification of pairs, the actual numerical sequence of the pairs varies as the size increase.

The different colors of the binder shall be readily distinguishable under normal lighting conditions. (e) Stranding A 50 pair cable consists of 5 number of 10 pair units A 100 pairs cable consists of 10 number of 20 pair units. These units shall be stranded into a compact and symmetrical cable. the sequence of the units in the cable shall be same throughout the length of the cable. An open lapping of 0.02 mm miler tape of any other suitable material of appropriate thickness shall be applied for each unit.

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The tapes shall be so colored and have lay not exceeding 200 mm. This tape is not necessary on the 5 pairs, 10 pairs and 20 pairs cables. Page 9 of 185

Underground Cable

In case of 5, 10, 20 and 50 pair cables, one spare pair will be stranded as the last pair. The color of the spare pair shall be in accordance with pair No. 21 of above table . In the case of 100 pair cable, 2 spare pairs shall be provided. the color of the pair shall be as specified for pair No. 21 & 22 of above table. The spare pairs in the case of 50 pairs and 100 pairs cables shall be provided within the cable core, but shall not be within any unit. The 200pair and 400 pair cables ( cables above 100 pr and unto 400 pairs) will be formed by super units of 50 pairs. and the units stranded in the form of layers The cable over 400 pairs is formed be the super units of 100 pairs and the units stranded in the form of layers. Identification of 50 pair super units in cables of 200 pair and 400 pair & 100 pair super units in cables of over 400 pairs

Position of the unit in the layer First (Marker) Intermediate Last (Reference)

Color binder Red White Black

Note:: The numbering of the units will be clock wise as running end. Different configurations of PIJF cables availability is given in table. Cable size In pairs 5 10 20 50 100 200 400 800 1200 1600 2000 2400 (f) RTTC, NAGPUR

No of Units / Super units Centre layer 1x5 (unit) 1x10 (unit) 1x20(unit) 5x10 (SU) 5x20(SU) 4x50(SU) 2x50(SU) 2x100 (SU) 3x100(SU) 1x100(SU) 1x100(SU) 2x100(SU)

Middle Layer

Outer Layer

6x50(SU) 6x100 (SU) 9x100(SU) 5x100(SU) 6x100(SU) 8x100(SU)

10x100(SU) 13x100(SU) 14x100(SU)

Nominal length in a drum 0.50mm 0.40mm 1000 1000 1000 1000 500 400 400 200 200 200 200 200 200 200

Armouring Page 10 of 185

Underground Cable When required the cable sheath shall be armoured. For armoured cable a close helical lapping of waterproof cotton tape shall be applied over the innersheath. The cable shall than be armoured with two applications of galvanized steel tape each applied helically with a gap of 25% + 10% of the width of the tape, the second tape covering the gap of the first. (g)

Overall Polythene Jacket A tightly fitting jacket of polythene shall be applied on the armoured cable. The minimum thickness of the jacket shall be 1.2 mm.

3.0 USES OF DIFFERENT TYPES OF CABLES 

Gauges 0.32 mm and 0.44 mm for primary cable.



Gauges 0.4 mm and 0.5 mm for secondary cable.



Gauge 0.5 mm and 0.63 mm for distribution cable.



Gauges 0.63 mm and 0.9 mm for distribution cable.



Higher gauges of cable for distribution side having longer lengths.



Unarmoured PCUT cable to be laid in duct and to be pressurized.

Armoured jelly filled cable may be laid direct in the ground and and Unarmoured jelly filled in Ducts not to be pressurized. 4.0 DISADVANTAGES OF PAPER INSULATED CABLES WITH POLYTHENE INSULATED CABLES 

4.1 Numbering of pairs is in coded form. Require more skill. Color markings also fade with due course of time. 4.2 Jointing of cables require skill and perfection is required while plumbing as even a slight pinhole will cause entry of moisture / water and damage all the pairs. 4.3 Extra care is required for handling like coiling, uncoiling to avoid damage. 4.4 Water / moisture entry will affect the complete cable at once instantaneously. 4.5 Termination in cabinet / pillars / DPs and at MDF is very expensive and time consuming & increases number of joints. 5.0 ADVANTAGES OF POLYTHENE INSULATED JELLY CABLES. 5.1 Counting of pairs is easy and human mistakes are avoided. 5.2 Jointing is easy and require no chamber or additional place. 5.3 Failure of joints is less. 5.4 Entry of moisture / water is prevented by Jelly in the core.

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Underground Cable 5.5 Cables can be directly terminated on MDF / Cabinet / Pillar and DPs, thus avoiding additional joints decreasing the cost and time. 5.6 Handling of cable is easy not delicate like paper insulated cables. 5.7 Life of cable is more. NOTE :: The systems used in our telecommunication underground network other than PIJF cables are discussed in brief at the end of this chapter.

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Underground Cable

6.0 CO-AXIAL CABLE RTTC, NAGPUR

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Underground Cable The coaxial cable consists of a inner solid cylindrical conductor placed along the axis of an outer hollow cylindrical conductor. A coaxial cable may consist of two or more cores layed up with suitable lay with proper insulation along with quads laid in the interstices between them all enclosed in a lead sheath. The cable is recognized with 1. Number of cores i.e. either 2 core or 4 core 2. Size of the inner diameter of tube - r i.e. 0.375 type ( large tube – 0.375” ) or 0.174 type (small tube – 0.174”). The interstice Quads or pairs having diameter of 0.9mm TWO CORE 375 coaxial cable Coaxial core Lead sheath Quads of 0.9 mm Polythene Disc

7.0 OPTICAL FIBRE CABLE :: Optical fiber is the latest underground cable that is being used extensively in all the networks including long distance trunks, junction circuits and even the local subscriber loops to enhance the data transmission. The OF cables are detailed extensively in the other modules of the basic course. How ever for academic interest the advantages of OF cables over copper cables are discussed here under 1. Optical Fibers are non conductive, hence does not require ground and surge suppression 2. Optical Fibers are immune to electromagnetic interference 3. Un authorized tapping is not feasible. 4. Easily upgradeable to higher bandwidth. 5. Low loss ( 5db per km to < 0.25 db per km on a typical fiber) 6. Long and unrepeated links , hence inexpensive 7. Small light, and hence cost is less and easy for installation. 8. It does not attract lightning, It does not carry electricity hence not hazardous The Application of the Fiber Optical cable in communications are :: 1. Is the common carrier nation wide networks 2. Inter connecting all Trunk automatic exchanges 3. Inter connecting all the Exchanges. 4. Under sea cable 5. Control systems RTTC, NAGPUR

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Underground Cable 6. Customer premises communication networks. 7. SDH systems •

8 MB MUX for 120 channels

•

34 MB for 480 channels

•

140 MB for 1920 channels

8.0 PAIR GAIN SYSTEMS :: The pair gain systems are introduced in to the local network to provide temporary relief to the Technically not feasible (TNF) areas. The PGS is a switching system which provides more subscriber lines using a single cable pair. The numerical value of pairs gained is therefore defined as Pair gained = No of customers connected – No of network pairs connected . The types of PGS are divided into basic groups depending on how pair gain is achieved Concentrator Grade of service requirement will limit the degree of concentration practically possible. Multiplexer Uses FDM or TDM technique to assign a dedicated frequency or time slot resulting in nonconcentration. Better pair gain is possible. Concentrating Multiplexer It is a combination of multiplexer with concentrator. The different types of PGS are given in the table.

PGS

Description

1+1 FM 4D PGS-1 4DPGS –2 SLC LCU RCM

Analog customer carrier 4 channel Digital PGS phase I 4 channel digital PGS phase II Small line concentrator Line concentrator Unit Remote customer multiplex

Customer Break even pairs to distance in network Km pairs 2/1 0.02 4/1 0.04 4/1 0.03 14 / 5 0.08 96 / 16 5.2 30 / 2 2.0

Benefits of PGS units : Primary Benefits : Flexibility to provide rapid service as less effort is needed to install it than conventional cable . RTTC, NAGPUR

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Underground Cable Secondary Benefits : To improve customer satisfaction with quick service and network benefits by restricting the cable pair re-arrangements to necessary cases only.

9.0 CONSTRUCTION OF solid polythene insulated fully filled under ground pcm telecom cables used for 2mbps digital system. RTTC, NAGPUR

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Underground Cable The cables are available in sizes 10+2, 20+4, 48+6, 96+8 and the nominal conductor diameter of 0.63 mm. The core shall be formed in units o 5 pair in the case of 10+2oair cable, units of 10 pairs in case of 20+4 cables and units of 12 pairs in case of 48+6 and 96+8 pairs. The conductor material and insulating material are same as PIJF cable construction. The color code for conductor insulation is : Pair No Color

st

1 wire 2nd wire

1 W B

2 W O

3 W G

4 W BN

5 W S

6 W BK

7 R B

8 R O

9 R G

10 R BN

11 R S

12 R BK

Color code for Binder for Unit identification : Unit No. 1 Color of Blue Binder

2

3

4

5

6

7

8

Orange

Green

Brown

Grey

White

Red

Black

Cable Laying Up :: As shown in the diagram Size of cable 10+2 pairs 20+4 pairs 48+6 pairs 96+8 pairs

No of Units 2 2 4 8

Size of unit 5 pairs 10 pairs 12 pairs 12 pairs

No of Extra pairs 2 4 6 8

Color code for conductor insulation for Extra pairs :: Pair No 1 1st Wire BK COLOUR 2ndWire B COLOUR

2

3

4

5

6

7

8

BK

BK

BK

Y

Y

Y

Y

O

G

BN

B

O

G

BN

Core separator Tape (Screen) A poly-al core separator tape screen is in continuous length to physically separate the core into two compartments. The thickness of the tape shall be suitable to meet the cross-talk requirements. In addition a Poly-al tape shield if provided with 0.2 mm thickness of al tape and 0.05 mm coating of polythene

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Underground Cable

PCM CABLE LAY

Job aid – I A

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Underground Cable 1.1

LEAD SHEATH CABLE (FOR REFERENCE ONLY , OBSOLETE) There are various types or lead sheath cables i.e. PCUT, PCQL, PCQT

etc.

1.1.1 (a)

PCUT (PAPER CORED UNIT TWIN) CABLE PCUT cables are used for all local telephone underground cables.

(b)

In this type of cable each unit is a self-contained group of pairs of conductors.

(c)

The insulating paper covering each conductor is painted with colored lines forming a group of rings on the outside of the covered conductor. The color and spacing of the marking is given in table-I.

(d)

Two insulated conductors are twisted to form a pair.

(e)

The lays of the conductors forming the pair are different for adjacent airs and pairs in adjacent layers have different lengths of lays. The lays are so chosen as to ensure that cross talk between pairs is kept down to the minimum.

(f)

Cables of less than 102 pairs dealt with one unit. The cable having more than 102 pairs are divided into groups of 51 pairs. Cable containing more than 408 pairs are in units of 102 pairs. The direction of stranding is reversed in successive layers.

(g)

All the units of the cables are stranded in rope like fashion to form the cable.

(h)

In all the large size cables with more than 51 pairs, one open helical whipping of cotton of not less than 3 strands is applied round each layer.

(i)

Each complete unit is covered with an open helical whipping of paper marked with black (or blue) printed figures repeated through out the length to identify the unit. Over this there is a helical whipping of cotton.

(j)

A final closed helical lapping of two thickness of insulating paper is laid over the formed cable core.

(k)

Table - II gives the lay up of pairs in the unit.

TABLE-I Pair numbers in No. of lines layer 1. Marker 2. Marker 3. 4. 5. 6. and so on

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Color of lines

A-wire

B-wire

1 3 1 3 1 3

2 4 2 4 2 4

Central layers Green Green Red Red Red Red

&

even

Odd layers Orange Orange Blue Blue Blue Blue

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Underground Cable TABLE - II No. of pairs in unit Centre of cable Layer 20 51 102

2 4 2

LAYERS Ist 6 10 8

2nd 12 16 14

3rd

4th

5th

21 20

26

32

Different sizes of the PCUT cables used in the DOT are 20,50,100, 150, 200, 300, 400, 600, 800, 1000, 1200 pairs 1.1.2 (i)

PCQL (PAPER CORE QUAD LOCAL) CABLE Lead covered paper core quad twisted local cables (PQCL) are used for junction circuits between local exchanges.

(ii)

In this type of cable, the pairs are twisted in Quad formation i.e., four insulated conductors of each core are twisted together in one operation so as to occupy the four corners of a square. The conductors diagonally opposite to each other in the quad form a pair. Inductive interference is kept down to minimum by this formation.

(iii)

Gauges on conductor are 0.63, 0.9 & 1.27 mm.

(iv)

Stiffening of the paper tubes has resulted in the accurate and permanent centralization of the conductors whilst a central string upon which the covered conductors are bedded is used to ensure symmetry of cable.

(v)

Numbering scheme is given by Table - III.

(vi)

The A wire of a pair is the one having the odd number of ink lines upon the paper insulation. Wires in alternate quads have the paper marked with red and blue lines respectively.

(vii)

PCQL cable are available of 14, 38, 54, 100, 200, 300, 400, 500, 600, 800 pairs. Position of quad in color of marking layer insulation paper First marker Intermediate etc. 3,5,7 etc Last reference

(vi)

Red 2,4,6 Blue Red Blue

on Color of quad Centre and even layer White with orange strands White

Whipping Odd layer Black with orange strands Black

White Black White with Black with orange strands orange strands

The lays of the conductors forming the quads differ for adjacent quads. The quads are then stranded into a compact and symmetrical cable. The direction of the stranding alternates in successive layers.

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Underground Cable (vii)

1.1.3

A final close helical lapping of two thickness of insulating paper formed cable core.

(red color) laid over the

PCQT (PAPER CORE QUAD TRUNK) CABLE

1. Lead covered paper core quad twisted trunk cables (PCQT) are used for trunk circuits. The construction of these cables is similar in all respects to PCQL cables. The essential points of difference between the PCQL & PCQT type cables are: 2. 0.90 mm and 1.27 mm dia copper conductors are used in PCQT as against 0.63, 0.90 & 1.27 mm dia in PCQL. 3. The mean mutual capacity in PCQT cables is smaller than in the

case of PCQL.

4. The permissible capacity unbalance in PCQT cables is much less than in PCQL cables. The higher gauges of wire and lower mutual capacity keeps the attenuation constant of cable low and the reduced permissible capacity unbalance serves to minimize crosstalk. 5. PCQT cables are in sizes of 6,14, 38 and 54 pairs. 1.2

COMPOSITE SHEATH CABLE During the last two decades the DOT imported various steps of composite sheath cables and the cables are named as per the construction of sheath. a) Al Path b) PAP c) Stall path d) PASP

-sheath construction -do-do-do-

(Aluminum- Polythene) (Polythene-Al - polythene) (Steel-Aluminum - Polythene). (Polythene - Al -Steel - Polythene)

Now the composite sheath cable is being manufactured in HCL indigenously on the ITD specification No. S/WT-129 dt 2.3.82 & ITD S/WT-143/B dt 30.7.88 and the name of the cable has been standardized as ‘Polythene insulated fully filled polythene sheathed underground cable’ (Jelly filled cables). PRACTICE Identification and constructional and Design features Polythene insulated Jelly filled cables, PCM CABLES, which are discussed in Chapter I are to be practiced in the practical classes.

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Underground Cable

CHAPTER - II CABLE LAYING OBJECTIVE :: THE

LAYING METHODS, THE PROCEDURES AND STEPS INVOLVED

ALONG WITH CERTAIN PRACTICAL PROBLEMS THAT ARE ENCOUNTERED IN THE FIELD ARE DISCUSSED AT LENGTH FOR ADOPTING BETTER TECHNIQUES.

* 1.

*

*

INTRODUCTION : In any large telephone exchange system, cable component constitutes nearly 50% of the capital outlay. Hence proper and standard cable construction can obtain economy and reduce the cost of maintenance and over and above help rendering efficient and un-interrupted service.

2

CABLE CONSTRUCTION PRACTICE MAY BE BROADLY CLASSIFIED INTO: (a) (b) (c) (d) (e)

2.1

SURVEYING THE SELECTION OF ROUTE : (a)

(b) (c) (d) (e)

2.2

Receipt, storage, handling and transport of cable Surveying and selection of routes, trenching and laying Jointing of cables and termination Preparation of cable plan, cable diagram and other relevant records Acceptance testing

The routes should be as short as practicable provided other requirements viz., future requirements and expansion of other services are take in to consideration. Normally the cable should be laid along road and railway tracks. Corrosive soil should be avoided. If unavoidable measures like covering the cable with sand or drawing the cable through non-reactive duct should be adopted. Opening of expensive pavements and roads should be avoided. The consideration should be given to the existence, alternation and growth of other services. While surveying along a new road under construction or newly developed area, proper coordination should be maintained with other underground services like water, electricity, sewage, gas etc.

DEPENDING UPON THE ROUTE SELECTED, PERMISSION FOR DIGGING TRENCHES ARE TO BE TAKEN FROM THE RELEVANT AUTHORITIES LIKE :

(1) Municipal or local authorities (2) Traffic authorities (3) High way authorities RTTC, NAGPUR

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Railway Department Post trust authorities.

2.3 AT THE TIME OF TRENCHING OPERATION CO-ORDINATION WITH THE FOLLOWING AUTHORITIES ARE TO BE MAINTAINED:-

3

(1)

Electric supply.

(2)

Water supple.

(3)

Gas pipeline.

(4)

Sewage system.

TRENCHING : The following are some important points to be given due consideration at the time of trenching (a) Trenching should be such that the top of the cable should not be less than 60 cms. from the soil surface. (b) The alignment should be straight at least 50 m at a stretch. (c) It should be at least 0.3m away from the boundary walls. (d) The depth of the trench should be 1.2 m. (e) The width of the trench should be between 30 cm and 40 cm minimum. (f) (i) A separation of 0.6 m (relaxable upto 0.2m) should be maintained While cable laid parallel to electric cables. (ii) Parallelism exceeding 0.8 km with 11KV and above should be referred to PTCC. (iii) At the crossing with electric cables, the telephone cable should be laid solid in between for 90 cm on either side. Cross-trenches (trial pits are to be made if records for existing services are not available. IMPORTANT NOTE :: The min. bending diameter for armoured cables should be 15 times of the diameter of the cable

4

ROAD CROSSING (a) (b) (c) (d)

Cable should be laid through G.I. pipes of suitable sizes. The depth of the pipe from the surface of the road should be 1m and with a slight slope to pass away water. The number of pipes laid at a time should be sufficient to cater to the requirements for 20 years. No jointing in the middle of the road.

5.

GUIDELINES FOR LAYING OF CABLES ALONG NATIONAL HIGH WAYS, OVER BRIDGES AND CULVERTS

5.1

ALONG NATIONAL HIGH WAYS (a) (b)

Permission from the Chief Engineer PWD is to be taken. The cables should be laid at distance not less than 457 cm from the Centerline of the road on formation. (c) The depth of the cable from the soil surface should not be less than 120 RTTC, NAGPUR Page 23 of 185

Underground Cable

(d)

5.2

cm. While laying along grove or avenue, due consideration to save the cable from the clutches of the roots are envisaged.

Along over bridges culverts & Fly– over 1. A culvert should be paid by a concrete channel of 12” depth below the bed of the culvert to correspond to the footpath alignment so that all the cables can be drawn through this opening. 2. In order to lay the cable across small bridges with piers the piers should be extended beyond the width of the road so that pipe for cables may be securely clamped on the piers. 3. In case of long bridges and fly over in cities, liaison should be kept with proper authorities to ensure that suitable arrangements are provided for laying cables. the present practice is to have a concrete channel 20 to 30 cm in depth 90 cm in width along the footpath with removable covers.

6.0

LAYING OF CABLES ALONG RAILWAYS 1. Instructions laid vide paras 464 and 465 of P & T Manual Volume X should be strictly followed. 2. Side of the track will be selected by DET in consultation with proper Railway authority e.g. either Divisional Operating superintendent or district Engineer, if the alignment falls within 3 to 5.5 meters from the centre line of any Railway Track. 3. Excavation and reinstatement for any underground cable within 3 meters of the centre of any Railway track or any attachment to any Railway structure should be attended by the Railway staff at the cost of DOT.

6.1

RAILWAY CROSSING 1. Railway track should be crossed by G.I. pipes of 75 mm dia. 2. Minimum depth of the GI pipe from below the rail level should be 1.25 meters. 3. The length of the pipe should be sufficiently long so that work on telecom alignment can be carried out without any hindrance to the railway traffic. This should extend at least 4.5 meters from the center of the last track.

7.0

OPEN GUTTER CROSSING In partly developed metro cities. wherever open gutters are constructed for storm water drainage for sewage, it is difficult to lay small cables across the gutters to multistoried buildings. It should be preferable to recommend to the local authorities to provide a small 25 to 30 mm dia. crossing GI pipes below the bed of the drainage opposite each multi storied building.

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LAYING METHOD OF THE CABLE There are three methods normally adopted by the DOT for laying the cable which are : (a) (b) (c)

Laying direct in the ground laying solid Drawing through duct or duct laying

8.1 LAYING DIRECT IN THE GROUND (DIRECT LAYING) (a) (b) (i) (ii) (iii) (iv)

This method of laying is comparatively suitable and also cheap from the point of view of initial investment. It involves :Digging the trench as per standard vide Rs. 3. The digging may be done manually or be thrust boring or by other mechanical means. Preparation of a bedding 5 cm high of soft soil (sieved earth) free from stones and corrosive elements. Thorough checking of cable which is to be laid. Paying out the cable in the trench by taking the help of cable wheel. If the wheel is not available the cable drum is to be mounted on a spindle supported by jacks on either ends. the jacks should be properly positioned on level surface and the rotation of the spindle should be smooth. Laying out of the cable is done by either moving the cable wheel along the trench of keeping the drum stationary at one end of the trench and pulling the cable

At the time of paying out special precautions to be taken so that :(a)

There should not be any twist in the cable and there should not be heavy strain (specially in the case of unarmoured cable)

(b)

Laying should be as far as practicable straight and along one side of bed of the trench .

(c)

If more than one cable are to be laid at a time, there must not be any crisscross of the cables.

the

Cable rollers at every 10 m in straight section and at all bends and corners are to be used on the bed of the trench to avoid strain on the cable at the time of pulling. In pulling unarmoured lead sheath cable it should be ensured that the lead sheath is gripping the wires of the cable finally so that pull is shared equally be the lead sheath and conductors. Unless otherwise indicated in the drum the free end of the cable should be laid near the exchange which is called the UP end of the cable route. The inner end of the cable should be laid away from this exchange i.e. Down end of the cable route. (v) Identification callers : RTTC, NAGPUR

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Cable identification callers (marker) normally PVC callers with details like size of the cable, route to the cable and number of the cable should be fixed are every 5 m along with length of the cable and at all joint locations. Whenever cables pass through pipe or duct cable marker should invariably be fixed at about 1 m away from the mouth of the pipe. (vi)

Pressure testing : It is sound practice to deep the cables under a pressure of 8 to 10 p.s.i. after laying. A fall in pressure signifies the damage in the sheath of the cable which is to be corrected.

(vii)

Flooding the trench : Sometimes it may happen that trench is dug along the existing cable route. In order to detect if any damage is caused to the existing cables, the trench is flooded with water and the cables are allowed to be immersed in water for 24 hours. After the lapse of 24 hrs the existing cables are tested from the test desk in order to detect any fault come up due to trenching.

(viii) Back filling & Reinstatement : After laying out the cable it should be covered by a consolidated layer of 80 mm of soft earth which should be free from stones or other sharp object, carefully pressed and lightly rammed. (ix)

Warning Bricks or tapes : As a protective measure a row of bricks (length wise or width wise depending upon the number of cables) or stone slabs are to be placed along with cable alignment. The modern practice is to lay a plastic tape with name of the Department printed on it at about 30 cms above and along with cable alignment. After placing the protective arrangement , remaining portion of the trench is filled in and well rammed. It is advisable to leave a crown of earth rising not less than 5 cm in the centre and tapering towards the sides of the trench. This allows for natural subsidence.

(x)

Route indicators & joint indicators: There are different types of indicators used in the department. The appropriate type of route indicators should be placed 200 m apart in the straight and at every point where the direction of the cable route changes. Joint indicator are to be used for each joint.

(xi)

Preparation of diagrams & records : All the diagrams relating to the cable alignment viz. line diagram for primary secondary and distribution side, cable plan for primary secondary and distribution side, records for Pillars and DPs etc. are to be prepared. A careful record of the dispositions of the underground structures of other utility concerns such as water, mains electricity, sewage etc. coming in close vicinity of, or crossing the departmental cables should be maintained.

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9.0

RESPONSIBILITIES FOR CABLE CONSTRUCTION

a) Checking the condition of the cable on drum which is to be laid and ensured that it is healthy and in pressurized condition. b) Ensuring that the trench is of standard dimensions, in case standard dimensions, cannot be maintained, additional protection is to be given. c) Offering the trench for A.T. before starting cable laying. d) Laying the cable as per standard method. e) Offering drums length and laid cable to A.T. f) Provision of mechanical protection, such as bricks, RCC tiles, split ducts, warning tapes etc., temporary re-instatement. g) Offering to A.T. h) Continuity and insulation test of all the pairs before jointing and ensuring that all conductors are in good condition. i) Offering joints to A.T. j) Termination the cable as specified. k) Offering to A.T. l) Updating the cable records including m) Location, sizes, gauges and code number of cable n) Location of the joints including branch joint o) Cable pair records for the entire route p) Average value of loop-resistance, transmission loss and Insulation.

CABLE CONSTRUCTION Any communication cable laid underground forms part of the network of telecommunication infrastructure and is a permanent asset which is expected to live up to its theoretical life span, if not beyond, with a reasonably satisfactory service to the user. Needless to say that telecommunications and in this modern information area, when entirely new services are being planed and more and more information carrying capability is envisaged, the manufacture of modern telecommunication cables and their induction into the existing network should be in line with the needs of the new technologies. Therefore, it is imperative on the part of the construction staff to look into carefully every stage of construction activity, right from selection of appropriate type of cable for a particular application up to testing and commissioning of each pair so as to plug all gaps of vulnerability leading to deterioration of characteristics of the cable. 3.0.

PARAMETERS.

The copper based telecom cable is required to meet certain standards set on the following parameters, so as to consider it suitable for satisfactory transmission and reception of speech and data in the form of analogue or digital signals. I.

Insulation resistance

II.

Conductor resistance

III Mutual capacitance RTTC, NAGPUR

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IV.

Capacitance Unbalance/

A thorough check on the following points must also be carried out before being recommended for network suitability. I. II. III. IV.

3.0

Conductor open fault Conductor cross fault Shield/sheath/core-separator tape continuity Low dielectric strength

STAGES OF CHECK

To keep the cable healthy in operation and satisfactory in Its set parameters, checks are to be carried out at every stage by the Construction staff. The following stages require careful analysis. I. Receipt, transport and storage. II. Physical deformity or manufacturing defects unnoticed by

the

QA wind.

III. Laying activity. IV Jointing activity V. Acceptance testing activity. 3.1

Receipt, Transport and Storage

Right from the dispatch of cable from the factory, duly cleared by the Quality Assurance ( QA) wing, the telecom cable should be carefully loaded transported, unloaded and stocked at the intermediate Stock Depots and finally brought to the Unit stores where detailed inspection of the received cable is carried out. Every drum length should be checked for correct length, visible damage, manufactures code, type & size and condition of end seal. These checks may be conveniently carried out by the JTO ( MM) at the Unit stores and the data fed into a computer memory, to be used for various management purposes, including giving feedback to the manufacture, QA Store Depot etc. The flow chart depicted at Figure 1 illustrates a typical method of checking the cable drums and follow up action in Unit store. 3.2

Physical Deformity and Manufacturing Defects

Physical deformities occurred during manufacture and overlooked by the QA wing rarely come across in the field units. There may be other damages that occur during transport or handling, which should not go unnoticed. This will help in taking up the defects with the manufacture or Central Store Depot immediately and either get replacement or claim compensation for loss/damage. This extra check is necessary to avoid problems at a later date during maintenance. RTTC, NAGPUR Page 28 of 185

Underground Cable

FLOW CHART FOR CHEK ON RECEIPT OF CABLE ::

no

Acknowledge Store Receipt

3.3

START Is the cable drum received in tact If , yes note down Drum No length, etc Want to ensure correct length Test length by APLAB Any difference with markings Uncoil the drum and inspect Any defect observed If no issue for usage in work Ear mark duct section or route section according to length

Furnish feed back to QA /store and all concerned officers to get replacement Append stock file

Laying Activity Great deal of attention is to be paid during laying of cables. As the cable laying is resorted to through outside agencies, departmental officials should exercise a close supervision of activities in progress . The contractor may be considered as a businessman interested in getting maximum profit for minimum effort. His as well as his worker’s intention, therefore maybe more on completion of work speedily rather than caring for standards, precautions, warning to pedestrians and vehicular traffic, damage to existing cable etc. Therefore supervision by departmental officials is necessary. Being an underground activity. once laid and the trench back filled, it is difficult for an inspecting official to see the defect directly. It is necessary to dig trial pits at suspected spots to check for correct depth, warning layer. GI Pipe, clearance between water pipe and cable etc. Alternatively the best way of supervision however will be to see on day-to-day basis and conduct surprise checks at random. It is suggested that the following nine commandments may be enforced on the contractor so as to achieve satisfactory results.

I. II.

Mark the route where cable is to be laid and a route map issued to the contractor who has to strictly follow the same. Mark the route where Telecom and Electric cables exist and ask him to take special care to avoid damage/accidental contact.

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Underground Cable III.

Clearly mark on route diagram the locations from where existing cables are proposed to be recovered, if any, so as to ensure recovery without damaging other cables.

IV.

Earmark BT/Berm cutting for strict compliance and avoid inconvenience to smooth flow of traffic or pedestrians. Enlighten contractor about precautions such as drawing cables using cable grip & cable rollers where necessary. Let him engage more men for paying out and laying in cities to avoid damage to the cable and inconvenience to traffic. He should use winch, cable rollers, pulley blocks, nylon rope etc while higher size cables are drawn in ducts. he should ensure that draw hooks are attached to the cable ends and only moderate pulling tension is applied on the cable. He should use proper warning layer over cable as per instructions and should the identification tags/collars at specified intervals before closure of trench.

V. VI. VII. VIII. IX.

3.3.1

He should properly mark all jointing spots and leave only optimum joint length on each cable as per requirement of DOT so that no cable is wasted at the time of jointing. He should immediately report to construction Officer DOT any instance of objection raised by PWD/Local Authority or private individual so that such grievances can be settled by the construction Officer amicably. Tender Conditions. The practice of calling sealed tenders, accepting the lowest rates and awarding the work for more than one financial year creates some practical difficulties. Since the labor rates and other incidentals are subjected to change year after year, the successful tenderer may try to backout after one year’s work or ask for enhanced rates. So it is desirable to call for tenders on year-to-year basis for cable laying work. In rural areas where close supervision is difficult, contractors may try to maintain insufficient depth for trench and avoid using warning layer. In semi urban and other developed cities, it is advisable to engage more men for laying so that the entire operation progresses quickly and gets completed with barest minimum inconvenience to shopkeepers and general public Unlike other civil construction works, tender conditions for carrying out cable laying works should take into account all these important aspects and give more stress on precautions to be taken while laying, as any defective practice will lead to network instability at a later date.

3.3.2

Some Common Wrong Practices and Their Remedies. Some of the wrong practices often noticed in laying cables on public roads by contractors are enumerated in the following paragraphs, which can be rectified as suggested.

3.3.3. Crossing Water Pipes. Wherever water pipes exist at insufficient depths and the contractor lays the cable over it, it causes unequal dynamic stress on the cable by vehicular traffic , ultimately developing a sheath crack and consequential failure of circuits. In such cases, the contractor should get specific instructions from the Construction Officer and lay the telecom cable through GI pipe further below the level of water pipe with a soft earth cushioning between water pipe and cable terrains may preferably be made using RTTC, NAGPUR Page 30 of 185

Underground Cable water blocking powder on the upstream side and protect the ends of cables by using insulation tapes during laying. The following diagrams in the next page illustrate better about the laying across water pipe lines and culverts.

CROSS- SECTION OF ROAD SHOWING TELECOM CABLE LAID OVER WATER PIPE WITHOUT CLEARANCE AND SUBJECTED TO EXCESSIVE DYNAMIC LOADS FIGURE-2 3.3.4

Crossing Culverts While laying cables across a culvert, the usual practice followed is by using GI pipes cut at the ends in V- shape on the outer surface and bend downwards so as to lead in the cable from end to the trench. This apart from weakening the strength of GI pipes, damages the outer sheath of cable due to abrasion. Moreover, the pipe itself is broken at this weak spot whenever any vehicle runs over it. The V-cut also reduces the inner volume of the pipe. making it difficult to draw further cables through it. the cut portion allows mud to enter the pipe and clog the inner space during heavy monsoon and in course of time renders the pipe unfit for further drawl of cables. The use of 45o bends of the same size as that of the pipe at the ends with necessary couplings and sealing at both ends using plaster of Paris or light cement mortar mix, after all cables are drawn through the pipe, is found to be an advantageous method. A typical arrangement is shown in figure 3 Where the pipe could not be taken close to the wheel guard of the culvert or below it, the pipe may be enclosed inside the parapet wall by dismantling and reconstructing it with the specific approval of the PWD. Sealing the ends of pipes in both the above cases is an important precaution to avoid accumulation of mud and prevention of entry of harmful rodents, rats etc. Where the culverts are not provided with parapet walls, it is preferable to enclose the GI pipe along with cable in cement concrete through the length of culvert as shown in Figure 4 Care should be taken to draw further cables in the same pipes where sufficient space is available and finally seal the mouths so as to avoid wastage of pipes.

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TYPICAL METHOD OF LAYING CABLE THROUGH PIPE OVER CULVERTS USING 45oBENDS FIGURE 3

3.3.5

Crossing 11KV Electric Cables

Instances we may come across where 11KV electric cables exist in parallel or across a proposed Telecom cable route. In respect of parallelism, it is advisable to take the telecom cable with maximum horizontal clearance as far as practicable but not less than 0.6 meters, so that the intensity of inductive interference can be minimized. Absence of sheath continuity and armour continuity in Telecom cable and it’s improper earthing in the vicinity of power cable will result in AC induction and consequent impairment of the telecom circuits. When the power parallelism is more than 0.8 kms the cable route should be referred to Power Telecom Co-ordination Committee (PTCC) for recommendation of protection measures. In case of crossings, care should be taken see that telecom cable crosses at right angles and at a vertical clearance preferably of 0.6 meters but not less than 0.3 meters at any point. When the specified clearances cannot be maintained, it is preferable to lay the telecom cable through cement concrete pipes for a length of 1 meter on either side of power cable at the crossing and seal the mouths at both ends. Electricity authorities should also be requested to lay the electric cable at crossing location in solid or through cement concrete pipe. Conventionally telecom cables are laid only on one side of the road and preferably on thru route through which telephone alignment runs. However if a 11 KV cable exists in any route, Electricity Board Authorities should be consulted and correct location of the electric cable, crossing location etc are to ascertained, before starting telecom cable laying work. Figure 5 shows a practical arrangement of telecom cable crossing an electric cable.

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LAYING CABLE THROUGH GI PIPES EMBEDDED IN PCC ACROSS CULTVERTS HAVING NO PARAPETS FIGURE 4 4.0

JOINTING ACTIVITY

It is very important to follow standard construction practices and good workmanship in cable construction work. This important task is vested with the DOT staff who are given necessary training in conductor jointing, splice closure technique earthing protection, mechanical protection to joints etc. Any physical cable pair can be jointed in a haphazard way in a number of through joints and made available at the distant end for working a circuit. This non standard practice not only causes difficulties to the maintenance staff in tracing the circuits at the time of faults, but also impairs the performance quality of the network, It is therefore necessary to follow standard construction practices only. Transmission properties could be maintained at a satisfactory level only when the conductor jointing is done in perfect 1:1 order. This means all pairs in layers should be jointed to the corresponding pairs in the other bit of cable in the same layer. Thus the correct pair jointing in through/ branch joints and in CT boxes and DPs forms a homogeneous medium for building up a satisfactory communication network. Unlike paper cored cables, polythene insulated conductors in the Jelly Filled ( JE) cables pose no problem, since the color of conductor insulation in polythene insulated conductors does not fade in course of time and identification of tip and ring conductors is easy. Making the joints hastily or without taking proper care should be avoided. Close supervision at every stage of cable construction activities is therefore necessary. Joints should not be allowed to be closed unless all cable pairs and sheath continuity are tested. Some cable splicers may have a wrong notion that water does not affect the JF cable and therefore they sometimes make joints in rains, keep the end of cable in water till joints are made etc. Experience has shown that water trapped inside joints flows through the crevices of the cable core and gets collected in the lower most joint. Even through UY-connectors and splice - modules are theoretically supposed to be watertight, instances have been noticed where water trapped inside a joints finds it’s way into the splice modules and UY-connectors and cause low insulation faults. This is observed to be due to the fact that jelly filling inside some cables is not viscous in nature but crystalline, which allows water to travel through the core of the cable, RTTC, NAGPUR

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Underground Cable causing low insulation faults. Water thus trapped inside a number of JF cable joints may be sufficient to cause a circuit go faulty. Such kind of faults are difficult to be localized in the APLB 4049 Cable Fault Locator or traced with the conventional method. Therefore joints in JF cables in the sloppy terrains may preferably be made using water blocking powder on the upstream side and protect the ends of cables by using insulation tapes during laying. 4.1

Necessity of Using Proper Tools and Implements.

Due to adoption of newer technologies in cable jointing, cable splicers are required to use different and entirely new tools. It is necessary to make them realize that the tools must be used for the purpose for which it is meant. Splicing staff must refrain from using ordinary blowlamp in place of low heat modified blowlamp. They should use only flat face crimping pliers for connecting polythene-insulated conductors in UY- connectors instead of using ordinary pliers. There are imported as well as indigenous type LSA PLUS Krone connecting tools for use in Krone type CTBs and Dps. Such connectors should be exclusively used for those works only 4.2

Precautions to be taken during Jointing of a Cable.

The following points require careful attention when joints are made. I. II. III. IV. V. VI. VII. VIII. IX. 6.0

Do not hesitate to use a tent or tarpaulin to protect joint and splicing staff from Sun and rain. This will not only reduce the fatigue of workers but also will protect the cable joints from possible entry of moisture and dust. Keep the cable on raised platform while joints are made, so that cable splicer is able to operate correct pair and layer conveniently. Keep all tools and hands of splicing staff clean before starting jointing operation. Clean the ends of cables using abrading cloth and cleaning liquid before fixing XAGA. When doing branch joints, take care to fix branch off clip properly and take extra care in shrinking the portion where branch off clip is fixed so as to avoid any gap through which water may enter. Remember tying the identification tags or collars on each and every cable at frequent intervals near joints. Do not operate all cables to trace a fault in a cable without referring to records or proper investigation and identification of faulty cable. Ensure keeping finished joints on joint stands inside the duct manholes so that the joints are not subjected to tensile stress. Ensure using exhaust fan and proper light inside duct manhole while joints are made.

CONCLUSION :

A reliable subscriber network is a basic requirement of any telecommunication installation. Taking into consideration the huge investment in the external plant, underground telecom cables used should be made less vulnerable to catastrophic faults. This could be achieved by adopting careful planning and construction practices and the impetus given on sanctioning sufficient field staff for patrolling, supervision of cable laying works, jointing operation, annual fault clearance checks etc. The success of introduction of any new technology switching systems largely RTTC, NAGPUR Page 34 of 185

Underground Cable depends on the reliable and efficient cable network. With reliable external plant DOT will be in a position to meet the challenges of Global information Revolution. MICRO TUNNELLING The frequent digging of downtown areas invite criticism from town planner and civilians as well. In view of this situation the following issues received the attention of telecom professional • • • •

How long the cutting and covering technique will be allowed and economical as well. Rehabilitation and repair of underground cables disfavors conventional cable laying in the crowded parts of localities. Ecological disadvantages are too much in cut and cover technique. Congesting at the depth 1 to 1.5 meters below the ground and prohibits further exploitation.

One of the options after studying the problems is MICRO TUNNELLING , which is trench less installation of piles and cables. It replaces the open cut trenching by using drilling suspension. The remotely controlled drill tool is advanced underground. High pressure drilling suspension is emitted from the three dimensions drill tool which rotates through the ground forming the pilot hole or tunnel. Larger spool are pressed against the walls of the tunnel and finer particles of earth are transported along the tunnel with aid of environmentally safe drilling fluid to start pit or the target pit. The remotely controlled rotating drill tool reaches the target pit with complete accuracy, the relevant reamer of the job is then attached and the pilot hole is widened to enable the simultaneous instillation of the products. The pipe or cable called product is attached behind the reamer. The Bentonite drilling suspension enables the installation to be carried out smoothly and without damaging the product. This drilling suspension acts as a lubricant and helps to reduce friction in the tunnel. The drilling suspension is a important part of the technique. Under high pressure, it forces it’s way through the ground, transports the spoils to the pit, supports the micro tunnel and reduces friction on the drill tool and products. This suspension consists of water mixed with Bentonite and water which is specially mixed for each job and the quantity depends up on the physical parameters of the ground. predominantly consists of natural clay minerals, which have swelling properties. This is determined in advance by a geological survey. Location technique is based on electro-magnetic waves. These waves are transmitted from drill tool and measured above ground by receiver. The precise position of the tool can be located and obstacles of underground in line can be avoided. Advantages of Micro tunneling technology: • • •

Ecological advantage, a little job-site waste to dispose off. Un-obstructive, No noise, no mess, no traffic disruption for the people. Economical Lowe costs but high instillation performance.

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CHAPTER – III CABLE JOINTING Objective of the Lesson :: The necessity of a joint in telecom underground cable and choosing of correct technique from the techniques available and adopting for better construction methods for jointing of conductors and joint closures for various types of cables available.

*

*

*

Different types of Jointing Techniques for U/G telephone cables, using different types of connecting techniques for jointing conductors and joint closures. One Of the oldest form of cable existing in our networks are lead sheath dry core (LSDC) paper insulated cable. As discussed its use has been discarded due to various reasons. These are being replaced by PIJF cables and OF cables in the networks. 1. Necessity of joints :

The joint of a underground telecom cable arises due to

a. Limited lengths available for different sizes of cables in new cables. b. Occurrence of Damages to the working cables , resulting in a joint or two.

THIS IS CALLED STRAIGHT JOINT c. An operation on a New cable or Existing working cable is made for diverting part of cable pairs to another direction / area.

THIS IS CALLED BRANCH JOINT d. To transfer the existing cable pairs of one area in an exchange system ( old pillar ) another area (new pillar ) in the same exchange system

e. To transfer the existing cable pairs from existing exchange in the area to another new exchange called area transfer.

AREA to be transferr

Old exchange

New exchange RTTC, NAGPUR

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THIS IS CALLED TEE JOINTING OR PARALLEL JOINT 1.1 The jointing of the Local cables are described as detailed below :a. Jointing of LSDC cables b. Thermo shrink joint technique. c. Jointing with ALSS technique. d. Jointing Jelly filled cables with TSF kits. 1.2 PRECAUTIONS TO BE OBSERVED FOR JOINTS Very often a large size of cable is required to be jointed with another same size or more than one cable of smaller sizes of cables. While proceeding for jointing following precautions are to be taken particularly in case of Brach joints and ‘Tee’ joints. •

The jointing of conductors should be done as per jointing schme ensuring that the smaller branch cabe is jointed to inner layer or main cable.

•

In case there is any spare cable pairs left, these should be bunched together and stumped in the joint, which can be utilized infutre (with recording )

•

Dressing of main sleeve should be done in such a way that the man sleeve flushes on all sides as far as possible.

•

In case of plumping of LSDC should be done proper at Branching point to fill any gaps or pin holes while dressing.

•

Suitable size of Kits should be used depending on the specifications.

1.3 ARRANGEMENTS TO BE MADE BEFORE THE START OF JOINTING •

Cable jointing pit suitable size be dug so as to accommodate the cable splicer along with his assitants and tools and facilitage easy jointing.

•

Guarding of work against public to avoid danger to vehicles , pedestrians and cable jointing personnel.

•

Beware of existing cables and particularly existing joints at that place.

•

Beware of underground Power cables at the place of joint.

•

Protection against weather and water toavoid low insulation in joint.

•

Pre arranging Joint tools and Joint materials.

1.4 GENERAL : Other instances of requirement of Jointing of underground cable is for the following purposes :RTTC, NAGPUR

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Underground Cable (a)

Jointing of cable - drum lengths to obtain the desired length of cable and to direct different amount of pairs in different directions as necessitated by subs-density.

(b) (c)

Incorporating additional joint on some working cable for removing faults.

(d) (e)

Replacement of a faulty portion of a cable length by incorporating two additional joints.

(f)

Replacement of faulty joint by a new one. 2.0 JOINTING TECHNIQUES Any jointing technique consists of the following operations.

(a) (b) (c)

conductor jointing. Protecting the joint against moisture entry and / or making the joint airtight. Protecting the joint against corrosion and mechanical damage.

2.1 CONDUCTOR JOINTING

A. CONVENTIONAL METHOD :It consists of twisting the conductor ( soldering also required for higher gauges) and putting a paper sleeve for insulation. This system though suitable for paper core cable is going to be abolished for the following reasons:(a) Not suitable for jelly-filled cable. (b) Time consuming operation and hence the efficiency of the splice is decreased.

Paper insulated conductors Paper sleeve Twisting of conductors

Finished conductors jointing

RTTC, NAGPUR

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B. USING CONNECTORS Three types of connectors were evaluated by TRC in 1980 which are as follows :(a) (b) (c)

B - wire connector (UK) Pica bond or AMP connector (USA) Scotch or UY connector (USA) (filled variety)

Out or these three DOT has accepted the scotchlok connector for the following reasons. (1)

Same connector holds good for all gauges of wire.

(2)

Smaller joint size.

(3)

Jointing operation very simple, insulation on wire need not be removed.

(4)

No chance of imperfect joint, as we can see through the connector.

(5)

Plastic outer cover quite firm.

(6)

Avoids corrosion as the connector is filled with jelly.

UY CONNECTOR BEFORE USAGE

PVC TRANSPARENT BODY

Contact plate

Copper Conductors with insulation Contact plate One conductor from onePVC direction and another conductors from another direction to be TRANSPAREN jointed are inserted into the UY connector without removing the insulation of the wires. The contact willTbeBODY made by the plate after cutting through the insulation. This technique is used for Polythene insulated jelly filled cables.

UY CONNECTORS AFTER USAGE RTTC, NAGPUR Two Insulated conductors through Body having jelly

Copper Conductors with insulation cut at plate Page 42 of 185

Underground Cable

C. JOINTING WITH 20 PAIR MODULES : The splicing of polythene-insulated conductors is done, preferably when the size of the cables to be jointed are 200 pairs and more with the 3M Super Mini Splicing Modules.

A single Modules is used for jointing of 20 pairs. The module contains 40 number of U-shaped Phosphor bronze contacts and 40 number of steel cutting blades. As the module is crimped each contact strips the insulation from the positioned wire and securely grips the conductor. The cutting blades inside module trims the excess wire. There are two model (a) Straight modules

(b) Half-tap modules

ADVANTAGES :: • • • • •

A single crimp completes a gas – tight connection of all 20 pairs in the module. It is simple and fast There is no need to strip insulation There is no need to trim the excess wires individually. It ensures error free joint as it is fully compatible with the 20 pair units in our cables.

D. JOINT PROTECTION AGAINST MOISTURE ENTRY In addition to the conventional system of closing with lead sleeve, different ways such as mechanical closure, Epoxy resin filled joints, XAGA closure etc. are used in different countries. 2.2 PROTECTING THE JOINT AGAINST MECHANICAL CORROSION ;

DAMAGE AND

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During splicing process the protective layers of the cable e.g. ply - jacket, Hessian tapes, steel armours etc. are removed. Hence after incorporating moisture barrier system in new joint, it must have some protection against mechanical and corrosive damages. The following are some of the processes adopted to achieve it by putting the joint in :(1) Cast iron or mild steel box and filling it with molten bitumen. (2) Brick chamber and filling it with molten bitumen. (3) Brick chamber and filling it with sand or soil. (joint must have anticorrosive jacket) The above methods are used particularly in protecting the joints of paper-insulated cables. The following additional precautions are to be followed at places of joints in underground telecom cables. (1) Putting joint indicator to indicate the actual location of the joint. (2) Putting the joint in Manhole, hand hole and joint chamber. (3) Placing RCC or stone slab over the joint. 3.0 DIFFERENT JOINTING PROCEDURES IN TELECOM CABLES The DOT evaluated number of jointing procedures from time to time and the systems approved by DOT are briefly described in the following paragraphs LEAD SLEEVE JOINTS This procedure is used for lead sheathed cables, where a lead sleeve is plumbed over the splice as moisture barrier. After doing this type of joint pressurization of cable is most suitable for maintenance purposes. Main advantages :(1) (2) (3)

Very effective moisture and pressure barrier. Life time is long. Re-entry is possible

Main disadvantages:(a) (b) (c) (d)

Very costly, as lead is now scarce material. Efficiency of the jointer is a fundamental criterion. This jointing procedure is not applicable to composite sheathed cable. Large number of tools and materials are required.

3.1 AUXILIARY LEAD SLEEVE SEAL (ALSS) JOINT. ALSS technique is applicable for jointing : (a) Dry core composite polyjacket cable. (b) A lead sheathed cable with a composite sheathed cable. RTTC, NAGPUR

Page 44 of 185

Underground Cable (c) Jelly filled cable. (d) Pressurized cable. The materials required for jointing is supplied in the form of kits, The different types of kits are given in table - V & table VI. The only special tool required for ALSS technique is a modified Kerosene blow lamp or are gas torch fitted to a 1.8 kg or 2.5 kg LPG container. (Yellow flame of about 250 mm and 40/50 mm dia. for blow lamp. Yellow or blue flame with small length for gas torch). A. SPECIAL PRECAUTIONS (1) Flaming of the thermo shrink sleeves is to be done form the center of the sleeve. Over heating must be avoided. (2) Heat resistant aluminum foil should be put in such a way that it does not become a source of entry of moisture.

B. MAIN DISADVANTAGES (1) Costly as two auxiliary and one main lead sleeves are required. (2) Complicated as both thermo-shrinking and plumbing are involved. (3) Utmost efficiency of the splices is essential otherwise failure of the joint is inevitable. (4) Corrosion protection is required. C. STEP IN ALSS JOINTING 1. Lay cables with overlap of L+700 mm, where L is the length of the sleeve. Mark with tape on both the cables. Main lead sleeves for DRY CORE cables TYPE OF MAIN Length ‘L’ Diameter ‘D’ in Thickness SLEEVE in mm mm ‘t’ in mm M1 450 70 4 M1 600 90 4 M3 600 100 4.5 M4 700 100 4.5 M5 800 110 4.5

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Underground Cable

M1

M1 Overlap L+700 mm

2. Mark M2 at a distance of 400 mm from M1 towards cable on each cable. Remove inner sheath and expose core tied and taped at ends 400 mm

M1

core

tape

M2

M2

M1

3. Position the Lead and thermo shrink sleeves and then cut layers. 4. Slide Auxiliary and main sleeves on one cable and auxiliary sleeve on the other.

main sleeve

core

tape

Auxiliary sleeve

Thermo shrink sleeve

5. On the poly-al sheath, connect sheath connector using crimp using pliers. If one side of the joint has no Armour connect Armour and sheath of one cable to sheath of other side cable. Armour

Sheath connector Cable A

Cable B

6. Tape the armouring with plastic and PVC tapes and carryout the splicing 7. Bring the auxiliary sleeve into position and dress it down on the cable. RTTC, NAGPUR

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8. Position the Thermo shrink sleeve so that part of sleeve is over auxiliary sleeve. Mark the auxiliary sleeve and cable at each end of thermo shrink sleeve 9. Clean the surface between marks on cable and auxiliary sleeve. Degrease the surface with cleaning tissue along with CTC. Abrade the surface with emery mesh . 10. Use aluminum foil wrap around the cable such that 25mm width will be under thermo shrink sleeve and 75mm outside it. Dress it with wooden handle. 11. Flame brush the cleaned surface of polythene for 15 sec , clean with cloth any soot or dust from the sheath of the cable. 12. Position Thermo shrink and sleeves.

Aluminum foil

Thermo shrink sleeve

Auxiliary sleeve

Sealant tape

PVC over armour Aluminum foil Thermo shrink sleeve sleeve

Auxiliary

13. Don’t disturb the sleeve till it is cooled to normal temperature. 14. Open a vent hole in the main sleeve. Slide over the Main sleeve into position. 15. Wipe the Main sleeve on to the auxiliary sleeves using plumber metal then only close the vent hole. 16. Wrap the armour continuity earth wire on both the cables 3 round and insulate the soldered portions. Continuity wire should be insulated throughout fully. 17. Give anti corrosive protection to the lead and aluminum by applying layer of black paint followed by layer of polyester tape. The earth wire should be under polyester layer. 18. Position the joint and cover it with soft earth. 19. Place warning braces or protective slabs over the joint. ALSS HEAT SHRINK KITS AVAILABLE LSDC CABLES RTTC, NAGPUR

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Underground Cable

M a x . S p li SUITABLE FOR CABLE SIZE c e o p e n

R L Kit No / main Sleeve.

N o .

J.1 / M1

131486

375

J.2 / M2

131487

525

J.3 / M3

131488

525

J 4 / M4

131489

625

J. 5 / M5

131491

725

J.6 / M6

131492

725

0.4 mm 0.5 mm 0.63 mm 0.9 mm 0.4 mm 0.5 mm 0.63 mm 0.9 mm 0.63 mm 0.9 mm 0.4 mm 0.5 mm 0.4 mm 0.5 mm 0.63 mm 0.5mm 0.63 mm 0.9 mm

200,300 pairs 200 pairs 100pairs 50 pairs 400 pairs 300,400 pairs 200,300 pairs 100 pairs 400 pairs 200 pairs 600 pairs 600 pairs 800,1000,1200 pairs 800 pairs 600 pairs 1000. 1200 pairs 800 pairs 400 pairs

ALSS HEAT SHRINK KITS AVAILABLE FOR JELLY FILLED CABLES

Kit No / main sleeve/ Aux. Lead Sleeve A B C D E F

/ / / / / /

M1 M1 M2 M3 M4 M4

/ A1 / A2 / A3 / A2 / A4 / A4

RTTC, NAGPUR

RL No. 131468 131470 137471 131472 131473 131474

225 225 225 350 350 350

Max. Splice open 10 20 20 50 50 50

Size of cable

0.4mm 0.5mm 10 20 20 50 50 50

0.63mm 10 20 50 50 50

0.9mm 1.27mm 10 -20 --

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Underground Cable G / M4 / A3 H / M5 /A5 I / M5 / A6

131475 131476 131477

350 350 350

100 100 -

100 100 -

100 100 -

100

3.2 PROCEDURE FOR JOINTING JELLY FILLED CABLES USING ALSS 1. Lay the cables straight with an overlap of 2 L as shown, L is the length of the main sleeve Main Lead sleeves for JF cables TYPE OF MAIN Length ‘L’ Diameter ‘D’ in Thickness SLEEVE in mm mm ‘t’ in mm M1 300 50 3 M1 300 70 3 M3 400 70 3 M4 400 90 3 M5 400 100 3

2L

2.

With marker tape, mark M1 with marking tape

0.5L+300 mm

M1

M1 2L 0.5L+300 mm For armoured cables :: Remove outer sheath from M1 to the end of cable & Mark M2 at 375 mm from M1 M2 M1 375 mm

M1

M2 375 mm

Then Remove Inner sheath from M2 to the cable M2 end.

RTTC, NAGPUR

M1

Page 49 of 185 M1

M2

38

Underground Cable

For Un armoured cables Mark M2 as shown below: For 10 pair and 20 pair cables - 70 mm from center of the over lap For 50 pair and 100 pair cables - 130 mm from the center of the over lap Remove the sheath and expose the core from M2 to end of the cables on both sides of the proposed joint. Centre of OverLap

M2

M1

M1

M2

3. Slide auxiliary and main sleeves on one cable, and auxiliary sleeve on the other cable. For a branch joint also, only one auxiliary sleeve is used for the branch cables. 4.

M1

10 mm Armour

M2

Main Sleeve

75 mm Thermo shrink sleeve

Auxiliary sleeve

5. On the inter play sheath make two longitudinal cuts 30mm long and 15mm wide so as to suit the sheath connector. With a paper punch, punch a hole outwards in the sheath, so that the hole is clear on the inner side. Fix the sheath connector to the poly sheath, by using a nut and bolt. While fixing the sheath connector, bent the 15 mm, wide cut portion gently, or ease the aluminum laminate may break. If sheath connector assembly is provided crimp the connector using pliers. 6.

Bare the earth continuity wire on both sides for the required length.

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Underground Cable Clean the armour tape with emery paper. Wrap the wire 3 times around the armour tape. Solder it to the tape at 4 points. Stretch the wire along the inter sheath and connect it to the sheath connector. Repeat the process on the other cable. The earth wire between the two sheath connectors should be with insulation. PVC insulated Sheath connecting wire

Cable B Cable A Cable C

7. Tape the armour with PVC cloth tape to ensure a smooth transition. Carry out conductor splicing by using UY connectors.. 8. Hold a cellophane sheet under the splice bundle. Fill the splice bundle with jelly. Wrap the cellophane around the bundle and close it with marker tape. Gently massage around the cellophane, so that the jelly moves in between the conductors. Wrap the bundle with a layer of paper tape followed by a layer of cloth tape. 9. Light up the modified blow lamp. About 5 minutes heating should be over before the lamp is used,. This ensures elimination of soot from the flame. 10. Bring the auxiliary sleeve into position. Dress it down onto the cable. For a branch joint, the cables should be touching each other. Note that the auxiliary sleeve should not be deformed except at the point of dressing down.

200 mm

11. 12.

250 mm

50mm

Temporarily position the thermo-shrink sleeve, so that 100mm of the sleeve is over the auxiliary sleeve. Mark the auxiliary and cable at each end of the thermo-shrink sleeve. Remove the sleeve. Remove the paper over the adhesive side of the 100mm wide aluminum foil, Wrap the foil around the cable such that 20mm width will be under the

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Underground Cable thermo-shrink sleeve and 80mm outside it. Dress the aluminum foil with a wooden handle.

Thermo shrink sleeve

Branch clips 10 0 5 0 2

13. Wipe the surface between the aluminum foil and the mark on the auxiliary sleeve. Degrease surface with the cleaning tissue. Use only isopropyl alcohol or trichloroethylene or CTC bought from a reliable source like medical store. Abrade the cleaned surface, using emery tape 80 mesh. Cleaning is done before abrading, to prevent oil being forced into surface pores during abrading. 14. Flame brush (slightly heat up) the cleaned surface; the polythene for 15 secs and heat the lead till it is warm to touch. 15. Place the hot melt adhesive strip or split adhesive tube under the earth continuity wire, between the auxiliary sleeve and the armour tape. This arrangement is done to ensure that no air pocket is caused by the earth wire. 16. Wrap the thermo shrink sleeve around the closure area. Insert the metal channel along the channel rails. This should be done with the fingers over the rails so as not to distort the channel while inserting. The channel should project slightly at both ends of the sleeve. At the points of projection, the channels are lightly tapped in wards. This ensures that during shrinking, the projected portion of the channel does not exert an upward pull. 17. Position the sleeve. In the case of branch joints, arrange the cables one below the other with largest cable at the top as shown. Allot the space of the thermoshrink sleeve approximately in proportion to the diameter of the cables. Insert branch off clips. 18.1

Thermo shrinking

18.2 Sectionalise the sleeve into two equal sections. Shrinking is done first of the section over the cable, and next section over lead. 18.3 Heat each section circumferentially from 2 o’clock to 10 o’clock, excluding the channel, which is 12 o’clock. RTTC, NAGPUR

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Underground Cable

18.4 When sleeve has shrunk, tap the channel with a wooden handle to shape along the transition. Now include the channel and continue heating all round. 18.5 Thermo shrinking is complete when adhesive oozes out from the sides of the sleeve and the color of the thermochromic paint on the sleeve becomes black. 18.6 When there are branch off cables, heat till adhesive on branch clip melts. The heat soaks in for about two minutes after the flame is removed. If the branch off clip adhesive is not melted, heat it till the adhesive melts and merges with the adhesive of the sleeve. 18.7 Heat the channel area for 15 sec. This ensures adhesive flow between the overlap as well as under the overlap. 18.8 Complete shrinking the other half of ALSS. i.e. from the middle towards the auxiliary lead sleeve. Post heat channel area again for 15 secs per section. 18.9 Do not allow the formation of air pockets at any point during the shrinking process. That is why shrinking is done from the centre outwards. 18.10 When any part of the sleeve is overheated, it emits smoke. When the rail area is overheated a lining under the rail will start coming out and will be clearly visible. In either case, shift the flame from that portion, Do not heat any portion which has turned black. 19.

Similarly seal the auxiliary sleeve on the other side.

20. Open a vent hole in the main sleeve. Bring the main sleeve into position. Wipe it onto the two auxiliary sleeves using plumber metal. Close the vent hole. 21. Give anticorrosive protection to the lead and aluminum, by applying a layer of black paint followed by a layer of polyester tape. 22.

Position the joint. Cover it with soft earth. Place warning bricks over it.

Al-Foil

Sealant tape &PVC Tape over Armour

RTTC, NAGPUR

Changed – shaped

Changed – shaped

Adhesive oozes

Adhesive oozes

Page 53 of 185

Underground Cable 4.0

JOINTING OF TECHNIQUE

JELLY

FILLED CABLES USING THERMOSHRINKING

XAGA 250 provides ideal closure for JF cables. In this joint one thermo shrink sleeve with an aluminum canister replaces the three lead sections and two ALSS of the auxiliary lead sleeve type closure. The advantages of this technique over conventional ALSS type closure are :: (a)As no lead dressing / plumbing is involved, time consumption is less and clean type joint closure is obtained. (b)Lesser material and weight and thus there is a major saving in handling, cost of store . (c)No of kit varieties / sizes reduced (d)No corrosion protection is required un like lead joints. 4.1 These joints are approved for straight joints & also branch joints up to 3 in and 3 out. In all types of joints, when required, sheath continuity is catered for by using a sheath connector assembly and armour continuity by poly insulated copper wire to inter connect the armours. The splice bundle is filled with an approved filling compound and pressure wrapped with PVC tape. An aluminum canister provides mechanical protection as well as a partial moisture barrier. The XAGA sleeve completes the seal from cable jacket to cable jacket.

Type

RL No

TSF 1 TSF 2 TSF 3 TSF 4 TSF 5 TSF 6

131500 131501 131502 131503 131504 131505

XAGA Sleeve X/ Y / Z 42 / 8 / 250-525 40 / 15 / 450-650 62 / 22 / 450-650 92 / 30 / 610-810 122 / 38 / 610-810 150 / 55 / 650-850

AL Canister Dia./Length 42 / 250 42 / 450 62 / 450 92 / 610 122 / 610 150 / 650

Cable Range in pairs / Gauge Up to 20/.063 20/0.9 to 50/0.63 50/0.9 to 100/0.63 100/0.9 to 400/0.51 200/0.9 to 800/0.51 600/0.63 to 400/0.9

Where X= Max splice bundle dia. :: Y = Min. Cable dia. :: Z = Shrunk / Normal length (TSF - Thermo shrink filled) (TSR - Thermo shrink Re-entry) 4.2 This jointing technique has been approved for use of telecom underground cables of all JF cables and it will replace all other jointing techniques if not otherwise required. The jointing materials are supplied in kits for various sizes. The instruction manuals are invariably supplied along with every kit. The procedure for these types of joints are detailed in these manuals.

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Underground Cable

4.3 The special tools required are :(1)

Modified blow lamp or Gas torch.

(2)

Crimping tool for wire connection.

4.4 SPECIAL PRECAUTIONS (1) (2) (3) (4) (5) (6) (7) (8)

Placing the A1- foil in proper place to avoid the entry of moisture. Shrinking to be done in three longitudinal sections. Starting the flame treatment from the centre of the sleeve circumferentially from 2 o’clock to 10 o’clock excluding the channel which is at 12 o’clock . When the sleeve shrunk tapping the channel with a wooden handle to shape along transition. Then heating all around including channel till thermonic paint changes (green spots abolished). Heating the channel area for 15 seconds per section. Starting the flame treatment in other section. Leaving no air - pocket any where.

A. MAIN ADVANTAGES (1) (2) (3) (4) (5) (6) (7) (8)

No lead dressing / plumbing is involved, a quick and clean type of closure obtained. No metal is involved, hence economical. Lesser material and weight hence easy in handling. Complete materials are available in a kit. Universality in use as 3 types of kits cover JF cable upto 800 pairs. No corrosion protection is required. Protection from mechanical damages is attained by the use of canister. Splicer can easily attain efficiency as the procedure is less complicated.

is

4.5 RE - ENTRY TECHNIQUES : TSR JOINT This technique involves in changing, if required, the thermo shrink sleeve of TSF. 4.6 JOINTING OF JF CABLES USING THERMO WELD (TWF) TECHNIQUE This technique is almost similar to thermo shrink joints so long as the installation procedures are concerned. There are two layers in the sleeve, the upper layer is cross linked polythene to similar to thermo shrink sleeve and inside layer is ordinary polythene which melts and welds with the polythene sheaths ensuring a hermitical sealed at the openings. The inside layer is in place of adhesive compound of thermo shrink sleeves. This technique is applicable to J.F. cables for distribution side and also for aerial joints. The joints kit is available in kits viz TWR 1 to TWR 6 4.7 WRAP - ROUND REPAIR, SLEEVE THERMOSHRINK (WRST). RTTC, NAGPUR

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Underground Cable

WRST provides a convenient repair closure to cables like minor sheath damage, minor cable - jacket damage leaky epoxy joint etc. Six types of repair kits have been standardized. A. MECHANICAL CLOSURE FOR JOINTING JELLY FILLED CABLE. The universal closure screw type is made of two halves and can accommodate upto 4 non pressurized distribution cable either filled or non filled. the closure can be re-opened for maintenance and closed again with new sealing materials. The materials are supplied in the form of kits. MC IA - For 20 pairs MC II - For 50 pairs MC IIIA - For 100 pairs MC III B - F or 200 pairs A special tool namely socket wrench is required for the joint. Re - entry kits are available in the form of MCR - I, MCR - II and MC - III. B. MAIN ADVANTAGES 1) Opening or re-closing of the joint is economical and simple. C. MAIN DISADVANTAGES (1) (2)

Efficiency of the splicer is essential other wise failure of the joint is inevitable. Mechanical protection is required.

4.0 SEQUENCE OF CLOSURE - TSF JOINT A. PROCEDURE FOR JOINTING J.F. CABLE USING XAGA TECHNIQUE 1.

2.

Cable Marking. 1.1 Lay the cables straight with an overlap of twice the canister length with fingers. 1.2 Centre the XAGA sleeve. Mark with chalk the cables at the ends of the sleeves. Call these marks M1. 1.3 125 mm (one hand width) from. M1, away from splice, mark M2. 1.4 Remove canister and sleeve,

Armour continuity2.1 Remove jacket and armour upto M2. 2.2 Remove only jacket for another 10 mm (one finger width) 2.3 Remove insulation from one end of copper wire. 2.4 Wrap wire 3 times around armour and solder wire to armour at 4 places. Alternately, at 2.2, open only a 10 mm wide flap of the jacket; push the bare copper wire (of 2.3) under the armour and solder to armour at 2 adjacent places. 2.5 Tape wire to cable jacket (away from splice). RTTC, NAGPUR Page 56 of 185

Underground Cable 2.6

Repeat for all the other cables.

3.

Conductor Jointing 3.1 Centre the Al canister. Mark the sheaths of the cables at the ends of the annister (canister fingers to be excluded). Call these Marks M3. 3.2 Remove play sheath from end to M3. 3.3 Twist the spare conductors together to ensure that splice length is not more than body of canister. 3.4 Separate the conductors into units. 3.5 Using first waste cotton and then cleaning fluid degrease conductors. 3.6 Splice conductor by approved method. 3.7 Ensure connectors are evenly spaced along the bundle.

4.

Sheath Continuity 4.1 Cut a flap on play sheath approximately 20 mm long and 10 mm wide. 4.2 Apply PVC tape under the flap. 4.3 With pliers, crimp the sheath connector clip onto the flap. 4.4 Similarly, crimp the sheath connector to the other cable. 4.5 In case of a branch joint, the sheaths are connected using additional connector assemblies. Filling of Compound 5.1 Wrap sealant tape around cables, allow slight overlap ; and then cut for each cable including branch off. 5.2 Remove backing paper from one side of the sealant tape. 5.3 About the sealant against the sheath connector and wrap around the cable. At branch end, wrap each cable once with sealant tape. 5.4 Temporarily bind the branch cables together using twice, a little away from the sealant. Place sealant tape rolls in the crotch on either side. Press the rolls into the tape. 5.5 With the plastic sheet, prepare a container around the splice bundle. Stick one side of sheet to the sealant on both sides. Wrap the sheet around the splice (do not allow to much slack). Hold the sheet in position by giving one wrap of PVC tape over each end of the sheet. 5.6 Slit open the bag containing the filling - compound. Squeeze the compound around the splice. Filling compound should first be filled at the bottom of the bag. Ensure that the compound goes only in the splice bundle by firmly holding the filling compound bag against the inside of the splice bundle. 5.7 Ensure that the splice is evenly covered by the compound and filling compound in not lumped at the centre of the splice. 5.8 Wrap the loose end of the bag firmly around the splice and tape. Tape the ends of the bag with 50 mm over poly bag and 25 mm over cable. 5.9 Squeeze the bag so as to spread the compound evenly around the splice. 5.10 Around the splice, apply three layers of half overlapped PVC tape. The first later should be loosely applied so as to form the splice bundle. The splice bundle should have approximately even diameter all round. To achieve this, the first layer should be taped from centre outwards. The third layer should be as tight as possible.

5.

6

Metal Canister 6.1 Install metal canister around the splice: Seal the parting line of canister with tape. RTTC, NAGPUR Page 57 of 185

Underground Cable 6.2 7

Staring from the middle of fingers, tape the fingers of the canister onto the cable with PVC tape. Tape maximum of 5 mm on the cable.

Cable Preparation7.1 Clean hands 7.2 With the cleaning tissue, clean the cable for approximately 150 mm on either side of the canister. 7.3 Abrade the cleaned portion well. Abrade circumferentially and not longitudinally. Position the XAGA sleeve and mark the cables 10 mm (one finger width) from the ends of the sleeve towards the splice. 7.4 Wrap Al foil around each of the cables with inner edge of the foil at the inner mark on the cable. Smoothen inner sides of the Al foils. 7.5 Flame brush cable between canister and Al foil till the cable gets a mild shine, but for not more than 30 secs.

8.

Install Sleeve 8.1 Wrap the XAGA sleeve around the splice. 8.2 Insert the channel along the rail. This should be done with the fingers over the rails, so as not to distort the channel while inserting. Where more than one channel is inserted, use the retaining clip at the junction of the channels. The retaining clip is put on one side at the meeting place of channels and snapped on the other side, using pliers. There should be about 5 mm spacing between the channels to allow for expansion. 8.3 Position the sleeve such that the end are equally over the Al foils. 8.4 In the case of branch joints, arrange the cables one below the other with the largest cable at the top. Allot the space of the thermo shrink sleeve approximately in proportion to the diameter of the cables. Insert branch off clip/clips. Tie the branch cables together tightly just next to the Al foils.

9.

Thermo shrinking9.1 Shrinking is done in three sections, middle and the two sides. 9.2 Shrink from middle, followed by the branch side, and next the remaining side. If there is a breeze start from end, next middle and next the remaining side. 9.3 Heat each section, circumferentially from 2 o’clock to 10 o’clock excluding channel which is 12 o’clock. 9.4 When sleeve has shrunk, with a wooden handle, tap the channel to shape along the transition. 9.5 Now heat all around, including the channel, till thermochromic paint changes. 9.6 Heat the channel area, for 15 secs per section. This ensure adhesive flow between the overlap as well as under the overlap. 9.7 Proceed to complete other sections. 9.8 Thermo shrinking is complete when adhesive oozes from the sides of the sleeve and the color of the thermochromic paint on the sleeve becomes black. 9.9

Do not allow the formation of air pockets at any point during the shrinking process. That is why shrinking is done from the centre outwards. RTTC, NAGPUR Page 58 of 185

Underground Cable 9.10

9.11 10.

When any part of the sleeve is overheated, it emits smoke. When the rail area is overheated, a lining under the rail will start coming out and will be clearly visible, In either case, shift the flame from that portion. Do not heat any portion which has turned black. Heat the branch clips till the adhesive just stress to melt. Residual heat will ensure that branch clip adhesive fully melts.

Armour Continuity Completed. 10.1 Wrap 25 mm wide sealant tape around the bared armour for each of the cables. 10.2 The sealant tape is held in position by a tape wrap depending on kit contents. 10.2.1 PE tape wrap, or 10.2.2 Rubber tape. 10.3 Bare the ends, twist and solder together all the armour continuity wires. Wrap the bare conductor joint area with sealant tape. Hold the sealant in position with PVC tape wrap. 10.4 Position the armour continuity wire close to the cable/XAGA sleeve with the help of PVC tape/twine.

5.0 SEQUENCE FOR REPAIR AND CLOSURE OF CABLE (WRST) illustrative Damages: 1.1 Epoxy Leak1.2 Minor Sheath/Conductor Damage1.3 Major Sheath/Conductor Damage1.4 Cable Jacket Damage Cutting Cable to Desired Lengths 2. Leaky epoxy joint : Leave 10 mm from end of auxiliary sleeve. Remove 125 mm of cable jacket and armour tape and expose the inner sheath. Conductor/Inner Sheath Damage 3.1 From the centre of the damage, mark 225 mm on either side. If damage is over a longer length, put the mark as required for the closure after repair. Remove cable jacket and armour tape between the mark. 3.2

Make a longitudinal slit 150 mm at the damage. Inspect the conductors for visible damage.

3.3

In case repair to affected conductors can be done without removing the inner sheath, then carry our repairs to conductors. Close the sheath opening by using polyester tape.

3.4

In case the inner sheath is required to be removed to affect conductor repair, remove the sheath for the required length, but not more than 900 mm. Repair the conductors.

Jacket Damage: 4. Cable not required to be cut. Loose jacket strands are point of damage can be trimmed. RTTC, NAGPUR

Page 59 of 185

Underground Cable Depressurize Cable 5. When repair area is ready for closure, check if there is a pressure leak. If the pressure leak is small, it can be temporarily blocked by a rubber tape. In case pressure leak cannot be stopped, depressurize cable . THERE SHOULD BE NO AIR PRESSURE ON THE WRST DURING ITS INSTALLATION. This is because the pressure working outwards will prevent WRST bonding to cable. When WRST is installed over epoxy joint as preventive maintenance and there is no leak, cable is not required to be depressurized. Armour continuity 6. At both ends where armour discontinuity has been created, expose 10 mm of armour. Clean the armour with emery tape. Bare the earth continuity wire at both its ends, for the required length. Wrap the wire 3 times around the armour tape armour tape and solder it at 4 points, Stretch the wire along the sheath, wrap it around the armour tape and solder it in a similar manner. 7. Tape the armour with cloth and PVC tape to ensure a smooth transition. 8. Lead Sleeve Closure when Inner Sheath in Removed: only in case of sheath removal, our of a lead sheet prepare a split sleeve whose length is 100 mm greater than the sheath opening, and dia adequate to accommodate the repaired section. Position the split sleeve; Solder the seam as per standard practice and dress it down. 9. Light up the modified blow lamp. About 5 minutes heating should be over before the lamp is used. This ensures elimination of soot from the flame.

10.

Install WRST Select the correct repair kit. For epoxy leak and when the sheath slit is less than 200 mm, use 400 mm WRST. Where sheath slit is more than 200 mm cut 1500 WRST to sheath slit length + 200 mm. Where inner sheath is removed. WRST length should be sheath removal length +600 mm.

11.

Temporarily position the WRST. Mark the cable/cable and lead sleeve if any at each and of the WRST. Remove WRST.

12.

Clean the surface between the two marks ; use water if necessary. Degrease surface with the cleaning liquid, Use only iso-propylalchohol, trichlorothylene or CTC brought from a reliable source like a medical store. Abrade the cleaned surface using emery tap (80 mesh). Cleaning is done before abrading, to prevent oil being forced into surface pores during abrading. Temporarily position the WRST. Mark the cable /cable and any lead sleeve at each end of the WRST. Remove WRST . Remove the paper over the adhesive side of the 100 mm wide aluminum foil. Wrap the foil around the cable such that 20 mm width will be under the thermo shrink sleeve and 80 mm outside it. Dress the aluminum foil with a wooden handle.

13.

14.

Using the modified blow lamp, or LPG torch, flame treat (slightly heat up) the polythene surface for 10-15 secs. The lead portions should be warm to touch. RTTC, NAGPUR Page 60 of 185

Underground Cable

15.

Place the hot melt adhesive strip or split adhesive tube around/under, the earth continuity wire for the portion which will be in contact with the WRST. The adhesive will melt and grip both sheath and wire, when the sleeve is shrunk. This arrangement is done to ensure that no air pocket is caused by the earth wire.

16.

Wrap the thermo shrink sleeve around the closure area. Insert the metal channel along the channel rails. This should be done with the figures over the rail. so as not to distort the channel while inserting. The channel should project slightly at to ends of the sleeve. At the points of projection, the channels are lightly tapped inwards. This ensures that during shrinking, the projection, the channels are lightly tapped inwards. this ensures that during shrinking, the projected portion of the channel does not exert an upward pull.

17.

Thermo shrinking

17.2

Sectionalise the sleeve into sections of approximately 150 mm length. Shrinking is done starting from the middle section and moving outwards, section by section. Move flame longitudinally on each section like a paint brush, bottom upwards. Space permitting, angle the flame towards the surface to be shrunk next.

17.3

Heat each section circumferentially from 2 o’clock to 10 o’clock, excluding channel which is 12 o’clock.

17.4

When the sleeve section has shrunk, tap the channel over transitions with a wooden handle. Now continue heating the sleeve and channel till the thermochromic paint changes to black. Post heat the channel for 15 secs per section. This ensures that adhesive both between the flaps and under the sleeve melts.

17.5 17.6

Repeat process for other sections of the sleeve. For the two end sections, in addition to change of thermochromic paint, adhesive should ooze out at the ends.

17.7

Do not allow the formation of an air pocket at any point during the shrinking process. That is why shrinking is done from the centre outwards.

17.8

When any part of the sleeve is overheated. it emits smoke. When the rail area is overheated, a lining under the rail will start coming out and will be clearly visible. In either case, shift the flame from that portion. Do not heat any portion which has turned black.

18.

Allow sleeve to cool. Pressure test the closure for pressurized cables.

19.

Provide anticorrosive protection.

20.

Position the repair closure. Cover it with soft earth. Place warning bricks over it. RTTC, NAGPUR Page 61 of 185

Underground Cable

AS REQUIRED

REPAIRING DAMAGES NOT INVOLVING INTER SHEATH CABLE JACKET ALUMINIUM FOIL WRST ARMOUR HOT MELT ADHESIVE STRIP LONGITUDINAL OPENING ON INNER SHEATH SHEATH DAMAGE ARMOUR CONTINUITY WIRE

REPAIRING MOINOR SHEATH DAMAGES WITHOUT REMOVAL OF INNER SHEATH

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Underground Cable

6.0 ENGINEERING INSTRUCTIONS JOINTING OF PAPER INSULATED CABLES

CABLE WITH JF

Scope This engineering instruction describes the method of jointing paper insulated non pressurized cable to jelly filled cables using thermo shrink technique which is termed as thermo shrink transition (TST) joints. General Jointing paper insulated cables directly to jelly filled cables often caused low insulation cross talk corrosion and consequent disconnection These joints are not filled with any splice filling compound. The jelly filled cables are not filled 100% and therefore possess voids through which water/water vapor is able to travel through the core and reach the joint. The paper used for insulation is highly hygroscopic and absorbs the moisture causing low insulation. In the presence of moisture, local action between the conductors at different potentials as well as between conductor and the sheath occurs. This results in corrosion of one of the conductor, posting of the sheath and consequent disconnection. In order to avoid such problem a water block on all jelly filled cables at the joint has been introduced as an additional construction is such transition joints. These water blocks are accommodated inside the metal canister and closed using a thermo shrink sleeve following the procedure explained under TSF joints. As the water block is kept inside the closure, the length of the aluminum canister and the thermo shrink sleeve have been proportionately increased. The water block is made using a special swilling powder. This powder, when comes in contact with water/moisture, swells and blocks all voids. The swelling will occur only when the powder comes in contact with water or moisture. Hence pressurized cables should not be connected directly as the air pressure may disturb the block. When a pressurized cable is require to be connected to a jelly filled cable, a pressure block has to be introduced on the paper cable side before the joint. These joints are not to be filled with any splice filling compound. The paper conductors are heated and impregnated at site using microcrystalline wax. Wax impregnation of paper prevents moisture absorption. In addition, the joints are packed with silica gel packets to keep the joints dry. 6.1 Description of the materials used Swelling Powder It is a highly hygroscopic cellulose or synthetic based material. On coming in contact with water/moisture, it swells and packs tightly all voids preventing entry of water or moisture into the joint. Each kit will be supplied with swelling powder in cans of 100 gms which is sufficient to make two blocks on two large size cables. Therefore, while making joints with small cables, there may be left over powder, which can be preserved properly and reused. Transparent PE sheet Transparent PE sheets are used to pack the swelling powder into the cable for making a water block. Sealant Tape RTTC, NAGPUR

Page 63 of 185

Underground Cable It is wrapped over the sheath of the cable on one side and over the cable core on the other which provides a sticky base for wrapping the PE sheet. It also seals the exterior of the water block and prevents the swelling powder from spreading outside the block. Adhesive PVC Tape This tape is used to wrap the water block tightly. Micro-Crystalline Wax This is melted at site to impregnate the paper conductors to prevent absorption of water by the paper. Silica gel Silica gel is packed into the joint to keep the joint dry. Other components In addition to the above items, TST kits contains all materials as supplied in corresponding TSF kits except the filling compound and wire connectors. The details are given in Table 2 A. Kit Selection A Kit selection chart is provided in table 1. Two limits, viz., the maximum splice bundle diameter and the minimum cable diameter, are given in the chart, which represent respectively the maximum and minimum diameters over which the thermo shrink sleeve can be shrunk. These limits have to be adhered to while selecting the correct kit for any joint in accordance with the following guidelines. Straight Joints a) When cables to be jointed are of same pair found on both sides, use the kit indicated in the kit selection chart b)When one cable is larger in pair count than the other, the kit indicated against the smaller one is to be used, e.g. to join a 100 pair cable to a 20 pair cable, TST 1 is to be used. Branch Joints Condition 1. The sum of the diameters of all the cables on the branch side plus the thickness of branch clips should not exceed the maximum splice bundle diameter indicated in the kit selection chart. Condition 2. If any side contains only one cable, the diameter of the single cable should not fall below the minimum cable diameter indicated in the kit selection chart. NB ; Use a diameter tape to measure the diameter. For examples see page 2. Therefore, it is very important to arrange the cables symmetrically on both sides as far as possible so that the sum of the dia of cable , on the A side is approximately equal to that on B side. Wherever , a different combination is closed, it is necessary to fulfill the two conditions mentioned above. RTTC, NAGPUR

Page 64 of 185

Underground Cable

Example 1

SIDE A

SIDE B 50 Pr. PIJF (22)

100 Pr. PCUT (25) 50 Pr. PIJF (22)

Maximum dia (side B) Minimum dia (Side A) TST 3 Kit is to be used.

= 22+22+10 = 54 mm = 22 mm

Example 2 SIDE A

SIDE B

20 Pr JF 14 mm dia

20 Pr JF 14 mm dia

50 PCUT dia 20 mm

20 Pr JF 14 mm dia

Maximum dia of A side + branch clip =20+14+10 = 44 mm Maximum dia of B side + branch clip = 14+14+10 = 38 mm With reference to the kit selection chart TST 3 is to be used. Note : When there are 4 cables in a joint, they should be arranged, as far as possible, symmetrically with 2 cables on either side of the joint. This will give a highly reliable joint. Also it can be seen from the above example that it is not possible to get a suitable kit if it is done in a different way as indicated below:

RTTC, NAGPUR

SIDE A

SIDE B

50 PCUT 20 mm

20 JF 14 mm 20 JF 14 mm 20 JF 14 mm Page 65 of 185

Underground Cable

Side A = 20 mm side B = 14+14+14+20 = 62 mm For this combination, TST 3 cannot be used as the cable dia falls below the minimum limit and TST 2 is also not suitable as the B side exceeds the maximum limit. Jointing Procedure. 1

Having selected a correct jointing kit, keep the cables to be jointing side be side and open the sheaths. The length of the conductor joint should be in accordance with the maximum sheath opening indicated in the kit selection chart.

2

Dry the paper conductors exposed by heating, immediately dip the end in molten micro-crystalline wax and quickly remove so that a thin coat of mc wax is applied over the conductors all over uniformly without forming any lump. In case any lump is observed, the same can be wiped clean. The m.c. wax can be melted at site in an aluminum pan. In case the paper insulated cable is through where the free end is not available, the molten wax may be poured over the exposed core after heating the conductors.

3

Clean the jelly on all JF cables using the cleaning liquid taking care not to disturb the pairs.

4

Tie the unit binders 150 mm away from the sheath opening of JF cables leaving space for the installation of the water block so that the unit identification is done without difficulty.

5.5

Install the sheath connectors as described in TSF joints and cover this portion with PVC tape.

5.6

Tie the conductor bundle including the sheath connector wire firmly together at a distance of 100 mm from sheath opening.

5.7

Loosen the conductors between the tie and the sheath opening.

5.8

Using the sealant tape make a collar over the sheath connector and the tie, keeping them centrally.

5.9

Cut the transparent PE sheet to required size and stick it around the sealant collars so as to make an enclosure around the core with an open top.

5.10

Pack the swelling powder liberally into the core by separating the conductors to make way for the powder to be filled in.

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Underground Cable

5.11

Note : Do not use any sharp tool which may damage the insulation of the conductors while separating them. Wrap the PE sheet tightly around the core.

5.12

Wrap the swelling powder pack tightly with two layers of adhesive PVC tape.

5.13

Repeat steps 5.1 to 5.12 on all JF cables entering the joint.

5.14

Complete the conductor joint by twisting. Insulate the conductor joint using PVC sleeves provided in the kit.

5.15

Join the sheath connector wires.

5.16

Wrap the joint with cotton tape, keeping the silica gel pads in between taking care so the splice bundle can be accommodated inside the Al. canister without any difficulty.

5.17

Install the aluminum canister as done in TSF joints.

5.18

Temporarily keep the heat shrinkable sleeve in position, mark the ends and install one round of adhesive aluminum foil such that 25 mm of the foil remains inside the marking.

5.19

Degrease the cable sheath between the Al canister and the all Al using cleaning Tissues.

5.20

Abrade the degreased portion using emery strip provided in the kit.

5.21

Flame brush the abraded portion.

5.22

Install the heat shrinkable sleeve and branch off clips.

5.23

Shrink the sleeve as indicated for TSF joints.

5.24

Install the armour continuity wire.

5.25

Place the joint in position and cover with soft soil free from stones.

5.26

Place a layer of bricks or split pipe or RCC slabs over the joint for mechanical protection and close the trench. 6.0 Reopening :Follow the same procedure adopted for TSF joints. The water barrier need not be remade during re-entry unless the same is physically damaged. As and when required, the water barrier can be cut open, the water blocking power can be removed and the barrier can be remade as explained under paras 5.6 to5.12. Wax impregnation need not be repeated. While re-entering the joint use a reentry kit. Heat Shrinking sleeve Cable to which applicable

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TST 1 TST R1 TST 2 TST R2 TST 3 TST R3 TST 4 TST R4 TST 5 TST R5 TST 6 TST R6

0.9

0.63

0.5

0.4

blew splice openingpermissiveMaxi mum

Max dia of cable in mm

Max dia of splice in mm

Width of overlap

Min Thickness

Width

Length

Kit No.

Underground Cable

675 + 175 + 0.9 15 10

18

42

8

375

10 20

10 20

10 20

10 -

850 + 175 + 0.9 15 10

18

42

8

550

50

50

50

20

850 + 260 + 0.9 15 15

30

62

22

550

100

100

100

50

1070 +15

355 + 0.9 20

30

92

30

650

465 + 0.9 25

30

122

38

650

200 300 400 600 800

200 400

100

1125 +15

200 300 400 600 800

1160 +15

635 + 0.9 15

30

150

55

700

1000 1200

1000 1200

600 800

400

Note 1.

200

T.S.T. Themoshrink Transition kits for jointing paper insulated Cable to PIJF Cable. 2. T.S.T.R Re-entry kit for TST Joints to be used for closing a reopened joint. 3. The Thickness of sleeves mentioned above is inclusive of adhesive and will be the average thickness over an area of 25 mm.

1.0

Heat Shrinkable sleeve with 1 channel clips as per Table 1 2.0 Aluminum canister as per fig 1 RTTC, NAGPUR

1

1

1

1

1

1

1

TST 6

TST 5

TST 4

TST 3

TST 2

TST 1

Item

S. No.

TABLE 2 A Materials to be supplied in T.S.T. kits

1

1 1 Page 68 of 185

Underground Cable 3.1 3.2 4.0 5.0 6.0 7.1 7.2 8.1 8.2 8.3 9.1 9.2 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0 21.0 22.0

Sealant Tape 400x35x3mm Sealant Tape 600x1580 mesh Emery Strip 600x1580 mesh Cleaning Liquid 100 ml bottle Cleaning Tissues Branch off clip (small size) Branch off clip (medium size) Sheath conn assembly 1000 mm Sheath conn assembly 300 mm Sheath wire connector Adhesive Al. Strip 400x100x0.12 mm Adhesive Al Strip 600x100x0.12 mm Adhesive PVC Tape 5 Mtrx25 mm Adheshive Polyester Tape 5 Mrx25mm Transparent PE Sheet 300 x200 x0.05 mm Water Blocking Powder 100 gm Cotton Waste 50 gms packet Soap Armour continuity wire 14 swg PVC Cu wire 2 mtr long Twine Installation Instruction 1 PVC sleeve 51mm long 2.5 mm Silica Gel (Indicator Type)gms Micro Crystalline Wax in gm Cotton Tape 500 mmx5 Mtr Roll

2 2 1 3 1 1 1 1 2

2 2 1 3 1 1 1 1 2

2 2 1 3 1 1 1 1 2

2 2 2 3 1 1 1 1 2

2 2 3 3 1 1 1 1 -

2 2 4 3 1 1 1 1 -

-

-

-

-

2

2

3

3

3

3

3

3

-

-

1

1

1

1

2

2

2

2

2

2

1 2 1 -

1 2 1 -

1 2 1 1

1 3 1 1

2 3 1 1

2 3 1 1

2M 1 45 25 250 1

2M 1 110 25 250 1

2M 1 220 50 250 1

2M 1 880 50 500 2

2M 1 1700 100 500 2

2M 1 2550 100 500 2

51 mm

4 mm

Heat shrinking sleeve with channel clip as 1 per table 1 2.0 Cleaning tissues 1 RTTC, NAGPUR

TSTR 3

TSTR 1

TSTR 6

0.9

TSTR 5

3 mm

TSTR 4

51 mm

TSTR 2

0.63

Item

S. No.

N.B. For higher gauges above 0.5 mm PVC sleeves as per details five below to be produced locally and used. Gauge Size of sleeves Length I.D.

1.0

1

1

1

1

1

1

1

2 2 2 Page 69 of 185

Underground Cable 3.2 4.1 4.2 5.0 6.0 7.0 8.0 9.0 10.0

Branch of clip (Medium) Adhesive aluminum strip 400x100x0.12mm Adhesive aluminum step 600x100x0.12 mm Cotton waste 50 gm pkt Soap Installation instruction Silica Gel (Indicator Type) Cotton tape 50 mm wide 5 mtr/rolls Emery strip 600x1580 mesh

-

-

-

1

1

1

1

1

1

-

-

-

-

-

-

1

1

1

1

1

1

1

1

1

1 1

1 1

1 1

1 1

25 gm

25 gm

50 gm

50 gm

1 1 100 gm

1 1 100 gm

1

1

1

2

2

2

2

2

2

2

2

2

CHAPTER – IV CABLE TERMINATION INSTALLATION OF CABINET, PILLAR & DPS Objective of the Lesson : The lesson gives the details of various cross connection points that are to be installed in the local cable network. It gives inside view of all the requirements and general points to be followed during the installation of the cabinet, Pillar and DPs. Also illustrations are given for the better understanding and utility in the field. 1.

GENERAL

Cabinet and pillars are provided in large telephone systems for provision of flexibility by means of cross connections 1.1.

Construction features of cabinets and pillars

The constructional features of cabinets and pillars are identical. They are fabricated steel or cast iron casings enclosing a frame- work on which cable terminal boxes are mounted. The term pillar is RTTC, NAGPUR

Page 70 of 185

Underground Cable used with reference to a flexibility point where secondary cable and distribution cables are interconnected. The term cabinet is used for a flexibility point where the main cable from the exchange and secondary cables to various pillars are interconnected. 1.2

SIZES OF CABINETS AND PILLARS

The following sizes of cabinets and pillars have been standardized: 300 pairs, 500 pairs, 700 pairs, 1000 pairs, 1400 pairs. The number of pairs indicated is the total number of cable pairs to be terminated including the exchange side and the distribution side. The krone type cabinets and pillars are available in sizes 800 pairs, 1000pairs, 1600 pairs and 2000 pairs. 1..3

CABLE TERMINAL BOXES (CONVENTIONAL TYPE)

Cable terminal ( CT) boxes are supplied in two sizes viz: 50 pairs and 100 pairs. They are used for terminating the dry core cable entering the cabinet or pillar. The boxes have inlets are of tinned brass so that they can be plumbed to the lead sheath of the tail cable. The CT box may be provided with a single cable inlet or two cable inlets. Single inlet CT boxes are used for type A wiring, while double inlet CT. Boxes are used for types B&C wiring. 2. STANDARD CONVENTION FOR NUMBERING TERMINALS It is essential to follow a uniform convention for numbering the terminals of CT boxes. The standard convention is shown in the next page gives the front view of a 100 pair CT. box and terminal arrangements. There are ten terminal blocks, each provided with 10 pairs of terminal screws arranged in two vertical rows. The terminal arrangements on the 50 pairs CT box is also similar but there are five terminal blocks instead of 10.

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Underground Cable

Front view of a 100 pair single inlet CT box Front view of a 100 pair double inlet CT Box

3. STANDARD CONVENTION FOR WIRING For simplicity and uniformity the wiring of the CT boxes are three types to be designated as type A type B and type C . They can be referred to as A 50, B100 etc. letters A,B and C indicating the type of wiring and the figures 50, 100 etc. indicating the size of CT box. NOTE - Krone type CT Boxes only A type wiring is being carried out. 3.1

STANDARD CT BOX TYPE A

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Underground Cable All single inlet CT boxes will be wired as A type CT boxes. The size of the tail cable has to be same as the size of the CT box ( 100 pair tail cable for a 100 pair CT box and so on). The pair from the tail cable will be terminated in the order given below. • Pair 1 to 5 on terminals 1 to 5 • Pairs 6 to 10 on terminals 6 to 10 • Pairs 11 to 15 on terminals 11 to 15, • So on up to 16 to 95 on terminals 16 to 95 • Pairs 96to 100 on terminals 96 to 100 As shown in the diagram each line represents 5 pairs and each small circle 5 terminals. This type of CT box can be diagrammatically represented as shown in the same figure. 3.2 STANDARD CT BOX TYPE B A double inlet CT box without through connected pair will be wired as type B CT box. Two cable tails one for the exchange side and one for the distribution side will be required for wiring each box, The exchange side cable tail will be taken into the box through left land side inlet and the distribution side cable tail through the right hand side inlet ( as viewed from to front). The size of each cable tail is half the size of the CT box (that is 50 pair cable tail for a 100 pair CT box and so on). The pair from the two cable tails will be terminated in the following order. • Pair 1 to 5 of exchange side cable tail on terminals 1 to 5 • Pair 1 to 5 of distribution side cable tail on terminals 6 to 10 • Pairs 6 to 10 of exchange side cable tail on terminals 11 TO 15 • Pair 6 to 10 of distribution side cable tail on terminals 16 to 20 • Alternatively the exchange side and distribution side 5 pairs are terminated • pairs 46 to 50 of exchange side cable tail on terminals 91 to 95 • Pairs 46 to 50 of distribution side cable tail on terminals 96 to 100 The diagrammatical representation is also shown in the figure. In the type B, CT boxes, the exchange and distribution side pairs appear on adjacent terminals and can be strapped together for setting up circuits. 30 pairs cable tails are used for 50 pairs CT boxes with the last 5 pairs stumped. 3.3 C-TYPE OF WIRNG: Normally this type of wiring of CT box generally discourage from being used as the failure of joint at cabinet / pillar will complicate the restoration. Krone type CT boxes however does not allow this type of wiring. Pairs 1- 5 of each side cable through connected to pairs 1- 5 of distant side cable Pairs 6to 10 exchange side cable tail terminated on terminals 1 to 5 Pairs 6 to 10 distribution side cable tail terminated on terminals 6 to 10 Pairs 11-15 of each side cable through connected to pairs 11- 15 of distant side cable Pairs 16 to 20 of exchange side cable tail terminated on terminals 11 to 15 Pairs 16 to 20 distribution side cable tail terminated on terminals 16 to 20 Pairs 91-9 5 of exchange side cable through connected to pairs 91-9 5 of distribution side cable Pair 96 to 100 of exchange side cable tail terminated on terminals 91 to 95. Pairs 96 to 100 of distribution side cable tail terminated on terminals 96 to 100. This type of CT box can be diagrammatically represented as indicated in same figure.

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Underground Cable

FIG. 3, 4, 5 & 6 TYPES OF WIRING WITH SYMBOLS 3.4

TIP JOINTING

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Page 74 of 185

Underground Cable A type ‘C’ CT box can be converted for use as a type A CT box by tip jointing the exchange side cable tail. As a result of tip jointing, the distribution side pairs 1 to 5, 11 to 15 etc. which are through connected in side the CT box get terminated via the exchange side cable tail on terminals 1 to 5 , 11 to 15 etc. Tip jointing is done at the end of the exchange side cable tail . Pairs 1 to 5 are jointed to pairs 6 to 10 ( in the order of pair 1 to 6 pair 2 to pair 7 etc.) Pairs 11 to 15 to pair 16 to 20 and so on as illustrated in figures above. 4.0 DISTRIBUTION POINT - ( D.P. ) Distribution Point box commonly known as DP box is a terminal arrangement where under ground cable pairs are connected to overhead wires or drop wires for providing connections at subs premises. It is a cast iron box with a facility for termination of distribution cable on pins fitted on an insulating plate. The distribution cable pairs can be connected to these pins by soldering at the rear. The overhead wires are connected by means of screwing nuts provided on the front side of insulating face plate. 4.1 TYPES OF DPS. There are two types of DPs suitable for External / Internal use. These are called internal DPs and external DPs and are generally available in 10 or 20 pair sizes. 4.2 LOCATION OF DPS External DPs are fitted on posts by means of suitable size of U backs Internal DPs are fitted inside buildings on the wall at suitable location or sometimes the distribution cables are terminated on tag blocks, fitted on the walls from where the internal wiring i.e. block wiring can be conveniently run to subs premises. In cases of Multistoried buildings, where the telephone demand is very high the distribution cables or sometimes even the primary cables are terminated on distribution frames at suitable locations from where the distribution cable of 20 pair or 10 pair size are taken to different floors or blocks and terminated on 10 or 20 pairs subs. DPs. The internal distribution wiring is usually provided by the owner of the building and is usually in concealed conduits. Individual wires are further provided from the subs DPs to the location of the telephone. 4.3 LEADING IN OF DISTRIBUTION CABLES. In case of external DPs, the cable is carried to DP box through a galvanized iron pipe with an internal diameter of 5 cms. The GI pipe is fixed to the post by means of suitable size of galvanized Iron clamps at suitable intervals to hold the GI Pipe firmly. The lower end of the GI pipe should be about 30 cms below the ground surface. In case of internal DPs, the cable is lead into the building through a leading in pipe usually provided by the owner of the building. 4.4 PREPARATION OF CABLE TAIL As the termination of distribution cables on DP box involves certain amount of skill and time e.g. testing of the cable, proper termination on the tags, soldering, filling of DP box with Wax, compound etc., it can be conveniently and effectively done in cable depot. DP box along with cable tails are RTTC, NAGPUR Page 75 of 185

Underground Cable therefore prepared in the depot, and are then taken to the site for fitting on the post and putting it through to the UG. cable. Use of jelly filled cables for preparation of tail has been standardized. LS armored cables which were widely being used for the purpose are being substituted by PE Jelly filled cables. About 5 meter length of cable, usually, is sufficient for preparation of tail cable. However the length of the cable tail may very depending upon the location of DP post and main distribution cable. Before termination of the cable on the DP box, continuity and insulation tests are taken. In order to support the cable and prevent ingress of moisture into the DP moisture proof seal between the cable sheath and the brass ferrule is provided. After the wires have been soldered, it is completely filled with the prescribed insulating compound, or wax or jelly and back plate fixed. In case, LS cables are used for tail cables, the lower end of the ferule should be plumbed to the lead sheath. Where PAP cable is used as tail cable, as epoxy resin barrier should be introduced in the PAP cable before the U/G cable joint. 4.5 LOCATION OF DP ON THE POST. DP should normally be fixed at minimum height of 6 feet from the ground or in cases where it is fitted still higher to avoid risk of damage or interference by unauthorized persons, its top should be 1 foot below the ultimate lowest bracket. 4.6 FIXING DP ON THE POST. After the position of the DP is marked on the post, the DP is fitted to the post with the help of U brackets. The cable tail is passed through the GI pipe and the pipe is pushed up so that the bottom of the DP sits on the upper end of the GI Pipe. The GI pipe is tied to the post with 4 bolts. The tail is then jointed to the distribution cable. The pairs are finally tested from Exchange MDF ( in case of direct Dps ) or pillar to DP terminal.

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Underground Cable

4.7

INSTALLATION OF DISTRIBUTION POINTS ( DPS) FIG.

:: EXTERNAL DP 4W BRACKET

DP BOX

A4 B C T U B U L A R P O

PIPE FIXING CLAMPS

GI PIPE

SOCK ET

GROUND LEVEL

SOLE PLATE

RTTC, NAGPUR

Page 77 of 185

Underground Cable 5.6 GENERAL DESCRIPTION OF KRONE LSA PLUS MODULE. KRONE LSA PLUS

IS A QUICK CONNECTION TECHNIQUE WHICH DOES NOT INVOLVE SOLDERING, SCREW

TERMINATION OR WIRE STRIPPING.

THE

WIRES TO BE TERMINATED ARE INSERTED INTO CONTACT SLOTS OF THE

MODULES AND THE INSULATION OF WIRES IS DISPLACED ON EITHER SIDES BY THE CONTACT EDGES OF THE BIFURCATED TAGS WHEN PRESSED THROUGH BY A SPECIAL CONNECTION TOOL SHOWN ABOVE. AUTOMATICALLY CUT OFF BY THE CONNECTION TOOL.

A GAS

TIGHT AIR TIGHT

THUS ACHIEVED WITHOUT REMOVING THE INSULATION OF THE CONDUCTORS.

&

TO

EXTRA

WIRE

IS ALSO

CORROSION PROOF CONNECTION IS

REMOVE THE WIRE FROM THE SLOT

WHEN THE CONNECTION IS NO LONGER REQUIRED, A HOOK PROVIDED IN THE CONNECTION TOOL ITSELF IS USED TO PULL THE WIRE UPWARD

5.7 THE MAIN FEATURES OF LSA PLUS TECHNIQUE ARE AS FOLLOWS: 1.

(a) (b) (c) (d)

No soldering is required No screwing is required No stripping is required An IDC ( Insulation Displacement Connection) and stripping off the extra length of insulated wire is achieved in one single operation.

2. Figure in previous page shows the layout of contact. As the wire is pressed into the slot of the contact (2) angled at 45o to the path of the wire the flexible contact tags ( 3) are pressed open in an axial direction and simultaneously turned. The tag thereby cut through the insulation material of the wire and notch in to the conductor core. Air tight contact points are created and are particularly secure due to the constant torsion and spring forces ( 6) & (7) of the contact tags. The four plastic clamping ribs of the module grip the plastic insulation on the wire and provide added protection, Thus. (a) An air tight gas tight contact is achieved. (b) The insulated wire is gripped in the plastic rib before and after the contact and protect the contact from vibration effect. 3. It is modular, each module is 10 pairs Any size of CT Box from 10 pair to any multiple of 10 pairs is possible. the module can be replaced easily. 4. Both cable wire and line wire ( jumper) can be reached from the front for test or Hand Test Telephone set with a suitable plug can be inserted with connecting cord without disturbing the main wire connections. 5. In disconnection type of modules the wires can be disconnected plug without disturbing the main wire connection

by simple insertion of

6. In disconnection type module both the line wires and cable wires of single pair can be segregated using suitable plug insert with connection cords and connected to test instrument or hand test telephone set without disturbing the main wire connection. 7. If necessary a GD Tube module can be procured and used as an add on clipping unit. The manufacture of these modules is also under consideration. 8.

The modules are suitable for (a) Internal Dps. (b) CT boxes of cabinets and pillars.

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(c) CT boxes at MDFs of SAX, MAX-II, MAX-III PBXs and PABX’S ( its use for MDFs of large electronic and other MAXs is under Lab. Trials in TRC. 9. The modules can be fitted on a stainless steel mounting frame with receptacle/spring which have slot to engage with module. 10.

A single connection tool is used for (a) (b) (c)

Connecting the wire to make IDC type connection Taking out the wire for removing the connection Taking out the module from the back mount frame.

In order to ensure optimum utilization of cables, it is very important to follow the “Engineering Instructions“ standards prescribed for the cable construction works. Strict supervision and stringent Acceptance Testing procedures are necessary in order to ensure efficient cable construction works.

5.8 THE FOLLOWING PROCEDURES CABLES / UNDERGROUND/E-3004”.

ARE GIVEN IN

ENGINEERING

INSTRUCTIONS

“LINES

AND

•

It is to be noted that the pillar base is made of RCC and no brick structure is involved in the construction of pillar base.

•

Cable entry into the concrete base is at a depth of 90 cm below the ground level.

•

Cables are not to be exposed any where near in the surroundings of the pillar.

•

Entry of cables through RCC base is through a smooth curved surface in order to avoid damages to the cables.

•

Cable entry portion in the concrete base should match with the provision made for cable entry in the bottom of the pillar under erection.

•

A skilled mason with suitable mould will be able to prepare the RCC base as per specification at the site.

•

The fixing of foundation bolts in the RCC during concreting activity is the major problem and it requires skill that they do not go out of alignment while ramming concrete. Otherwise this will cause non suitability of the fixing of pillar shell to the plinth firmly.

•

As the inner walls of the shell of pillar will not be fully accessible after termination of cables it should be made a point to paint it.

•

All the cable inlets after completion of work should be sealed to arrest entry of rodents, reptiles, ants, etc. and falling of tools while works.

•

The Covers of Krone type CT boxes should be compulsorily placed to avoid dust on contacts.

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Underground Cable •

The numbering of Pillars naturally will not be more than 79 pillars and usual numbering scheme is 21 to 99.

5.9 THE FOLLOWING PROCEDURES ARE GIVEN IN ENGINEERING INSTRUCTIONS “LINES CABLES / UNDERGROUND/E-5003” B FOR MAINTENANCE OF PILLARS.

AND

•

Frequent cleaning of CT boxes and removal of cobwebs will avoid ill-effects of dust on contact.

•

The painting of shell as per the atmospheric conditions and requirements of the place.

•

The hinges should be lubricated to have free movement of doors.

•

The Lock and keys should be in tact as entry of rain water will damage it.

6.0 Advantages and dis-advantages of Cabinet, Pillar system : 6.1 Advantages: •

Seperation of primary, secondary and distribution network.

•

Flexibility at cabinet / pillars permits a very good grade of utilization of cable especially in case of primary cables.

•

Private wire and external extensions in the same areas can be conveniently provided by a cross connection jumper at cabinet / pillar with out additional primary or bringing back to exchange.

•

A simple and perfect record can be maintained.

•

Repeated digging for re-arrangement for diversions of cable pairs is not necessary.

6.2 DIS ADVANTAGE : •

Unsuitable for very humid areas resulting in low insulation.

•

Location of cabinet / pillars in congested areas may cause problems.

•

Additional jumper introduces fault liability point.

7.0 MAIN DISTRIBUTION FRAME : This is the interface stage between the external plant and exchange equipment. 7.1 General Facilities provided by M.D.F. :: RTTC, NAGPUR

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Underground Cable

• • • • •

A point of termination of internal and external cables. A suitable location for mountings fuses, heat coils and protective devices. A convenient place to isolate any circuit to test the condition of both internal equipment and outdoor network A means for interchanging the external cable pairs used for circuits if necessary. A means for cross-connecting the external circuits to the appropriate internal circuit.

7.2 MDF of E-10B exchange : •

accommodates 128 line terminals from exchange side

•

Accommodates 100 line cable terminal strips for accommodating underground cable.

•

Accommodates provision to have GD tubes to earth heavy voltages.

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CHAPTER V POWER TELECOMMUNICATION CO-ORDINATION COMMITTEE AND PROTECTIVE DEVICES

POINTS FOR CONSIDERATION FOR UNDERGROUND TELECOM. CABLE Objective for the Lesson :: To familiarize the necessity of protective devices on the telecommunication systems. Need to avoid the hazards of power induction due to electrical lines and lightning and railway traction. The necessity to prevent the equipment and personnel from the unexpected source of dangers. *

*

*

The power telecom co-ordination committee came into existence in 1949as per Resolution No. EL.11-151 (7) dated 30th May, 1949 from Govt of India by the Ministry of works, Mines and Power . Its earlier name was Central standing committee. Various committees constituted are Central PTCC

:: Three meetings in a year. Power lines above 33 KV

State level PTCC :: Frequency is once a month. Power lines above 11 KV up to 33 KV. 1.0 IMPACT OF POWER PARLLELISM ON TELECOM NETWORK :: Parallel running of Power and Telecom Underground cables / lines may cause electrostatic and electromagnetic induction and interference on the telecom circuits existing on the telecom lines / cables. Development of hazardous longitudinal voltage on telecom circuits under single line to ground fault condition of the power line / power cable. Circuits under worst fault condition of the power line / power cable can be limited to the safe value recommended by the CCITT / ITU. In case this safe separation is not possible protective measures are to be taken so that no electrocution hazard is caused to the operating and maintenance personnel and no damage is caused to the telecom equipment. Crossing of Power and Telecom cables / lines require keeping adequate vertical and horizontal clearances between the power wires and telecom wires or cables. 1.1 EFFECT OF ELECTRIC TRACTION ON TELECOM CIRCUITS 1.10 ELECTRIC INDUCTION :: RTTC, NAGPUR

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Underground Cable The overhead category and contact wires of the traction system will be at a high voltage of 25 KV with respect to earth. This produces in the neighboring telecom wires , thereby endangering the equipment and working personnel and also causing interference to circuits. The extent of induction depends on a number of factors the most important of which will be separating distance between the two parallel networks. The CCITT mentioned that if current exceeding 15 milli amperes is traversed in the body of a person for a certain length of time endangers the life of the personnel. 1.11 Remedial Measures :: Shifting of Telecom lines / cable to safe separating distance Use of suitable type of cables. ( where long parallelism occurs, use Aluminum sheathed cables) Use of booster Transformers and return conductors by the Railways. Electrical Bonding of Rails to have higher screening effect of Rails. Installation of Gas Discharge tubes at both ends of the telecom line / able involved in parallelism and at individual points along the line as may be necessary as per the induced voltage calculated theoretically. The fuses and heat coils may also be used. 1.12 PROTECTION FOR UNDER GROUND CABLES :: The following general conditions to be observed during laying in view of safety of personnel and hazard to equipment and cable. a. All the cable should be referred to PTCC for clearance so that the induced voltage under earth fault condition of neighboring power line and cables may be assessed theoretically and protections may be advised. b. How ever as mentioned in EI G-2000, U/G cables can be laid even with out referring to PTCC for a length of 800 meters subject to minimum horizontal clearance of 2 ft from the nearest power cable. In such a case , care should be taken to have as much horizontal separation as possible from the power cable. c. Cable passing near the power lines especially the power line supports are subjected to grave hazards of burning. To prevent this at least 50 meters separation will be necessary. d. Laying of underground cables just below the alignment of HT & EHT power lines should be avoided. Cases of burning and damage to the telecom cables have been reported under earth fault condition of the power line. e. While laying, safe separating distances should be observed. f. When it is not possible to keep the safe separation, the cables may be laid in PVC piles /Ducts. g. In case of poly-al cable, it is essential to maintain the continuity of the poly-Al and armour at every joint to provide proper screening effect.

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Underground Cable h. It is also important to earth the poly-Al and armour at as many points as possible, but at points where earth potential rise is encountered beyond 430 volts , the cable and joints have to be well insulated. i. When the cable enters a power station area the earth potential rise can not be avoided. Top prevent the hazards due to this, it is necessary to break the armour and play screen continuity at a point where the voltage due to earth potential rise reaches 430 volts. Further, all cable conductors at this point and at the subscribers premises should be provided with GD tube protection. No Joints or Tees are allowed with in the zone of earth potential rise. j. While crossing a power cable, a minimum vertical clearance of 2 ft should be observed and crossing should be as nearly right angles as possible. In case it may not be possible, laying of cables solid in bitumen for a distance of 3 ft on either side of the crossing point should be done. k. For laying Telecom cable sin the vicinity of power cables, the EI G –2000 prescribes the following separation. Minimum Horizontal and Vertical clearance – 2 ft. less than 18 “for single core power cable & power cable.

In no case 12” for multi core

1.13 SAFETY MESURES FOR STAFF :: While attending faults or laying cables the safety measures mentioned below must be adopted. a. Cable routes subject to dangerous induction should be permanently marked by warning indicators along the route. This will warn the workers and remind them of the precautions they must take. b. During storms the likely hood of power line faults are more and so workmen should be forbidden from working on the cables during storms in the vicinity. c. Workmen must not be allowed to carry on single handed. They should always work in parties. d. When using insulated clothing, gloves, shoes, etc or tools or electrical equipment which are insulated form earth, soldering irons and lamps and line man’s telephones sets, care must be taken before work begins to ensure that insulation is adequate and intact. e. Before cutting a cable sheath a low resistance electrical connection has to be made between two parts of the sheath to be separated by the cut. This applies to the armour of the cable also. f. The cable sheath should be earthed on both sides of the proposed cut. g. All cable conductors should be handled by insulating gloves and tolls. Before any conductors is cut it must be earthed on both sides of the proposed cut. This earthing can be achieved by connecting to the cable sheath. In addition a spike earth prepared with 1 RTTC, NAGPUR

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Underground Cable metre GI spike must be used. The earth connection should be removed only after completing all the work. h. The cable sheath at all joints should be bonded i. The GD tubes provided should be in proper functioning state. j. Maintenance staff should handle the coaxial cable after disconnection at both the repeaters to restrict the induced voltage on one repeater. 2.0 LOW FREQUENCY INDUCTION :

The induction effects of power line / cables on telecom Lines / cables can be examined under the following conditions A.

Induction under normal working condition of a power line / cable :: The magnitude of this induction depends on the magnitude of the unbalanced load current of the power line or power cable. It can be calculated by following formula Induced voltage on Telecom Circuit

Unbalanced Load = current in the power line

X

Mutual coupling between power line / cable and the telecom circuit for the length of parallelism

The maximum value of the unbalanced load current has been restricted to 1.5% of the normal load current of the power line by the Central Electricity Authority. In the speech circuits overhead or cables noise will occur. B.

Induction under Earth fault condition of a power line / cable :: The induced voltage on telecom wire can be calculated as under Induced voltage on Telecom Circuit

=

Fault on their power line

X

Screening factors ( if any )

X

Mutual coupling between power line / cable and the telecom wire

Theoretically it can be calculated by the following formula :-

e = 2fjmlk x 10 –6 volts. Where e = Induced voltage f = 50 (for 50 Hz frequency ) j = Faults current in amperes m = mutual inductance in micro henrys per kilometer l = length of parallelism in kilometers. RTTC, NAGPUR

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Underground Cable K = screening factors or product of screening factors. The mutual coupling depend on the following factors :i. ii. iii.

Separation power line and telecom line. Length of parallelism. Soil resistively In case of calculations for 11 KV, 22KV and 33KV power lines, detailed simplified procedure will be followed. In other cases calculation will be done by Member Power, Electricity Board ( for lines above 33 KV and upto 132 KV) and by Central Electricity Authority for power lines above 132 KV.

C.

The effect of Induction on speech circuits In the speech circuits, the induced voltage may cause noise which is known as the loop effect. It can be measured with the help of psophometer. The psophometric noise must be within one millivolt as prescribed by CCITT. The effect will be less if the telecom circuits are well balanced.

D.

Effect of Induction on Interference in signaling circuits may arise because of i. ii. iii.

Longitudinal emf’s due to electromagnetic induction acting on a signaling device in a closed earth return circuits. Resistive coupling between a signaling circuits and neighboring earthed power line, if the circuit has more than one earth connection ( In many open wire telecom circuits this phenomena is there) Current in signaling device due to electrostatic induction from a neighboring line if the device is connected between earth and a line otherwise insulated from earth throughout its length. In underground cables, the interference listed at A & B arise but because of screening effect of cable sheath it is less serious.

iv. v.

vi.

Interference may arise due to wire to earth capacitance. Electromagnetic interference from neighboring power lines may effect signaling if they use earth or cable sheath as conductor or even when suing pairs, if they are un balanced to earth. In such case, a voltage of 5 volts is sufficient to cause interference with signaling. In Voice frequency signaling systems, it may be necessary to limit the circuit noise to avoid false signaling.

3.0 Procedure for PTCC clearance of Telecom Lines / Cables All the telecom lines / cables proposed are to be referred to PTCC for clearance along with the following documents : ( a ) Topographical route map :-

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Underground Cable The telecom line / cable should be marked on a topographical route map which should have the scale 1 cm = 0.5 km. The route map should contain the topographical details up to 8 km on either side of the telecom line / cable. If possible, it should contain latest topographical details like constructed roads, dams, canals, railway tracks with the location of the existing railway station. ( b) Questionnaire :In case of telecom cables, the following details may also be supplied. (i)

Type of cable, gauge of conductors and number of pairs.

(ii)

Type of insulation and conductors.

(iii)

Type of armouring – Lead sheath, aluminum foil / Sheath.

(iv)

Number of steel tapes.

(v)

Thickness of steel tape.

(vi)

Diameter under the sheath.

(vii)

Operating voltage.

(viii) In case of coaxial cables location of power feeding repeaters. (ix)

Any screening wire laid or proposed to be laid on the cable. In case of co-axial cables whether two 300lbs copper wires are proposed to be laid for protection against lightning.

(x)

In case of ducts whether any ACSR screening wires have been laid or proposed to be laid in the Duct along with the cable, If so gauge of the ACSR screening wire should be mentioned ( C ) Soil Resistivity :The soil resistively should be measured in the dry season by 4 electrode method using inter electrode spacing of 50 meter, keeping all the 4 electrodes in the same straight line. The electrodes should be inserted in to the ground for a depth of 2 or 3 feet. The measurement should be made at every 2 or 3 km along the route of lines. The connections of the Ever shed Earth Tester are to be made as shown below :Soil Resistively = 2 AR in Ohm meters. Where A = spacing between the electrodes in meter R = Reading of the Ever shed Earth Tester.

P1 C1

A RTTC, NAGPUR

B

P2 C2

C

SOIL

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Underground Cable

( D ) Correct Marking of Telecom Line / Cable on the map. The telecom lines / cables should be correctly marked with respect to power lines / cables. If due to incorrect marking the telecom line / cable has been shown to be having more separation from power line / cable as compared to the actual value, the induced voltage calculated will be less than the actual induced voltage resulting in under protection of telecom line / cable. 4.0 INDUCED VOLTAGE PER KILOMETER Soil Resistivity in Ohm / cm3 5000 10000 25000 50000 100000

LENGTH AT PARALLELISM FOR A FAULT CURRENT OF

1000 AMPERES.

Induced voltage in volts for separation of between telecom line and power line 1 10 50 100 200 500 1 2 3 5 8 mtr mtr mtr mtr mtr mtr km km km km km 360 255 165 120 83 89 17 4 3 3 3 380 276 180 140 102 56 27 9.6 4 3 3 405 300 210 168 129 78 45 18 10 3 3 435 330 230 185 150 400 60 30 17 6.75 3 465 360 250 205 170 100 80 45 28.5 13.5 5.4

5.0 Separation beyond which induced voltage is less than 200 V Length of parallelism for shirt circuits current values of ‘1’ AMPS I=1000 I=2000 I=3000 1 0.5 0.33 2 1 0.66 5 2.5 1.66 10 5 3.33 20 10 6.66 50 25 16.66

Minimum separation in meters for values of soil resistibility ‘p’ p=10 17 80 250 400 600 1000

p=100 50 250 800 1300 2000 3000

p=1000 150 800 2500 4200 600 9500

p=10000 500 2500 8000 >10000 >10000 >10000

6.0 DISTANCES AT WHICH VOLTAGE RISE IS 430 VOLTS FROM THE FAULT OR POWER SUPPORT DISCHARGING THE CURRENT

Ip r

= 2 x 430

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Sl.No. Sl.No. 1 21 32 43 54 65 76 87 98 10 9 10

Soil Resistivity OhmSoil‘p’ Resistivity meter ‘p’ Ohm10 meter 20 10 50 20 100 50 200 100 500 200 1000 500 2000 1000 5000 2000 100005000 10000

Minimum safe distance for fault current I Ampere I-100 I=200safe distance I=500 forI=1000 I=2000 I=5000 Minimum fault current I Ampere I-100 0.5 10.15 20.5 41 82 20 4 40 8 75 16 185 32 370 80

1 I=200 1.5 0.5 41 82 15 4 40 7 75 16 150 32 370 64 740 160

2I=500 41 10 2 20 4 40 8 100 16 185 40 370 80 925 160 1850 400

4I=1000 82 20 4 40 8 75 16 180 32 370 80 740 160 1850 320 3700 400

8I=2000 15 4 40 7 75 16 150 32 370 64 740 160 1500 320 3700 640 7400 1600

I=5000 20 40 8 100 16 185 40 370 80 925 160 1850 400 3700 800 9250 1600 18500 4000

160

320

800

800

3200

8000

7.0 Distance at which voltage rise is 1000 volts from the faults point of power support discharging the current. Ip r

= 2 x 1000

8.0 SALIENT POINTS TO BE REMEMBERED

AND FOLLOWED AS A ROUTINE::

1. Effective guarding of all power lines crossing. 2. Vertical and horizontal clearance of power lines. 3. Guarding by Telecommunication to be earthed effectively. 4. GD tubes to be provided at required locations. 5. All loose lines should be tightened to avoid sag and possibility of contact with electric lines. 6. Frayed and non-standard service leads to be replaced. 7. All power and telecom lines and cables should find a place in the map. 8. Care to be taken while enacting new lines that that PTCC codes are not violated. 9. Inspections by local officers to ensure that no violations are present 10. Protections to be used. GD tubes and PCP’s ( Power contact Protectors ) to be provided as per standards.

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Underground Cable 11. Periodical checking of the earth resistance to be done so as to ensure that the protection done is well maintained and with in tolerable limits. 12. All precautions are to be taken before commencing of work involving power and telecom. Lines. 13. Supervision is necessary and shut down of power is required while performing maintenance operations in the vicinity of power lines. 14. Insisting that protection devices are used during the execution of work. 15. Patrolling and identifying defective guarding. 16. In case of minimum clearance is not available, additional safety precautions in the form of PVC sleeves may be provided.

PROTECTIVE DEVICES Introduction Telecommunication apparatus connected to transmission lines (overhead or underground) must be protected against damage from electrical hazards such as : -

Effects of lightning Direct strikes Electrostatic induction Rise in ground potentials (by lightning strikes from thunder clouds).

Direct Contact with or Induction from Power Circuits Lightning, direct contact or induction from power circuits induces voltages in Telecommunication lines. These foreign voltages are much higher than the voltages for which telecommunication systems are designed. They may puncture the insulation or cause excessive currents in the telecom equipments. Such high voltages may also endanger maintenance personnel and property. It is, therefore, essential to incorporate some protective arrangements to effectively guard the telecom apparatus, open wire lines and cables against the effects of thunder storms and contacts with power lines. The protection arrangements to guard the telecom apparatus and lines against power hazards need to fulfill the following requirements : RTTC, NAGPUR

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Underground Cable •

Should not be very costly.

•

Must not operate with speech and signaling currents.

•

Must not reduce the transmission or signaling efficiency.

•

Must ensure that no voltage dangerous to life, exchange equipment or cables is allowed to persist.

Present Position Strategy for Exchange Interfaces In exchanges deemed by local management to have a high risk of lightning damage, protection is provided in two stages. The primary protection consists of a gas discharge tube fitted to each line at the MDF, and the secondary protection is a network of components located in the subscribers line unit (SLU). The circuit diagram of a typical scheme is shown in Fig.2. The main function of the primary protection is to clamp the line voltage to a reasonably low level during a surge. Fig. 1

BINR 315 – Lightning Surge Generator

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Underground Cable Fig. 2 Protection Network for an Exchange Interface

To achieve this the primary protector must shunt a large current (up to several hundred Amps) to earth. The gas discharge tube performs this task admirably, but it 'fires' too slowly and at too high a voltage to provide complete protection by itself. The function of the secondary protections is to deal with the 'residual voltage' passed by the primary protector. This voltage can consist of a transient occurring before a large surge triggers the primary protector, or a longer term over voltage condition which does not reach the required firing voltage and hence creeps under the primary protection. In low risk areas, only secondary protection is provided. In practice, the SLU is designed with on-board secondary protection which can operate in a 'stand-alone' mode in low risk areas, and also operate in conjunction with a primary protector in high risk areas. The series element ensures that the primary protection (when fitted) fires for all voltages in excess of 1.5 KV and is not prevented from operating by the earlier triggering of the secondary protection. The series element also limits power dissipation in the secondary network during mains contacts. For the most common source of interfering signal, lightning induced surges, all the elements of protection network must survive, thus, minimizing both the remedial maintenance and interruptions to customer service. However, for other less frequent over voltage conditions (such as mains contacts) failure in a pre-determined manner is acceptable. The secondary protection series element should fall open circuit and the shunt element should fall short circuit, to avoid the damage spreading to the remainder of the SLU. It is also important that failure of the protection circuit does not constitute a fire hazard. As well as ensuring that the sensitive components in the SLU never see a voltage surge beyond their maximum operating limits, the protection must not interfere with normal operation. It must, therefore, pass the required line voltages and currents, and not degrade the transmission properties of the line. These requirements limit the type of component which can be used in protection networks, and call for tight quality control on the components which are used.

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Underground Cable Components used in Protection Networks Having decided on a protection strategy for exchange interfaces. British Telecom (BT) found that the components already offered by manufacturers for protecting sensitive electronic equipment did not always fulfill the requirements. Over the past few years, there has, therefore, been considerable collaborative effort between British Telecom (BT) and component manufacturers based in the UK to develop suitable versions. Since protection components are fitted to every exchange line, the market is large enough to enable 'specials' to be developed without unduly increasing the unit costs. Some examples of the components developed in this way are given below. Secondary Protection – Series Elements A wide range of components is now available, including inductors, fuses, resistors (discrete and thick film hybrids) and thermistors. The choice depend on the particular requirements of the equipment being protected, and the type of shunt element used. Secondary Protection – Shunt Elements Traditionally, specialised zener diodes have been used in this role. However, more recent developments include the fold back diode, a three-layer semiconductor device. G. D. Tubes Gas Discharge Tubes are recommended by the Power Telecommunication Coordination Committee (P.T.C.C.) for fitting on Telecommunication lines in the Department as protection against induced voltages in the event of an earth fault on the paralleling power lines. Use of G. D. Tubes These tubes are essentially gap protection of the self restoring type. Depending upon the gap setting during manufacture, the filler gas and its pressure, and other constructional features, they can be designed to strike at the desired predetermined voltage and with required current carrying capacity. Suitable tubes can, therefore, be used by connecting between each wire and earth for draining away light induced potentials above a set limit from the communication wires.

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Underground Cable These tubes are manufactured in two broad types, viz. the two electrode type and the three electrode type. A single two electrode type arrestor can serve as protector for one wire only, one electrode being connected to the line wire and the other to an efficient earth. The three electrode type can serve for a pair of wires. The wires of a pair are connected to the line electrodes, while the third electrode is connected to earth. The P.T.C.C. generally recommends the three electrode type. The tubes are fitted on the wires along the affected route, an interval indicated by the P.T.C.C. In the event of induced voltages arising equal to or more than the striking voltage of the tube provided on the wires, the tubes operate and drain away the charges, reducing the line potential to earth. The potential on the wire then depends on the voltage drop across the G.D. tube and the resistance of the earth connection; this voltage is called the residual voltage. For properly spaced and fitted tubes, this is much less than the induced voltage. The wires are thus rendered comparatively safer for the personnel who may happen to handle them while the induction persists. General Gas discharge tubes, with their mounting boxes, are at present stocked by C.T.S., Calcutta under Rate List No. 252873 and 252874. The R.L.No. 252873 relates to ten-tube protector boxes, i.e. ten three-electrode tubes mounted as one unit to cater for twenty wires, while the R.L. No. 252874 is a protector box with one threeelectrode tube only. Normally, the item against R.L.No. 252873 should be procured only when the alignment carries a large number of wires and a majority of them require protection. In addition to the number of gas discharge tubes required for fitting on the alignment, then initial procurement itself should include about 5% extra tubes as spares for maintenance. These may be kept with the sectional supervisors. The maintenance routine of G.D. tubes is described by E.I. protection, General, C500 and should be strictly followed, after installation to ensure the safety of the lines and the personnel handling them.

Installation RTTC, NAGPUR

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Underground Cable (i)

The tubes are to be connected between line wires and earth. The connection from the line wires to the tube electrodes may be made with weather proof leads of 15 to 20 Amp. current carrying capacity. The common earth wire may be of 3 strands of 300 1b/m bare copper wire or equivalent, with connection to individual tubes earth electrode by a wire of current carrying capacity of about 30 amps.

(ii)

The tubes are supplied in metal boxes which are suitable for pole-mounting. When a number of tubes are to be fixed on one pole, as will mostly be the case, it is better to fix all the protector boxes in a locally assembled wooden or metal box similar to the DP boxes. The protectors should be fixed at a height sufficient to guard against tampering of unauthorized persons.

(iii)

The earth connection provided at the protector should be low resistance, below 3 ohms. This is very important for the efficient functioning of the protectors.

(iv)

Each tube should be tested before being mounted. For this purpose, apart from visual physical check, for checks, damage or other defects, it should be tested with a 500V megger between the earth electrode and the wire electrodes in turn. When the megger is running near full speed, the tube should strike. This will be evident by the resistance indicated falling from near infinity to very low values and in some types of G.D. tubes by visible glow also.

(v)

Unless otherwise directed by the P.T.C.C., G.D. tubes are to be fitted on all the wires on the alignment involved in the power parallelism.

(vi)

The locations for fitting G.D. tubes is indicated by the P.T.C.C. These can be shifted by a few posts either way to suit local conditions and easy access for maintenance and inspection.

(vii)

Any new wire added to an alignment on which G.D. tubes are already fitted or recommended for such provision by the P.T.C.C., may be presumed to need protection and should be similarly protected. In case of doubt the P.T.C.C. may be consulted.

POWER CONTACT PROTECTORS (P C P ) :: These are the devices used on the top of the telecom lines where there is possibility of the electrical lines coming into contact live with the live power lines. These will earth the power lines and trip the source of supply preventing the damage to the equipment and personnel working on the telecommunication systems. These are used when the voltage of the power line carries over and above 650 Volts and are installed on the top bracket of the telecommunication lines.

METAL OXIDE VARISTORS ( MOV ):: The metal oxide varistors are used for protecting the line equipment, subscriber premises equipment from the surge voltages that occur due to induction. These are used generally at Line cards, Subscriber instruments, etc. RTTC, NAGPUR

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CHAPTER VI CABLE RECORDS AND PREVENTIVE MAINTENANCE OF CABLE NETWORK OBJECTIVE OF THE LESSON :: THE IMPORTANCE AND NECESSITY OF RECORDING THE EVENTS OF INSTALLATION AND CONSTRUCTION AND UPDATING THE RECORDS IS GIVEN IN DETAIL. THE REQUIREMENT OF MAINTENANCE TO PREVENT BREAKDOWN OF THE SYSTEM BY DOING THE CORRECTIVE MEASURE BEFORE THE DISASTER.

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Underground Cable INTRODUCTION The following activities are the integral part of preventive maintenance of cables and these will help discovering and localizing a cable fault when the fault is still in incipient stage. (a)

Proper maintenance of cable records.

(b) Regular time bound inspections of cable installations like cabinet pillar DP indicators, cable routes etc. (c)

Pressurization of cables.

MAINTENANCE OF CABLE RECORDS 1.

GENERAL

Proper Maintenance of cable records will help discovering and localizing a cable fault when the fault is still in incipient stage. 1.1

MAINTENANCE OF CABLE RECORDS.

Cable records are very effective tools for the maintenance of cable networks. The cable records may be divided into three categories viz ( a) Plan 1.2

( b) Line diagram and

( c) cards.

PLAN OR MAPS

Cable plan gives the actual existence of a cable installations in the locality. These are drawn upto scale on city maps. The following types of plans are generally maintained:1.3

THE EXCHANGE AREA LAYOUT MAP

This is necessary for all existing Exchanges. It may be drawn to any convenient scale say 5 cm to 10 cms. to a km and may show the following details:i..

Boundaries of existing exchange area defined precisely

ii.

Proposed boundaries of future exchanges but liable to alterations.

iii.

Location of existing exchanges

iv.

Localities where future exchanges may be situated.

1.4

THE CABINET AND PILLAR AREA LAYOUT MAPS.

A separate map is to be prepared for each exchange area. Depending upon the extent of the exchange area, it may be of scale 10cm to 40 cm to a km and may show the following details. RTTC, NAGPUR

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Underground Cable 1. The location of the cabinets, the primary cable routes, the duct lines, the manholes etc.

2. The location of pillar, the secondary cable route, the location of secondary cable joints, the duct lines, the manholes etc. 3. The location of DPs ( either internal or external ) the distribution cable route, the location of joint etc. 1.5

LINE DIAGRAM

These diagrams show the actual orientation of the cable network including the size of the joints, type and size of the DPs etc. These diagrams are not drawn upto scale.. The following are the different types of line diagrams maintained for cable networks. 1.6

Primary line diagram

(When the primary is laid through duct the diagram is named as primary duct lines diagram). These diagram show all relevant information in respect of configuration of the primary cable, the ducts and manholes for primary cables.

1.7

SECONDARY LINE DIAGRAM OR SECONDARY DUCT LINE DIAGRAM

One diagram is prepared for each cabinet to cover all the pillars terminated to it. All relevant information’s in respect of number of pillars the length and sizes of the secondary cables and their joints, the ducts and manholes for secondary cables, the gauge of the cables etc are available with this diagram. For small network one diagram may cover both primary and secondary cables. 1.8.

DISTRIBUTION LINE DIAGRAM

This diagram represents the cable orientation for all the distribution cables emerging out of a particular cabinet one diagram is meant for a pillar and all the DPs connected to it. 1.9.

JUNCTION CABLE DIAGRAM

These diagrams show the junction cable network in multi exchange area 1.10.

PRESSURISATION DIAGRAM

This diagram shows the pressurization system of a cable network. 1.11

CARDS

A. DP CARDS RTTC, NAGPUR

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Underground Cable These cards show the number, size type (internal or external) and location of the DP and how each terminal of the DP is unutilized. They also indicate the distant end terminal code corresponding to each terminal of the DP one card is required for each 10 or 20 pairs DP for DP’s larger than 20 pairs ( as in the case of distribution frames for large buildings) two or more cards have to be used. fig. shows the obverse of a DP cards. The reverse is for terminals 11 to 20 . The entries shown are typical of a DP served from a type BCT box at the pillar. B. THE CABINET CARDS AND PILLAR CARDS One set of cards is required for each cabinet or pillar. The set contains one card for each 50 pair or 100 pair CT. box fitted in the cabinet or pillar. Each card shows the following particulars Number size and type of the CT. box, size of shell, location of the cabinet or pillar, circuit working one each terminal of the CT box, the terminal to which it is jumpered or strapped for setting up the circuit, the distant end terminal code corresponding to each terminal of the CT box and the codes of cable pairs connected to the terminals. These cards must be filled in at the time of installation of each cabinet or pillar and subsequent additions or alterations effecting the entries must be incorporated.

C. THE MDF CARDS It contains the following particulars, distant end terminal code corresponding to each terminal (or tag) or the fuse strip, circuit working on the terminal and address where the subscriber is located. One card is required for each fuse strip. Entries for tags 1-10 are made on the observe and those for tags 11-20 on the reverse. D. SUBSCRIBERS INDEX CARDS While in the DP Pillar, cabinet and MDF cards the circuit particulars are given terminal wise the subs. Index cards show the terminal particulars circuit wise. The routing of any circuit can be readily ascertained from these. Two types of cards are necessary, one for direct exchange lines and other for the non - exchange lines. These cards must be introduced along with the DP and the MDF cards. Non exchange lines must be assigned, suitable serial numbers for the purpose of identification and recording. 1.12

MAINTENANCE OF CABLE RECORDS.

All the cable records are prepared at the time of construction and are handed over to the cable maintenance section. As the time goes on the cable network undergoes changes required for extension and maintenance purpose. These changes viz. addition of new cable, cabinet, pillar, DP etc., diversion of cable route, incorporation of additional joints for faults rectification and these types of changes must be incorporated into the records. The utility of the records, if not updated, is reduced drastically and at the same time un-updated record may lead to serious difficulties to the maintenance and construction party. The modern practice is to maintain the master copy of the records in the form of transparencies and the changes are incorporated to these transparencies as and when required. 1,13

INSPECTION & MAINTENANCE OF CABLE INSTALLATIONS

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Underground Cable Cabinets should be inspected at least once in every 3 months and pillars once in every 6 months. An inspection schedule is given for guidance of inspecting officers. Schedule for inspection of cabinet/pillars. 1.

2.

(a)

What is the general condition of paint outside and inside?

(b)

When was the cabinet/pillar last painted? Is there any sign of rusting?

(a)

Does the door move freely on its hinges?

(b)

Are the hinges and key holes oiled with bearing oil?

(c) In case of stiff hinges, has the kerosene oil and /or graphite bearing grease been applied? 3. (a) What is the condition of bitumen seal at the bottom of cabinets? If there are cracks, what has been done to close up the cracks?

4.

(b)

Is the floor of the cabinet cleaned of dirt, wire clipping etc.?

(a)

Is the plinth and earth surrounding it firm?

(b)

Is the shell rigid on the plinth? Are the foundation bolts

tight?

5.

Can the locks be operated satisfactorily?

6.

Are the CT boxes fixed firmly to the frame? Are the fixing screws tight?

7.

Is the jumper field tidy? is there any unnecessarily long jumper wire? if so, has it replaced by a shorter jumper wire?

8.

Is the position of spare pairs according to records ?(to be checked once in a year)

9.

Are the wire gauges, and /or dust filters in their proper places is are they clean?

10.

Are dust, cobwebs etc. removed from the cabinet

the ventilation pockets ?

Effective steps are to be taken to rectify the faults noted in the inspection report. 1.14

FOOT PATROL

Regular foot patrolling of cable routes are to be carried out by cable maintenance party. They will keep watch on the cable routes, the indicators and the condition of Dps. The foot patrolling will effectively reduce the damages to the cables caused by the digging operation carried out by other agencies. It is desirable that foot patrol is so organized with existing staff that all junctions & primary cable are covered within a week and other cables in a fortnight. 1.15

DIAL BEFORE YOU DIG SERVICE.

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Underground Cable A few non metered telephone services may be provided so that other public utilities such as electricity, water supply organization, drainage and sewage maintenance wing etc. may utilize these services for intimating in advance their digging operations to the cable maintenance section of the concerned localities. 1.16

CO- ORDINATION WITH OTHER ORGANISATIONS.

Periodical meeting should be arranged with authorities of other public utility services in order to ascertain the work proposed to be under taken by different organizations.

CABLE RECORDS GENERAL DESCRIPTION After the cable laying operations are completed & cables are commissioned into service, all the relevant drawings should be prepared and incorporated in the existing drawings. While preparing the drawing, it is preferable to have certain fixed reference points which normally do not alter their positions without the knowledge of drawing section such fixed points are cabinets, pillars, pressure testing points pillars, Route and Joint indicators , DPs etc. The following diagrams are to be prepared a) b) c) d) e) f) g) h)

Route Index diagrams of cables. Offset drawings of all the joints mentioned in route Index diagram with reference to fixed reference points. For junction cables offset drawing of loading coil location & joints. Offset drawing of main leading in joint outside the exchange Pillar and cabinet face panel drawing showing the allocations of pairs. Offset drawings of the cabinet & pillar joints. For distribution cables, offset drawings of straight joints, pot head joints and LI cable joint of building. The area maps, block maps, pillar maps & route index cable maps for entire exchange area should also be updated and incorporated.

In addition to this relevant cards should be prepared entering all the details as required in cards. The important cards are MDF cards, cabinet pillar cards and DP cards. EXTERNAL PLANT RECORDS:(a)

Numbering schemes of cabinet / pillar / DP

i) Cabinets are given two digits number in the series 01 to 20 Pillars are also given two digits numbers but in the series 21 to 99 . It is not expected that the number of cabinets in one exchange area will exceeds 20 or pillars exceeds 79. Once the number is given to the Pillar it must not be changed unless it is transferred to another exchange area. ii) DPs are given four digit number. The first two digits corresponds to the number of pillar from which the DP is fed. In case of Inner zone DP the first two digit will be 00,. The last two digits denote the serial number of DP with the pillar area or the inner zone. RTTC, NAGPUR

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Underground Cable (b)

Terminal code for exchange MDF

The verticals are numbered serially commencing from non growing end in two digit 01 to 99 . the fuse strips are numbered serially in single digit 0 to 9 . The terminal tags on fuse strip are numbered serially in two digit series 01 to 40, Thus 148/06 refers to terminal 6 of 8th fuse strip on vertical 14. (c)

Terminal code for cabinets/pillars.

The coding of terminal in the cabinet/pillar is fully specified by the number of cabinet/pillar and the position of CT box. In order to specify the position of a CT box in cabinet/pillar, each horizontal row on the panel in assigned a single letter code A,B, C,D,E,F,G etc. commencing from topmost row. Each horizontal row is divided into section corresponding to 50 pairs each. The 300, 500 & 700 pair shells will have two section per row and 1000 and 1400 shells will have 4 section per row. The sections are numbered 1,2,3,4 commencing from left hand side. 50 pair CT box will occupy one section and its position in particular row is specified by the number assigned to that section A 100 pr CT box occupy two section & its position in the row is specified by the number assigned to Left Hand section. Thus 06 C2/38 refer terminal 38 of 50 pr CT box occupying second section in third row of cabinet 06. (d)

Terminal code for DPs

The position of a terminal on DP is fully specified by the DP number and the terminal number on DP. Thus 4306/05 refer terminal number 5 of DP 06 controlled by pillar 43. If DP consist of distribution frame work as in case of large building then vertical number is denoted by single digit (0-9) & terminal number is denoted in two digit ( 00 to 99), Thus 36th tag no the 2nd vertical of DP 4813 will be coded as 4813/236. A detailed example is shown at the end of the chapter for scientific numbering of DPs properly depending on the pars in CT BOX termination. (e)

Coding of primary ,secondary & Distribution cables.

Primary cable is given a single letter code A,B,C,D........ etc. the letter I&O omitted, If there are more than 24 cables a two letter code for example AA, AB, AC,........etc. are used. For example C cable is 3rd primary cable & AB cable is 26th primary cable. Secondary cable is coded with the cabinet number followed by single letter A,B,C,D,......etc. for example 12 C is third secondary cable original from cabinet. 12. Distribution cable is coded with the pillar number followed by single letter A, B, C, D,.etc. for example 43 F is 6th distribution cable originated from pillar 43. (f)

Coding of Junction cable

Each exchange is assigned a letter preferable first letter of exchange name. For example C for city exchange P for park exchange. The junction cable code will consists of two letters denoting the exchanges at which the cable is terminated and digit denotes the serial number amongst the cable terminated between these exchanges. For example junction cable between city & park exchanges are coded as CP 1, CP2 CP3.....etc. (g)

Coding of cable pairs

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Underground Cable Cable pair are designated by the cable code followed by the pair number within that cable for example pair 86 of cable 50 A will be coded as 50A/86. CARDS ( shown at the end of chapter ) (a)

The DP Cards

DP cards shows the number, size type, location and how each terminal of DP is utilized, they also indicate the distant end terminal code corresponding to each terminal of the DP . One card is required for each 10 or 20 pair DP. For DPs larger than 20 pairs two or more cards have to be used. Terminal 1 to 10 details are prepared in the obverse &^ 11 to 20 in the reverse of DP card. These cards must be introduced soon after the scheme for changeover to cabinet and pillar area system is finalized & DPs are assigned numbers in the new series. there after the card must be kept updated by incorporating all additions and alternations effecting the particulars contained in the cards. (b)

Cabinet / pillar cards.

One set of cards is required for each cabinet/ pillar. the set contains one card for each 50 pr CT box fitted in cabinet /pillar. The following particulars are shown on each card. Number, size type of CT box , size of shell location of cabinet/pillar, circuit working on each terminal of CT box, terminal to which it is jumpered or strapped for setting up the circuit, the distant end terminal code corresponding to each terminal of the CT box and the code of cable pairs connected to the terminal. Obverse maintained terminal 1 to 50 of G box & Reverse is for terminal 51 to 100 . The same card can be used for cabinets as well as pillars. these cards must be filled in at the time of installation of each cabinet or pillar and subsequently addition or alteration effecting the entries must be incorporated in the corresponding cards. (c)

MDF CARDS

MDF cards contain following particulars. Distant end terminal code corresponding to each terminal on fuse strip, circuit number working on that terminal, address of the subscriber. One card is required for each fuse strip. entries for tag 1-10 are made on obverse & tag 11 to 20 on the reverse of the card. If junction cable pairs are terminated on fuse strip, the terminal code at the MDF of the other exchange is entered in column 2 . The name of other exchange is entered at the top of the card. In the last two column. Junction circuit number and the exchange between which it works respectively. For miscellaneous circuit subscriber address should be entered in the last column. The MDF cards must be introduced after the DPs are assigned number in the new series.

(d)

Subscriber Index Card.

The subscriber Index card is maintained to get the particulars for the termination’s of subs lines. the terminals particulars circuit wise can be easily ascertained from this card. There are two types of cards required for this purpose. One is for Direct exchange lines & other for non exchange lines. RTTC, NAGPUR

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Underground Cable These cards must be introduced along with DP & MDF cards. Non exchange line must be assigned suitable serial numbers for the purpose of identification and recording.

SUBSCRIBER INDEX CARD Subs NO 0

MDF F.S.

CABINET

PILLAR

D.P.

Term No E.side D.side No E.side D.side

1/3/4 06

06

B1/01

C1/51

47

B1/51

C2/12

No 4 741

Term 2

ADDRESS ABK Rao Station Rd

1 2 3 4 5 6 7 8 9

D.P. INDEX CARD D.P. NO.

TYPE & SIZE

NO OF PAIRS CONNECTED TO PILLAR

4700

Krone – 10 pair

10

Market Entrance

4701

Krone – 20 pair

20

Market inside

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LOCATION OF THE D.P.

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05

04

03

02

01

Terms No

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1/3/2

Term PT

06

Term

C1

06

CT Box Termim

Dist End Term code Locally jumpered to

64300

Circuit No.

0647

Pillar No.

C1/1

5

Layer

Details of cable out

TyPE & SIZE : B100

CT box no. C1

16

C1

1

8

16

C1

6

No.Pair BoxCT nationTerm CodeCable Layer No.Pair BoxCT Termination

Details of cable in

Exchange :: 64

Term CodeCable

Dist end Term code

Location : Junction of Station Road & Raja chowk

Cabinet No. 06 Size of Shell 2000 pairs

Cabinet card

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05

04

03

02

01

Terms No

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06C1

Term PT

06

Term

C1

06

CT Box Termim

Dist End Term code Locally jumpered to

64300

Circuit No.

4705

Pillar No.

1

11

Layer

Details of cable out

TyPE & SIZE : A100

CT box no. A1

16

C1

1

16

16

C1

6

No.Pair BoxCT nationTerm CodeCable Layer No.Pair BoxCT nationTerm

Details of cable in

Exchange :: 64

Term CodeCable

Dist end Term code

Location : Junction of Station Road & Hanuman Street

Pillar No. 47 Size of Shell 1000 pairs

Pillar card

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Underground Cable AN EXAMPLE FOR NUMBERING OF D.P. IN A PILLAR AREA It can be used to install 10 CT Boxes of 100 pairs each. Each CT Box is having 10 modules. On each module 10 pairs can be terminated. If the Pillar No. is 47 the 1st two digits of All the D.P.s connected to the Pillar will be 47. If the DP pairs are terminated in A1 CT Box then the 3rd digit is fixed accordingly. PILLAR NO. 47 ( 1000 PAIRS KRONE TYPE) LOCATED AT MARKET PLACE A2

A1

Primary cable pairs

B1

B2

C1

C2

D1

D2

E1

E2

CT BOX LOCATION

1ST THREE DIGITS OF D.P.

A1 C1 E1 A2 C2 E2

470 471 472 473 474 475

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Distributi on cable pairs

PAIRS IN A1 CT BOX A1 1-10 A1 11-20 A1 21-30 A1 31-40 A1 41-50 A1 51-60 A1 61-70 A1 71-80 A1 81-90 A1 91-100

DP NO. 4700 4701 4702 4703 4704 4705 4706 4707 4708 4709

So for a DP connected to A1 CT Box of Pillar 47 at pairs A1 / 91-100 the DP NO is 4709

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CHAPTER VII COMPUTERISATION OF CABLE RECORDS INTRODUCTION Objective of cable records management system (CRMS) i.e. digitization of cable records & drawings , to facilitate BSNL 1) Design & maintain a communication network model. 2) To analyze the network model in different ways, distribute information as needed & interact with variety of enterprise systems. 3) To manage the planning , design , construction , operation & maintenance of cable network. 4) Development of centralized telecom database. DISADVANTAGES OF CABLE RECORDS IN PAPER FORM 1) Land base map available in form of municipal development plans , not to scale. 2) Deterioration of drawings due to frequent handling. 3) Loss of data & accuracy every time the drawing is redrawn. 4) Delay in updating. 5) High cost of updating. 6) Non availability of simultaneous access. 7) Delay in meeting the needs of other departments. CRMS IMPLEMENTATION 1) Generation of updated land base map for entire operational area using high resolution satellite data. 2) Survey of precise locations of telecom assets viz pillars, DPs , manholes, cables , joints etc. 3) Digitization the map & telecom assets for entire area using CRMS software as shown in figure. 4) Interface to fault repair system. 5) Comprehensive training for CRMS software &network configuration. Once the data has been brought to current state it needs to be maintained in up to date condition. Competent technical staff has to be identified on the server side & client side who will shoulder the responsibility of maintaining the system. For data security reasons, the client side has not been given the rights to directly update the database, but he is responsible to report any changes on field. The client software has been provided with which the official can draw the changes on the map, add comments , notes & report changes in the data. The system administrator at the server end can view these suggestions , validate them & post the same to the server. RTTC, NAGPUR

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BENEFITS OF CRMS 1) Complete telecom network information available at centralized data base to be shared across enterprise. 2) Updated information about exchange details , MDF details, primary & secondary network details now available centrally. 3) Module for generating customized reports for CKM as per requirement, provides structured information on telecom assets. This assists BSNL for organized monitoring & planning of telecom network to address future growth , day to day maintenance & operations. 4) The system has been developed to handle the various facets of telecom asset management like copper, fiber, wireless etc. The solution has been designed to plan , monitor & maintain all telecom networks. 5) The complete lifecycle of the telecom, assets can now be managed in a singular system. 6) Upgrading of existing network is simple & can be done on regular basis for example inventory required for replacement of paper core cable to jelly filled cable can be calculated with in no time with minimum approximations. 7) The integration with the existing fault repair system (FRS) avoids any duplication of data , also helps keep the network loading & subscriber status on line & up to date. 8) Estimates for new installations/expansion can be generated in short span of time. 9) To spot exact location of fault is much easier after using testing equipments as every detail needed by the official is available on one map. 10) Provision to carry out DB loss analysis for telecom network. 11) Smart tools to locate telecom assets based on parameters like feature ID, feature name etc.

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CHAPTER – VIII RTTC, NAGPUR

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FAULT REPAIR SERVICE, TRAI PARAMETERS Objective of the Lesson :: The necessity of having an interface with customers for the redress of their problems in a short period of time is stressed in introducing the topics of Manual FRS and computerized FRS. Also stress is done in the newly introduced DOTSOFT FRS system and the steps involved in dealing with all the types of FRS systems are dealt to have a better understanding of the customer needs. *

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MANUAL FAULT REPAIR SERVICE :: MAINTENANCE OF THE LINE AND WIRES AND SUBSCRIBER’S APPARATUS -FAULT CONTROL 1.

The maintenance of Line and Wires and subscriber’s apparatus consists of two parts.

i)

Clearance of faults reported by Subscriber’s on day to day basis.

ii) Preventive maintenance of the lines to reduce incidents of faults and thereby the complaints. In this lecture I shall deal with the fault Repair Service procedure and the method and control over the clearance of faults reported by the subscribers. 2.

Fault Repair Service.

2.1 Faults in the local telephone system are normally observed and reported by the subscribers or by Trunk Exchanges. Local assistance positions, auto exchanges, test positions and petrol maintenance sections etc. Subscriber may also make oral or written complaints to Telephone Administration at its various levels. All these complaints should ultimately reach the proper test point for localization and fault clearance in the shortest possible time. Proper maintenance of statistics of faults and proportion of certain statements are also essential for proper control and direction of maintenance efforts. 2.2

Fault recording :-

A fault reported on fault repairing service (complaints, ‘198’) positions shall be noted in a fault docket. The nature of faults may not often be clear from the subscriber’s version of their difficulties. While receiving information the operator should be extremely polite. After recording the fault, docket number should be given to the subscribers. 2.3 Docket Dispatch position :All dockets except enquiry dockets will be booked with the respective exchange over the order wire lines and docket numbers exchanged. The inquiry dockets will be handed over to the Monitor who will investigate the progress of clearance of the fault and inform the subscribers suitable. When the telephone number reported against appear in the list of telephone numbers disconnected for non-payment of bills as per the daily check sheet, maintained by the Test Desk monitors at the respective exchanges, the reporting subscribers should be told that the telephone has been disconcerted temporarily. In case the subscriber insists on the reason for the disconnection and if the caller is subscriber himself he may be given the details about the disconnection due to non-payment. RTTC, NAGPUR

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Underground Cable

2.4

Movement of dockets and information :-

i) Tally position should be located adjacent to the docket Receiver/FRS position. the tally position should maintain a tally sheet shown in annexure, Every telephone number reported against the particular period of occurrence. In the case of repeated reports about the same telephone number, action should be taken as follows:ii) If a clearance report has not been indicated in the tally sheet for the fault reported earlier, the docket shall be endorsed as duplicate and the telephone number noted in the tally sheet shall be encircled. The duplicate docket should be sent to the Monitor who will investigate the progress of clearance and attach the duplicate docket to the fault Card along with the earlier docket . iii) If an earlier fault on a particular number has been indicated as cleared in the tally sheet, the new docket shall be endorsed as a ‘Repeat’ fault and routed in the normal way. All dockets except duplicate ones will be passed on to the ‘Fault Card ‘ Position. 2.5

Fault Card Position

i) At this position , a separate fault card is maintained for each telephone. ii) On receipt of a fault dock, the operator at the fault Card position should remove the relevant fault card and make an entry of the date and time of fault reported.

2.6

iii) The docket with the Fault card clipped to it should then be forwarded testing’ position. Initial Testing Position

to

the

‘Initial

i) Initial testing for localization of faults as prescribed in the relevant Engineering Instructions will be done on these positions. ii) The result of the tests should be indicated on the docket in the appropriate grid and the dockets passed on to the appropriated Directing position. 2.7

Directing Position :

Depending upon the procedure being followed at a particular station staff at the directing position shall make over the fault to the lineman who speak regularly to these positions or alternatively to the sub Fault control Centers, the docket should be forwarded to the Testing Position. 2.8

Testing Position :

The Lineman shall get access to these positions by dialing a code (say 192) for testing the faulty telephones. The operator on the position will give the prescribed tests to the line staff. After the faults have been removed, he should speak to the subscribers to ensure that the telephone has been set right to the latter’s satisfaction. A suitable entry should be made on the docket. The operator should also ascertain the actual fault observed and rectified and enter those detail in the docket. Where the Lineman in unable to rectify the fault to the satisfaction of the subscriber, the relevant docket will be returned to the Directing position after suitable endorsement. The directing RTTC, NAGPUR Page 116 of 185

Underground Cable position operator should report the matter to the sectional JE for further action. After clearance, the docket will be sent to the Tally position. At the tally position the telephone numbers which have been rectified are scored off in the tally sheet. The docket is then dispatch to the statistics position 2.9

Statistics

All the dockets pertaining to the previous day will be analyzed here for preparation of the various statements prescribed by the department. 2.10 There might be variations to the above procedure depending upon the local conditions, for example i) At smaller exchange systems, the work of booking, directing, tally etc. positions shall be the same positions. ii) At stations where ‘198’ is not centralized, like in Delhi, the complaint will be received by the exchange test desk directly and accordingly fault receiving positions shall be the FAS positions. iii) In systems where are the fault card is not attached to the fault docket, there will be an address positions where the subscriber’s address and cable pair details end sub. section shall be available in the form of a register. These details shall be noted on the fault docket before it is sent to directing position. 3.

Lineman to go first to Subs. premises

3.1 Different procedures are followed by the line staff for removal of outdoor faults. In many exchanges the line staff first give the test from the junction box; later on they inspect the line and then check the subscribers offices. Analysis of faults in exchanges reveal that the majority of outdoor faults are in subscriber’s premises or on overhead lines and least on underground cables. 3.2 The following procedure should be followed in dealing with outdoor faults. the attention of all line-staff be drawn to theses interactions. i)

The lineman should first proceed for inspection at the subscriber’s office.

ii) On no fault being found at the subscribers premises he should proceed for inspection of the overhead line, from the subscriber’s premises to the junction box starting with loop. iii) Test should be given from the junction box only on no fault subscriber’s office and on the overhead line.

being found at the

iv) In case the subscriber’s premises are closed test should be given from an outside point easily accessible, to make sure that there is no fault on the block wiring, overhead line section and underground cable pair etc. 3.3 Line case of cable break downs, there would be no need to follow this procedure. During and after cable rearrangement work, incidence of faults in cables due to rearrangement should be kept in view. 4.

No major repairs at Subs. premises :

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Underground Cable The lineman should not be allowed to repair the telephone instrument at the subscriber’s premises accept for very minor faults like tightening of loose connections. replacement of transmitters, receivers, oiling of dial etc. Each line man should be given impress telephone. Whenever an instrument needs attention, the same should be replaced by line man with his imparts telephone . the Faulty telephone shall be brought be the lineman to the Exchange Repair shop and got replaced by good one for his further similar use. 5.

Control over fault clearance - some refinements :

5.1 Good operators at complaints positions should be manned by experienced operators who should be able to talk to the subscribers intelligently and access and note down the actual complaint of the subscribers. Care of course case has to be maintained that this “Conversation” with the subscriber does not cause delay in answering on this service. Therefore a balance has to be maintained between electing information from the subscribers about the actual nature of his trouble and the time taken to answer the complaints. 5.2

Special attention to Right on Tent (ROT) cases :-

Another important aspects will be such of those complaints which are tested, right on test (ROT). The general tendency on the part of testing organization is to close these case immediately after testing. It will be noted that many of these complaints shall reappear if no action is taken at the first booking stage. There are man faults which are transient in nature loose line, loose card connections, dry joints in the line, rosette, high resistance transmitter etc. Similarly there might be frequent held ups in indoor equipment. Arrangement should be made that such of these dockets which are tested as “right on test” should be segregated and each of these telephone connections is rung back by Junior supervisor or an experienced operator who should talk to the subscriber and should ascertain his problem and then take necessary action. special attention shelled be paid on such of these ROT cases which are booked by the user of the telephone himself. 5.3 CHECK OF LINE RESISTANCE AS AN IMPORTANT INDICATION OF LINE CONDITION. While clearing a fault on a telephone connection of otherwise while getting it tested with the test desk the resistance of the telephone connection shall measured by the test desk with the transmitter (with and without the dial being of normal). special care should be taken be Lineman to attend to such of the cases where the line resistance is higher than the normal expectation depending upon the distance of the area from the Exchange. This action will greatly reduce the number of “fault not found” (F. N. F.) “nothing found wrong” (N. F. W.) cases because such telephone connection will otherwise be noisy, will have disconnection during dialing and conversion etc. 5.4 Action on repeat faults :- There are many times fault of complicated nature or otherwise of a transient nature which defy clearance in the normal course of our line man working, In these cases the fault is tested fight on test or nothing found wrong etc. there might be cases, for example where the line is not properly maintained and it develops contact or low insulation to earth etc. In these cases the lineman somehow is able to get the dockets cleared, but actually the fault does not get removed and the subscriber has to complying repeatedly. It is therefore necessary to watch such cases and to take special corrective action. While the subscriber complaints are being noted in the subscriber’s history cards. The official doing this job should not if there have been two earlier complaints on the telephone connection within a period of proceeding 30 days. The list of repeat faults should be prepared by the Traffic Section. RTTC, NAGPUR

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Underground Cable J.E. Section wise and made over to the respective Jest and the Switch room and M.D.F. staff in immediate through check of the line and internal equipment. 5.5

Control over the duration of faults.

The Traffic Section of the exchange should be asked to make a check over the pending dockets at least thrice a day say 110 Clock and 30 clock and at the closing of the Day. this check should consists of :i) Detection of missing dockets i.e. to see that dockets are physically available in the Traffic Section for all the faults pending as per the tally sheet and ii) To make a list of all the cases where the fault rectification has got delayed or is likely to get deleted. These lists should be made over to the officer in charge for his perusal and action.

COMPUTERISED FAULT CONTROL SYSTEM 1.0

INTRODUCTION

1.1 The Telephone Engineers are facing a lot of difficulties in the management of telephone complaints in the manual fault control system. At present the amount of faults to be handled are quite high. the fault booking operator has to refer to a number of manual records, lime list of telephones disconnected for non-payment, telephones under safe custody, telephones under shift, telephone complaints already booked etc, This process takes time. Therefore, as a short cut the operator simply books a complaint as and when a subscriber lands on complaint booking position. This results in repeat booking of faults, booking of those numbers which are disconnected for nonpayment or which are under shift etc. Further, in case the subscriber wants to know the position of his pending complaint from the complaint booking position, the operator is not able to reply him properly as no ready record is available with him. On account of this the subscriber gets a feeling that his complaint is not being attended to properly. 1.2 After booking of a complaint, with the existing manual system, the movement of the fault docket to address position with testing position, directing position for making over the fault to the concerned section etc. is very slow. thus it becomes difficult to rectify the faults as per standards prescribed by the department. The manager i.e. A.E. (FRS) or D.E. has to spend a lot of time to ensure quick movement of the fault dockets to different stages. 1.3 Once the complaints have been attended to, suitable entry has to be made in the respective subscriber cards. then detailed analysis of all the complaints booked is required by the management on daily/monthly basis for taking suitable. It is generally received late (after about a month or so) and thus is not able to act as an effective tool for the proper analysis and control of various tapes of faults. 1.4 Another problem observed in this manual fault repair system is in regard to the maintenance of up to date MDF and subscriber records. In an expanding network, like ours, these changes are very frequent and enormous. A number of records such as MDF termination, DP records, fault cards, subscriber address records etc. have to be corrected for each change. RTTC, NAGPUR

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Underground Cable 1.5 In the modern times the Telecom Services have become very important. The subscriber not only desire reliable service but also desire quick response to their complaints. In case of delay they want proper reason. The department has to give rebate in rents in case the fault penises for more than 7 days. It is very difficult to diced such cases in manual system. 1.6 To overcome these inherent limitations and the drawbacks of the manual procedure, the computerization of fault control system has become necessary. this is a must for a large network where in one building itself 20,000 to 40,000 telephone lines are installed. 1.7 This handout describes the general features of the computerized fault control system and the advantages of adopting it in our telecom network. 2.0

OBJECTIVE OF THE COMPUTERISED FAULT CONTROL SYSTEM

2.1 A computer system offers large facilities and therefore, the objective of computerization of fault control system is not only to overcome the limitations of the manual fault control system but also to help the management in the effective monitoring of the fault system. Thus the broad objectives of this system can be stated as :a. To provide computerized record of telephone complaints and other related activities for fault clearance. b. to help the field executive in the effective monitoring of the fault performance of any exchange on day to day basis. c. To help the management in working out the long term strategy for the improvement of the telephone system on the basis of various up to date reports made available by this system as and when required. to get these large variety of reports in the manual system is not only difficult but also time consuming. Most of the time, these reports are received so late that the real purpose is defeated. 3.0

REQUIREMENTS OF COMPUTERISED FAULT CONTROL

SYSTEM.

3.1 The computerization of fault repair service is required for all types of exchanges i.e. stronger, crossbar, NEC, OKI, E-10B Fetex etc. It is felt that in case of electronic exchanges it is better not to used the call processor for this purpose as it is going to reduce the call processing capacity of the processor. Therefore, separate computer with multi terminals will depend upon the capacity of the telephone system to be computerized. 3.2 The computerized fault control system should have fault recording on the basis of “ON-LINE WORKING”. The existing technical arrangement at the complaint position., initial testing position and final testing position will continue . In addition each of these positions will be provided with one computer terminal, Video display Unit and a Key Board. The computer terminals will also be required for supervisor, sub-fault control centers etc. the printer can be provided with different terminals depending upon the requirements. The number of terminals required will bray with the size of the unit. However, the terminals are required at each of the following positions :i. Complaint booking position ii. Initial Testing position iii. Final Testing position iv Supervisor position RTTC, NAGPUR

viii. ix. x.

A.E. (FRS) S.D.Os. A.E. (Cables) xi. DE Indoor/Outdoor Page 120 of 185

Underground Cable v. switch room xii. vi. M.D.F. vii. Sub-fault control Centers 4.0 DATA INPUT TO COMPUTER

Computer center

The complete subscriber information referred in manual fault control system is required to be fed to the computer in a suitable manner before the system can be made operation. Brief details of the data required for the system are. a. directory number of the subscriber, name and address of the subscriber, facilities provided to the subscriber e.g. plug and socket, long cord, plan 103, departmental wiring or subscriber’s own internal wiring etc. b.

Category of telephone e.g. STD/STD barred, CCB, spare number etc.

c. Type of subscriber e.g. VIP, service connection, temporary connection, Primary number of a PABX/PBX group etc. d.

MDF termination details

e.

Cabinet and Pillar termination details

f.

DP termination details

g. In case of non-exchange line suitable termination details including type of line e.g. private wire, TP/Ticker/speech/data circuit etc. 4.2 The data is entered in a set manner so that all the relevant files are updated automatically. the entry of the new data or corrections of the data has to be at single entry point to ensure guarding against any manipulation of the date before recording in the files. This is important for the integrity and purity of data for all times. further, the day to day information in regard to fail booking and fault attending process is entered in such a manner that the various files are updated immediately so that the data can be interpreted in any manner required for the fault recording and analysis purpose.

5.0 SALIENT FEATURES 5.1 The system is designed for “ON-LINE FAULT ENTRY” working and to give analysis of the various types of faults whenever rewired. Therefore the input data to the system must be arranged in the various filed. Some of these files are 5.1.1 Status of Telephone numbers :- The list of working telephone numbers as well as spare numbers are available in this file. the list of working telephones in further categorized into telephone in the serviced, kept under safe custody, under shift or disconnected due to non-payment. the detailed information for each of these categories can also be given e.g. in case of telephone disconnected for non-payment, the date of disconnection, amount for which disconnected, period of the bill etc. can be provide. 5.1.2

Sub-fault control wise Data :- The details of working telephone can be affianced in terms of pillar, DP, sub-fault control center, SDO and division wise. This will enable to transfer the RTTC, NAGPUR Page 121 of 185

Underground Cable fault to the concerned sub-control center. Each SDO can have access to the telephone under his jurisdiction and can take steps for monitoring/controlling of faults of his area. D.E. can monitor his whole division. 5.1.3 complaint Data :- Each complaint booked can be given individual complaint number, date and time of booking. It is possible to feed the details of complaint booked along with the nature of fault reported. similarly the type of fault observed e.g. Indoor, Outdoor, MDF, Cable etc. along with the date and time of clearance of fault can be entered in this system. 5.1.4 Holiday Data :- It has a list of dates on which Sundays as telegraph holidays fall during the calendar yea for granting rental rebate in case of files are created, fresh data can be entered. This will be required to calculate the duration of fault and later on will be helpful for granting rental rebate in case of fault continuing for 7 or more than 7 days. 5.2 After all the files are created, fresh data can be entered in such a manner that all the files are suitably updated. It is possible to make changes, take listing, generated reports and maintain files. 5.3 Password Facility :- To safeguard against the un-authorized modification of data as well as unauthorized clearance of complaint, the facility of Password is incorporated in the system. also various terminals can be given certain categories on which only pre-defined facilities of operation can be provided e.g. complaint booking operator can only book the complaint, he can not have access to any other information. Initial testing operator can have access to complaints pending for initial testing only for taking suitable action accordingly. He can not clear the fault or can not have access for the modification of the data. 6.0

FAULT CONTROLS PROCESS

6.1 The steps involved in the computerized fault repair service are similar to the manual fault repair service except the process is comparatively simplified in regard to movement of dockets, record of dockets, clearance particulars, status of the complaint etc. The process of fault control in this system in described briefly in there following paragraphs. 6.2

Complaint booking position :-

6.2.1 In the “ON-LINE FAULT BOOKING” System there is a display on the monitor screen of complaint booking position indicating that the system is reedy for booking of a complaint. When the subscriber dials the complaint number, the operator answers in a manner similar to that of manual system. Instead of booking the complaint on the docket, the operator enters the telephone number in the computer system through the key board. The system before registering the complaint, automatically checks for the following possibilities :i. Whether the complaint is already pending If some the complaint number, date and time of booking, the nature of fault and action taken so far is displayed on the screen. The operator can immediately tell the complainant the status of his complaint. He can even give all the details of initial booking and action taken so far. ii. Whether the number is disconnected due to non-payment. In this case, the details of pending hill i.e. amount, period etc. is displayed on the screen and the complainant be given these details.

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Underground Cable iii. Whether the number is in safe custody. In this case if proper entries have been made, the subscribers can be told about the duration of safe custody along with the date of keeping it under safe custody. iv. Whether the number is under shift. The complainant can be told accordingly by the operator. v. Whether the number is spare. the screen will display the number as spare and the complaint can be informed accordingly. 6.2.2 If the telephone number does not fall into any of the above categories, it means a fresh complaint in s being booked by the subscriber. The system accepts the number and then displays the subscriber name, address, other facilities provided on this telephone , DP and MDF termination details etc. on the screen. The system asks for the nature of complaint and the calling number. The operator gets this information from the complainant and enters into the computer. Generally the nature of fault is entered in the form of a prescribed code e.g. 1 for dead, 2 for wrong number on outgoing call, 17 for no dial tone etc. when all the information required for booking of the complaint are entered, the docket number is displayed on the screen. This docket number is given to the subscriber, a sample of fault docket is given at Annexure-I. Then by pressing a suitable key of the key board, this complaint is recorded and screen is cleared for the booking of next complaint. the booked complaint is automatically transferred to initial test position. 6.2.3 The computerized arrangement thus avoids the repeater false booking which is a great irritant both to the public and allotted and this compiling will over-ride all other pending complaints for display at the initial testing position and all throughout the processing of this complaint. 6.3

Initial testing :-

6.3.1 The operator at this position can have access to the system through the password allotted to him. On pressing the suitable code any pending complaint for initial test is displayed on the screen. the operator will test the number through the desk circuit i.e. as being done in manual fault control system. the nature of fault found on testing is entered into the computer system. On completion of these details, the complaint is automatically transferred to the concerned unit e.g. to sub-fault control section on the basis of DP detail provided in the record if the fault is in the outdoor plant or to the switch room if the fault is in the exchange. then on the screen next complaint pending for initial testing is displayed. 6.4

Sub-fault control centers :-

6.4.1 The respective sub-fault control centers can have access to the pending faults in their section through the monitor provided for them. The details of each compliment can be noted down and made over to the concerned lineman. the name of the lineman to whom the fault has been made can be entered in the computer. 6.4.2 If required a print out of the complaint can be taken by the sub-fault control center and the same can be made over to the lineman. Generally this print out is avoided to reduce the unnecessary paper work. 6.4.3 The fault is attended by the respective unit i.e. sub-fault control center or switch room or MDF. After the fault is cleared, the concerned unit can feed the clearance details into the system. these details along with time of entry will be accepted by the system but the fault will not be cleared. The clearance of fault docket is entrusted with the final testing position only. RTTC, NAGPUR Page 123 of 185

Underground Cable

6.5

Final testing position :-

6.5.1 The lineman can reach this position in a manner similar to that of the conventional fault repair service. On giving the docket number and/or telephone number, the final testing position operator can get the display of that compliant on his VDU terminal. The operator then tests number through the normal testing chain. If the number if found OK and the subscriber is satisfied, the operator enters the clearance details as told by the lineman. The cleared docket is transferred to the record file for analysis. 6.5.2 In case the clearance is entered by the concerned sub-fault control center or switch room or MDF, the final testing position operator gets the display of this complaint on his screen along with the clearance detail entered by the concerned unit. the operator then tests the number and if found rectified gives signal for its clearance. the time and details of clearance of the fault is as per information entered by the concerned section. 6.5.3 In case the fault has not been cleared to the subscribers satisfaction, the fault is again displayed to concerned SFC/ Switch room /MDF with the remarks of the final testing position operator. In this way only properly cleared faults can be transferred to the record file. all the remaining faults appear on the screen as pending. 6.6 VDU TERMINALS AT THE OTHER LOCATION. 6.6.1 The VDU terminals provided to the AE (FRS), SDOP etc. can be utilized by them for monitoring and controlling the faults. They can know the status of faults pending, faults cleared, nature of fault observed etc. the officer need not physically move to the fault repair service for actual screening of dockets as required in a manual system. Depending upon the alertness and actives of the controlling officer the faults can be got effectively cleared without any undue loss of time. This system enables the management to monitor the status of complaints at any instant of time and accordingly initiate suitable steps for improvement of the telecom services. 7.0

COMPARISON OF COMPUTERSED SYSTEM WITH MANUAL SYSTEM :-

7.1 In case of manual fault repair service, the various stages through which complaint docket travels are - complaint booking position, tally position, address/fault card position and statistics unit. These position, directory position, final testing position and static unit. These positions may be individual or some of them may be merged but all these steps have to be followed for effective working of fault repair service. However in computerized fault repair service, some of these functions are done automatically. In this system at the time of booking of complaint itself the work of tally position is done, As soon as the complaint is registered, the work of address/fault card position is cone automatically and the complaint is transferred to initial testing position. Thus the three functions (booking, tallying and address) get completed as soon as a complaint is booked. the initial testing position tests the nature of fault and then fault is automatically transferred to the concerned section there is no need of directing position the final testing position is required in this case also. However, separate statistical unit is not required for the record of dockets and preparation of various report s as is required in manual system. The details of cleared fault is transferred to the system memory and any type of report can be obtained by suitable code by the various controlling officers from their terminals. this is shown in a tabular form at Annexure-2 RTTC, NAGPUR

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Underground Cable 7.2 Thus the delay in the movement of docket from one position to another is avoided in the computerized system. further lot of time is saved in this method as there is no need to enter the details of the DP, Subs, address etc. on the docket as it is done automatically. similarly the manual updating of the subscriber card is not required as this job is done by the computer. No staff is required for the maintenance of the dockets and for the preparation of various statements desired by the administration. All these statements can be obtained from the computer as and when desired. 8.0

MANAGEMENT INFORMATION GENERATION :-

8.1 In the manual fault control system, a separate statistics unit is responsible for the record of the dockets after the fault has been attended to and for the preparation of various statements required by the management. theses statements are not readily available as lot of manual work is involved in the analyses of these dockets and preparation of various statements. However these inflammations are readily available in the computerized system. In fact large vanity of reports can be obtained from this system without any delay. Thus this system enables the management in effective monitoring as well as control of faults. It also enables the management to work out the long term plans for improvement of Telecom services. 8.2

Some of the reports which can be obtained in this system are : a.

Details of complaints booked, pending faults, faults cleared with nature of faults, analysis of total faults booked etc. on daily basis. These statements can be for a lineman section, JOT section, SDO section or for the whole exchange as per the requirements.

b..

Dockets pending for initial testing/final testing at any instant of time.

c. List of telephones which recorded two or more than two faults during a particular period (monthly, fortnightly etc.) This statement can be obtained for lineman section, JOT section, SDO section or for the whole division. d. Analysis of total complaints booked in the month along with complete analysis of the various types of fault found e.g. MDF faults, switch room faults, outdoor faults, right on test, no fault found etc. These reports can give even details of various types of faults observed in each section e.g. in outdoor it can give details of lines disconnection cases, dry joint cases, DP tag token etc. The report can also give average number of faults/100 stations, total RM and average RM etc. e. Fault analysis reports can be obtained in the form of total complaints booked, complaints only, partial service, no service, faults/100 stations, % of total faults/complaints, faults cleared between 0-2 hours, 4-6 hours 1 t0 7 days etc. These reports can be taken on daily, weekly, fortnightly or monthly basis. f. 9.0

Details of cable faults .

ADVANTAGES OF COMPUTERISING THE FAULT CONTROL

SYSTEM

9.1 Thus it is observed that process of fault control gets significantly simplified by computerization. the field executives can now spend their time on proper planning and taking steps for improving the telecom network instead of spending time on crisis management. RTTC, NAGPUR Page 125 of 185

Underground Cable some of the important advantages which enable this system to rank far superior to manual fault control system are : a. It handles very huge data very efficiently with far greater accuracy and speed as compared to manual system. b. Flow of information from one position to another is almost instantaneous. c. Various reports are prepared accurately without any errors as and when desired by the management. d. Fault analysis by this method is very reliable and assessment of relative performance of different units is possible. also management is able to get the true picture of the system. e. the current status of any complaint booked can be retrieved and thus better customer relation is possible. f. Duplication of dockets are avoided and the statistics are more reliable. the report generating process is made very easy. g. computing details for granting rebate case for a telephone faulty for more than 7 days is made very easy. h. The information can be updated on line by different authorized units and hence always updated information’s can be made available. 9.2 In this system, it is possible to indicate cable breakdown and then make over the information to AE ( Cables). All the telephones affected by cable breakdown cab be given one docket number. then suitable monitoring of this fault and clearance of all the affected telephones can be pursued. 9.3 In case of large number of pending complaints at any position e.g. initial 1testing, final testing or any of the field units, suitable automatic alarm condition can be given to the supervisor or AE ( FRS) for initiating proper action. 9.4

THE PAPER WORK IS ALMOST COMPLETELY ELIMINATED. THERE IS NO NEED TO PREPARE COMPLAINT DP MDF/CABLE RECORDS. ALL THESE INFORMATION’S ARE AVAILABLE IN THE COMPUTER AND AT SUITABLE INTERVALS PRINT OUT CAN BE TAKEN. DOCKET, PREPARE

ON-LINE COMPLAINT BOOKING AND COMPLETION RTTC, NAGPUR

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Underground Cable

FLOW DIAGRAM OF THE MODULE :

SFCSWRM COMPLAI NT BOOKING

INITIA L TEST

FINAL TEST

SUPERVISOR CLEARANCE

601. D D

SFC-MDF

CLOSURE OF FAULT

601. E D

SFCCABLE

601. F

SFC-OUTDOOR

Tables Used : 1. Working lines 2. Break_down_faults 3. Break_down_register 4. Complaint_history 5. Complaint_register 6. Frs_details 7. Jto _Code 8. Non_wkg_complaints 9. Opr_performance 10. Opr_performance_history 11. Staff_Code 12. Current_status_code 13. Location_code

(C100) (F3) (F4) (F8) (F9) (F22) (F30) (F38) (F39) (F40) (F44) (M27) (M43)

ROLES USED : 601A – FRS_BOOKING RTTC, NAGPUR

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Underground Cable 601B – FRS_INITIAL_TESTING 601C - FRS_JTO_OD 601D - FRS_JTO_CABLE 601E – FRS_JTO_SWRM 601F – FRS_JTO_MDF 601G –FRS_FINAL_TESTING 601H – FRS_SUPERVISOR_TESTING 601 J – FRS_DBA 601K – FRS_ENQUIRY Name of the Form :

ONCMPBKG ( Version 2.0 )

Status Flag :

F9.FLOW_CODE

Description : Complaint Phone Number is entered. Blank phone number is not accepted. Entered phone number is checked for existence in working lines. if the phone no is not present in the working lines table then, it is checked with non working complaints. If NOT present , a message is given 'This phone is under supervisor Inspection!'. And the details are displayed. If Phone No is present in working lines, and more than one phone is there then LOV of exchange is presented to choose the exchange. If only one phone, then status is verified with the current status code table. If the Phone is presently not working, a message is given accordingly but an option is given to book the complaint (as non working complaint) . When the complaint is already booked and pending clearance, a message is displayed depending on flow code about the status of clearance .It is also displayed that the complaint phone number falls in cable or equipment beak down. It is displayed as repeat fault if the complaint phone number is available in complaint history and repeats within 30days. All the details of the subscriber and subscriber line data are displayed. The details of the complaint like source of complaint, complaint nature , complaint code, VIP priority and phone no to which the clearance is to be intimated are entered. Previous faults history, subscriber door closed information, cable breakdowns if any are displayed in a separate page. Complaint is prevented from booking if the subscriber owns the instrument and the complaint is about an instrument fault. A record is inserted in the complaint register / nonworking complaints and the flow code is as follows. Sl No 1. 2. 3. 4. 5.

Routed to Initial test Supervisor verification – Not in Working Lines Supervisor verification – In Working Lines but Status not working Supervisor verification – Not in FRS Details Supervisor verification – In FRS Details but no JTO Code

Flow Code T V1 V2 V3 V4

A Complaint no is generated with exchange code with prefix followed by 5 digit sequence no and is given to the complaining subscriber for reference. INITIAL TEST : RTTC, NAGPUR

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Underground Cable

Name of the Form :

INITTEST.FMB ( Version 2.0 )

Status Flag :

F9.FLOW_CODE

ROLES USED :

FRS_INITIAL_TESTING

Description : Complaint dockets with same exchange code as prefix and same exchange type are routed to the initial test positions at MDF. The initial test operator has to choose the type of exchange like OCB, EWSD, E10B etc to test the complaint dockets presented in a queue in the order of VIP dockets and booking time seniority. If there are no dockets in the queue then a message is given as such. The initial test operator tests the phone line and equipment and enters the initial test fault code depending on the test result. The dockets are further routed to different fault control sections depending on the fault code entered. He should also enter the state of service available to the subscriber at present. If any complaint cannot be tested to reasons such as testing equipment not available, the initial tested can be suspended temporarily by choosing appropriate initial test fault code, the flow code is changed to ‘S’ and next in queue is available for testing. When the phone is found ‘RIGHT ON TEST’, the complaint is closed at initial test itself and the flow code is changed to ‘R’. Pillar to out door lineman and cable lineman relationship is available in pillar details table. The faults marked for outdoor/ cable with flow code ‘O’ or ‘C’ are then ordered automatically to corresponding lineman who are present for duty. Complaints cleared at initial test are now transferred to the complaint history table. Once the present complaint docket is cleared at initial test as above , next complaint docket is presented for initial testing from the queue. If all the dockets are tested and cleared as above, a message is given that ' No Complaints are pending for Initial Testing!!'.

Sl No 1. 2. 3. 4. 5. 6.

Routed to Suspended at initial test Subs Faults Control – Switch Room Subs Faults Control – MDF Supervisor verification – Cable Supervisor verification – Outdoor Cleared at initial test – Right On Test

Flow Code S I M C O R

SUSPENDED COMPLAINTS : RTTC, NAGPUR

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Underground Cable Name of the Form : Status Flag : ROLES USED : Description :

SUSPCMP.FMB ( Version 2.0 ) F9.FLOW_CODE FRS_INITIAL_TESTING

Similar to above Initial testing , except that the complaints dockets with flow code ‘S’ are presented to this module for initial testing. SFC INDOOR: Name of the Form : ID_ORDER.FMB ( Version 2.0 ) Status Flag : F9.FLOW_CODE ROLES USED : FRS_JTO_SWRM

Description : Complaint dockets with flow code ‘I’, which are cleared from the initial test with same exchange code as prefix and same exchange type are routed to the fault control in the switch room. The Switch Room JTO has to order the faults for clearance to the technicians who are on duty. Technician’s code is entered and the fault is ordered to him. A record is inserted into the lineman report table. If the clearance report is not entered the flow code remains as ’I’ , if cleared the flow code changes to ‘F’ . The fault can be reordered to another Technician if it not yet cleared. SFC MDF: Name of the Form :

MD_ORDER.FMB ( Version 2.0 )

Status Flag :

F9.FLOW_CODE

ROLES USED :

FRS_JTO_MDF

Description : Complaint dockets with flow code ‘M’, which are cleared from the initial test with same exchange code as prefix and same exchange type are routed to the fault control in the MDF. The MDF JTO has to order the faults for clearance to the technicians who are on duty. Technician’s code is entered and the fault is ordered to him. A record is inserted into the lineman report table. If the clearance report is not entered the flow code remains as ’M’ , if cleared the flow code changes to ‘F’ . The fault can be reordered to another Technician if it not yet cleared. ATTENDENCE : Name of the Form :

ATENDNCE.FMB ( Version 2.0 )

ROLES USED :

FRS_JTO_OD FRS_JTO_CABLE

Description :

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Underground Cable THE FORM IS USED FOR MARKING ATTENDANCE TO THE LINEMAN ATTENDING THE FAULTS IN THE CABLE / OUTDOOR JTO SECTIONS. SFC CABLE: ORDERING CABLE FAULTS TO CABLE LINEMAN Name of the Form :

CB_ORDER.FMB ( Version 2.0 )

Status Flag :

F9.FLOW_CODE

ROLES USED :

FRS_JTO_CABLE

Description : Complaint dockets with flow code ‘C’, which are cleared from the initial test with same exchange code as prefix and same exchange type are routed to the fault control in the Cable Section. The Cable JTO has to order the faults for clearance to the Cable Linemen who are on duty. If Cable Line man Code is posted on the Pillar Details and the Lineman is present for duty the faults of the same pillar are ordered automatically. Line man’s code is entered and the fault is ordered to him. A record is inserted into the lineman report table. If the clearance report is not entered the flow code remains as ’C’ , if cleared the flow code changes to ‘F’ . The fault can be reordered to another Cable Line man if it not yet cleared. SFC CABLE: REPORTING CLEARANCE BY CABLE LINEMAN Name of the Form :

CBREPORT.FMB ( Version 2.0 )

Status Flag :

F9.FLOW_CODE

ROLES USED :

FRS_JTO_CABLE

Description : Cable Lineman can report the clearance of fault here at SFC Cable. Clearance code , time of report, clearance of fault can be recorded. Flow code changes to ‘F’ .

SFC OUT DOOR : ORDERING FAULTS TO OUTDOOR LINEMAN Name of the Form :

LM_ORDER.FMB ( Version 2.0 )

Status Flag :

F9.FLOW_CODE

ROLES USED :

FRS_JTO_OD

Description : Complaint dockets with flow code ‘O’, which are cleared from the initial test with same exchange code as prefix and same exchange type are routed to the fault control in the Outdoor Section. The Outdoor JTO has to order the faults for clearance to the Outdoor Linemen who are on RTTC, NAGPUR

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Underground Cable duty. If Outdoor Line man Code is posted on the Pillar Details and the Lineman is present for duty the faults of the same pillar are ordered automatically. Line man’s code is entered and the fault is ordered to him. A record is inserted into the lineman report table. If the clearance report is not entered the flow code remains as ’O’ , if cleared the flow code changes to ‘F’ . The fault can be reordered to another Outdoor Line man if it not yet cleared. SFC OUT DOOR : REPORTING CLEARANCE BY OUTDOOR LINEMAN Name of the Form : Status Flag : ROLES USED :

LMREPORT.FMB ( Version 2.0 ) F9.FLOW_CODE FRS_JTO_OD

Description : Outdoor Lineman can report the clearance of fault here at SFC OD. Clearance code , time of report, clearance of fault can be recorded. Flow code changes to ‘F’ . FINAL TEST : Name of the Form : Status Flag : ROLES USED :

FNLTEST.FMB ( Version 2.0 ) F9.FLOW_CODE FRS_FINAL_TESTING

Description : Complaint dockets with flow code ‘F’, which are cleared from the SFCs with same exchange code as prefix and same exchange type are routed to the FINAL TEST. The faults cleared and reported to the SFC will appear through the button ‘Through Control’. The Outdoor Lineman can also report to the Final test position directly after clearance of fault without going to SFC. Such cases the FT operator has to enter the fault code and clearance of fault in addition to his test result and the clearance code. The FT Operator can also redirect to other SFC if fault repair is still pending. The flow code changes to ‘Y’ if the fault is cleared. SUPERVISOR CLEARANCE : Name of the Form : Status Flag : ROLES USED :

SUPTEST.FMB ( Version 2.0 ) F9.FLOW_CODE FRS_SUPERVISOR_TESTING

Description : Complaint dockets with flow code ‘Y’, which are cleared from the FINAL TEST with same exchange code as prefix and same exchange type are routed to the supervisor clearance. The supervisor can contact the complainant and ascertains the satisfactory repair. If satisfied the fault is then closed. A record is inserted in the complaint history table and is deleted from the complaint register.

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Underground Cable

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Underground Cable

TRAI PARAMETERS S.N. 1.

Parameters Response Time to the customer for assistance

Benchmarks (i) % age of calls answered (electronically) : within 20 seconds = 80%, within 40 seconds = 95%

(ii) % age of calls answered by operator(voice to voice): 2. 3

4

5

Time taken for refund of deposits after closures Fault incidences (No. of faults/100 subscribers /month) Fault repair by next working day

Call Completion Rate within a local network

Within 60 seconds = 80%, Within 90 seconds = 95% 100% within 60 days. 3 DAYS AND 7 DAYS AND 15 days: rent rebate for 1 month >55%

Should be better than

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CHAPTER – IX UPGRADATION & REHABILITATION OF EXTERNAL PLANT, POLELESS SCHEME Objective of the Lesson : The principle of a stitch in time saves nine is also applicable to the external plant in a telecom network. A developing cable fault if noted early by any means will certainly save the network from disastrous breakdowns. The emphasis in this chapter is to stress the importance of replacement of damaged or low performing equipment from the system to make it more efficient. *

*

*

WITH THE INTRODUCTION OF SOPHISTICATED ELECTRONIC SWITCHING TECHNOLOGY, FAULT LIABILITY IN SWITCHING EQUIPMENT HAS COME DOWN TO A GREATER EXTENT. HOWEVER, EXTERNAL PLANT IS GENERALLY FOUND TO BE A SOURCE FOR MINORITY OF FAULTS ( 60% TO 80% OF TOTAL FAULTS) IN THE LOCAL TELEPHONE SYSTEM. Following may be come of the reasons for development of faults in external plant. I. Improper cable works and lack of Co-ordination with other public utility services in cable construction wings. II. Incomplete and sometimes absence of documentation and records, and negligence of preventive as well as annual maintenance of external plant. III. Use of the poor quality material and poor workmanship. The external plant in a local telephone system from MDF to pillar and from pillar to DP. I. II. III. IV

Underground cable termination from MDF to pillar and from pillar to DP. Overhead drop wire from DP to rosette/window terminal. Internal wiring from window terminal to rosette in subscribers office and Subscriber telephone instrument.

The external plant is not only exposed to nature and its affects, but also some man made troubles, may be unintentional or intentional. Hence, the maintenance of external plant is the most important and the roughest job. Following are some guidelines suggested .

BASED ON THE EXPERIENCE, FOR EFFICIENT MAINTENANCE OF EXTERNAL PLANT SO AS TO PROVIDE BEST POSSIBLE SERVICE QUALITY AND CUSTOMER SATISFACTION. 1. Adequate provision of funds in the project for external plant and proper planning of cabling. 2. Adoption of better cable construction practices. 3. Protection of external plant from power induction. 4. Use of good quality telephone instruments in subscriber’s premises. 5. Ensuring periodical inspections by officers concerned at various levels 6. Opening of customer service center and responding promptly to communications from public/subscribers. 7. Computerization of commercial Management system. RTTC, NAGPUR

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METHOD OF LAYING DISTRIBUTION CABLES TO ELIMINATE JOINTS AT Dps FIGURE 1 2.0.

ADEQUATE PROVISION OF FUNDS

The external plant accounts for 50 to 60% of total cost of installation of any telephone exchange and major portion of it is for the underground cabling. Efficiency of external plant depends mainly on the underground cabling and it’s reliability . By proper cable planning, the cable laying works can be minimized, so that the same cable route need not be dug for laying additional cables for at least 5 years, which further helps to minimize not only the damages to the existing cables, but also the road reinstatement charges to be paid to municipal authorities. 3.0

BETTER CABLE CONSTRUCTION PRACTICES.

UNDERGROUND CABLES CAN BE CONSIDERED AS A BURIED TREASURE WITH AN AVERAGE LIFE OF 40 YEARS. HENCE, PROPER PLANNING AND UTMOST CARE IS NEEDED FOR INITIAL CABLE LAYING OF A TELEPHONE SYSTEM AS IT FORMS FOUNDATION FOR THE CABLE NETWORK TO BE BUILT UP IN FUTURE. EXECUTION OF CABLE LAYING WORKS IN HURRY MAY IMPAIR THE QUALITY OF CABLE CONSTRUCTION OR SOME BETTER CABLE CONSTRUCTION PRACTICES ARE ENUMERATED BELOW. 3.1

Elimination /Minimization of Joints near MDF Pillar and DP 1. Directly terminate jelly filled cables on MDF by laying higher capacity cables. 2. Provide joints on either side of the pillar at considerable distances instead of jointing all the cables in front of the pillar, and directly terminate the cable on to the CT boxes. This will eliminate cluster of joints surrounding cabinets/pillars.

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Underground Cable 3. Eliminate joints at the bottom of the DP posts by laying lengthy distribution cable tails from the Dps and grouping into single joint at a common branching point as shown in figure 1. This also reduces the cost of external plant. 3.2 Elimination of Un-terminated Link Cables Interconnecting Pillars.

two

Adjoining

Two pillars installed at some distance and are interconnected with un-derminated cable for sharing. The jumpering is seen criss crossed and shabby, which contributes to large number of jumper faults in the pillars. This can be eliminated by positioning the pillars side by side and coupling them with 4” GI pipe for taking the jumpers for sharing. It looks neat and tidy too. 3.3

Training in Better Workmanship and Jointing Techniques.

Certain uncared operations in cable constructions, though simple in nature, may lead to serious faults during life time of the cables. The tendency of some cable splicers to develop their own theory of jointing in the absence of full complement of jointing kit should be discouraged, which otherwise results in large number of point failures. 4.0

Protection of External Plant Against Over Voltages and Excess Currents.

In thickly populated urban and rural areas where the power lines at low voltages criss cross. the telephone lines, the hazard of power contact is extensive. Lengthy paralleling of telecom lines with power lines and electrified railway tracks pose danger from power induction. also , lightning discharge may cause over voltages in telephone networks both through direct strokes and through electrostatic and electromagnetic induction. Intermittent sparking of isolation switches on the pole mounted transformers is another source of noise as well as electromagnetic induction. In areas where the soil resistively is high the external plant is more exposed to over voltages. The importance of use of proper jointing kit and its, full complement of jointing materials and precautions to be taken while splicing should be reiterated to all the cable splicer from time to time. Figure 3 shows one such refresher training camp conducted to cable splicers and supervisory staff at Guntur ( AP). Following are some tips for improving quality of jointing. 1. In case of PIJF cables ensure use of crimping tool for pressing UY connectors for jointing the conductors instead of ordinary pliers to avoid break faults. 2. Ensure use of filling compound or jelly in the splice to avoid any possibility of ingress of moisture setting in. 3. Ensure sheath continuity at every joint and earthling at DP pillar and MDF. A missing continuity can result in noise due to power induction. similarly armour continuity also must be provided in addition to sheath continuity for better screening against power induction and to discharge surge voltages in case of lightning and power contacts etc. 4. An epoxy resin cannot stick to polythene satisfactorily and hence use Aluminum foils and canisters in cable splicing and while shrinking use thermo shrink sleeve or heat RTTC, NAGPUR

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Underground Cable shrink sleeve to close the joint. 5. As the minimum require length of heat shrink sleeve for shrinking is 250 mm, do not use WRST or repair sleeves of less than 250 mm by cutting from the lengthy sleeves of sizes 400mm or 1500 mm. 6. Provide mechanical protection to joints against crowbar hits during subsequent digging by proper positioning of the joint and by covering with napha slabs or joint enclosures. 4.1

Protective Measures.

Following are some of the methods for protecting the external plant against over voltages. Provide sheath continuity at year cable joint and ensure earthling of DP , pillar and MDF similarly armour continuity also must be provided in addition to sheath continuity which provide certain degree of screening against power induction. 1. Use invariably self supporting drop wire from DP to subscriber premises. 2. Use of heightened poles by electricity authorities may be instead where necessary in order to maintain adequate vertical clearance between power and telecom lines. Also power guarding are to be erected wherever required as per PTCC Code of Practice. 3. Elimination of sparking on transformer knife switches ( AB switches) by proper coordination with power authorities. 4. Telecom installations should be as far away as possible beyond a minimum distance of 50 meters from the electrified railway track. Only armoured underground cables are to be used and laid at right angles for crossing the electrified railway tracks. 5. Wherever the electrified railway tracks run very close to a large local telephone network provision of pole mounting type Booster transformers by Railways at intervals of 2.6 kms or 1.3 kms as per necessity should be insisted upon in order to reduce the hazards of electromagnetic induction considerably. 6. Provision of two screen wires of 2mm dia. copper of 300 lbs GI wire at half the depth of cable trench may be considered in lightening prone areas, depending upon the importance of the cable, in order to ensure rapid discharge of electrical energy from lighting and also to provide a certain degree of additional screening against power induction. 7. As electronic exchanges have very sensitive components, presence of foreign potential beyond prescribed limits may cause large number of the cars to fall. Hence protective devices are to be provided at Main Distribution Frame ( MDF) based on the immunity level of the components. Modern protective system uses Fast operating ( double acting) fuse as a current protection against excess currents and a Gas Discharge tube ( GD Tube) for protection against over voltages. the choice of GD tube are available with breakdown voltages right from 90 volts onwards. 8. In coastal areas and in areas prone to lightning and where the subscriber lines are lengthy and run across cross country ( mostly in SAXs) GD tubes may be provided at both ends as additional protection. Long SAX lines running cross country should be referred to Power Telecom Co ordination Committee ( PTCC) and protection measures got incorporated accordingly. A plug in GD tube module of two lines of RTTC, NAGPUR Page 139 of 185

Underground Cable Krone type termination fitted in a plastic box with proper earthling should be installed inside the subscriber premises at a location having easy accessibility to maintenance staff. For protecting subscriber’s telephone instrument, Metal Oxide varistors ( MOV) of proper rating may be provided across the line in Electronic Push Button Telephones ( EPBTs ) as a second line of protection against surge voltages.

5.0

USE OF GOOD TELEPHONE INSTRUMENTS.

The electronic exchanges are providing better facilities combined with greater flexibility. In order to improve customer satisfaction, a good quality telephone instrument may be provided for all subscribers. This can be achieved by, 1. Replacing all conventional rotary dial telephone instruments including main and extension types by EPBTs. 2. Providing re- dial facility to all the subscribers 3. Providing DTMF facility to all the subscribers in electronic exchanges and 4. Ensuring periodical replacement of outlived telephones, which will otherwise affect aesthetic look of the subscriber premises. Analysis of faults in external plant reveals that about 30% are due to faults in telephone instruments in subscriber premises. Some common faults observed are as follows. 1. 2. 3. 4. 5.

No ring. No outgoing speech. No incoming speech. No dialing. No dial tone.

In case of EPBTs, resorting to various private sources in the absence of supply of spares from manufactures may impair the quality of service. Repair of the telephone instruments at the subscriber premises, except for tightening of loose connections in the rosette or in the internal wiring, may be avoided. the faulty telephone may be replaced by another good one and the faulty one sent to repair center for repairs. In most of the telephone systems subscribers’ satisfaction is impaired if the original telephone of the subscriber is frequently changed by instruments of various models as and when fault occurs. To obviate this a good Test Telephone with serial number may be provided temporarily in place of the original instruments, sending the faulty one to central Telephone Repair Shop for repairs, and replace the same after repairs, collecting the test telephone provided earlier. to achieve this a separate store receipt system for controlling/monitoring telephone instrument replacements may be adopted and followed scrupulously. A specimen Performa of one such store receipt ( to be printed in triplicate in different colors with machine serial number) for replacing telephone instruments is given in Plate 1. This is to be prepared in triplicate. The JTO will issue two copies to Store Lineman ( SLM), retaining office copy. the SLM has to return one copy to JTO after receipt of the test telephone from subscriber premises. RTTC, NAGPUR

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Underground Cable Also a specimen Performa for LM Receipt of Telephone instrument is given in Plate 2 ( to be got printed in duplicate with machine serial number). The receipt is to be issued to subscriber by LM whenever telephone instrument in the subscriber premises is brought for repairs keeping test telephone in lieu of it . these receipt books may be issued to each section JTO. 6.0 Corrective and Preventive Maintenance Maintenance of external plant can be classified into two ways. 1. Corrective maintenance which includes attending to faults reported to Fault Repair Service 198 by the subscribers as and when occurred, and attending to the defects noticed during routine testing of subscriber lines and during periodical visits/ Inspections of installations of external plant. 2. Protective maintenance which includes reducing incidence of faults and thereby complaints by taking advance action in identifying the defects and attending to them before commencement of monsoon and also by adopting annual maintenance program. 6.1

Corrective Maintenance Methods Majority of faults in the external plant occur in the section from DP to subscriber’s telephone instrument. Following may be some of the reasons for such high fault rate. 1. Loose connections at DP and rosette in subscriber premises due to missing of terminal screws, washers in the connecting strips. 2. Loose connections between overhead GI wires and connecting wires to DP or at subscriber premises window terminal and number of dry joints in drop wire etc., which may cause bi-metallic corrosion forming oxidation and thereby causing high resistance faults. 3. Open Dps without the covers and frequent handling of Dps by cable splicers, LM and construction parties, not only expose inside wiring to rain and wind but also cause formation of birds nests, cobwebs etc. in the DPs which cause faults. 4. Meddling of Dps installed at lesser height by unscrupulous elements. 5. Use of switch board cables or drop wires at road crossings with less headway. 6. Missing of drop wire due to thefts or due to breaks. 7. Adopting non standard methods for erection of drop wires instead of using proper clamps such as wrapping round the bracket, insulator and then tying to pole, criss crossing power lines and lengthy spans with wires causing sag etc. Such non standard works cause high resistance, partial earth or any combination of faults and also cause crackling noise and bad reception. STORE RECEIPT OF TELEPHONE INSTRUMENT O/o SDE External Sr.No.:1

1.

Date

Telephone No.

JTO Section

-------------

---------------------------

-------------------

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Underground Cable 2.

Details of faulty telephone instrument of subscriber: Make

Type

Year of Mfg.

Sl.No. Type of Fault Observed

---------

------

---------------------------

------------------------------

3.

Number of Test Telephone issued for replacement temporarily.

---------------

4.

Staff number & Name of Sl/SIO/LM/PM/ relating the faulty telephone------

5.

LM Receipt number given to subscriber while bringing the telephone for repairs.

6.

-------------------------------------------------------------Signature of Signature of Signature of LM/PM PI/JTO SLM ---------------------------------------------------------------------------------------------------(To be filled by SLM) 7.

Date of sending the faulty telephone for repairs to repair workshop------------

8.

Date of receipt of telephone from repair workshop after repairs

9.

Date of issue of original telephone to SI/SIO/LM/PM for providing in the subscriber premises after repairs. --------------Date of return of test telephone to stores --------------------------------------------------------------Signature of sectional Signature of SI/SIO/LM/PM SLM & Date ----------------------Signature of SDE

10. 11. -

---------------

LM RECEIPT OF TELEPHONE INSTRUMENT O/o SDE External (To be filled by LM at Subscribers Premises) 1.

Date ------------------

2.

Details of faulty telephone instrument of subscriber:Make Type Year of Mfg. Sl.No. Type of Fault Observed

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Telephone No. --------------------------

JTO Section -----------------------

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---------

------

---------------------------

------------------------------

3.

Number of Test Telephone Provided temporarily

4.

Staff number/Name of SI/SIO/LM/PM collecting the subscriber telephone for repairs

5. -

---------------------------Signature of Subscriber Representative

---------------------Signature of SI/SIO/LM/PM ----------------------Signature of PI / JTO

6.1.1

Use of Drop wire with Accessories.

As far as possible a single length of drop wire should be run from DP to subscriber premises upto maximum length of four spans. The drop wire span should not be more than 30 meters . Elimination of joins in drop wire reduces high resistance faults. Following accessories are to be used. Distribution clamp is made of reinforced plastic material. The drop wire is taken round the grooves of the distribution clamps. The distribution clamp is attached to the support clamp hook by means of any of the three holes provided in the distribution clamp as per requirement. At subscriber premises a driver bolt is to be fixed to the wall for holding the distribution clamp. The support clamp is made of not dip galvanized steel. The support clamp is fixed on the CI bracket with U clamp. The support clamp holes two distribution clamps and thus two drop wires.

DPs OPENING REGISTER Sl. No

Date

Time

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Reasons for DP opening i.e. for attending fault or new work

Nature of Fault found

Name of Official opened the DP & Signature

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Underground Cable 6.1.2

Proper Maintenance of DPs

In the external plant DP is a very important point whose maintenance has great bearing on the telephone services. Following steps may be taken for proper maintenance of Dps. 1. DP location is one of the most important parameters for controlling the faults. The location of the DP should be such that the length of overhead alignment is kept minimum. 2. The DP post is to be properly erected Slanting post causes hanging of drop wires. 3. Height of DP may be 4.5 meters. The DP box is to be located at 1.25 meters from the top of A4BC post of DP is to be fitted at 30 cms below the ultimate lowest bracket. 4. Handling of Dps may be restricted to specified officials. for attending and sectionalizing a fault the LM should first go to subscriber premises and move towards DP and not the other way. This reduces handling of Dps to some extent. Details of DP openings are to be recorded in a register and maintained section wise . A specimen Performa is given in Plate 3 . This is only for keeping watch over DP openings and fixing responsibility for proper maintenance of Dps and also to find out Dps, which have been opened frequently, for their improvement. This procedure also reduces the NFF ( Not Fault Found ) cases. 5. Installation of 10 pairs Dps instead of 20 pairs may be resorted to reducing the area served by DP from 200 to 150 meters. This will considerably reduce the fault rate. 6. New Dps may be opened whenever the existing cable fill exceeds 70% so that the balance 30% can cater for future demand. 7. There should not be any criss-cross connection working from one DP to another DP. 8. Street crossings of overhead lines are a weak point. Often the wires are broken by speeding lorries loaded to greater heights. As far as possible, DPs may be provided on both sides, especially for wider roads in order to minimize road crossings. 9. DP post should not be erected below power lines or in the close vicinity of electrical transformer or electrical post. 10. Adjustable clamps with jumper rings are to be fixed on the DP Post at intervals to hold and keep the drop wires in position along the post. 11. Proper locking of DP box is to be ensured always. If necessary an outer metal box, called DP locking box enclosing the DP box, may be provided for protecting DP boxes. 6.2 Preventive Maintenance Methods Number of digging operations by various agencies may cause sheath damages to the underground cables . These sheath damages accumulate and result in cable breakdowns after the first rains. The worst aspect of undertaking repair work of these cables due to moisture entry is that the faulty portions are to be cut and replaced with bits of cables, thereby the number of joints increases. Following preventive measures may be adopted. 6.2.1 Patrolling of Cable Routes RTTC, NAGPUR

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Underground Cable It is the most effective preventive measure against cable faults Nearly 70% of the monsoon breakdowns can be avoided if rigid route patrolling is ensured with proper follow-up action. Patrolling of cable route should be done exclusively on foot to keep a track of digging activities taking place. The patrol man should inform JTO on day to day basis about the status of the cable routes giving details of pits or trenches observed, location and digging agency etc. for taking necessary immediate action. 6.2.2

Flooding

Whenever a trench is dug for laying new telephone cables or some other department digs the trench for installation of their services, the trench may be filled in with adequate quantity of water for two or three days to simulate the monsoon conditions. If the water is not allowed to remain in the trench for adequate period some sheath damage, which is small in size, may escape. the cables involved should be kept under observation keeping in touch with the Test Desk. If no fault is reported by the Test Desk the trench can be closed, otherwise fault is to be localized and attended to. 6.3

Pressurization

Gas pressurization is a preventive maintenance work for dry core cables Dry air or Nitrogen is fed into dry core cables either by use of cylinders or compressor dryer units at a pressure of 0.7 KSC either by static feed system or continuous feed system. The Gas Pressure Alarm System ( GPAS), if installed, should function properly. When sheath damage occurs an alarm is given to enable necessary action to be taken before the pressure falls below 0.3 KSC. If GAPS does not exist in the system, cable pressure readings are to be taken at PTVs (Pressure Test Valves) and recorded daily. These readings are to be checked for any leakage due to sheath damage and timely action taken to avert the cable breakdown. All repairing works of cables must be flash pressure tested for any leak. Test the sheath enclosure at 1.4 KSC, or 20 PSIG for 20 minutes and no bubbles indicate OK. Note that pressurized cable should not be left unpressurised for a long time. 6.2.4

Pre monsoon Precaution

A check list of pre monsoon precautions as listed below may be prepared and necessary action taken to reduce the incidence of cable faults. 1. Updating cable diagrams and records. 2. Procurement of jointing materials and testing equipment. 3. Obtaining clearance from local civil authorities for the period of monsoon for digging of road, footpaths, etc. for suspected cable faults. 4. Printing of subscribers intimation cards for cable breakdowns and their distribution to each outdoor Sub division for issuing to subscribers affected by cable faults. 5. Permanent closure of katcha joints made for want of regular jointing kits at the time of fault repair. 6. Dressing up of all DPs. 7. Commissioning of new exchanges/area transfers preceding monsoon may be avoided as far as possible. RTTC, NAGPUR

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IN ADDITION TO THE ABOVE THE FOLLOWING STEPS MAY BE TAKEN FOR FURTHER IMPROVEMENT. 1. Closer liaison with public utility services may help in getting advance intimation of excavation operations, so that cable protection activities can be planned timely . The more the monitoring of the digging activities of other departments the more breakdown free Is the external plant network. 2. Dial before you dig service may be opened with easily remembered telephone number giving wider publicity among public in general and public utility services in particular. They should be requested to call that number whenever they proposed to dig up a road so that a telephone representative can be posted at the digging site to oversee the digging operations.

ANNUAL MAINTENANCE PROGRAMMED FOR IMPROVEMENT OF EXTERNAL PLANT GENERALLY CONSISTS OF FOLLOWING ACTIVITIES. Identification of the telephone instruments which have become very old & outlived in the network and their replacement in a phased manner. 1. Replacement of worn-out drop wires. 2. Replacement of fault prone overhead lines by insulated wires, aerial cables and underground cables. 3. Rehabilitation of Dps. 4. Replacement of fault prone underground cables whose maintenance is uneconomical. They may include cables, which have served for more than 40 years, cables where 50% or more cable pairs are abandoned or faulty or having low insulation and/;or cables having number of joints ( more than three for every 200 meters). 6.2.6

Measures for speedy Removal of Faults

The complaints of the subscribers be attended to promptly. Computerization of fault repair Service (FRS) 198 will ensure prompt action on the subscriber complaints right from the time of booking till rectification. After the faults have been removed the Test Position Operator should speak to the subscriber to ensure that the telephone has been set right to laters satisfaction. The Fault Repair Services may be reviewed by the section officer’s daily at 10.00 hrs and 16.00 hrs to know the faults position and the Daily Faults Analysis Report analyzed and action taken to minimize repeat faults. 6.2.7

Maintenance of Cable Diagrams and records.

Upto date maintenance of cable records and diagrams will facilitate quick localization and removal of faults and also enables speedy execution of works. Standard documentation in book from helps in preserving the records and computerization of records and diagrams may be implemented and followed. 7.0 REGULAR INSPECTIONS Telecom installations can be maintained in good shape for giving good service, provided they are kept all the time in good working order and this can be done by taking remedial measures wherever defects are noticed or deficiencies found. This is possible if inspections are carried RTTC, NAGPUR Page 146 of 185

Underground Cable out regularly and observations are recorded correctly. It is reiterated that periodical inspections by concerned officers at various levels followed by remedial measures would automatically improve the quality of service. 8.0

CUSTOMER SATISFACTION

Opening a Customer Service Center in each external plant Sub division help in taking prompt action in attending to complaints or to answer the queries of the subscribers in matters relating to telephone service, Further, the Customer Service center can ascertain about the service quality and telephone problems by dialing a group of subscribers as a routine daily. the telephones of public utility services, VIPs and heavy calling rate subscribers may be daily tested. Always prompt and timely action may be ensured and courteous replies given to written communications from customers and members of the public Where delay is anticipated in sending a final reply, an interim reply may be sent within a fortnight, indicating the possible date by which a final reply can be given. Where the request could not be accepted to for any reasons, the reasons for not acceding to such request may be given This will go along way in improving customer satisfaction

9.0 COMPUTERIZATION OF COMMERCIAL SYSTEM

OFFICE

MANAGEMENT

Introduction of Dot soft integrated package made the Management easy I. On line registration of NPCs by issuing demand notes , Recording payment details registration, issue of acknowledgment letters and allotting waiting list number on the spot. 2. Prompt issue of advice notes for subscriber requests like shifts, safe custody, provision of accessories, provision of accessories, provision of STD facility and barring of STD facility etc. 10.0

CONCLUSION.

The Department of Telecommunications is a public utility organization run on a commercial basis As the subscribers pay adequately for the services, they are entitled to prompt and courteous attention at all times. Hence, by following the better maintenance practices detailed above, the external plant can be maintained reasonably well so as to ensure better service quality and customer satisfaction.

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REDUCTION OF FAULT RATE IN EXTERNAL PLANT With The Introduction of state of the art technology into the switching and Transmission equipments the faults due to indoor equipment have been reduced drastically increasing in the satisfaction of the customer. But the rate of faults occurring in the external plant is causing worry to the Managers of the plant. By adopting two methods of • •

Implementing Pole less External plant Replacement of obsolete / fault prone telephone instruments

These methods have to detected during inspection and implemented by the way of rehabilitation of the external plant, which results in reduction of heavy fault rate in the outdoor network thereby increasing the satisfaction of customers and managers. By implementing the pole less external plant the overhead section in the outdoor network including poles, AI wire and drop wires will be replaced by a 5 pair underground cable which is proposed to be laid from the nearest Distribution cable to the subscribers premises and terminated at the LJU. An average of 50 meters of 5 pair cable perhaps have to be laid in the premises of subscriber. With in the subscriber’s premises it may not require digging of trench to a depth of 1 meter and a easy method of laying in cost free earthen or PVC pipes can be laid under the flooring which it self is a mechanical protection. This also reduced cost and easy replacement in future. Implementation of pole less scheme should be done in phased manner. In order to get quick results in reducing fault rate with minimum expenditure and time, the following points should be kept in mind while identifying the priority area where ::      

Maximum Over head lines exist Maximum faults are booked and noticed Many overhead road and power crossing exist. DPs are in bad condition due to traffic congestion. Different gauge drop wires exist. Many DPs for which the Phone Mechanic is Removing the pair from DP termination and twisting the UG cable pair to Drop wire directly.

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 Non feasible areas exist.  High telephone density exists  One subscriber is a customer of many number of telecom services. Detailed survey and preparation of Estimate:: After identifying the area, a detailed survey should be carried out and perfect record should be prepared as shown in the figure 1. Based on the survey report the requirement of 5 pair, 10 pair and 20 pair cables should be assessed. The requirement of 5 pair cables should be prepared inb two parts, i.e. the requirement of 5 pair cable in the customer premises and remaining part of cable on the public road. The later part ma\y included in the cable estimate where as the first part should be provided as a part of replacement of overhead lines in lieu of L&W component. If the expenditure exceeds more than the norms of project estimate and separate Mission for Better communication estimate should be prepared for excess portion of the cost. Procurement of 5 pair Cable :: The 5 pair cable is usually purchased by Circle level according to provisions in the sanctioned estimates. In order to procure adequate quantity of 5 pair cable, the preparation of estimates in advance and procurement will also contribute in the reduction of the cost of the work as 5 pair cable can be laid in the trenches already made for normal laying. Hence the procurement of 5 pair cable is the essence of implementation of the pole less scheme. Typical estimate of the work :: Store required for OH line Subscriber AB Posts Drop wire in mars 1 4 100 2 2 115 3 2 130 4 1 110 5 1 125 6 1 165 7 3 225 8 5 290 9 1 205 10 1 220 Total 21 1685

RTTC, NAGPUR

Store for Pole less Method 10 / 0.5 UGable 5 / 0.5 UG cable 5 / 0.5 for subs loop

140 mts 470 mts 160 mts

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Underground Cable

Cost particulars OVER HEAD LINE Description AB post complete Support Bracket Drop wire DP Box 10 pair GI Pipe Saddle Labours Transportation

Quantity 21 21 1685 1 2 mars 21 51

Rate Rs

Total (Rs) 1075 22,575 270 5,670 3 4,875 400 400 120 240 100 2,100 112 5,712 2,100 Total 43,672 Cost per line is Rs. 4,367 only

POLELESS TECHNIQUE Quantity 10/0.5 CABLE 5/0.5 CABLE Bricks 510 x 5 x1.5 Trenching +Laying cable on Road Trenching at Subs. Premises @ Rs. 10 Internal DP TSF 1 kit Joint Kit

104 630

Rate Rs. 20 13

510 x 6+140x6+470x6

Total Rs. 2,800 8,190 3,825 11,820 1,600

10 10 10

TOTAL

125 360 151

1,250 3,600 1,510 34,595 Cost per line is Rs. 3,460 only

Even though the calculations are approximate and vary from place to place the average in the per line savings is about Rs. 907 /- only the liability of fault and its rectification and revenue lost during the period of fault and the customer satisfaction counts very much for the development of business and reliability for us. Because we are proposing to lay the cable in subscriber premises through PVC pies or earthen pipes it is easy for us to recover the cable and can be used else where with out much difficulty and damage. The parameters of line condition also improve with the removal of overhead and drop wire Particularly Drop wire which is prone for low insulation as it wears and tears in the atmosphere and requires frequent replacement. The cost of frequent replacements also is avoided with this pole less technology i.e. with the introduction of 5 pair cable direct to the customer premises.

RTTC, NAGPUR

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Underground Cable

CHAPTER - X INSPECTION PROCEDURE Objective of the Lesson : The tough inspection will bring out the lacuna in the procedures adopted in various activities of the planning, construction, installation and other maintenance works which has a being on the efficiency of the system and ultimately the customer satisfaction is the barometer for the efficiency. So the importance of inspection in various are discussed here in this chapter. *

*

*

INTRODUCTION When there was only electromechanical SXS Auto Exchanges the Acceptance Testing of External Plant was carried out only for the conversion of manual C.B. Exchanges to S&S Auto Exchange. No A/T was done subsequently on expansion of the system unless there was cutover at the same of the system. With the introduction of Electronic Exchanges fault liabilities in the Switching Equipment have reduced considerably. It is well known that a well maintained External Plants provide an improve service to subscribers. therefore it has been decided to conduct 100% Acceptance Testing for the external plants before they are put into service. Equipment’s provided in subs premises and its wiring are subjected to Acceptance Testing by choosing 20% of the equipment at random selection ( In MTNL 100% check is conducted. No telephone connection can be opened without Acceptance Testing of the subs equipment & wiring. 2. Preparation before offering External Plant for A/T Some of the important points which requires attention of all concerned before external Plant is offered for A/T 2.1

CABLE SCHEMES EXCHANGES . a. b. c. d.

2.2 2.3

SHOULD BE GIVEN TOP PRIORITY IF THE AREA WILL BE EXPANDED BY ELECTRONIC

Fault Prone cables with low insulation should be replaced. All heavy over head alignment should be replaced by new DPs. Cabinets and pillars should be installed for more than 500 line exchanges. Old DPs should be rehabilitated.

Subscribers loops of less than 4 spans should be replaced by drop wire. Drop wire should be provided from DP to rosette.

Pressurization of junction primary and secondary cable may be done and if possible cable should be laid in ducts. RTTC, NAGPUR Page 151 of 185

Underground Cable

2.4 2.5

Good quality telephone instruments for all subscriber should be ensured. Old fitting at subs office should be rehabilitated.

2.6

All the testing parameter for each subscriber’s line should be measured and recorded in subscriber’s fault cards before commissioning the exchange.

2.7

Electronic dial/loop resistance testers should be procured for a quick testing.

3.

Definitions

3.1

Service line:- Service line is the portion of the subscriber line from pole mount DP to the terminal points.

3.2 Subscriber’s Installations:- Subscriber’s installation is the portion subscriber’s line starting from the distribution points and ending at rosette.

of

3.3 Subscriber Line:- Subscriber line is the portion of the line starting from the line side of the MDF and ending at rosette 3.4 Subscriber Local System:- Subscriber local system includes subscriber’s line and exchange feeding bridge.

telephone

set

3.5 Resistance of Subscriber Loop :- Resistance of subscribers line loop is equal to the sum of resistance’s of each limb of subscriber’s line and telephone set. Internal DP when underground cable is laid directly to the subscriber’s premises the distribution point is know as internal DP

PROCEDURE OF A/T OF EXTERNAL PLANT. Details of O/D plant of cabinet, pillar, DP lines, to be connected are to be procured and first of all physical inspections of External Plant is carried out by checking Dps/cabinet Pillars and subscriber lines. After rectification of faults detected in physical inspection, electrical parameters of the lines and dials are tested. For Acceptance Testing of External plant the following should be physically inspected and tested. a.

Cabinets and pillars.

b.

Pole- Mounted DP

c.

Internal DP

d.

Service line.

e.

Indoor House Wiring

g.

Electric Parameters of Line

h.

Dial of subscriber’s instrument

I.

Junction cable

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Underground Cable 4.1

Points should be carried out at cabinets and pillars for the following:-

a) b) c) d) e) f) g) h) i) j) k) l)

The Cabinets /pillars should be located at obstruction free place on concrete base and height should be above flood level. The cabinet / pillars should be numbered properly General condition of the plant outside and in side should be without any rust. The doors should open and close freely. The cabinet/pillar should be neat & clean from inside. The cabinet/pillar shell should be firmly fixed and bolts should be tight. CT Box should be fixed firmly to the frame and all fixing screws should be tight. The jumper field should be tidy there should not be unnecessary long. The position of spare pairs should be according to the records. all the records should be available in the cabinet /pillar. There should be no dust. cobwebs inside the cabinet/ pillar. Check the locks.

4.2

Points to be checked of pole mounted DP 100% check of DP is necessary.

a)

m) n)

DP should be located at obstruction free place and no way in the vicinity of electric poles etc. The DP should be painted and numbered. Minimum height of DP should be 9’feet (2.75M) from the ground. The DP should be properly fitted to the post by means of standard U back and saddles. The back of the U backs should be flattered for giving good grip on the tubular posts. The cable should be taken to DP base through GI pipe of 50 mm internal diameter. The GI pipe should be securely fixed to the posts with the usual galvanized iron fixing clamps . The lowest clamp should be 50 to 60 cm from the ground level and the upper most clamp should be 50 to 60 cm below the top end of the pipe. The third clamp should be fixed in midway. Distance between two clamps should not be more than 200 cm. The DP should be properly fitted using washer O/H connections of GI Wires and drop wires ( if provided) should be soldered. Earthing arrangement should be provided. Updated DP cards should be available. The drop wire lead should be properly secured on the wooden batton / board. The DP should have locking facility. A bracket should be provided below the DP to facilitate maintenance. The lowest bracket on DP pole should be fitted at the minimum height 2.75m from the ground. All the brackets should be fitted with ties and struts. DP Post should be fitted with proper stays.

4.3

Points to be checked of internal DP

a)

100 % Dps should be checked.

b) c) d) e)

f) g) h) i) j) k) l)

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Underground Cable b)

The height of the line terminating / Distribution tag block/internal DP should be approximately 2.5M above the floor.

c)

The same should be on the inside wall building and easily accessible for inspection.

d)

Location for telephones termination box should be different from that of the power meter. Where it is unavoidable, a minimum distance of 1M between the two should be insured. 4.4(A) Check of service line:-

a)

Selected at random minimum 20% service line should be checked.

b) c) d) e) f)

In city/town areas open wire should not be used only drop wire or overhead cable should be used in such areas Drop wire should be erected on standard fittings Drop wire should not be loose Jungle should not touch the drop wire/open wire. All the bare wire at the power crossing should be properly guarded.

g)

The open/open wire should be properly secured at the two ends.

h)

Parallelism for a long distance with power line should be avoided ( In case of long distance telephone connection). If the length of open wire lines exceeds 400 m. protection in the form of GD tubes should be provided at subs premises . The value of earth resistance should be less than 5 ohms.

i)

4.4(B)

FOR O/H SERVICE LINES FOLLOWING SHOULD BE CHECKED.

a)

On DP pole brackets should be fitted properly with ties and struts. All the brackets should be perpendicular to the alignment and straight.

b) c)

No broken insulator should be provided on line Stays should be fitted at angles, Dps and terminals and they should be tightened

d) e) f)

Post should be fitted with lightening spikes. Headway and leveling should be proper. At all power crossings the power guarding arrangement should be provided

g)

There should be no kite threads, cobwebs and touching of vegetation on O/H lines.

h) i)

All the joints should be soldered. Wire should be properly bounded on insulators. A certificate from concerned SDO regarding guarding of all power crossing should be obtained.

4.5

CHECK OF INDOOR HOUSE WIRING. a)

RTTC, NAGPUR

minimum 20% house wiring should be checked at random. Page 154 of 185

Underground Cable b)

Cable used for house wiring whether it is twin 4 pairs or 10 pairs should be of .63 mm dia PC insulated PVC sheathed.

Nominal dia of conductor .63mm .63mm .63 mm

No. of Wires 2 8 20

No. of pairs. 1 4 10

construction Flat Round Round

Now standard has been reduced to .5mm. c. d. e. f. g. h. J. k. l. m. n. p. q. r. s.

Wooden batton used for house wiring should be straight, painted or varnished on all the sides not less than 10mm thick and of suitable size to accommodate the cables ( Use of teak wood is banned). The cable should be properly clipped at intervals of about 20cm. Corners should be used where the cable has turned from one plane to a perpendiculars plane. Bends should be used where the cable is bent in the same plane. Telephone wiring and power wiring should not be on the same batton. If both run parallel due to unavoidable circumstances than minimum 15 cm separation should be provided between power wiring and telephone wiring. The telephone wiring should cross the power wiring perpendicularly on wooden bridge. The rosette should be fixed either on wall with teak would board or on the side of the table. Floor crossings should be done in a steel conduit and it should be properly bushed at both ends with porcelain or would. There should be no joint in fitting. The wooden batton can be fixed to the wall of ceiling. But these should be fixed by means of wood screws and rawl plugs. The screw used to fix the battens should be flat headed and the screw holes should be counter sunk to receive the head of screw. The space should be 75 cm between successive screws. Clips on the batons should be fixed at intervals. of 4.7 cm. If wiring has to pass through a wall a conduit or a porcelain tube of sufficient diameter and length should be fixed inside the wall and cable should be taken through it. If the wiring is concealed the wire terminal should be provided at the desired location of the telephones. The rosette or plug and socket should be installed at the desired location and wires should be terminated onto it. Wire should be fitted inside the rosettes properly ( Proper washer should be used to give firm grip)

4.6

Check the points if directly clipped on wall

a)

For nailing the indoor PVC cable plastic clip clamp with nail should be used.

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Underground Cable b) c) d) e)

The nails should be fixed at the distance of 300 mm where the cable is running horizontally. The nails should be fixed at the distance of 500 mm where the cable is running vertically. The cable should run either vertically or horizontally never at an angle to the horizontal or vertical. The cable should run along a cornice or skirting to give a neat appearance.

f)

Any curves or obstructions should be negotiated with gradual angles and clamp should not be put at curved surfaces.

g)

Equal spacing in clamps along the whole length should be followed.

h)

If direct nailing is not possible on the wall the rawal plug should be used to fix plastic clamps after drilling the holes in the wall.

i)

The cable ( PVC installation ) should not be exposed to the sun/rain.

j)

If the telephone instrument is to be fixed on the table the PVC cable should be installed through a plastic pipe fixed on the floor and separate conduit should be used for telephone and electric wiring.

5.

ELECTRIC PARAMETERS AND DIAL TEST.

In case of strowger and cross bar exchanges the insulation test, loop resistance and dial tests are conducted from Test desk fitted with voltmeter and Dial test circuit. 5.1 Insulation between a & b limb should not be normally 1 m - ohm. -do-do1) Rotary 1.7 to 2.1 MH 2) Push button 0.3 to 0.5 MF 3)Capacitance value of the instrument.

6.2(b) Instrument Parameter P10 R

Open circuit time measurement to 70m sec. (break). P11R Closed circuit time 20 to 40 m sec. measurement ( Make) P11R Break to make ratio 1.5 to 2.33 P11R Dial Speed 9 to 11 IPS P12 R Pulse Count As per dialed digit. P13R Power supply current on line. Normal line. 3 to 60 mA Long Line. 30 mA RTTC, NAGPUR

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Underground Cable P14R

Loop resistance Normal line. 1500 ohms Long line 2400 ohms Flash measurement of open loop line caused by earth button. 220 to 320 MS

P15R 6.3.

Particular cases of Low Insulation

In case low insulation is shown by the TTY sets ( Parameters L5, L6, L7 ) it may be due to foreign potential on line ( L1 , L2 parameters). In such cases 100 V megger may be used . The lines may pass under insulation test by this method. 6.4

Low insulation due to Teed Joints:-

It has been noticed that tested for subscribers capacitance and insulation are distorted due to long length of Teed pairs. These lines may be offered for A/T after Tee joint is removed. 6.5

Relaxation :-

Relaxation in case of External plant is granted by the Member (TO). For electronic Exchanges in Bombay and Delhi the power has been delegated to the Chairman and director ( see ANNEXURE 9 to 10)

7.

ELECTRICAL PARAMETERS FOR ELECTRONIC EXCHANGES. Sl.No .

Exchange

Max.Loop Resistance

Insulation between A&B

1

C-DOT 128 RAX PRX & NEAX FETEX ILT E-10B

1000

-0.5 M

1900

“

2000 1000 1500

“ “ 1.0M

2 3 4 5 8.

Acceptance and testing of Junction Cables.

a) b) c) d) e)

The following information should be noted about the junction cables Type of Jn cable. Places between junction cables is used. Total length of Junction cable Gauge & Capacity of junction cable Loaded of Unloaded.

9.

Flowing test should be conducted at the time of AT for all junction pairs.

a) Conduction test. b) Transmission loss c) Cross talk RTTC, NAGPUR

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Underground Cable d) e)

Noise Insulation test.

9.1

CONDUCTION TEST.

Loop resistance of all the pairs should be measured separately and noted. The limits of loop resistance for different cable is as given below. Gauge of Cable .4mm or 4 lbs .51mm or 6.5 lbs .63mm or 10 lbs .90mm ir 20 lbs 1.27mm or 40 lbs 88mH loading coil 9.2

Loop resistance per KM 270 Ω 172 Ω 116Ω 56 Ω 28Ω 10Ω

Transmission Losses.

A frequency of 1000 Hz. at an impedance of 600 ohm is fed on each pair of the cable from an oscillator at zero db and should be measured at the other end with a level of 600 ohm Limits of transmission Loss Gauge of cable 4.mm or 4 lbs .51mm or 6.5 lbs .63mm or 10 lbs .90mm or 20 lbs 1.27mm or 40 lbs

Unloaded db /Km 1.75 1.40 1.10 0.80 .45

Loaded. db/Km. 1.10 0.70 0.50 0.25 0.10

9.3 Crosstalk Measurement:20% pairs should be checked Selective level meter and X- Talk meter should be used and 800 Hz tone is used for test. For quad cable the X- talk should be measured in the following pairs. I.

Side to side within quads.

II.

Pair to pair between the adjacent quads.

III.

Pair to pair between quads in adjacent layers.

For unit twin cable X- talk should be measured from adjacent pairs in the same layer. RTTC, NAGPUR

Page 159 of 185

Underground Cable X talk limit: X talk limit should be better than 65 db e.g. 50 db is not permissible 75 is OK. 9..4

Noise

Limits Maximum permissible noise. Voltage is 2mv psophometer.

9.5

PERMISSIBLE LIMIT FOR JN CABLES.

Type of junctions. Single Junction cases.

Permissible resistance

Total transmission loss.

1

Strowger-strowger

1900 ohms

12db

2.

Strowger- Crossbar

2000 “

12 db

3

Crossbar -Strowager 1900 “

12db

4.

Crossbar-Cross Bar (Penta conta) Crossbar- Crossbar (Ericsson)

2400 “

12db

2000”

12db

6.

Strowger-Crossbar TAX/Trans

1900

5 db minimum 7 db maximum

9.6

If Cable is pressurized , the pressurization test should also be conducted.

5.

10(B) Following records should also be checked at the time of A/T for their proper maintenance. a) b) c) d) e) f)

10 (A) a) b) c) d) e)

MDF diagram Updated junction cable diagram with location of joints. DP cards Cabinet & Pillar cards MDF cards Subs Index card

MAPS TO BE CHECKED. The exchange area layout map Cabinet/Pillar layout map Straight line primary and secondary cable diagram with joint location. Distribution cable diagram Pressurization records with location of pneumatic pillars, pneumatic joints etc.

RTTC, NAGPUR

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Underground Cable

CHAPTER - XI TESTING OF CABLES, CABLE FAULTS & LOCALISATION Objective of the Lesson :: The chapter deals with the necessary information regarding the types of faults and the causes of faults occur in underground cables. It also deals with the detection, localization and rectification of the faults *

*

*

1.

CABLE FAULTS - DETECTION & LOCALISATION

1.1

On analysis it has been found that about 70% of the external faults are noted as under cable faults so the efficiency of the maintenance of external plants largely depends on the proper planning, execution, constructional practices and maintenance of cable network i.e. the primary, secondary and distribution cables, cabinets, pillars, DPs etc. Moreover one cable fault normally effects a large number of circuits even upto 3600 circuits. So proper care and vigilance on the cable network is of utmost importance.

1.2

THE GENERAL TYPES OF CABLE FAULTS:(A)

Earth fault :: When the insulation between the earth and the conductor in the cable becomes very low.

(b)

Low insulation fault.:: When the insulation between conductors in the cable or between the pairs or between pair and earth falls below a prescribed limit (normally 0.5 meg ohm) This may be due to entry of moisture or due to failure of wire insulation.

(c)

Disconnection Fault :: When the Conductor is cut then the fault is called break fault or is called High Resistance fault when High Resistance is introduced in the circuit.

(d)

Short Circuit Fault :: When the resistance between the wires or between the conductors becomes very low even without any loop in the circuit on the pairs. This is also called contact fault. Foreign potential :: The existence of potential, even when the circuit is idle or isolated from the potential of exchange

( e) RTTC, NAGPUR

Page 161 of 185

Underground Cable and subscriber premises equipment is foreign potential or contact of the conductor with other circuit having potential. 1.3

THE ABOVE FAULTS OCCUR DUE TO :(1)

Corrosion :- Chemical and electro chemical action, which damages the outer sheath and the conductor of the cable.

(2)

Inter-crystalline fracture :- Sheath is effected due to mechanical stresses longitudinal, transverse, tensional oscillation or periodical variation of temperature or repeated overheating of the sheath. Faulty materials in manufacturing of the Cable

(3)

1.4

(4)

Bad constructional practices like in-efficient, nonstandard and careless workman ship, specially during the time of laying & jointing of cable.

(5)

Natural causes and accidents :- Due to termites, rodents borers etc., & due to earth quack, floods, penetration by tree roots, contact with power lines etc.

(6)

Digging operation by other public utility authorities and individual public.

(7)

Causes unknown and untraceable.

Majority of the above reasons can be avoided during the time of laying and jointing of the cable. As for example all the dry core cables are supplied in a pressurized condition with a Schrader valve fitted at a free end of the cable drum. Before laying the cable pressure inside the cable should invariably be checked. No pressure in the cable signifies the sheath fault in the cable and hence the whole cable drum should be sent back to the manufacturer. Proper laying can prevent a large number of the aforesaid reasons. Joint is the weakest portion in the length of the cables. So proper and utmost care should be taken at the time of jointing by using standard type and quantity of jointing material and employing efficient workmen. Any how cable faults cannot be totally avoided and any of the above faults or a number of faults together may crop up due to any reason. The effect of the fault is either disconnection of communication or impairment or transmitted signals.

2.

DETECTION AND LOCALISATION OF CABLE FAULT The detection and localization of cable fault is the major time consuming factor in the regular maintenance aspect due to various reasons. Detection is the first step in reaching a developing cable fault early. A timely detection & localization of cable fault will help to avoid and lessen the interruption period. Which ultimately give better satisfaction to the customer.

The procedures used for fault detection, diagnosis and location on subscriber lines are 1. Self supervision – is a permanent feature and fault is noticed physically also. 2. Performance monitoring – Gives the indication of the quality of the service. 3. Routine testing – Indicate the faults that are not noticed physically in normal course. 4. Demand testing – After detecting the side effect of fault. RTTC, NAGPUR

Page 162 of 185

Underground Cable Once the fault is reported by any a\of the above means The steps to follow are • • • • 2.1

2.2

Verifying the fault Pinpointing the fault Determining the cause of fault. Rectification of fault with standard methods.

THE BASIC REQUIREMENTS FOR DETECTION AND LOCALIASATION OF CABLE FAULTS ARE :1.

Thorough idea about the cable network.

2.

Availability of up-dated cable records viz., cable diagram, cable plans, DP cards and cable route and joints indicators etc.

3.

Availability of proper type of testing instruments in god working condition and skilled staff.

GENERALLY THE FOLLOWING ARE THE MEDIA THROUGH CABLE FAULTS ARE DETECTED

WHICH

1.

Complaints from the subscriber, testing of the circuits from test desk or OMC.

2.

Routine testing from test-desk or OMC.

3.

Non availability of pair at the time of putting through a new connection.

4.

Alarm from the control panel of the pressurization system.

2.3

Location of a fault in working cable caused due to the digging of any agency can be easily identified / detected by cable route patrol or through information’s from local people. These types of faults and breakdowns are immediately brought to notice or identified by the complaints given by the effected subscribers.

2.4

Failure of weak and imperfect joint due to entry of moisture is a common phenomenon in this country. Presently usage of polythene insulated jelly filled cable has made this type of joint failure a rare phenomenon and detection an easy affair. If there is any damage in the sheath, the entry of the moisture will be avoided due to the presence of jelly. However even the entry of moisture can not create any fault as polythene insulation remaining unaffected by moisture or water. The following is an example of the detection of joint failure (low insulation and earth fault) :-

RTTC, NAGPUR

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Underground Cable

Conditions :1. 2.

Cable used is jelly filled Cable diagram is very much up-to-date

The above diagram is a part of the cable diagram of a pillar. For example the telephones of DP nos. 1 and 2 are reported to be faulty. Now consulting the pillar diagram it can immediately be referred that joint - 2 is faulty. No necessity of localization testing is required. Now by consulting the cable plan and with the help of route and joint indicator the faulty joint - 2 can be physically localized. For paper insulation cable, this type of localization is not possible because fault may arise any where in the body of the cable between joint - 1 and joint - 2 due the entry of moisture through sheath puncture. Hence the localization of this type of fault by proper instrument is unavoidable. 2.5

Localization of Fault by instruments The following instruments are generally in use for the localization of cable fault.

2.5.1

Multimeter or A.V.O. meter: These instruments are used for finding out(a) (b) (c)

2.5.2

Resistance of wire or of a pair (loop) continuity of a wire between two points Numbering of the pairs, if there is reversal at any intermediate

point.

BRIDGE MEGGAR : This instrument is extensively used in all the cable maintenance sections. This works on Whetstone Bridge principle and is used generally for the following purposes :: (a) (b)

Accurate measurement of loop and wire resistances Measurement of cross insulation between the wires of the same or between the pairs of a cable. (c) Earth insulation between a wire or pair and earth. (d) Localization off dead-earth fault (when resistance between the wire and earth is very low). (e) Very rough localization of ‘Disc.’ fault (principle of condenser discharge). 2.5.3 EARTH FAULT LOCALISATION BY BRIDGE MEAGER RTTC, NAGPUR

pair

Page 164 of 185

faulty

Underground Cable

THE FOLLOWING CONDITIONS MUST BE SATISFIED :1.

The fault must be dead – earth

2.

One good wire must be available between the testing station and the point from where test is given at the looping end. the length and gauge of the good wire is not required to be the same as that the faulty wire. The good wire may have a separate route than the faulty wire.

3.

No presence of foreign battery.

4.

Useful for localizing four faults (a) (b) (c) (d)

Condition of the fault (whether dead earth or not) Earth insulation of the good wire Resistance of the faulty wire and good wire looped at the distant Valley loop test. –used for localizing earth or contact faults. ( constant arm radio Bridge )

(e)

Murray test - used for localizing earth or contact faults on short lines. (variable arm radio bridge)

end

The procedure for connections, testing and formula for manipulating the test-data to find out the distance of the fault from the testing end are available with each instrument. 3.0 PULSE ECHO TESTER OR ECHO METER This is the modern method and reliable method for measurement of cables of any type. This instrument provides reasonably an accurate distance measurement. This instrument works on the pulse reflection principle. The pulses (sin2 form ) which are created by a generator and which are suitable for the location or places of error are transmitted through cable, the part of the pulse power is reflected at the fault according to magnitude of power. This is observed on the CRT screen. It makes use of characteristic impedance of the conductor pair whose deviation from the nominal characteristic impedance determines the intensity of reflection or the reflection coefficient The pulse echo test method provides quantitative as well as qualitative information on any transmission cable - impedance loss, Rise time, electrical length and discontinuities in a single measurement. Pre-requisite :- while using this instrument for localization of fault, the gauge of the conductor and type of insulation of the cable under test must be known. This instrument can detect and localize various types of faults in open wire and under Ground cable provided the impedance irregularity on the pair at the fault-point is large enough to cause a distinctly visible reflection of the screen. The type of the faults those can be localized by this instrument are:RTTC, NAGPUR

Page 165 of 185

Underground Cable (a) (b) (e) (g) (h)

Open circuit/disc (b) Short circuits High resistance point (d) Partial contacts Low insulation fault (f) Split pairs Water logged section in PE insulated air core cable Dent in outer conductor of coaxial cables etc.

In some situations it can also localize the multiple faults in a circuit. It can also display the condition of impendence irregularities i.e. the quality of a newly made joint. This instrument can be very efficiently used for checking up the length of the cable in the drum before laying . Operation of this instrument takes a very little time in some cases a few seconds only. One commercial brand of this instrument is of Brand and is known as APLAB cable fault locator- 3039 manufactured in our country having the facility of direct digital distance reach out display of the distance. During the time of jointing the cable, or terminating the cable at terminal points like MDF, Cabinet, pillar, DP etc. a good number of wires become break or looped due to bad workmanship. The disconnection & loop faults may arise due to various other reasons. The localization of disc and loop fault simple with the help of the above meter.

3.1 FUNCTION OF CONTROLS AND INDICATORS :: 1. CRT intensity control :: Controls intensity or brightness on the screen. 2. CRT focus control RTTC, NAGPUR

:: For focus or sharpness of Oscilloscope display. Page 166 of 185

Underground Cable

3. CRT screen

:: Viewing transmitted pulse and reflection from fault.

4. Horizontal position

:: For controlling right & left movement of pulses

5. Vertical position

:: For controlling right & left movement of pulses

6. Horizontal expansion :: Expanding pulse in order to obtain accurate display. 7. Vertical Gain :: Controls vertical amplification of the pulse reflection on the oscilloscope screen 8. Velocity selector

:: For selecting one half the velocity of propagation value for the cable under test.

9&10.

:: For connecting pair under test and reference pair respectively.

L1 & L2

11. Battery charge Low Battery level :: To indicate the sufficient level of battery when LED requirement of recharging when LED is on. 12. Distance readout

:: Five LED type digits to display distance in meter.

13. Power on / off

:: To switch power on / off for the instrument.

14. Range selector

:: To select ranges of distances expected to be fault for providing progressively wide pulses required for00.3km, 3 km, 0-10km ranges respectively.

15. Alternate trace selection :: When pressed CRT shows complete trace of the cable under test and allows the reflection to be shifted towards the transmitted pulse as controlled by Trace shift control. When not pressed only one trace is displayed. 16. Shift / measure selector :: In depressed (SET) position, the trance shift control can be used to pinpoint a reflection. When pressed (READ) allows digital readout of the distance to the selected pulse reflection. 17. Reference pair selector :: When pressed allows reference pair connected to L2 to be shown on alternate trace for comparison to faulty pair connected to L1. 18. Trace shift

:: A 10 turn control allows alignment of reflected pulse with the leading edge of the transmitted pulse to obtain the distance measurement.

19. External DC power

:: Jack for external 12 to 15 V DC -ve ground source.

20. Chassis ground 21. Sun shied RTTC, NAGPUR

:: Jack for chassis ground for user safety. :: To operate the test set in bright sunlight. Page 167 of 185

Underground Cable

3.2 PROCEDURE TO TEST :: a. Check Battery level before taking to the place of testing. Battery charge LED should be off on the panel. b. There should be no voltage on the pair to be tested. c. Set the V/2 value for the cable using velocity selector switch ( one half the velocity of propagation value for the cable under test. d. Adjust the vertical gain sensitivity control to obtain pulse height of two divisions height. e. Adjust the horizontal position control so that the foot of pulse is aligned with vertical line. T

f. Connect the meter to the pair to be tested at L1 and reference pair at L2 g. Adjust the horizontal expansion control to show the reflected pulse on the right side of the screen. h. Depress the Depress the alternate trace selector switch. Adjust the trace shift control, so that the foot of the transmitted pulse is observed as below.

T+ i. Depress the SET / READ switch. Read the distance in display. Subtract the length of the test leads to obtain the actual distance. 3.3 OPERATING CONSIDERATIONS :: 1. 2. 3.

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A good cable with a matched termination displays a flat trace with no reflection. If the measured fault location is near a splice, or if near a construction site where recent digging has been done, it is quite probable the fault is located there. Water existing in a splice case or in a jelly filled cable may produce a very small reflection due to the confined area of water. Water reflections can be seen on the Model 3039 long before actual deterioration of the cable insulation occurs as the water changes the velocity factor of the cable, making the measured distance to the wet section subject to error. Page 168 of 185

Underground Cable A cable pair may have more than one fault, so the first fault can easily mask a more remote fault. Then locate the closest fault then locate and repair the more distant faults. 4.0 INDICATION OF TYPICAL FAULTS :: WHEN THE FAULT IS WITH IN FEW METERS FROM THE TESTING POINT IT IS DIFFICULT TO GET AN ACCURATE READING. THIS CAN BE OVERCOME BY CONNECTING A DUMMY 50 TO 100 METER LENGTH OF CABLE BETWEEN METER AND PAIR TO BE TESTED. THE FINAL ACTUAL MEASUREMENT IS GOT BY SUBSTRACTING THE LENGTH FROM READING SHOWN IN THE METER.

1. Open circuit :: Open circuit gives a positive reflection at the point of break. If both conductors are open, reflection amplitude is grater and reflection at open far end of cable is not seen. 2. Short circuit ::The contact or short gives a negative reflection and far end reflection is not seen. If low resistance is across pair, a smaller negative reflection is seen and smaller positive reflection may show open far end.

3. Sheath fault ::A short or low resistance between one or both conductors shows a negative reflection, which is smaller as resistance increases. A small reflection is seen at the fat end. Connect the meter between the sheath and one or both conductors. Sheath should not be grounded when making this test 4. Open sheath :: Connect as many good pairs as possible to one test lead and the sheath to the other lead. A positive reflection is seen.

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Underground Cable 5. Resistive splice :: Cable splice shows positive reflection, which is higher as resistance increases.

6. Good splice :: Even good splices show a reflection because of capacitance change. This shows as a small positive reflection followed by a negative one.

7.Split pair.:: Wires between two pairs are split as shown at right. The reflection is a positive pulse, but is smaller than that for a resistive splice.

8.Water in cable :: Water in section of cable affects dielectric. A negative reflection shows where water begins and positive where water ends. Amount of reflection shown by degree of saturation. To better pinpoint watered section, make tests from each end of cable. 9. Cable Measurements if V/2 is known :: a. It is recommended that voltage not to be present on the cable. b. If far end of cable is terminated temporarily remove the termination. c. Connect the instrument to the cable and measure the length.

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Underground Cable 10. To find V/2 if cable length is known :: a. Connect the instrument to a cable pair of good insulation but with out far end termination. b. Measure the cable in the normal manner by aligning the reflected pulse with the transmitted pulse. c. Adjust the value on the V/2 velocity selector switches until the distance readout shows the actual cable length.

11. Comparison of faulty cable or pair with one known to good cable or pair a. Connect the instrument to a cable pair of good insulation to the L2 jacks, and faulty one to the L1 jack. b. With the line select pushbutton in the out position, measure the fault location in the normal manner. c. Press the line select pushbutton. Note that the screen provides a simultaneous display of the two cables and shows the fault location relative to the far end of the good cable. 5. CABLE TESTER MODEL 5199 :: Is also used for testing underground telecommunication cables to find out all the varieties of faults the operation is similar to the above description of APLAB instrument MRPC – ISRC consultants Instrument for detecting Low insulation, Contact & earth with foreign potential faults. 6.0

In addition to the above various types of instrument for localization of fault and maintenance of the cable used are generally :(a) (c) (e) (g)

cable route detector (b) Halide leak detector Pressure gauge tester (d) Digital cross talk & attenuation Capacity unbalance tester(f) Insulation & resistance tester. Line man Hand set (Recently developed by TRC vide specification No. 52-101/86 Issue dtd. 5.2.87

7.0 LOCALISATION OF MIXED GAUGE FAULTS :In a mixed gauge the gauge of the faulty pair is not same throughout the length. It has some gauss of conductor upto certain length and of different gauge after that. It may have several section of different resistance. In above case the faulty pair is having three different section. The resistance to the fault is obtained as in case of normal faults. But for calculating distance to the fault, the conductor gauge at different section must be considered. EXAMPLE :: Let a = 50 ohms/km, b = 75 ohms/km, c= = 40 ohms/km. Length of first section = 2 km. Length of second section = 3 km. Length of third section = 4 km. RTTC, NAGPUR Page 171 of 185

Underground Cable Let resistance to the fault obtained from cable fault locator in 150 ohms. Now first we have to find out in which section our fault may exist. the royal resistance of first section is 2 x 50 = 100 ohms, therefore, our fault can not lie in this section. therefore our fault may exist in this section only. Distance to the fault (In second section)

=150 - total resistance of first section 75 = 150 - 100 = 50 = 2/3 km. (Line section) 75 75

8.0 Other various meters in the market are :: •

APLAB-Seba FERROLUX Model PCT 01 ::

Audio frequency system for cable route Location and Depth indication. •

Low insulation fault locator :: Model 3 AT Aishwarya Telecom PVT Limited with printer attaching facility. To locate low insulation, contact, battery, moisture, single limb and construction defects with a range of 0 – 20 km • Fault master - 011 & 011 :: To locate short, open, foreign potential, etc

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QUESTION BANK FOR UNDERGROUND TELECOM CABLES

Chapter I I. Fill the blank with suitable word:: 1. The circuit between two exchanges in a local network is called …..… …….. . 2 .……………. Is the last cable termination point from where subscriber line is connected. 3. The cable connecting Pillar and DP is called ………………………… 4. In ducted cable system we use ……………………….. cables are used 5. Entry of moisture into the core of cable is prevented by filling …….. ………… …… in PIJF cables. 6. In Telecommunication cable network cables are required to be protected from …………………….. ………….prevent damages from external sources. 7. PCM cables are designed with a conductor diameter of ………..mm. 8. Paper Insulated cables are prone to more faults due to entry of ……… ……… ….. 9. Over lay of conductors in a pair is done during manufacture of telecom cable to prevent effect of ………………………. 10. A 400 pair cable consist of ……………. No of super units of ………….. …… ………… size. II.

INDICATE WHETHER TRUE OR FALSE

11. The material used as conductor in local telecom under ground cables is high conductivity annealed copper . ( ) 12. The sheath of a underground cable protect the conductors from damage due to entry of moisture to safe guard the insulation resistance of pairs. ( ) 13. Jacket is the sheathing arrangement made over armoured cable to protect the armour against corrosion and rusting. ( ) RTTC, NAGPUR

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14. Paper Insulated cables are now being replaced with Polythene insulated Jelly filled cables to improve efficiency of cable network ( )

Chapter II I. Fill the blank with suitable word:: 1. while selecting the route for laying cable ------------------ -----------route should selected. 2. While crossing power cables the telecom cables should be laid at ---------------- ------- to the power cables. 3. While crossing roads it should be seen that any no point ---------------- ---------- should not fall in between road crossing. 4. While laying cables near bends the bending should be minimum of---------- ------- ------------time the diameter of the cable. 5. The laying of telecom cables across railway crossing should be laid in ------------------------------pipes. 6. While paving out cable it should be seen that damages to the sheath is to be -----------------.------7. Flooding of the trench after fresh digging and laying will help in detecting --------------------------- caused to the existing cables. 8. The protective stone slabs which are placed over the cables after laying in the trench are called -------------- ---------------- and they help in preventing damages due to digging by other service utility personnel. 9. Indicator kept at 200 m apart in the route of the cable is called ----------------- -------------------- . 10. The indicator kept at every joint place is called ------------ -------. 11. While crossing the power cables the telecom cables should be laid in solid for a distance of ------------ ------m on either

II. Answer the following questions in one sentence. 12.Write the standard mechanical protections that are used normally. 13.Indicate the two important checks to be done after receiving the cables from store depot and before laying the cable.

CHAPTER III I. Fill the blank with suitable word:: 1.During Area transfer the pairs from one exchange are extended to another exchange using -----------------type of jointing of the pairs. These pairs are available to both the exchanges till the switch over of area is completed. 2.The jointing of pairs of one large size cable to two or more smaller size cables is called --------------- jointing. 3.The jointing of one cable to another cable of same size is called ------------------- jointing. RTTC, NAGPUR

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Underground Cable 4.Conventional twist jointing methods of conductors is used generally for the ---------------------- insulated conductors and it requires a material called -------------------------------or preventing the contact between the de-insulated conductors from each other. 5.For jointing 100 pair PIJF cable conductors----------------number of UY connectors are required. 6.For jointing conductors of bigger sizes of PIJF cables ------------------sized module are used. 7.The ALSS joint is generally more used for closing the joints of -------------------type of cables because of its reentry technique

II. Answer the following questions in one sentence. 8. Write the three cases where the necessity of joint occurs. 9.Write the three techniques that are in use in jointing of cable conductors. OBSERVE : : 1. Jointing procedures shown in practical sessions 2. Conductor jointing using 20 pair modular technique CHAPTER IV

I. Fill the blank with suitable word:: 1. THE INTRODUCTION OF PILLAR OR CABINET IN A LOCAL CABLE NETWORK MAKES IT ---------------------- . 2. In a local cable network where there are no cabinets and pillars then the network is called -------------------- system 3. In a local cable network where there are Pillars only then the cable connected to DP and pillar is called-------------------- cable and the cable connected to pillar and Exchange MDF is called ----------------------- cable. 4. The size of the module used in Krone type CT Box termination of underground cables at Pillar or cabinet is ------------- . 5. In krone type CT Box ---------------------- type of wiring is only done. 6. No soldering, no screwing and no stripping of insulation is required for termination of cable pairs on a ----------------- type of termination points. 7. Stripping of extra length of insulated wire is achieved in krone type CT Box by using the tool ------------------------ -----------. 8. The contact used in krone CT Box is an --------------- contact. 9. The disconnection or isolation of wires in a Krone CT Box can be achieved by simple insertion ---------------------

II. Answer the following questions in one sentence. 10. Write two types of DPs basing on the Installation procedure. 11. Write important point to be kept in view while laying cable at the termination points for preparing leading in cables for terminations. RTTC, NAGPUR

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PRACTICE :: 1. CT Box location, counting of Pillar pairs and Identification of primary and distribution. 2. Termination of cables and also jumper wire connecting primary and distribution. CHAPTER V

I.

Fill the blank with suitable word::

1. Power induction in telecom lines is due to -------------- of power and telecommunication wires. 2.

At the crossing of power lines, telecom wires or cables should be crossed at almost ------------------ with sufficient vertical separation.

3. For arresting induction from Railway traction ------------ transformers and -----------------------------are used by railways. 4.

Installation of ------------- -------------- ----------- at both ends of telecom line or cable involved in parallelism and at individual points along the line will protect the equipment and personnel from dangers of electrocution.

5. The PTCC clearance is to be obtained if the length of parallelism between telecom and power lines is ---------------------- and above. 6. The minimum vertical clearance between power and telecom line is --------- . 7. While crossing power cables the telecom cables should be laid at right angles and should be laid in -------------------------. 8. For preventing any danger of power line and telecom line coming into contact and before actual tripping of power line -------------------- -------------- ---------- are installed on top most wires of the telecommunication lines. 9. The quality of telecommunication circuit and signals are affected by the type of induction called ---------- ------------- ----------10. The arrangement provided above telecom lines or below the power lines to safe guard the personnel and equipment due to contact of the lines is called ---------11. Gas discharge Tubes are of --------------- ---------- restoring type. They come to normal position once the induced voltage drops down to with in limits.

II.

ANSWER THE FOLLOWING QUESTIONS IN ONE SENTENCE.

12.Write short notes on impact of power lines on telecom network. 13.Write two safety to be observed for cables while handling cable at places where power induction may occur. 14.Write two safety measures to be observed by the staff to avoid danger of electrocution. 15.Write effect of induction on signaling circuits. CHAPTER VI RTTC, NAGPUR

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I. Write short answer for the following questions. 1.Write important cable record to be maintained. 2.Write important features of maps and diagrams to be maintained. 3.Write the details a DP card shows. 4.Write the details a pillar card shows. 5.Write importance of foot patrol.

PRACTICE OF FILLING CARDS : 1. Filling of various columns in a DP card 1. Filling of various columns Pillar / Cabinet card 2. Filling of various columns Subscriber Index Card. 3. Filling of various columns MDF card 4. Numbering of Pillars and DPs scientifically as illustrated in lectures. CHAPTERVII 1.CRMS stands for ? 2.Benefits of CRMS ?

CHAPTER VIII

Short answer questions: 1. What is the purpose of Fault card position? 2. AT WHAT POSITION, THE RESULTS OF THE TESTING OF A FAULTY TELEPHONE LINE ARE INDICATED ON THE DOCKET? 3. WHAT ARE THE CHECKS TO BE MADE BY THE TRAFFIC SECTION OF THE EXCHANGE OVER THE PENDING DOCKETS? RTTC, NAGPUR

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4. GIVE BRIEF DETAILS OF THE COMPLAINT TO BE FED TO THE COMPUTER IN CASE OF COMPUTERIZED FRS. 5. WHAT ARE THE REPORTS CAN BE OBTAINED IN A COMPUTERIZED FRS? 6. MENTION THREE ADVANTAGES OF COMPUTERIZING THE FAULT CONTROL SYSTEM. CHAPTER IX I. FILL THE BLANKS WITH SUITABLE WORDS. 1. Incomplete and sometimes absence of documentation and records, and negligence of preventive as well as annual maintenance of external plant result in --------------------------- . 2. Improper cable works and lack of Co-ordination with other public utility services result in cable ------------------------. 3. It is correct method to directly terminate ----------------------MDF by laying ---------------------------- type of cables.

------------ on

4. It is not good to provide joints before the plinth of the pillar, instead it is better to terminate the cable ------------------------on to the CT boxes. This will eliminate cluster of joints surrounding cabinets/pillars. 5. Eliminate joints at the bottom of the DP posts by laying sufficient length of distribution cable ----------------------common branching point and it also reduces the cost of external plant. 6. Certain uncared operations in cable constructions, though simple in nature, may lead to -------------- ----------- during life time of the cables. 7. The tendency of some cable splicers to develop their own theory of jointing in the absence of full complement of jointing kit should be ------------------------, which otherwise results in large number of joint failures. 8. In case of PIJF cables ensure use of -------------- for pressing UY connectors for jointing the conductors instead of ordinary pliers to avoid break faults. 9. Ensure use of ---------------------------- in the splice to avoid any possibility of ingress of moisture setting in to the joint of PIJF cables. 10. Ensure sheath continuity at --------------------- and earthing at DP pillar and MDF. 11. A missing poly-al sheath continuity can result --------------------------due to power induction. RTTC, NAGPUR

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Underground Cable 12. As far as possible a single length of drop wire should be run from ------------------------------up to maximum length of four spans 13. Elimination of ----------------------in drop wire reduces high resistance faults. Following accessories are to be used. 14. Whenever a trench is dug for laying new telephone cables or some other department digs the trench for installation of their services, the trench may be filled in with adequate quantity of water for two or three days to simulate the monsoon conditions. This is called --------------------------- of trench. 15. If the water is not allowed to remain in the trench for adequate period during flooding operation detection of small faults --------------------16. Gas pressurization is a preventive maintenance work for -------------------------------------------. Dry air or Nitrogen is fed into dry core cables either by use of cylinders or compressor dryer units at a pressure of 0.7 KSC either by static feed system or continuous feed system

CHAPTER X I. FILL THE BLANKS WITH SUITABLE WORDS. 1. Fault Prone cables with low insulation should be -------------- -----------. 2. All heavy over head alignment should be --------------------by new DPs. 3. Cabinets and pillars should be installed for more than ------------------------------------line exchanges. 4. Service line is the portion of the ------------------------- from pole Mount DP to the terminating points. 5. Subscribers --------------------- is the loop is equal to the sum of resistance’s of each limb of subscriber’s line and telephone set. 6. Internal DP is the cable termination Point where underground cable is laid directly to the ------------------7. The Inspection of

---------------------- consists of the inspections carried out by

checking DPs / cabinet Pillars and subscriber lines. 8. During inspection & -physical inspection, electrical parameters of the lines and dials are to be ------------------------.. 9. What are the points to be checked during inspection of External plant. 10. Points should be carried out at cabinets and pillars for ? 11. Points to be checked of pole mounted DP 100% check of DP is

necessary.

12. Write the tests for Subscribers Dial . RTTC, NAGPUR

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Underground Cable 13. Write the dis advantages of teeing of underground cable. 14. write some test for Junction Cables.

CHAPTER XI

I. Fill the blank with suitable word:: 1. When the insulation between the earth and the conductor in test in a cable becomes very low the fault is called ----------------------------------2. When the insulation between conductors in the cable or between the pairs or between pair and earth falls below a prescribed limit (normally 0.5 meg ohm) the fault is called ------------------------------------------3. When the Conductor is cut then the fault is called ----------------------------4. When the resistance between the wires or between the conductors becomes very low even without any loop in the circuit on the pairs the fault is called ----------------. 5. The existence of potential, even when the circuit is idle or isolated from the potential of exchange and subscriber premises equipment then the fault is called ------------------------------------6. Chemical and electro chemical action which damages the outer sheath and the conductor of the cable is due to ------------------------------7. Sheath is effected due to mechanical stresses during construction and hence------------------------------------ happen longitudinal, transverse, tensional oscillation or periodical variation of temperature or repeated overheating of the sheath 8. Bad constructional practices like in-efficient, nonstandard and careless work-man ship, specially during the time of laying & jointing of cable result in ----------------------------9. This instrument is extensively used in all the cable maintenance sections for testing all types of faults which on Wheatstone Bridge principle is --------------------

II. Write short notes On :: 10. Write different procedures adopted for fault detection. PRACTICE :: 1. Practice and simulation of faults 2. Testing of all the above types of faults using Megger. 3. Localizing the fault using APLAB fault locator for various types of faults. 4. Practicing all the functions of the knobs on test panel of APLAB. RTTC, NAGPUR

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KEY TO QUESTION BANK UNDERGRUND TELECOM CABLES. Answers to Chapter I:: 1. Junction circuit 2. Distribution point (D.P.) 3. Distribution cable 1. Unarmoured cables 5. Jelly compound 6. Mechanical protection. 7. 0.63 mm 8. moisture or water 9. cross talk 10. 8, 50 pairs. 11. True 12. True 13. true 14. True

Answers to Chapter II 1. Shortest 2. Right angles 3. Cable joints 4. 15 times 5. GI pipes 6. avoided 7. damages 8. warning Bricks 9.route indicators 10. Joint indicators 11. 90 cm 12. The standard mechanical protections that are normally used are warning bricks over the cable. Rcc tiles, Split pipes, and GI pipes in concrete. 13 Physical deformity over looked by QA, which is rare and Damages caused during loading and unloading or at stores.

Answers to Chapter III:: 1. Tee joint 5. 200 numbers

2. Branch. 3. Straight joint. 4. Paper insulated, sleeves 6. 20 pair 7. Lead sheathed

8. Limited lengths availability, for jointing new cable to existing cable, for transferring one cable pair from one area to another area. 9. Twisting, Using UY connectors and Modular jointing techniques are the three types of conductor jointing that are used in the telecom cable networks.

Answers to Chapter IV:: 1, Flexible cable system 2. Rigid cable system. 3. Distribution , Primary. 4. 100 pairs 5. A type of wiring. 6. Krone 7. Insertion. 8. Air & Gas 9. Disconnection plug or Test plug 10.The two types of DPS are External DP and Internal DP (or wall DP). 11. While preparing leading in cables at MDF, Cabinet, Pillar or at DPs the end cables laid at the termination points additional length is to be kept to directly terminate the cable pairs with out any joint near the termination point to avoid additional joints. Answers to Chapter V:: RTTC, NAGPUR

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1.Parallelism 2. 90 degrees 5. 800 meters. 6. 2 feet 8. Power contact protectors. 10.personnel

3 Booster, Return conductors 4.GD tubes. 7. Solids or pipes. 9. Low frequency induction. 11. guarding .

12. Serious hazards to Equipment and personal of telecom equipment due to unaware ness of induction as the equipment is designed to take 50 v or less voltage. The fact that 50 V is our working voltage, which is not dangerous weighs heavily in the mind of the staff handling lines. 13. (a)Get PTCC clearance the routes as per the norms and Lay cables below 2 feet in solid or pipes at 90 degrees to the power cable. (b) The poly-al sheath continuity should be invariably provided continuity at all joint places. 14. While using insulated tools like pliers and gloves, etc. proper care must be taken to ensure that insulation is adequate and intact. 15. The low frequency induction has a serious effect on the quality of telecom circuits and signaling as a whole. The effect varies with the length of parallelism, distance of separation and soil receptivity.

Answers to Chapter VI : 1. Cable records are very effective tools for the maintenance of cable networks. The cable records may be divided into three categories viz ( a) Plan

( b) Line diagram and

( c) cards.

2. This is necessary for all existing Exchanges. It may be drawn to any convenient scale say 5 cm to 10 cms. to a km and may show the following details:i..

Boundaries of existing exchange area defined precisely

ii.

Proposed boundaries of future exchanges but liable to alterations.

iii.

Location of existing exchanges

iv.

Localities where future exchanges may be situated. 3.These cards show the number, size type (internal or external) and location of the DP and how each terminal of the DP is unutilized. They also indicate

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the distant end terminal code corresponding to each terminal of the DP one card is required for each 10 or 20 pairs DP 4.Each card shows the following particulars, number , size and type of the CT. box, size of shell, location of the cabinet or pillar, circuit working. One each terminal of the CT box, the terminal to which it is jumpered or strapped for setting up the circuit, the distant end terminal code corresponding to each terminal of the CT box and the codes of cable pairs connected to the terminals. 2. Regular foot patrolling of cable routes are to be carried out by cable maintenance party. They will keep watch on the cable routes, the indicators and the condition of Dps. The foot patrolling will effectively reduce the damages to the cables caused by the digging of various other service utility departments and individuals. Answers to chapter VII 1.Cable record management system. 2.Cetralised data base, telecom assets management in a singular system, integration with FRS, ease of fault localization, Estimates for up gradation/expansion can be generated quickly. Answers to Chapter VIII Key to Short Answers :: 1.At this position, a separate fault card is maintained for each telephone. On receipt of a fault docket, the operator make an entry of the date and time of fault reported on the fault card. The docket with the fault card clipped to it should be forwarded to the Initial testing position. 2. At Initial Testing Position 3.Detection of missing dockets, make a list of all the cases where the fault rectification has got delayed or is likely to get deleted. 4.Directory number of the customer, name and address and other accessories, category of the telephone, type of subscriber, MDF termination details, Pillar and DP termination details. 5.Details of complaints booked, pending faults, faults cleared with nature of faults, details of dockets pending for initial testing / final testing at any instance of time, list of telephones which recorded two or more than two faults during a particular period, RTTC, NAGPUR

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analysis of total complaints booked in the month, fault analysis reports, details of cable faults. 6.

1. It handles very huge data very efficiently with far greater accuracy and speed as compared to manual system. 2. Flow of information from one position to another is almost instantaneous. 3. The paper work is almost eliminated. Answers to Chapter IX : 1. Break down of cables 2. cable faults 3. Underground cables , PIJF 4. tails directly. 5. directly from 8. Crimping pliers 12. DP

6. cable joint faults 9. Jelly. 13.Joints

10. Joints

7. discouraged. 11. noise or induction.

14. Flooding of trench.

15. go unnoticed

16. Dry core cables

Answer to Chapter X : 1. replaced 2. removed by erection of 3. 500 line capacity line 5. loop resistance 6. Customer premises 7. external plant 8. Tested as per norms a. d. g. I.

4. Subscriber

Answer to question No.9 Cabinets and pillars. b. Pole- Mounted DP c.Internal DP Service line. e. Indoor House Wiring Electric Parameters of Line h.Dial of subscriber’s instrument Junction cable

Answer to question No.10 m) The Cabinets /pillars should be located at obstruction free place on concrete base and height should be above flood level. n) The cabinet / pillars should be numbered properly o) The doors should open and close freely. p) The cabinet/pillar should be neat & clean from inside. q) The pillar shell should be firmly fixed and bolts should be tight. r) CT Box should be fixed firmly to the frame and all fixing screws should be tight. Answer to question No.11 o) DP should be located at obstruction free place and no way near the vicinity of electric poles etc. p) The DP should be painted and numbered. q) Minimum height of DP should be 9’feet (2.75M) from the ground. RTTC, NAGPUR Page 184 of 185

Underground Cable r)

The DP should be properly fitted to the post by means of standard U back and saddles. The back of the U backs should be flattered for giving good grip on the tubular posts.

Answer to question No.12 By dialing 0.-10 IPS ::: Acceptable standard 10+1 IPS Answer to question No.13 It has been noticed that tested for subscribers capacitance and insulation are distorted due to long length of Teed pairs. These lines may be offered for A/T after Tee joint is removed.

ANSWER TO QUESTION NO.14 The following information should be noted about the junction cables f) Type of Jn cable. g) Places between junction cables is used. h) Total length of Junction cable i) Gauge & Capacity of junction cable j) Loaded of Unloaded.

Answers to Chapter XI : 1. Earth fault. 2. low insulation 4. Loop or short circuit. 5. Foreign potential moisture. 7. Inter crystalline sheath damages network. 9. Meggar

3. Break or high resistance. 6. Corrosion due to 8. Break down of

10.The procedures used for fault detection, diagnosis and location on subscriber lines are 1.Self supervision – is a permanent feature and fault is noticed physically also. 2.Performance monitoring – Gives the indication of the quality of the service. 3.Routine testing – Indicate the faults that are not noticed physically in normal course. 4.Demand testing – After detecting the side effect of fault.

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