DBR_Cable Selection and Sizing_E-TSC1-725!14!3001
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2 X 600 MW SINGHITARAI THERMAL POWER PROJECT SINGHITARAI - CHHATTISGARH Owner: ATHENA CHHATTISGARH POWER PVT. LTD., In Front of Carmel School, Near Guru Building, Govind Garden, Laxmipur, Raigarh, Chhattisgarh - 496001
Owners Engineer:
ENERGY INFRATECH PVT.LTD. Thermal Power Divison, 7-1-24, B Block, 5th Floor, Roxana Towers, Greenlands, Begumpet, Hyderabad-500016 Ph No.:91-40-66570881, Fax No.:91-40-66570888
EPC Contractor:
ABIR Infrastructure Private Limited, Thermal Power Divison, 7-1-24, B Block, 5th Floor, Roxana Towers, Greenlands, Begumpet, Hyderabad-500016 Ph No.:91-40-66570881, Fax No.:91-40-66570888
Consultant To EPC Contractor:
TPSC(I) PRIVATE LIMITED (Wholly owned subsidiary of Toshiba Plant Systems & Services Corporation, Tokyo, Japan)
A-1 Module, D - Quadrant, 2nd Floor, Cyber Towers, Hi-Tec City, Madhapur, Hyderabad - 500 081, INDIA
Document Title:
DBR FOR CABLE SELECTION AND SIZING ABIR Document No.:
STPP-5311-E-11-03-3001, Rev-00
Consultant Doc. No.
E-TSC1-725-14-3001, Rev. 0
DBR FOR CABLE SELECTION & SIZING
DOCUMENT CONTROL SHEET
0
20-04-11
First Issue
REV NO
AM INTLS
DATE
RB SGN
INTLS
DN SGN
INTLS
MS SGN
INTLS
STATUS
SGN
ISSUE PREPARED BY
CHECKED BY
APPROVED BY AUTHORISATION
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
Doc. No.: E-TSC1-725-14-3001
AT SINGHITARAI, CHHATTISGARH Date 18-04-2011
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Page 1 of 17
DBR FOR CABLE SELECTION & SIZING
CONTENTS
Sl. No
Particulars
1.00.00
PURPOSE
2
2.00.00
PLANT INFORMATION
3
3.00.00
REFERENCE DOCUMENTS:- CODES & STANDARDS
4
4.00.00
CABLE SELECTION & SIZING CRITERIA
5
5.00.00
ELECTRICAL NETWORK CHARACTERSTICS
5
6.00.00
TECHNICAL REQUIREMENT OF CABLE
6
7.00.00
SIZING OF POWER CABLE
9
8.00.00
SIZING OF CONTROL CABLE
16
9.00.00
CONCLUSION
16
ANNEXURE
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Page No.
POLYCAB CATALOGUE FOR DERATING FACTOR
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
1 SHEET
Doc. No.: E-TSC1-725-14-3001
AT SINGHITARAI, CHHATTISGARH Date 18-04-2011
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DBR FOR CABLE SELECTION & SIZING 1.00.00 1.01.00
2.00.00
PURPOSE The aim of this document is to give the method and parameters enabling the calculation for selection and sizing of power cables taking into account the rated current, length between main distribution switchboard and electrical consumers, and the de-rating factors due to site and installation conditions and philosophy for selection of control cables for 2X600 MW Coal based Thermal Power Plant at Singhitarai in Chhattisgarh State of India. PLANT INFORMATION 1
Owner
:
ATHENA CHHATTISGARH POWER PVT LTD.
2
Project Name
:
2X600 MW SINGHITARAI THERMAL POWER PROJECT.
3
Location
:
4
Ambient Temperature
:
(i)
Minimum
:
8 degree C
(ii)
Maximum
:
46.5 degree C
6
Relative Humidity
:
35% Min , 88 % Max
6
Seismic Zone
:
Zone – III, as per 1893-2002
7
Auxiliary Power Supply
:
(i)
Motors rated 1500 KW &
:
above. (ii)
11000 V (±10%), 3 phase, 3W, 50 Hz, non-effectively earthed.
AC motors at 200 KW &
:
below 1500 KW. (iii)
Singhitarai, Chhattisgarh
3300 V (±10%), 3 phase, 3W, 50 Hz, non-effectively earthed.
AC motors upto 200 kW.
:
415 V, (±10%), 3 phase, 3 wire, 50 Hz, effectively earthed
(iv)
DC alarm control & Protective
:
220 V DC, 2W, unearthed
devices. (v)
DC motors.
:
220 V (±10%), 2 wire, unearthed DC
(vi)
Lighting fixture and Space
:
240 V, 1 phase, 50 Hz, AC effectively
Heaters.
earthed
(vii)
DCS Power supply
:
240 V AC, 1 phase, 50 Hz, UPS
(viii)
Solid state controls &
:
240 V AC, 1 phase, 50 Hz, non UPS
:
415 V (±10%), 3 phase, 4 wire, 50 Hz
annunciation/
local
control
panel (ix) Project
Construction Power
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
Doc. No.: E-TSC1-725-14-3001
AT SINGHITARAI, CHHATTISGARH Date 18-04-2011
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Page 3 of 17
DBR FOR CABLE SELECTION & SIZING ±5%, AC with effectively earthed 8
Suitability
for
Power
:
Supplies (i)
AC Supply
:
Voltage variation ±10%, Frequency variation ±5%; Combined Voltage and Frequency variation 10%
(ii)
DC Supply
9
Design
Ambient
for
:
198 V to 242 V
:
50.0 degree C
Electrical Equipment
3.00.00
REFERENCE DOCUMENTS-: CODES & STANDARDS IS-1554-1
:
PVC insulated electric cables for working voltages up to and including 1100V.
IS-7098-1
:
Cross linked polyethylene insulated PVC sheathed cables for working voltages up to and including 1100V.
IS:7098-II
:
Cross linked polyethylene insulated PVC sheathed cable for working voltage from 3.3kV upto & including 33 kV.
IS:9968-I
:
Specification of Elastomer Insulated cables for rated voltages upto and including 1100V
IS:6380
:
Specification of elastomeric insulation and sheath of electric cables
IS : 3961
:
Recommended current ratings for cables
IS : 3975
:
Low Carbon Galvanized steel wires, formed wires and tapes for armouring of cables.
IS : 5831
:
PVC insulation and sheath of electrical cables.
IS : 8130
:
Conductors for insulated electrical cables and flexible cords.
IEC:287
:
Calculations of the continuous current rating of cables(100% load factor)
IEC:228
:
Conductors for insulated cables
IEC:502
:
Extruded solid dielectric insulated power cables for rated voltages from 1.00 kV upto 30 kV
IEC-754-I
:
Test on gases evolved during combustion of electric cables.
IEEE-383
:
Standard for type test of Class IE Electric Cables.
IEC -332 Project
Tests on Electric cables under fire conditions.
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
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AT SINGHITARAI, CHHATTISGARH Date 18-04-2011
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DBR FOR CABLE SELECTION & SIZING Part-3 : Tests on bunched wires or cables (category -B) IEC: 230
Impulse tests on cables and their accessories
IEC-331
Fire resisting characteristics of electric cables
IEC-364-5-
Current-carrying capacities in wiring systems-Section 523
52
Second Edition 2001-08
4.00.00
CABLE SELECTION AND SIZING CRITERIA
4.01.00
Cable sizing criteria for Power cable The calculation and technical choice of power cables consist of the determination of the normalized conductor in applying simultaneously the three following conditions: a)
Continuous current capacity: The overheating, in permanent overload (thermal protection current setting), taking into account the site and installation conditions, so that cable components are not exposed to excessive temperature value.
b)
Short time rating: The possibility to carry without degradation, an accidental over current at the end of the cable, taking into account protection devices.
c)
Voltage drop criteria: The voltage drop caused by the current flowing in cores restricted to a value allowing the starting and the permanent loading of the consumers.
The conditions (a) and (b) give the minimal cross section of the conductor. Condition (b) will be applied for all HT feeders and for feeders controlled by ACB’s in case of LV system. Cables shall be sized for rated short circuit current of the respective Swgrs/Boards/MCCs. Feeders controlled by fuses/MCB’s/MCCB’s will not be sized for short circuit rating. The condition (c) gives the maximum length, which can’t be exceeded, in order to comply with the maximum admissible voltage drop. If the length permitted by conditions (c) is insufficient, it will be necessary to increase the cable cross-section consequently. 5.00.00 5.01.01
ELECTRICAL NETWORK CHARACTERISTICS Electrical Network Characteristics A For HT system
Rated voltage (General network)
:
11 kV AC 3 phase & 3.3 kV AC 3 phase.
Frequency
:
50 Hz
Maximum Voltage drop in the cable
from
transformer
to
:
2% (rated conditions)
Panel. Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
Doc. No.: E-TSC1-725-14-3001
AT SINGHITARAI, CHHATTISGARH Date 18-04-2011
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DBR FOR CABLE SELECTION & SIZING
Maximum Voltage drop in the cable from Panel to Motor
:
Maximum voltage drop in the cable during starting of motor. Short Circuit Current for HT Switchboard. Calculated
Maximum
:
:
Short :
Circuit Current.
3% (full load running conditions)
15%
40kA for 1 sec for both voltage grading. (Shall be decide as per short circuit study) As per short circuit study
B For LT system
415 V AC three phase / 240V AC Single phase Rated voltage (General network)
: / 220V DC.
Frequency Maximum Voltage drop in the cable from transformer to MCC. Maximum Voltage drop in the cable from MCC to Motor. Maximum voltage drop in the cable during starting of motor. Maximum
voltage
:
50 Hz
:
2% (rated conditions)
:
3% (full load running conditions)
:
15%
drop from
5% (full load running conditions)
UPS to load end. Short Circuit Current for LV Switchboard Calculated
Maximum
Circuit Current. 6.00.00
Short
:
:
50 /65 kA rms (Shall be decide as per short circuit study) As per short circuit study
TECHNICAL REQUIREMENT OF CABLES A.For HT System
Core
:
Single/Multi core, Multi stranded bare Aluminum
Shape of conductor Grade
:
Compacted Round
:
11/11(UE) kV for 11 kV System & 3.3/3.3 (UE) kV for 3.3 kV System.
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2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
Doc. No.: E-TSC1-725-14-3001
AT SINGHITARAI, CHHATTISGARH Date 18-04-2011
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DBR FOR CABLE SELECTION & SIZING Conductor Screen
:
Triple Extruded semi-conducting compound.
Insulation
:
Extruded XLPE
Insulation Screen
:
Extruded semi-conducting compound in combination with a layer of lapped copper tape.
Maximum permissible conductor temperature: A ) For continuous operation
:
90 deg C
:
250 deg C
:
Extruded PVC Compound type ST-2
B ) Short circuit condition Inner sheath Armouring (Directly buried cable) A ) For single core cable
Aluminium round wire Galvanised steel round wire
B ) For multi core cable External sheath
:
Extruded FRLS, anti termite & anti rodent PVC type ST-2. Flame retardant property shall be as per IEC-60332 Cat C.
Oxygen index
:
Acid gas emission
:
Smoke Density
:
Min. 29 (As per ASTMD 2863) Max. 20% (As per IEC-754-I) Light transmission of min. 40% after the Test.
** For Cable area >= 240 sqmm, shall be considered as single core cable.
B. For LT System (Power Cable)
Core
:
Single core/ Multi core, Multi-stranded bare compacted plain aluminium for sizes greater or equal to 6 sq. mm. Less than 6 sqmm shall be copper Conductor.
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2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
Doc. No.: E-TSC1-725-14-3001
AT SINGHITARAI, CHHATTISGARH Date 18-04-2011
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DBR FOR CABLE SELECTION & SIZING
Grade
1100 V
:
Insulation
XLPE:- For area >= 120 sqmm. PVC:- For area < 120 sqmm
Maximum permissible conductor temperature: A ) For continuous operation
90 deg C for XLPE, 70 deg C for PVC
B ) Short circuit condition
250 deg C for XLPE, 160 deg C for PVC Extruded PVC compound type- ST2 for
Inner sheath
XLPE insulated cable. Extruded PVC compound type- ST1 for PVC insulated cable. Armouring (Directly buried cable) A ) For single core cable
Aluminium round wire Galvanised steel round wire
B ) For multi core cable External sheath
Extruded FRLS, anti termite & anti rodent PVC compound type- ST2 for XLPE insulated cable. Flame retardant property shall be as per IEC-60332 Cat C. Extruded FRLS, anti termite & anti rodent PVC compound type- ST1 for PVC insulated cable. Flame retardant property shall be as per IEC-60332 Cat C.
Oxygen index
Min. 29 (As per ASTMD 2863)
Acid gas emission
:
Smoke Density
:
Max. 20% (As per IEC-754-I) Light transmission of min. 40% after the Test.
Cores of the cables shall be identify by coloring of insulation. Following color scheme shall be adopted:
Project
1 core -
Black
2 core -
Red & Black
3 core -
Red, Yellow & Blue
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
Doc. No.: E-TSC1-725-14-3001
AT SINGHITARAI, CHHATTISGARH Date 18-04-2011
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DBR FOR CABLE SELECTION & SIZING 4 core -
Red, Yellow, Blue and Black
For reduced neutral conductors the core shall be black. ** For Cable area >= 240 sqmm, shall be considered as single core cable. C. For Control Cables
Core
: Multi stranded plain annealed copper. (Class-2 as per IS 8130)
Shape of conductor
: Circular : 2.5 sq. mm
Conductor cross section
: 1100 V
Grade Insulation
: Extruded PVC compound type-A
Maximum permissible conductor temperature: A ) For continuous operation
: 70 deg C : 160 deg C
B ) Short circuit condition
: Extruded PVC compound type ST-1
Inner sheath Armouring ( Directly buried cable) For multi core cable
: Galvanised steel round wire
External sheath
: Extruded FRLS, anti termite & anti rodent PVC compound type –ST1. Flame retardant property shall be as per IEC60332 Cat C.
Oxygen index
: Min. 29 (As per ASTMD 2863)
Acid gas emission
:
Smoke Density
:
Max. 20% (As per IEC-754-I) Light transmission of min. 40% after the Test.
Cores of the cables of upto 5 cores shall be identified by colouring of insulation. Following colour scheme shall be adopted.
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2 core
-
Red & Black
3 core
-
Red, Yellow & Blue
4 core
-
Red, Yellow, Blue and Black
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
Doc. No.: E-TSC1-725-14-3001
AT SINGHITARAI, CHHATTISGARH Date 18-04-2011
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DBR FOR CABLE SELECTION & SIZING 5 core
-
Red, Yellow, Blue, Black and Grey
For cables having more than 5 cores, core identification shall be done by numbering the insulation of cores sequentially, starting by number 1 in the inner layer (e.g. say for 10 core cable, core numbering shall be from 1 to 10). All the numbers shall be of same color. The color of insulation for all cores shall be grey only. 7.00.00
SIZING OF POWER CABLE A. Cable sizes based on short circuit current consideration Short circuit current and the time duration are related with the following formula : I 1 2t 1 = I 2 2t 2 Where, I 1 = Short circuit current for t 1 second I 2 = Short circuit current for t 2 second The short circuit current & interrupting time shall be as under: 1. For 11kV –
40kA – 0.2 sec for outgoing motor feeders. 40kA – 0.2 sec for outgoing transformer feeders 40kA – 1 sec for tie feeders
2. For 3.3kV – 40kA – 0.2 sec for outgoing motor feeders 3. For 415V---
50/65kA – 0.2 sec for outgoing motor feeders 50/65kA – 0.2 sec for outgoing transformer feeders 50/65kA – 1 sec for tie feeders
For Fuse/MCB/MCCB protected feeders, minimum cross section criteria will not apply. In that feeders continuous current rating and voltage drop will be the deciding factor for selecting the suitable cables. Also Outgoing feeders where only IDMTL protection is provided, 1 sec shall be considered for cable sizing. With the above formula the equivalent fault current for 1 second is calculated and the corresponding cable cross sectional size is selected from cable catalogue. B. Cable sizes based on maximum continuous load current (1)
The allowable continuous current rating of cable shall be calculated using the following formula:
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
Doc. No.: E-TSC1-725-14-3001
AT SINGHITARAI, CHHATTISGARH Date 18-04-2011
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Page 10 of 17
DBR FOR CABLE SELECTION & SIZING
Io
≥
Ie / K R
Io
-
Allowable continuous current rating of cable in Amps
Ie
-
Rated current of equipment in Amps
KR
-
Overall Derating factor due to temperature and grouping of
Where
Cables (2)
Derating factors
a) Ambient temperature derating factor : K T
KT =
Θ2 - Θ1 Θ2 - Θ3
Θ 2 = Core maximum temperature (90° C for XLPE insulation)
(70° C for PVC insulation)
For cables in trays, trenches, racks Θ 1 = Design temperature for aerial cables: 50° C Θ 3 = Reference ambient air temperature: 40° C (as per vendor catalogue)
KT =
90 - 50 = 0.89 (For XLPE cable) 90 - 40
KT =
70 - 50 = 0.81 (For PVC cable) 70 - 40
For cables laid directly in ground Θ 1 = Design temperature for aerial cables: 40° C Θ 3 = Reference ambient ground temperature: 30° C (as per vendor catalogue)
KT =
90 - 40 = 0.91 (For XLPE cable) 90 - 30
KT =
70 - 40 = 0.86 (For PVC cable) 70 - 30
b) Cable Group derating factor: K L This factor depends on the type of laying (touching / spaced), type of cable (single / multi Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
Doc. No.: E-TSC1-725-14-3001
AT SINGHITARAI, CHHATTISGARH Date 18-04-2011
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DBR FOR CABLE SELECTION & SIZING core), number of trays and number of cables. The cable group derating factor is considered in line with manufacturer`s catalogue & the same is attached as ANNEXURE-I. As per manufacturer`s recommendations, the group derating factor for cables in cable trays are listed below.
Sl. No. 1
2
Group Derating Factor
Type of Cable
Type of laying
Single Core
Trefoil formation with 2
Cables
Dia Spacing
Multi Core Cables
(KL) 0.79
Touching Formation
0.66
Touching formation
0.73
Touching Formation
0.75
Single core 3
cable directly laid in ground
Multi core 4
cable directly laid in ground
c) Overall Derating Factor: K R For cables in trays, trenches, racks Overall Derating factor (K R ) = Temperature Derating factor (K T ) X Group Derating Factor (K L ) Sl.No.
1
2
Project
Type of Cable
Single Core Cables
Type of laying
Overall Derating
Overall Derating
Factor (KR) for
Factor (KR) for
XLPE cable
PVC cable
Trefoil formation with 2 Dia
Not required 0.70
Spacing
Multi Core
Touching
Cables
Formation
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
0.59
0.53
Doc. No.: E-TSC1-725-14-3001
AT SINGHITARAI, CHHATTISGARH Date 18-04-2011
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DBR FOR CABLE SELECTION & SIZING For cables laid directly in ground Overall Derating factor (K R ) = Temperature Derating factor (K T ) X Group Derating Factor (K L ) X Derating for depth of laying X Thermal resistivity of soil.
For 11kV / 3.3kV cables, depth of laying is considered as 0.9M as per IS 1255 and Thermal resistivity of soil is 2000Ccm/W (assumed). Based on Manufacture’s catalogue attached in Annexure-1, derating factor for depth of laying and thermal resistivity of soil are considered 1 & 0.89 respectively.
Sl.No.
Type of Cable
Type of laying
Overall Derating
Overall Derating
Factor (KR) for
Factor (KR) for
XLPE cable
PVC cable
0.59
Not required
0.60
0.57
Spacing of 45cm 1
Single Core
between trefoils,
Cables
directly laid in ground Spacing of 45cm
2
Multi Core
between trefoils,
Cables
directly laid in ground
(3) Rated Current Computation: The rated current (Ie) of the equipment shall be calculated using the following equation. (a)
At normal operation. P x 1000 Ie = Ki x V x η x Cosθ
Where:
Project
Ie
=
Rated current of equipment in Amps.
P
=
Rated output of equipment in kW
V
=
Rated voltage in Volts.
η
=
Efficiency.
Cosθ =
Power factor.
Ki
Coefficient
=
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
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AT SINGHITARAI, CHHATTISGARH Date 18-04-2011
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DBR FOR CABLE SELECTION & SIZING
(b)
At starting of the motor Is = Ks x Ie Where: Is
=
Starting current of motor
Ks
=
Starting current ratio
The rated values of equipment (Ie, Is, Cosθ etc.) shall be obtained from the single line diagrams, motor data sheet etc. or the same may be taken as per Table-1. TABLE-1 RATED CURRENT OF EQUIPMENT
ITEM
415V / 240V MOTOR
MOTORISED VALVES & DAMPERS
SYSTEM CIRCUIT
3φ 3W
AC 1φ2W
Ki
√3
1
DC MOTOR & FEEDER S
TRANSFORMER & OTHER FEEDERS
1φ2 W 1
3φ3W & 4W
DC 1φ 2W
√3
1
RATED
P
P x 1000
Px1000
P x1000
CURREN
(kW)
√ 3 x V x η x Cosθ
V x η x Cosθ
√3xVxηx Cosθ
T (AT
Px1000
NORMAL
Px1000
OPERATI
P
P x 1000
Px1000
ON) , Ie
(KVA)
√3xVxη
Vxη
V
V
Px1000 √3xVxη
(Amps)
P(kW)
η
Cosθ
P(kW
η
Cosθ
ηxCosθ
ηxCosθ
ηxCosθ
)
Power Factor & Efficiency
Ks
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2.2 0.85
0.65
6.0
1
0.8
1
0.8 0.85 6.0
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
1.0
2
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DBR FOR CABLE SELECTION & SIZING
For 11Kv / 3.3kV MV Motors, efficiency of 0.95 and power factor of 0.9 can be considered and the starting current can be taken as 6 times of full load current for motor rated upto and including 1500kW, 5 times of full load current for motor rated above 1500kW and 4.5 times of full load current for motor rated above 5000kW. NOTE : THE ABOVE DATA IS BASED ON INFORMATION FROM VARIOUS MANUFACTURERS AND OUR STANDARDS USED FOR VARIOUS PROJECTS.
C. Cable sizes based on voltage drop calculation criteria The allowable voltage drop of cable over the rated voltage of equipment shall be limited to 2% between Transformer to MCC and 3% between MCC to Motor at full load running condition and 15% during motor starting condition. Lighting cables shall be sized to limit the voltage drop from main lighting distribution board (MLDB) to lighting panel (LP) as 3%. The voltage drop is calculated using the maximum size calculated in 7.00.00(A) and 7.00.00(B) above by the following formula. (a)
At normal/running operation Vn = Kv x Ie x L x (R Cosθ + Xc Sinθ)
(b)
At starting of motor Vs = Kv x Is x L x (R Cosϕ + Xc Sinϕ)
Where: Vn, Vs
=
Kv
=
Coefficient
Ie
=
Rated current of equipment
Is
=
Starting current of equipment
L
=
Length of cable in KM
R
=
Resistance of cable (Ω / Km) at max continuous
Voltage drop of cable
temperature of conductor Rac- for AC circuit & Rdc- for DC circuit Xc
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=
Cable reactance (Ω/ Km)
Cosθ =
Normal/running Power factor
Cosϕ =
Starting Power factor
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
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AT SINGHITARAI, CHHATTISGARH Date 18-04-2011
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DBR FOR CABLE SELECTION & SIZING TABLE-2 VOLTAGE DROP IN THE CABLE
ITEM
415V MOTOR
MOTORISED VALVES
TRANSFORMER & OTHER FEEDERS
&
DC MOTOR & FEEDERS
DAMPERS SYSTEM
AC
3φ 3W
CIRCUIT
DC
1φ 2W
1φ 2W
3φ 3W &
1φ 2W
4W √3
2
2
√3
AT NORMAL OPERATION
AT NORMAL OPERATION
2x
√3 x
√3 x Ie x L x (Rac Cosθ+ Xc
2 x Ie x L x (Rac Cosθ+
Ie x Lx
Ie x Lx
Sin θ )
Xc Sin θ )
(Rac Cosθ
(Rac Cosθ +
AT STARTING OF THE
AT STARTING OF THE
+
Xc Sin θ )
MOTOR
MOTOR
Xc Sin θ )
√3 x Is x L x (Rac Cosϕ+ Xc
2 x Is x L x (Rac Cosϕ+
Kv Vn VOLTAGE DROP
OF
Vs
CABLE (V)
2x Ie x L x Rdc
For Motor feeders 2x Is x L x Rdc
Xc Sin ϕ )
Sin ϕ ) Sinθ
P
2
Cosθ
P
Sin θ
Cosθ
KW
KW
Sin θ = 0.52
AT NORMAL OPERATION
----
Cosθ = 0.85 POWER FACTOR
90
0.53
0.8
2.2
0.76
0.65
Cosθ & Sin θ
AT STARTING OF MOTOR
2.2
0.76
----
0.65
For 11Kv / 3.3kV MV Motors, running power factor of 0.9 and starting power factor of 0.3 will be considered. NOTE : THE ABOVE DATA IS BASED ON INFORMATION FROM VARIOUS MANUFACTURERS AND OUR STANDARDS USED FOR VARIOUS PROJECTS.
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2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
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AT SINGHITARAI, CHHATTISGARH Date 18-04-2011
Rev 0
Page 16 of 17
DBR FOR CABLE SELECTION & SIZING 8.00.00
SIZING OF CONTROL CABLE Minimum size proposed for control cables will be 1.5 sq. mm. For current transformer secondary circuits 4.0 sq. mm minimum cross section shall be used for each phase and for potential transformer secondary circuits, the minimum cross section of the conductors shall be 4 sq. mm. The minimum number of spare cores in control cables shall be as follows: No. of cores in cable
9.00.00
Min. No. of spare cores
2C, 4C
NIL
5C-6C
1
7C-13C
2
14C & above
3
CONCLUSION According to 7.00.00(A) & 7.00.00(B) calculations the cable cross section is sufficient to carry the current during normal as well as short circuit conditions. As per 7.00.00(C) calculation the cable voltage drop with the cross sections calculated will always be limited to 2-3% during normal operation and 15% during the motor starting condition. The above criterion defines the basis for selection and sizing of the cables. For package vendors, this will be used as a broad guideline. The final selection of the cables shall be the maximum of the sizes calculated according to 7.00.00(A),(B) &(C) and shall be standardized so as to optimize the number of cables sizes proposed for this project. The cable sizing calculation shall be submitted as a separate document.
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
Doc. No.: E-TSC1-725-14-3001
AT SINGHITARAI, CHHATTISGARH Date 18-04-2011
Rev 0
Page 17 of 17
ANNEXURE-I
Sheet 1 of 2
ANNEXURE-I
Sheet 2 of 2
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