Product-CB,PT,IT,DC

© ABB Ltd - 1

Training Module

HV Circuit Breakers

$%%

© ABB Ltd., India - 2

CVT SA

DS

CB CT

DS

SA

Transformer

SA

Incoming line

DS

CT

CB

DS

CVT

BPI

SA

Role of a Circuit Breaker

Ground wire Outgoing line

Circuit Breaker

© ABB Ltd., India - 3

A mechanical device capable of making, carrying and breaking currents under normal conditions as well as under specified abnormal conditions such as those of short circuit.

Role of Circuit Breaker

•Offer least resistance for normal load current •Provide electrical isolation when open •Must switch different types of current

© ABB Ltd., India - 4

•Must open & close fast and safe against short circuit

Fault Clearing

Fault Occurs

© ABB Ltd., India - 5

Relay • Senses & Relay Contact Closes

Circuit Breaker • Trip Coil Energises • Operating Mechanism Starts • Contacts Separate • Arcing between Contacts • Arc Extinguishes • Circuit Breaker Fully Opens

Fault Cleared

Product Portfolio - Circuit Breakers ELF SP (Puffer, Pneumatic Mechanism)

50 kA

LTB D1/B (Self Blast, Spring Mechanism)

40 kA

© ABB Ltd., India - 6

31.5 kA

EDF/EDI (Self Blast, Spring Mechanism)

36-72.5 kV

LTB D1/B (Self Blast, Spring Mechanism) ELF SF (Puffer, Pneumatic Mechanism) 145 kV

ELF SL (Puffer, Pneumatic Mechanism) LTBE1 (Auto Puffer, Spring mechanism Mechanism)

245 kV

ELF SL (Puffer, Pneumatic Mechanism)

420 kV

Rating Type

ELF SL 6-2

ELF SL 4-1

LTBD1/B

EDF SK 1-1

Rated voltage

420 kV

245 kV

145 kV

36 - 72.5 kV

Normal current

4000A

4000A

3150 A

2500 A

Breaking current

40 kA

40 kA

40 kA

31.5 kA/ 25 kA

100 kAp

100 kAp

100 kAp

79 kAp/ 63 kAp

50 Hz

50 Hz

50 Hz

50 Hz/ 60 Hz

Making current

© ABB Ltd., India - 7

Frequency

Inside SF6 Arc Chamber - Puffer Interrupter

1 Fixed contact 2 Nozzle 3 Stationary arcing contact 4 Moving arcing contact 5 Stationary main contact 6 Moving main contact 9 Puffer/compression volume 10 Puffer cylinder © ABB Ltd., India - 8

11 Refill valve 13 Stationary piston 14 Lower current path

© ABB Ltd., India - 9

SF6 Puffer Interrupter - Current Breaking Operation

Inside SF6 Arc Chamber - Self blast Interrupter 1 Upper current path 2 Nozzle 3 Stationary arcing contact 4 Moving arcing contact 5 Stationary main contact 6 Moving main contact 7 Self blast volume 8 Self blast valve 9 Puffer/compression volume 10 Puffer cylinder © ABB Ltd., India - 10

11 Refill valve 12 Overpressure valve 13 Stationary piston 14 Lower current path

© ABB Ltd., India - 11

SF6 Self blast Interrupter - Fault Current Operation

© ABB Ltd., India - 12

SF6 Self blast Interrupter - Load Current Operation

ELF/EL(V)F SL 6-2 Construction

Voltage grading capacitor

Double Arc Chamber

Corona Rings Support Insulator Actuator (Drive) Density Monitor Support Structure

© ABB Ltd., India - 13

Air Compressor

Air Receiver Switch Cubicle

ELF/EL(V)F SL 6-2

Pole – EL(V)F SL 6-2 • Arc

Chamber

Terminal Closing Resistor Fixed Contact (Closing Resistor Chamber) Moving Contact (Closing Resistor Chamber) Fixed Contact Moving Contact Branch Housing

Insulating Nozzle & Auxiliary Nozzle

•Earth Insulation Operating rod Support Insulator

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•Actuator ( Drive )

ELF/EL(V)F SL 6-2 Operating mechanism (Pneumatic actuator) Type PKA Mechanical closing interlock Protection cover

ON - OFF indicator Hood

Magnet ventile

Drive assembly

© ABB Ltd., India - 15

Copper pipe

Cable

Drive chamber

Operating mechanism - Opening operation

OFF

Operating rod Coupling piece

Piston of Magnet ventile

Piston Driving piston

© ABB Ltd., India - 16

Damping piston Opening coils

ELF/EL(V)F SL 6-2

Air Compressor Unit „

Rated Pressure: 31.5 bar

„

Delievery Rate: 6m3/hr

„

Parts of the compressor air unit:

3 2

4

1- Connecting rod and crank shaft assembly 2- Piston assembly 3- Inter cooler 4- Cylinder and cylinder head

© ABB Ltd., India - 17

5- Crank case

5 1

ELF/EL(V)F SL 6-2 EL(V)F SL 6-2: General Arrangement – IE Rule

© ABB Ltd., India - 18

dimension

Maximum width

Maximum height

Insulation height (2.4 m)

Cubicle

Safety working clearance (6.4 m)

Phase difference

Routine tests on Circuit Breaker (Reference Standard : IEC 62271 - 100) • Mechanical Test • SF6 leakage ( Tightness ) • Contact resistance measurement • Dielectric test ( Power frequency test ) • Dielectric test on auxiliary and control circuit ( 2kV test)

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• Visual checks

Specified parameters Parameter

ELF SL 6-2

ELF SL 4-1

LTBD1/B

EDF SK 1-1

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(72.5 kV) Closing time

150 ms max

130 ms max

45 ms max

60 ms max

Opening time

25 ms max

30 ms max

30 ms max

35 ms max

CO time

45 ms max

45 ms max

45 ms max

45 ms max

Closing velocity

3.2-4.7 m/s

4-6 m/s

3.5-4.5 m/s

2.5-3 m/s

Opening velocity

6.7-8.5 m/s

7.5-9.5 m/s

4.4-4.9 m/s

3-3.5 m/s

Contact resistance

50 µΩ max

51 µΩ max

44 µΩ max

42 µΩ max

SF6 gas pressure

600-700 kPa abs

ELF/EL(V)F SL 6-2

Transport & Unloading at site • Transportation units • Unload packing case in upright position

© ABB Ltd., India - 21

• DO NOT ROLL CASES

ELF/EL(V)F SL 6-2

EL(V)F SL 6-2 Outdoor Storage Poles Double arc chamber Grading capacitor Resistor stack Structure DAC

© ABB Ltd., India - 22

Pole High Flood Level

Equipment stored outdoors must be located at a place with no possibility of water logging

ELF/EL(V)F SL 6-2

EL(V)F SL 6-2 Indoor Storage Pneumatic actuator (Drive) Switch Cubicle Compressor Accessories Terminal connector Copper pipes Cables Lifting fixture

© ABB Ltd., India - 23

Drive

Switch cubicle Lifting fixture

Anti-condensation heaters provided in the Operating mechanism and switch cubicle should be connected to supply during outdoor storage

ELF/EL(V)F SL 6-2

EL(V)F SL 6-2 Unpacking •Pole column •Open packing case

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•Remove Pole column

© ABB Ltd., India - 25

General Scheme

© ABB Ltd., India - 26

Out of step protection

© ABB Ltd., India - 27

Compressor control schematic

© ABB Ltd., India - 28

Air pressure (bar)

34.65

31.5

30.5

30

24.5

23 30.2

24.7

23.2

SF6 gas (bar - absolute)

Pressure scale:

6.2

6

6.4

6.4

Check list - Erection •Position of leveling nut below structure •Verify direction of structure as per GA •Leveling of structure done? •All nuts tightened as specified? •Insulators not damaged •Verify positive pressure of SF6 gas •Water presence in the drive – Overhauling required? •Temperature compensation for SF6 gas

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•Check for SF6 gas leakage after filling 2 bar absolute •Gas monitoring system fixed as per GA drawing •Heaters are working in drive/cubicle? •Note operation counter reading

Contact Preparation (Aluminum) •Clean contact surfaces •Brush surfaces with clean steel brush •Apply grease on contact surface immediately •Fix connector pad and tighten

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•Wipe off grease squeezed out of the joints

LTBD1/B: Pre-commissioning •Check erection as per general arrangement drawing •Fill SF6 gas to nominal pressure according to pressure temperature curve •Check pressure after one hour and correct •Check for leakage •Check wiring according to schematic •Trial mechanical operations •Measure breaker operating timings

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•Check antipumping feature •Check for leakage •Record all measurements

LTBD1/B : Construction (three column stand version) •Poles •Operating mechanism •Tripping device •Support structure •Linkage (Protecting tubes, pull rods)

© ABB Ltd., India - 32

•Gas supervision system

LTB D1/B : Operating mechanism A Trip spring 1 Trip latch 2 Tripping arm 3 Closing arm 4 Closing latch 5 Main shaft 6 Closing spring 7 Worm,worm wheel

© ABB Ltd., India - 33

8 Universal motor 9 Limit switch 10 Charging handle 11 Dashpot

Operating mechanism - Operation •A universal charging motor charges closing spring •The limit switch disconnects power to motor after the closing spring is charged. •When the closing coil is energized the closing latch (catchgear) releases energy of closing spring •The opening spring is charged during this closing operation.

© ABB Ltd., India - 34

•When the trip coil is energized, the trip latch (catchgear) releases energy of opening spring.

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LTB D1/B: Storage •Indoor Storage • Operating mechanism • Marshalling box • Accessories Box

•Outdoor Storage •Poles with supports above HFL

© ABB Ltd., India - 35

•Structure

HFL

LTBD1/B : Handling Breaker pole •Place a sling under the top flange of the arc chamber insulator and prepare for lifting •Do not remove the sling till all bolts are properly tightened

© ABB Ltd., India - 36

•Special care for gas valve

LTBD1/B : Handling Breaker pole •Do not remove the sling till all bolts are properly tightened

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•Special care for gas valve

LTBD1/B : Handling Operating Mechanism

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•Ensure the weight of mechanism is supported by all the four lifting hooks

LTB D1/B : Erection •Prepare foundation •Mount support structure •Ensure distance between structure •Ensure alignment of structure at top

•Mount poles one by one •Check SF6 gas

© ABB Ltd., India - 39

•Mount mechanism on structure •Ensure drive is in open position and there is no gap between the flange and mechanism housing

Alignment of support structure

Foundation bolt

Nut for alignment

© ABB Ltd., India - 40

Foundation

LTB D1/B : Erection Pull rod connection •Check that poles are open •Insert pull rod in protective tube and mount the protective tube •Ensure left hand thread of pull rods are towards drive

© ABB Ltd., India - 41

•Make connections of pull rods •Match the holes on setting disc and mechanism housing in all three poles •Match holes of A-pole, then Bpole and then C-pole.

C

B

A

EDF SK 1-1 Construction of Circuit Breaker: •Poles •Operating and control Mechanism •Support structure

© ABB Ltd., India - 42

•Supports and Linkage

EDF SK 1-1 EDF SK 1-1: Operating mechanism - Construction Closing Cam & Prawl

Cam Follower Whom wheel

Limit switch

Locking prawl Tripping Spring

(CO Spring)

(O Spring)

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Closing spring

Auxiliary switch

Motor for charging the closing spring

EDF SK 1-1 EDF SK 1-1: Transport

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• One packing case containing poles, mechanism & accessories

EDF SK 1-1 EDF SK 1-1: Transport •Transportation units •Unload packing case in upright position

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•DO NOT ROLL CASES

EDF SK 1-1 EDF SK 1-1: Unpacking •Open Packing case •Remove mechanism

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•Remove accessories box

EDF SK 1-1 EDF SK 1-1: Storage •Indoor Storage • Operating mechanism • Accessories Box indoor •Outdoor Storage •Poles with supports above HFL

© ABB Ltd., India - 47

HFL

© ABB Ltd., India - 48

© ABB Ltd - 49

Operation, Maintenance, Trouble shooting & life extension of Power Transformer

ABB LIMITED POWER TRANSFORMERS

$%%

Transformers - Definition IEC 60076-1 A static piece of apparatus with two or more windings which, by electromagnetic induction, transforms a system of alternating voltage and current into another system of voltage and current usually of different values and at the same frequency for the purpose of transmitting electrical power.

IEEE C57.12.80-2002

© ABB Ltd., India - 50

A static device consisting of a winding, or two or more coupled windings with or without a magnetic core for introducing mutual coupling between electrical circuits.

© ABB Ltd., India - 51

TRANSFORMER BASICS

Transformers - Application Areas & Standards Application Areas: Power stations (Thermal, Hydro, Nuclear, Wind farms) Transmission Substations Factory Substations Railway Traction Supply Aluminium Smelters / Arc Furnaces

© ABB Ltd., India - 52

Application Standards: CBIP Technical Publication No.275 (1999). Manual on Transformers (Sections A ~P) IEC60076-8 (1997) Application guide / IS 10561: 1983 IS10028 (Part I) : 1981 Selection of Transformers

© ABB Ltd., India - 53

Transformers - Types & Applications

Generator Transformers

: For stepping up the generator voltage to transmission line voltage. Used in Generating Stations only.

Power Station Transformers

: Station transformer used for feeding the substation/Power Station Auxiliaries.

Transmission & Auto Transformer

: Transformers for bulk supply of power and to interconnect separate EHV transmission systems.

HVDC Converter Transformer

: Used for HVDC systems.

Phase Shifting Transformer / Quadrature Boosters

: To control the power flow in an interconnected network.

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Transformers - Types & Applications Interconnected Star Earthing Transformers

: To provide a neutral point for connection to earth on a system which would otherwise not have one.

Distribution Transformers

: To step down the voltages to distribution Levels

Rectifier Transformers

: Step down transformer to feed rectifiers.

AC Arc Furnace Trafo.

: Step down transformer to feed arc furnaces.

Traction Transformers

: For use in Traction applications on locomotives.

Generator neutral Earthing Transformers

: Generally used to connect the generator stator neutral to the earth to limit the short circuit current in the event of a fault.

Power Transformer - Main Parts

© ABB Ltd., India - 55

Active Part

Tank

: Core Windings (HV, LV, Regulating, Tertiary) Tap Changer(s) (On Load / Off Load) Cleats & Leads : Tank body

Accessories

: Radiators

Auxiliaries

: Bushings Buchholz Relay/Oil Surge Relay Temperature Indicators Oil Level Indicators Pressure Relief Device Marshalling Box/Control cubicle

Oil Preservation Systems : Conservators (gas sealed, Bellows/membrane sealed) Breathers Thermo-siphon Filters

Power Transformer - Active Part

Core Windings Leads

© ABB Ltd., India - 56

Tap Changer

100MVA 220kV Power Transformer Radiator Bank Conservator Prismatic Oil Level Indicator Bushings Buchholz Relay Fans Tank

© ABB Ltd., India - 57

Marshalling Box /Control cubicle

© ABB Ltd., India - 58

DISMANTLING & TRANSPORT

DISMANTLING & TRANSPORT After test, oil is drained & external fittings & accessories (bushings, coolers, conservators etc) are disassembled TRANSPORT MODES z

Oil Filled

z

Nitrogen Gas filled z

When oil filling would exceed the permissible or economical maximum transport weight or if specifically demanded by the customer

z

Filled with dry nitrogen at a positive pressure of 0.175 kg/sq cm( 2.5 psi) before dispatch.

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CHECKS FOR TRANSPORTATION z

Prevent the transformer from sliding during transport.

z

The positions of lifters, hauling to be used as anchoring points

DISMANTLING & TRANSPORT HANDLING DURING LOADING, AND ON SITE LIFTING TRANSFORMERS z

Hydraulic hoists to be used at the jacking pads provided (see outline drawing).

z

Lifting to be carried out simultaneously and uniformly for at least two adjoining jacking pads.

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Note: Never use Pipe flanges and valves as lifting or support points.

DISMANTLING & TRANSPORT

SUSPENDING TRANSFORMERS The transformer must be suspended from points shown in the outline drawing.

© ABB Ltd., India - 61

The ropes must never form smaller angle than 60 degrees to the horizontal. Thus, dimension “L” must be equal to or larger than dimension “M”

DISMANTLING & TRANSPORT

© ABB Ltd., India - 62

SHIPPING z

Large Power Transformers are normally shipped on special low bed trailors.

z

Accessories dispatched separately by road, oil drums by road.

z

Regular check of tank pressure during shipping and storage times necessary to ensure that there is no leakage.

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DISMANTLING & TRANSPORT

Transformer shipping showing tie-rods and blocking

© ABB Ltd., India - 64

DISMANTLING & TRANSPORT

ARRESTING TRANSFORMER MOVEMENT ON TRAILOR BED

© ABB Ltd., India - 65

RECEIVING INSPECTION & ARRIVAL ON SITE

RECEIVING INSPECTION AND ARRIVAL ON SITE- CHECKS Inspection to be carried out: z

Measurement of core insulation resistance to ground.

© ABB Ltd., India - 66

(Min. Acceptable value : 500KΩ when measured at 1000V DC, corrected to 20oC.) z

All tie rods must be undamaged and nuts and cables must be tight

z

Is all blocking tight and in good condition?

z

Any evidence of load shifting in transit

z

Does the impact recorder indicate any impacts beyond the acceptance zones?

z

Indications of external damage : broken glass on gauges, broken welds etc.

z

Paint finish damage

z

Whether attached fittings are still in place and undamaged (see the outline drgs)

© ABB Ltd., India - 67

RECEIVING INSPECTION AND ARRIVAL ON SITE- CHECKS z

Evidence of oil leakage around valves, fittings, flanges and tank seams

z

Damages to Bushings : Porcelain chipping

z

Bushing Oil level

z

Delivery of all major components and accessory boxes as per packing list

z

Do crates or boxes show evidence of damage or moisture ingress?

z

Temporary shipping silica gel breather desiccant color

z

Detached radiators, coolers and pumps must have openings closed with blind flanges and plugs.

z

Any pressure loss in gas filled transformer tanks must be included in the acceptance report.

z

Excess pressure of 0.05 bar should be maintained as minimum.

RECEIVING INSPECTION AND ARRIVAL ON SITE- CHECKS Pressure variation w.r.t. temperature 30

20 Pressure kPa 10

0 -20

-10

0

10

© ABB Ltd., India - 68

Temperature OC

20

30

© ABB Ltd., India - 69

RECEIVING INSPECTION AND ARRIVAL ON SITE- CHECKS

RECEIVING INSPECTION AND ARRIVAL ON SITE- CHECKS

© ABB Ltd., India - 70

INTERNAL INSPECTION z

Necessary if transport damage is suspected.

z

Avoid internal inspections to the extent possible. If necessary carry out inspection only in the presence of transformer manufacturer.

z

Before removing the tank cover or any other cover, ensure there is no overpressure in the tank.

z

Do not leave tools or other objects inside the tank, they can cause shortcircuits and failure of transformer.

© ABB Ltd., India - 71

UNLOADING, MOVING & STORING

UNLOADING, MOVING & STORING

© ABB Ltd., India - 72

UNLOADING

z

Use suitable overhead crane.

z

Raise transformer from the car bed with jacks and then skid or roll in to the desired position. Jacking should be done at designated jacking pads only.

UNLOADING, MOVING & STORING MOVING TRANSFORMERS z

Special Moving devices

z

Skids

z

Sliding surfaces (with the aid of lubricants) can be used.

z

Armored rollers can be placed under the transformer

© ABB Ltd., India - 73

List of tools & Equipment needed for moving, available in the instruction Manual

UNLOADING, MOVING & STORING

STORAGE

© ABB Ltd., India - 74

STORING INDOORS IN A DRY ROOM z

Insulating material such as paper, pressboard, Bakelite, wood, cottons tape etc.

z

Insulated items as paper insulated conductors, pressboard insulated shielding body etc.

z

Chemicals as solvents, glues, varnishes, hardners etc.

z

Breathers and drying agents

z

Terminal boxes, connection boxes, control cabinets

z

Turrets with built in current transformers.

STORAGE z

Gas relays, oil-level indicators, thermometers, pressure valves etc.

z

Pipes to oil conservator, pipes to radiators, pipes to turrets etc.

z

Bushings

z

Marshalling box, OLTC motor drive, fans, pumps, instruments and fittings

z

Control cabinets

© ABB Ltd., India - 75

( If Heating elements provided, they shall be connected to supply)

STORAGE

© ABB Ltd., India - 76

STORING OUTDOORS z

Main transformer with mounted accessories.

z

Oil conservator with blanking plates for all openings.

z

Radiators and coolers with blanking plates for all openings.

z

Structures, A frames, pipe supports, oil conservator supports, radiators, control cabinets etc.

STORAGE LONG DURATION STORAGE TRANSFORMER DISASSEMBLED : WITH LOWERED OIL LEVEL A transformer with lowered oil level (i.e. the entire insulation of the core and coil assembly has to be completely covered with oil) must be provided with a dehydrating breather during storage, in order to avoid the ingress of humid air in the transformer tank.

© ABB Ltd., India - 77

In case heating elements are installed in the motor drive cabinet, and control cabinet, they must be connected to a power supply system to prevent the formation of condensation water. The heating elements shall be checked at regular intervals.

STORAGE The silica-gel content of the dehydrating breathers is to be checked every 2 weeks. When more than 2/3 of the blue silica gel filling have turned light, the filling has to be exchanged. However, it can be reused after having been dried at 120 °C (24 hrs.).

© ABB Ltd., India - 78

At the same time the tank has to be examined for oil traces. Should any leakage be detected, they have to be sealed immediately. Before commissioning and after a long storage the oil is to be checked for moisture content. Motor drive cabinet and control cabinet have be checked for Condensation of water.

STORAGE

TRANSFORMER WITH DRY-GAS FILLING

In case it is not possible to store the transformer completely mounted or with oil filling, the trans-former is to be filled with dry gas in order to prevent the ingress of moisture during storage. After the transformer has been filled with dry gas/ air, one or several gas cylinder attached to the tank has to be connected. In order to provide a constant positive pressure in the transformer tank, the gas cylinders are connected via pressure reducing and pressure relief valve. The valves have been adjusted to maintain a positive pressure in the tank i.e. approx. 0.25 bar. The pressure is to be checked every two weeks.

© ABB Ltd., India - 79

Caution:The pressure must not fall below 0.05 bar.

STORAGE

© ABB Ltd., India - 80

The condition of the silica gel content in the dehydrating breathers has to be checked every 2 weeks. Should more than 2/3 of the blue silica gel filling have turned light, the filling must be exchanged. However, it can be reused after drying at 120 °C (24 hrs.). At the same time it is necessary to check the oil level in the conservator, and to examine the tank for oil traces. Should any leakage be detected, they have to be taken care of immediately. Before commissioning and after long storage the oil is to be checked for humidity.

STORAGE

ACCESSORIES

The accessories shall be stored in compliance with the printed-on storage instructions and the hints given in the brochures for the individual accessory parts. In principle the accessories should be stored in their respective transport packing in dry rooms. Possibly, desiccant bags have to be enclosed in the crates.

© ABB Ltd., India - 81

All accessories shall be protected against damages.

STORAGE CHECKLIST FOR PACKAGE

© ABB Ltd., India - 82

Time periods SUBJECT

CHECK

YEAR MONTH

Insulating oil

Dielectric strength 1 Moisture content

Oil level

Conservator

1

Oil tightness

Tank Conservator, piping, Buchholz relay, Bushings

1

Earthing

Tank

6

Fans

Test run

3

Control cabinet

Heating

1

Oil circulation pumps

Trial run

3

Silica gel breathers

Silica gel

1

REMARKS

1 1 1 1 Hr. 1 Hr.

© ABB Ltd., India - 83

TRANSFORMER INSTALATION INSTRUCTIONS

TRANSFORMER INSTALATION INSTRUCTIONS EXTERNAL ASSEMBLY z

Check all factory assembled air/gas oil fitting joints for leaks and reseal.

z

Use new gaskets supplied with transformer when installing radiators,

© ABB Ltd., India - 84

coolers or pumps

TRANSFORMER INSTALLATION INSTRUCTIONS

© ABB Ltd., India - 85

INTERNAL ASSEMBLY z

To remove the nitrogen, it is advisable to pull vacuum to fully remove all nitrogen and Break vacuum with oil.

z

Bushings to be assembled as per the instructions of the bushing manufacturer which is available in the instruction manual.

z

Bushing CT - Check the CT ratios, lead continuity & polarity at the terminal points in the control cabinet.

z

An energized CT is dangerous if the secondary is open circuited. Death or serious injury can result from contact with the terminals.

TRANSFORMER INSTALLATION INSTRUCTIONS

© ABB Ltd., India - 86

If transformer is to be stored after assembly; z

Seal it and pressurize with dry air or nitrogen to 20 kPa; [ 3 PSI (0.2 bar)].

z

If the exposure time has been excessive or there are other factors that suggest the transformer may have been exposed to excessive moisture contamination then: z

Evacuate transformer to 2 Torr (.266 Pascal) or less and hold for 4 hours.

z

Break the vacuum with dry air or nitrogen till the pressure reaches 20 kPa 3-PSI (.2 bar).

z

Retain it under pressure for at least 12 hours until equilibrium is reached, and then measure the dew point.

z

For surface moisture less than 0.8%, proceed with the final vacuum filling procedures.

z

If the dew point is unacceptable, the transformer insulation must be dried.

© ABB Ltd., India - 87

TRANSFORMER INSTALLATION INSTRUCTIONS

z

It is advisable to take the dew point measurement in the early morning hours prior to sunrise.

z

If the dew point measurement is taken during periods of extreme ambient temperature variation or during the afternoon hours, the insulation temperature should be measured directly after the dew point is taken.

TRANSFORMER INSTALLATION INSTRUCTIONS Surface moisture content % 2

-20º

-10º

0º

10º 20º

1.5 Temperature inside transformer 1

30º

0.7 40º

0.5 0.4 0.3

Water vapor pressure inside transformer

0.2

© ABB Ltd., India - 88

0.01

-60º

0.03

0.1

-50º

-40º

0.3

mm Hg

-30º

Dew- point of air inside the Trafo.

-20º

TRANSFORMER INSTALLATION INSTRUCTIONS ELECTRICAL TESTS 1. Measure the power factor and capacitance of the bushings before installing the bushings in the transformers.

Refer to the appropriate

bushing instruction leaflet for the proper procedures. (Optional Test) Measure the core resistance to ground. 2. The minimum acceptable value is 500 k Ohm when measured at 1000 volts. 3. Measure the core clamp resistance to ground. The minimum acceptable value is 500 k-Ohm when measured at 1000 © ABB Ltd., India - 89

volts.

TRANSFORMER INSTALLATION INSTRUCTIONS

4. Measure the ratio of all bushing current transformers and verify proper polarity. 5. Check the turns ratio of the transformer (TTR) at all tap positions. The

© ABB Ltd., India - 90

measured turns ratio should be + 0.5 % of the nameplate voltage ratio

© ABB Ltd., India - 91

OIL SPECIFICATION, TESTING, PURIFICATION & STORAGE

OIL SPECIFICATION, TESTING, PURIFICATION AND STORAGE SPECIFICATION FOR INSULATING OIL (IS:335)

© ABB Ltd., India - 92

TESTING OF THE OIL – Recommended Tests A. Dielectric dissipation factor B. Neutralization value C. Interfacial tension D. Electric strength E. Water content F. Sludge content G. Dissolved gas analysis

OIL SPECIFICATION, TESTING, PURIFICATION AND STORAGE

© ABB Ltd., India - 93

(Electrical Strength) Breakdown Voltage Operating Voltage

New Transformers prior to the first Energisation

Transformers having been in service

(kV)

IEC 156 KV / 2.5 mm

IEC 156 kV / 2.5 mm

> 170

≥ 50

≥50

70 - 170

≥ 50

≥40

< 70

≥ 50

≥30

OIL SPECIFICATION, TESTING, PURIFICATION AND STORAGE FREQUENCY OF CHECKS

Years after initial operation (initial operation)

OPERATING VOLTAGE (kV) ≤ 73

73 - 170

> 170

Test (A to F)

Test (A) to (F)

Test (A) to (G)

1

(G)

2 3

(G)

(G)

Test (A) to (F)

Test (A) to (F)

4 5

Test (A to F)

6 © ABB Ltd., India - 94

afterwards

(G) In 5 years intervals

In 3 year intervals (G) in 5 year intervals: all tests (A) to (F)

In 2 year intervals (G)

OIL SPECIFICATION, TESTING, PURIFICATION AND STORAGE INTERPRETATION OF TESTS ON OIL Criteria

Breakdown voltage

Water content

Operating Voltage

Test Method

Permissible limiting value

Measures to be taken if values are not permissible

> 170 kV

IEC 156

> 50 kV

Filtering

70 - 170 kV

> 40 kV

Drying

< 70 kV

> 30 kV

(Purification)

< 20 mg / l

Drying

< 30 mg / l

(Purification)

15 mN/m

Exchange of oil

> 170 kV

ISO R760

© ABB Ltd., India - 95

< 170 kV Dielectric dissipation factor

All voltages

Neutralisation value

All voltages

Inerfacial tension

IEC 247 IEC 250

OIL SPECIFICATION, TESTING, PURIFICATION AND STORAGE

© ABB Ltd., India - 96

OIL SAMPLING z

Take Samples only at the provided extraction points.(drain valves / oil sampling valves as shown in the outline drawing).

z

Before taking an oil sample clean the drain valve and slowly drain off at least 5 liters of oil.

z

Use clean and dry sample containers only. Be sure to remove all residue of cleaning fluids. Shape of the sampling container and sampling method shall be in accordance with standard procedures and IS :9497

OIL SPECIFICATION, TESTING, PURIFICATION AND STORAGE

z

© ABB Ltd., India - 97

z

Rinse it with the oil to be sampled. Protect the oil sample from light. The following sampling containers are recommended: o

Tinted glass bottles with ground glass stopper

o

Aluminum cans with screw-on caps (preferable for long transportation distances

o

Untinted glass bottles, wrapped in non-transparent foils for protection against light

Take at least 1 liter of oil for testing.

OIL SPECIFICATION, TESTING, PURIFICATION AND STORAGE Care to be taken during sampling „

The sample bottle shall be free from moisture, dirt, old oil residues, leakage or breathing holes

„

Oil sample should not be allowed to come in contact with the atmospheric air, during sampling or later

„

The sampling shall be carried out preferably in bright sun shine, at least not in damp weather.

„

The sample bottle shall be marked, immediately on sampling, with the clear

© ABB Ltd., India - 98

identification of the equipment to which the sample belongs to. „

The sample shall be deposited at the earliest at the Laboratory

OIL SPECIFICATION, TESTING, PURIFICATION AND STORAGE „

Oil Sampling Methods

„

Following methods can be used for sampling:

© ABB Ltd., India - 99

„

„

Sampling by vacuum

„

Sampling by liquid displacement

Sample can be collected by following means: „

1. Sampling by syringe

„

2. Sampling by Amber colored bottle

OIL SPECIFICATION, TESTING, PURIFICATION AND STORAGE

© ABB Ltd., India - 100

„

3. Sampling by tube or SS Bottle

OIL SPECIFICATION, TESTING, PURIFICATION AND STORAGE Fig: EXAMPLE OIL SAMPING FOR TESTING (DGA & Moisture Content)

1. OIL DRAIN VALVE 2. ADAPTER FLANGE 3. SYNTHETIC RUBBER HOSE 4. HOSE CLIP

© ABB Ltd., India - 101

5. GLASS BOTTLE

OIL SPECIFICATION, TESTING, PURIFICATION AND STORAGE

© ABB Ltd., India - 102

DIELECTRIC STRENGTH z

The average value of the six results is considered to be the dielectric strength of the oil which must comply with the values of table one.

z

If any one of the six breakdown voltages lies more than 15% below the specified value the test must be repeated with a new sample:

z

The dielectric strength of the oil can be improved by filtering and drying.

OIL SPECIFICATION, TESTING, PURIFICATION AND STORAGE

GAS ANALYSIS ON TRANSFORMER OIL

It is recommended that analysis of dissolved gases in transformer oil by gas chromatographic equipment is made at the time of commissioning and then at an interval of maximum six months.

© ABB Ltd., India - 103

Gas 1 Analysis: Gases to be analyzed normally

O2, N2 , H2,CO, CO2, CH4

2

Gases to estimate abnormality

H2, CH4, C2H2,C2H4,C2H6

3

Gases to estimate deterioration

CO, CO2, CH4

OIL SPECIFICATION, TESTING, PURIFICATION AND STORAGE GAS CONTENT IN OIL BY FAULTS:

Sl. No.

Type of faults

Decomposable Gases In Transformer Oil

1

Over heating of oil

CH4,C2H4,H2, (C2H6,C2H2,C3H6,C3H8)

2

Arcing in oil

H2, C2H2, (CH4,C2H4)

3

Over heat of solid insulating material

CO, CO2, ( H2, C2H4)

4

Over heat of solid insulating materials and oil combination.

CH4, C2H4, CO, CO2,H2

5

Arcing of oil and paper combination

H2, C2H2,CO, ( C2 H4)

© ABB Ltd., India - 104

Gases in ( ) shows contents which appear rarely.

OIL SPECIFICATION, TESTING, PURIFICATION AND STORAGE Permissible Concentrations of Dissolved Gases in the Oil of a Healthy Transformer (In ppm)

Gas

4 - 10 years in Service

More than 10 years in Service

Hydrogen H2

110- 150

200- 300

200- 300

Methane CH4

50- 70

100- 150

200- 300

Ethane C2H6

30- 50

100- 150

800- 1000

Ethylene C2H4

100- 150

150- 200

200- 400

Acetylene C2H2

20 - 30

30- 50

100- 150

200- 300

400- 500

600- 700

3000 - 3500

4000- 5000

9000- 12000

Carbon Monoxide © ABB Ltd., India - 105

Less than 4 years in Service

Carbon Dioxide

OIL SPECIFICATION, TESTING, PURIFICATION AND STORAGE

„

Interpretation of DGA results in terms of ratios of dissolved gas quantities.

Key Ratio Ratio 1

C2H2 C2H6

2

H2 C2H4

3

C2H4 C2H6

© ABB Ltd., India - 106

4 5

Value Indication >1 >10 >1

Electric discharge Partial discharge Thermal fault

CO2

>10

Cellulose degradation due to overheating

CO

2

Un-tight tap changer

OIL SPECIFICATION, TESTING, PURIFICATION AND STORAGE OIL PURIFICATION – STAGES z

Drying removal of free and dissolved water

z

De-gassing removal of dissolved gasses

z

Filtering removal of all floating solids above a size to be defined.

© ABB Ltd., India - 107

Employ only those purification plants which employ vacuum processing.

OIL SPECIFICATION, TESTING, PURIFICATION AND STORAGE

FIG. FLOW DIAGRAM FOR TRANSFORMER OIL PROCESSING

1. Oil tank (preferably vacuum tight) 2. Oil purification plant

© ABB Ltd., India - 108

3. Connection to vacuum pump or silica gel breather

OIL SPECIFICATION, TESTING, PURIFICATION AND STORAGE STORAGE z Stored oil in clean containers specially designated for its storage z Mixing with other type of oil such as used oil, cable oil, lubricating oil, fuel oil and contamination with solids must be strictly avoided. z The containers must be protected against penetration of moisture during storage. z Oil in drums should be stored in a closed room.

© ABB Ltd., India - 109

SAFE HANDLING z Avoid inhalation of any mist, fumes or vapour generated during use. z Avoid contact with the skin. z Avoid contact with the eyes. z Wash hands carefully before eating and drinking. z Change heavily contaminated clothing.

OIL SPECIFICATION, TESTING, PURIFICATION AND STORAGE

© ABB Ltd., India - 110

FIRST AID z First Aid due to inhalation is unlikely to be needed under normal use z For skin contact, the first aid is to wash " with soap and water”. z For eye contact, wash out eyes thoroughly with water. z Better consult a doctor if there is risk of swallowing

© ABB Ltd., India - 111

ERECTION AND ASSEMBLY

ERECTION AND ASSEMBLY

© ABB Ltd., India - 112

Erection and assembly: z

To be carried out by trained staff, familiar with the relevant safety regulations.

z

Assembly preferably on a dry day.

z

All openings to be re-closed as soon as possible to prevent dust & moisture entry.

z

Accessories to be assembled as per the relevant instructions

z

After assembling locking strip/card /pin shall be removed for correct functioning of Oil Flow Indicator

z

ABB supplied gaskets or gaskets of similar quality must be used.

© ABB Ltd., India - 113

ERECTION AND ASSEMBLY

z

Ensure sealing surfaces are not damaged & they are free from rust, paint, oil, and grease

z

Tightening of screws to be done with applicable torque as per table given in the instruction manual.

z

Complete connection of all cables as per the relevant cable connection diagram

z

Repair damaged paint coatings. The paint supplied by ABB or equivalent must be used for this purpose.

ERECTION AND ASSEMBLY

© ABB Ltd., India - 114

z

Complete the assembly of : z

Conservator and Brackets

z

Cooling Equipment

z

Fans (specific Attention to be paid to the direction of rotation)

z

Bushings

z

Pipes & Fittings

z

Other Accessories as detailed in the outline drawing

OLTC DRIVE MOTOR MECHANISM NORMALLY MOUNTED ON THE TRANSFORMER TANK DURING TRANSPORT. SHOULD BE RIGIDLY MOUNTED ON TANK SO THAT THE STRUCTURE DO NOT VIBRATE DURING TAP CHANGE OPERATION.

© ABB Ltd., India - 115

ALIGNMENT OF DRIVE SHAFT SHOULD BE CAREFULLY DONE & REALIGNED.

© ABB Ltd., India - 116

ON LOAD TAP CHANGER „

OLTC IS MOUNTED IN TRANSFORMER TANK.

„

ALWAYS REFER TO TRANSFORMER MANUFACTURER FOR ANY PROBLEM IN TAP CHANGER.

„

FOR MAINTENANCE REFER TO DETAILED MAINTENANCE SCHEDULE FROM OLTC MANUFACTURER.

© ABB Ltd., India - 117

CONSERVATOR ASSEMBLY „

CONSERVATOR ASSEMBLY SHALL BE MOUNTED AT SITE AS PER GENERAL ARRANGEMENT DRAWING.

„

ALL OTHER ACCESSORIES SHALL ALSO BE MOUNTED AS PER GA DRAWNG.

© ABB Ltd., India - 118

CONSERVATOR ASSEMBLY

OIL FILLING c o m po und g a uge va c u u m g a u g e tra nspa rent hose fo r le vel m o ni tori ng Buchholz rela y va c u u m filter stora g e ta nk

© ABB Ltd., India - 119

c o m p o u n d g a u g e ri g ht b e f o re fill va lve

Oil filling from lower filter valve

va c u um p um p

OIL FILLING ARRANGEMENT FOR OIL FILLING - SCHEMATIC PICTURE

© ABB Ltd., India - 120

1 2 3 4 5 6

Transformer Vacuum Treatment Plant Vacuum hose Oil hose Oil filling connection Gate valve for oil treatment plant 7 Air vent valve 8 Manometer 9 Lower shut-off gate valve 10 Vac. Flange with sight glass 11 Connection for vacuum Gauge 12 Oil inlet slide valve 13 Inlet pump 14 Filter 15 Heater 16 Degassing chamber 17 Discharge pump 18 Oil outlet gate valve 19 Vacuum pump 20 Gas ballast valve 21 Vacuum valve 22 Vacuum gauge

ERECTION & ASSEMBLY

OIL FILLING FOR TRANSFORMERS WITH AIR CELL CONSERVATORS

© ABB Ltd., India - 121

OIL FILLING PROCEDURE WITHOUT VACUUM IN THE COSERVATOR(AIR CELL) „

Place the separator inside the conservator

„

Inflate the same to 0.1 bar (Max.) leaving vent hole open on the conservator. Adjust the pressure 6 hours later.

„

Watch for a possible loss of pressure 24 hours later at appx. same temperature.

„

If there is no loss of pressure, then the separator and its fittings on conservator are considered perfectly tight.

„

Push oil slowly by the lower part of conservator till oil overflow by the vent holes in the upper part.

„

Close the vent hole and keep introducing oil by the lower part, while leaving the separator progressively deflate.

„

Stop oil filling at the level selected for the filling temperature.

ERECTION AND ASSEMBLY

© ABB Ltd., India - 122

OIL FILLING PROCEDURE WITH VACUUM IN THE COSERVATOR(AIR CELL) „

Conservator, with its separator as above is connected to its oil filling reserve in its lower part.

„

Create a vacuum in the separator.

„

With the same source of vacuum, create vacuum in the conservator.

„

Open the oil filing valve on the lower part.

„

Because of vacuum in the conservator the oil rises automatically.

„

Stop the filling once the required oil volume enters into the conservator.

„

Release vacuum inside separator by ambient air or nitrogen. Then the separator inflates itself to take all the free space.

„

During the operation oil shall rise to the top of the conservator.

„

Inflate the separator to a max. pressure of 0.1 bar (Max.)

„

Allow oil to overflow from vent holes, then close vent holes.

© ABB Ltd., India - 123

ERECTION & ASSEMBLY (AIR CELL FAMILIARIZATION)

„

Air cell supported from top of the conservator (top left.)

„

Complete picture of air cell supported from top(Top Right).

„

Seating structure for air cell inside conservator(Bot. Left).

„

Opening for oil entry/exit into conservator protected from seating structure(Bot. Right).

© ABB Ltd., India - 124

ACCEPTANCE TEST & ENERGISATION

ACCEPTANCE TEST & ENERGISATION

© ABB Ltd., India - 125

STANDING TIMES Highest operating voltage (kV)

Standing time (days)

≤ 72.5

1

> 72.5 - 123

3

> 123 - 170

3

> 170- 245

5

> 245- 420

7

> 420

7

ACCEPTANCE TEST & ENERGISATION

© ABB Ltd., India - 126

Recommended Electrical Tests z

A functional test has to be performed on all protective devices of the transformer.

z

Measure Winding resistances and converted to the same reference (say 75° C) operating temperature and compared with the test certificate values.

z

Insulation Resistance Measurement Between windings & between each winding to Ground with a 5 kV MeggerTester. Core to ground and Secondary wiring to ground with a Megger-Tester of 1 kV only.

ACCEPTANCE TEST & ENERGISATION OIL SAMPLES

Sample has to be taken and the dielectric strength must be tested. If the results of test do not comply with the requirements, the oil must be dried and de-gassed by circulating through an oil purifying plant. RECOMMENDATIONS FOR ENERGISING

© ABB Ltd., India - 127

A transformer should always be connected to the main power supply on the HV side. If the HV-winding is provided with an on-load tap-changer, the latter should be adjusted to the tap position with the maximum number of windings (TAP 1).

ACCEPTANCE TEST & ENERGISATION

© ABB Ltd., India - 128

z

When energizing 3-phase-transformers, the synchronism of the circuit breakers has proved to be important with respect to formation of switching surges. Measurements have shown that the smaller the time delays between the third pole and the second one, the smaller the over voltage level. Therefore, an examination of the synchronism of the circuit breakers should be made during the first commissioning of transformers with a voltage rating 245 kV and above. If necessary adjustment of the synchronism must be performed.

ACCEPTANCE TEST & ENERGISATION

© ABB Ltd., India - 129

z

Lightning arrestors are the best protection against switching surges for all terminals, which are not grounded. To prevent capacity transmitted voltage peaks, the low voltage terminals of generator transformers and the tertiary terminals of system interconnecting transformers should be connected to capacitors installed between terminal and ground. Protection with capacitors is not necessary if the capacity to the ground of the connected bus bars or cables is approximately 0.05 µF/phase.

ACCEPTANCE TEST & ENERGISATION

z

Before energising an unloaded transformer ensure that all short-circuit connections are removed from the secondary terminals. If there is a shortcircuit, it must be eliminated before energising the transformer.

© ABB Ltd., India - 130

Recommendations for over-voltage protection for energising unloaded transformers with regard to the voltage ratio.

ACCEPTANCE TEST & ENERGISATION REQUIREMENTS OF INSTRUMENTS USED FOR PRE-COMMISSIONING TESTS

© ABB Ltd., India - 131

Sl No.

Test

Measuring Instrument

Instrument Range

Required Accuracy

Least Count

1

Ratio, polarity and phase relationship

Voltmeter

0-500 V

+/- 2%

5V

2

Resistance

Bridge

0-100 ohms

+/- 2%

1x10-6 ohms

3

Insulation resistance

Megger

0-50,000

+/- 5%

5M-ohms at the lowest scale

4

Excitation Current

Ammeter

0-200 mA

+/-5%

1 mA

5

Oil BDV

BDV meter 2.5mm gauge

0-100 kV

+/-2%

kV GO-

2.5mm

+/- 0.1 mm

NO-GO

Moisture meter

0-100 PPM

1 PPM

1 PPM

6

Moisture in Oil

M-ohms

ACCEPTANCE TEST & ENERGISATION OVERLOAD PROTECTION FOR ENERGISING UNLOADED TRANSFORMER

Voltage ratio of the Putting in circuit on transformer the HVHV/LV or side HV/LV/TV

© ABB Ltd., India - 132

kV 110/30 110/6,3...30 110/6,3...30/10 110...245/15...27 245/110...132/10 345...525/15...27 345...525/110...24 5/10..20 750/15...27 750/245...525/30

X = is recommended

Lightning arrestors on all not earthed terminals >30kV

Protection capacitors on the LV-or TV-side

Examination of the synchronism of the circuit breakers in case of a 3-phase transformer

X X X X X X X

X X X X X X

X X X X

X X X

X X

X X

X X

X X

PRE-COMMISSIONING CHECKS

© ABB Ltd., India - 133

Following pre-commissioning checks need to be carried out: z

Oil leakage from Gasketted joints

z

Bushing Damages

z

Condensor Bushing

z

Oil Level

z

Tightness of top cap

z

Release trapped air through air release plugs and valves fitted for the purpose on various fittings like headers, radiators, and oil communicating bushings, buchholz petcock etc.

© ABB Ltd., India - 134

DEMAGNETIZING OF CORE z

Select battery with sufficient voltage to saturate the core.(12 V)

z

Select HV or LV for the process (HV is better).

z

Select R1 so that V/R1 > saturation current.

z

Select R2 so that R2 14000 CTs in India and abroad

CT – Theory & Application „

What is a CT used for?

I1

Measurement of Current Measurement of Power Isolation between High voltage and Low Voltage I2

© ABB Ltd., India - 155

Inputs to Relays & Protection Systems

Ip

Np

Is

Ns

Ip = Ns Is = Np

I1 x N1 = I2 x N2 = Ampere turns (always in balance)

CT – Theory & Application Equivalent circuit CT Is = Np X Ip Ns

Is

Is - Ie Ie

© ABB Ltd., India - 156

Ideally But Ip x Np = Is x Ns - Ie x Ns

Burden

Exciting impedance Introduces Error in CT

CT – Theory & Application Io ISKT

IP

Vector Diagram Io

β

IW

α IM θ IS

© ABB Ltd., India - 157

ES

Ø IP- PRIMARY CURRENT IS- SECONDARY CURRENT KT- TURNS RATIO NS/NP Io- EXCITATION CURRENT IW- CORE LOSS COMPONENT IM- MAGNETISATION COMPONENT ES- VOLTAGE DEVELOPED ACROSS SECONDARY Ø-FLUX DEVELOPED β- PHASE ANGLE ERROR Θ-BURDEN ANGLE α-ANGLE BETWEEN FLUX AND EXCITATION CURRENT RATIO ERROR: KT+IOSIN(θ+α)/IS PHASE ANGLE ERROR: IOCOS(θ+α)/KTIS

CT – Theory & Application Metering

Types of Cores Metering Core VA Burden, Accuracy, ISF

Protection

e.g. 15 VA, 0.5 Cl., ISF < 10 Protection Core VA Burden, Accuracy, ALF e.g. 15 VA, 5P20 PS Core © ABB Ltd., India - 158

Vk, Io, Rct e.g. Vk > 400 V, Io < 50 mA at Vk/2, Rct < 5 Ohms

CT – Theory & Application Design Criteria for Metering Core: „

How much can we offer?

© ABB Ltd., India - 159

„

Without Mumetal

Voltage Rating Possible Ratios

Burden/Accuracy

66 & 132

1000/1

30VA, 0.5Cl.

66 & 132

500/1

15VA, 0.5Cl.

220

1000/1

20VA, 0.5Cl.

220

500/1

10VA, 0.5Cl.

„

When ratio is low or Burden is high or Accuracy is stringent than indicated above, Mumetal is foreseen. Cost increases to 15times.

„

0.2Cl. always requires Mumetal

„

400kV CT always requires Mumetal

CT – Theory & Application „

B – H Characteristics

E/B

E = 4.44BmAfN2 Volts 2 Tesla ÝSaturated CRGO

Eknee Ý1.5

© ABB Ltd., India - 160

Bnx

Working Flux Density Metering Core: Bs CRGO – 0.4 to 0.8 T 0.8 Tesla ÝSaturated Mumetal μmetal – 0.3 to 0.35 T Protection Core: x Bn CRGO – 1.5 to 1.6 T I0 /H

CT – Theory & Application Current error (%)

+ 1.5

Class 0.5

1.0

Accuracy Curves

Class 0.2 25% of rated burden

0.75 0.5 + 0.2

Phase displacement (min) 90

Class 0.5

60

- 0.2

Class 0.2

0.5

30

0.75 1.0

© ABB Ltd., India - 161

- 1.5

100% of rated burden 5

20

50

100

120

10 5

20

Rated primary current (%)

Example: Plotted curves for class 0.5

50

100 120

IMB CT – Construction P1

Nitrogen Gas Oil Level Ind.

Expan. Tank

Conn. Head

Pri. Terminal

Pri. Conductor

Pri. Insulation Insulator

Terminal Box

© ABB Ltd., India - 162

Bottom Tank Sec. Cores

P2

Manufacturing Cycle – IMB CT Primary Insulation

Assembled Primary

Drying

Secondary Winding Tanking & Secondary Assembly.

© ABB Ltd., India - 163

Expansion Tank Assly Evacuation, Oil & Gas Filling

Quartz Filling Testing

Insulator & Connection Head Assembly Packing & Despatch

CT – Construction Why Drying?? To remove moisture from the insulating paper. Paper, being Hygroscopic in nature, has the tendency to absorb moisture from the atmosphere. This moisture can deteriorate the Dielectric Strength of the primary insulation. Hence this moisture has to be removed.

© ABB Ltd., India - 164

Why Evacuation?? It is nothing but applying vaccuum to the assembled CT to remove atmospheric gases which are trapped during assembly.

CT – Construction Why Oil filling and pressing?? Pressing of oil is done after filling to ensure that oil is absorbed into the innermost part of insulation imparting the desired Dielectric Strength of the primary insulation. This process is called Impregnation.

Why Waiting and Soaking??

© ABB Ltd., India - 165

This is an extended impregnation without applying oil pressure to ensure that no pockets of insulation are left without oil.

CT – Construction Why Evacuation??

© ABB Ltd., India - 166

It is nothing but applying vaccuum to the assembled CT to remove atmospheric gases which are trapped during assembly.

CT – Construction Primary Conductor Carries current through the CT Made of Aluminium; Copper when high current densities are involved

Primary Insulation Provides isolation between High Voltage and Low Voltage Electrical Grade Insulation paper.

© ABB Ltd., India - 167

Insulation in a special room with strict control over humidity, temperature and dust levels Drying by special process combining high temperature and high vaccuum Impregnation in vaccuum to avoid formation of air pockets in the insulation

© ABB Ltd., India - 168

CT – Manufacturing

IMB Primary Winding

CT – Manufacturing

© ABB Ltd., India - 169

Secondary Winding

Pri+Sec Oven Loading

© ABB Ltd., India - 170

CT – Manufacturing

Insulator Assembly + Sec Wiring

Oil + Nitrogen Filling

CT – Construction Quartz in IMB CT Reduces the quantity of oil Provides mechanical strength for the conductors Improves the quality of oil by absorbing moisture Being a bad conductor of heat, it allows slow heating / cooling of the CT. Hence it eliminates the possibility of gas generation due to rapid cooling of CT

© ABB Ltd., India - 171

During CT in service, the diffusion of moisture through OilQuartz layers becomes slow over years Received from vendor in treated form and free from Magnetic particles Treated at Works for removing moisture before filling Filled into the CT at a temperature of 80 oC

CT – Construction Oil Cushioning Compensates Volumetric changes in Oil due to Temperature Variations IMB CT uses Nitrogen Gas

Top Sealing All Gaskets are under/ below Oil level giving positive indication for leakage

© ABB Ltd., India - 172

Enhances life of gaskets

Manufacturing Highlights Quality Control Raw Material Primary Insulation / Secondary Winding Drying & Impregnation Assembly Oil Filling

© ABB Ltd., India - 173

Final CT

CT – Routine Tests Tests as per IEC: 60044-1 and IS: 2705 Verification of Terminal Markings and Polarity Power Frequency Withstand Test on Primary and Secondary Partial Discharge Measurement Inter-turn Over Voltage Test

© ABB Ltd., India - 174

Determination of Errors

CT – Type Tests Tests as per IEC: 60044-1 and IS: 2705 Short Time Current Test Temperature Rise Test Lightning Impulse Test Switching Impulse Test Radio Interference Voltage Test

© ABB Ltd., India - 175

Determination of Errors Facilities for conducting all Type Tests on CTs except Short Time current Test (ERDA / CPRI) and Seismic test (IIT Chennai / University of Roorkee) are available at our works.

CT – Special Tests Tests as per IEC: 60044-1/ IS: 2705 Chopped Lightning Impulse Test Measurement of Capacitance and Dielectric Dissipation Factor Multiple Chopped Impulse Test on Primary

© ABB Ltd., India - 176

Special tests as prescribed in CIGRE have also been conducted

CT – Packing and Transportation Generally all CTs are packed in Steel Cases Vertical Trans. – IMB 73, IMB 145

© ABB Ltd., India - 177

Hor. Transportation – IMB 73, IMB 145, IMB 245, IMB 420

CT – Unloading, Unpacking & Storage Unloading of CTs should be carried out using a crane of requisite capacity (Details in Instruction Manual) When received at site, the CT is to be first inspected for any damages or leakages

© ABB Ltd., India - 178

They are to be unpacked and stored on a hard, even and raised ground (platform) in Vertical direction only

Checks Before Installation „

© ABB Ltd., India - 179

„

Visual „

Check for any sign of Leaks or breakage

„

Check Oil level

Mechanical „

Check that the ’D3’ terminal meant for Tan Delta measurement is properly earthed

„

Check that Earthing of tank is done by Copper or suitable strips and properly tightened with M10 bolts of 4.8 Quality Fine Thread with a Tightening Torque of 30 Nm minimum

„

Check levelling of Structure by Spirit level

„

Ensure fixing of CT on Structure with M16 bolts of 8.8 Quality Fine Thread with a Tightening Torque of 250 Nm minimum

Checks Before Installation

© ABB Ltd., India - 180

„

Electrical „

Ensure that in case of idle cores, the terminals meant for highest ratio are shorted, if possible preferably by connecting resistor equivalent to the rated burden to restrict short time current

„

Ensure that the cores which are in use should have their balance terminals left open

„

Ensure contact surfaces of CT Primary Terminations thoroughly cleaned and apply good quality contact grease like Servogen and brush contact surfaces with wire mesh. Apply thin layer of contact grease before making Primary Connections

„

Ensure the fixing of CT Primary terminations with Terminal Connectors by M12 bolts of 4.8 Quality Fine Thread with a Tightening Torque of 55 Nm minimum

© ABB Ltd., India - 181

Checks Before Commissioning „

Continuity Test/ or Rough Ratio Measurement

To ensure internal connections of Pri. and Sec. are intact

„

Tan Delta at 5 or 10 kV

To ensure that ‘D3’ connections from inside Tank are intact For comparison with future measurement during Maintenance Values should be < 0.5%

„

Sec. Resistance Measurement

Values should match with Rating or Test Certificate Measure with Resistance meter and avoid DC Source

Refer Instruction Manual 1HYN520002 for IMB for complete details

Capacitor Voltage Transformer Product Range Theory & Application Construction and Manufacturing Routine, Type and Special Tests Packing and Transportation Unloading, Unpacking and Storage Checks before Installation & Commissioning

© ABB Ltd., India - 182

Care and Troubleshooting

Product Range Capacitor Voltage Transformers Type WN 36 / WN 73 / WN 145 / WP 245 / WS 420N2 This is the mixed di-electric design of CVTs The insulation consists of a combination of paper and Polypropylene film (Mixed Dielectric)

© ABB Ltd., India - 183

This design has been indigenously developed Metal Bellow used to compensate for oil expansion

Product Range Coupling Capacitors Type KN 36 / KN 73 / KN 145 / KP 245N2 This is the mixed di-electric design of CCs The insulation consists of a combination of Paper and Polypropylene film (Mixed Dielectric)

© ABB Ltd., India - 184

This design has been indigenously developed Uses metal bellow to compensate for oil expansion

CVT – Theory & Application What is a CVT used for ? Measurement of Voltage Isolation between High Voltage & Low Voltage. Inputs to Relay/Protection systems PLCC (Power line Carrier Communication)

© ABB Ltd., India - 185

Main Parts of a CVT Capacitor Part -

Capacitor Stack, Insulator

EMU

PT, HV Choke, FR circuit

-

CVT – Theory & Application Design Principles

V

e.g. V = 132 kV, C= 4400 pF V1/V2 = C2/C1 = 1199 V/V2 = C2/C = 1200

C1

V1=131.9 kV

Therefore, C2 = 52.8 lakh pF (This is 180 times larger Cap.) LIMITATIONS: 1) To tap 110 V from C2 is therefore a problem as effective burden fed by this is only 0.22 VA 2) Any attempt to load this system results into uneven voltage distribution between C1 and C2 and inaccurate output

C2

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V2=110 V

CVT – Theory & Application Design Principles

V

HOW TO OVERCOME? Tap the voltage at suitable medium voltage I.e. 20 kV, adequate to handle from insulation point of view by intermediate PT

C1

V1=131.9 kV

This will fetch effective burden e.g. 200 VA and above The charging current will be very low giving accurate output e.g. V = 132 kV, C= 4400 pF V1/V2 = C2/C1 = 5.6 V/V2 = C2/C = 6.6 Therefore, C2 = 29.04 thousand pF

C2

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V2=20 kV

CVT – Theory & Application

C1 LT

IP

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VP=20kV/√3

RT

C2 BURDEN

VS=110/ √3

CVT – Theory & Application

ISXCE VP

β

Ø IS

VS ISRT

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HV Choke adjusted to give Zero Phase Angle Error at 50Hz

ISXLT CE=C1+C2 β-BURDEN ANGLE Ø-PHASE ANGLE BETWEEN VP & VS IS-BURDEN/VS e.g. 300/110/√3=4.72 A IP= 4.72/PT VOLTAGE RATIO = 4.72/20000/110=4.72/181.8 = 30mA

CVT – Theory & Application Ratio error %

Class 0.5

Accuracy Curves

80% of Rated Voltage

+0,5 „

+0,2 0

Example: Error curves for class 0.5

-0,2 -0,5

25

100% Class 0.2 Rated burden 120% of Rated Voltage Phase angle error +20’

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+10’ 0 -10’ -20’ 25

100%

CVT – Theory & Application CVT is a tuned device and hence the errors are prone to variations with frequency.

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The errors are guaranteed from 25 % to 100% of the rated burden and for a frequency range of 49.5 to 50.5 Hz.

CVT – Construction Pri. Terminal Metal Bellow Insulator

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Cap. Stack HF Bushing

20 kV Bushing

Terminal Box

Spark Gap

Epoxy PT

EMU

CVT – Construction – Cap. Stack Top Lead

Mtg. Stand Cap. Elements

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Bottom Lead Insulation

Split Pin

CVT – Construction – EMU Bottom Tank

FR Circuit

PT Resistor Capacitor FR Choke

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HV Choke

CVT - Schematic FR Ckt Characteristic

V1

I m

C1

p

50

Freq

Step Down PT V2

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C2

Vs HV Choke Spark Gap Sealed Unit Protects the EMU from overvoltages

FR Ckt Resistor

Manufacturing Cycle – CVT Coil Winding EMU Assembly

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Finishing

Oil Filling

Stack Assembly EMU Testing

CVT Testing

Packing & Despatch

Pressing & Soldering Drying & Impregnation

Capacitor Part Assly.

Stack Calibration & Testing

CVT – Manufacturing

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Capacitor Coil Winding

Coil Stacking

Stack Soldering

CVT – Manufacturing EMU Assembly

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CVT Assembly

Insulator Assly On Stack

CVT – Advantages over PT CVT

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MODULAR CONSTRUCTION EASY TO TRANSPORT EASY TO HANDLE EASY TO ERECT

PT SINGLE AND BULKY UNIT

UNIFORM ELECTRICAL STRESS DISTRIBUTION THUS MORE RELIABLE DESIGN

NON UNIFORM ELECTRICAL STRESS DISTRIBUTION DUE TO INTER-TURN & INTER-LAYER CAPACITANCE

CAN BE USED AS COUPLING CAPACITOR FOR PLCC

NO SUCH APPLICATION POSSIBLE

OUTPUT: 200 - 300 VA IN PRESENT CONTEXT, BURDEN REQTS. HAVE DRASTICALLY REDUCED TO 50 VA (ref. PGCIL) ON ACCOUNT OF DIGITAL METERS AND RELAYS

OUTPUT: 500 VA

ALL CVTs ARE PROVIDED WITH INTENTIONAL FR SUPPRESSION CKTs HENCE WELL PROTECTED AGAINST FR OSCILLATIONS

SIMILAR FR DAMPING CKTs ARE NOT PROVIDED. HENCE PTs ARE SUSCEPTIBLE TO FAILURES (NEXT TO LA)

CVT – Advantages over PT CVT

PT

SUCH PROBLEMS ARE UNRELEVANT AND UNKNOWN FOR CVTs

PTs COME INTO RESONANCE WITH GRADING CAPACITORS PROVIDED WITH CBs WHICH CREATE TRANSIENT/PERMANENT OVERVOLTAGE LEADING TO FAILURE (ref. BBMB)

CVTs USE CAPACITOR COILS IN SERIES FOR STEPPING DOWN VOLTAGE. DURING IMPULSE TEST, VOLTAGE DIST. IS UNIFORM ACROSS EACH COIL. IMPULSE WAVE SHOWS PRESENCE OF HIGH FREQ WHEN ANALYSED WITH FOURIER SERIES. SO CAPACITOR PART OF CVT OFFERS LOW IMPEDANCE RESULTING INTO UNIFORM DIST.

PTs ARE INDUCTIVE DEVICES. VOLTAGE STRESS AT START OR END ARE HIGH. HENCE THEY ARE INSULATED MORE. THIS DECREASES INTER TURN CAP. AND COILS GET FURTHER STRESSED. HENCE DESIGN BECOMES DIFFICULT AND ONLY OPTIMUM IS POSSIBLE. PROBLEM IS MORE APPARENT FOR HIGHER VOLTAGES.

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CVTs ARE EVEN PREFERRED WHERE PLCC IS NOT IN USE.

CVT – Packing & Transportation Generally all CVTs are packed in Steel Cases All CVTs are transported Vertically

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Ensure that CVTs are not made Horizontal during emergency transshipment

CVT – Unloading and Unpacking Unloading of CVTs should be carried out using a crane of requisite capacity (Details in Instruction Manual) When received at Site, the CVT is to be first inspected for any damages or leakages

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They are to be unpacked and stored on a hard, even and raised ground (platform) in Vertical direction only

Checks before Installation „

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„

Visual „

Check for any sign of leaks or breakage

„

Check Oil level

Mechanical „

Check that the ’HF’ terminal meant for C & Tan Delta measurement is properly earthed

„

In case of use with PLCC, ensure the earthing of ’HF’ terminal through PLCC device

„

Check that Earthing of tank is done by Copper or suitable strips and properly tightened with M10 bolts of 4.8 Quality Fine Thread with a Tightening Torque of 30 Nm minimum

„

Check levelling of Structure by Spirit level

„

Ensure fixing of CVT on Structure with M18 bolts of 8.8 Quality Fine Thread with a Tightening Torque of 350 Nm min.

Checks Before Commissioning „

Continuity Test/ or Rough Ratio Measurement

To ensure internal connections of Capacitor Part and EMU are intact

„

C & Tan Delta at 5 or 10 kV

To ensure that Divider connections from inside are intact For comparison with future measurement during Maintenance Tan Delta should be < 0.5% For ‘C’ – refer Manual

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Refer Instruction Manual 1HYN525002 for complete details

Care for CTs and CVTs Carry out regular Visual Inspection of Oil Level Clean the insulator periodically, Hot Line Washing can be used No Oil Change or Oil Filteration is required as the CTs and CVTs are hermetically sealed During Annual Inspection, on de-energized CT, the tightening of Primary and Ground Connections shall be checked with recommended Tightening Torques. Measure the Primary contact resistance: IMB – 200 μOhms max

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If possible, carry out online checks for any Hot Spot at Primary Connections by ThermoVision Camera Tan Delta should be measured every year and recorded. Acceptable values are: IMB 145 – 2 %, IMB 245 – 1 % : IMB 420 – 0.8 % : CVTs – 0.5 %

Care for CTs and CVTs Tan Delta values found beyond the Acceptable Limits in CTs call for further investigation by Oil Sampling for DGA and check of moisture content Abrupt changes in Tan Delta are alarming than its absolute values higher but constant In case of Fuse Failures in CVTs, the reason for fault shall be investigated and rectified before fuses of 16 A rating are replaced

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Higher rating of fuse than required will not protect the CVT and lower rating will add burden and affect accuracy

Care for CTs and CVTs Incase of saturation of CT core during fault, they are required to be Demagnetized in order to let them perform accurately after the fault is cleared. The following method may be adopted Gradually excite the core upto its Output Voltage and reduce it to zero.

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Repeat it 3 – 4 times. This will make the core free of Residual flux and it is now ready to function as desired.

~

Trouble Shooting for CTs and CVTs Minor Leakage from Sealing Joints In case of leakage from any part like Insulator and Tank Cover, carry out tightening of nuts successfully by about 1/6th of a turn until uniformly tightened If leakage still persists, the joint may require replacement. The factory or nearest Regional office should be contacted Major Irregularities/ Damage/ Faults

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Inform the factory or nearest Regional office with atleast the following details alongwith Site and Commissioning history: Problem observed with background of earlier Care records alongwith details given in the Name Plate Disturbance Recorder, Relay operation sequence Logbook record of voltage and frequency before fault

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DISCONNECTOR

Training

$%%

© ABB Ltd., India - 210

What is disconnector? „

Definition - A mechanical switching device which provides, in the open position, an isolating distance in accordance with the specified requirements - IEC 50(441-1405)

„

Appropriate for switching small currents, between the terminals, when no significant change in voltage occurs

„

Equipped with either one, two or no earth switches

„

Available for rated voltage from 72.5 kV to 420 kV and for rated current up to 2500 A

„

Designed according to the IEC 129 -1984 and 694 -1980

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Switchyard

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SGF

© ABB Ltd., India - 213

Earth Switch

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Disconnector parts

Current Products Products currently marketed CENTRE-BREAK DISCONNECTOR (ISOLATOR) TYPE SGF Their application areas „

Disconnectors are used to isolate a part or complete network for maintenance or long shutdown. They are also used for switching small currents during transfer/changeover in the system.

„

For maintenance and operational safety it is also used for earthing the

© ABB Ltd., India - 215

system through earth switch.

Current Products

Specifications (including GTPs) and their Significance „

Type

: SGF (centre-break)

„

Current

: 1600A or 2500A

„

Voltage

: 36kV to 420kV

„

Op. Mech.

: Motor or manual

„

S.T.C

„

Earth switch

„

Control voltage

„

Motor voltage

: 40kA/3sec. : none, one or two : 110/125/220/250 Vdc /1ph,50Hz,240VAC : 110/125/220/250 Vdc /1ph,50Hz,240VAC No. Of auxiliary : 12 NO + 12 NC maximum

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Switch Contacts „

Type of interlock

: mechanical & electrical

„

Service temperature

: -40 to +50 ºc

„

Applicable standard

: IEC 60227-102 / IS:9921

DISCONNECTOR TYPE SGF (FEATURE) CONVENTIONAL APPROACH

ABB PHILOSOPHY / FEATURES

ARMS OVER TRAVEL PREVENTION In case motor continue to run even

In such case, position of disconnector

after the end position, excessive force

does not get affected due to self

will be exerted on the stopper and

releasing feature in the drive.

contact position may get disturbed. CLICK HERE

DEAD CENTRE CROSSING The total rotation is 90 degree therefore

As the rotation is greater than 180 degree,

transmission link will always exert power

there will be automatically self dead-center

to disturb internal setting of drive

© ABB Ltd., India - 217

consequently to the disconnector.

inter lock.

DISCONNECTOR TYPE SGF (FEATURE) CONVENTIONAL APPROACH

ABB PHILOSOPHY / FEATURES

SPRINGLESS CONTACTS Make-Break contacts are spring loaded with open execution which is subjected to intense environmental effects.

No external spring used Cu, Cr, Zr .

Cu

OPERATION AT UNIFORM SPEED In Motor drive, induction or universal motor is used. Inferior speed-torque characteristics of such motor leads to non-uniform speed of operation.

© ABB Ltd., India - 218

Torque

Compound DC motor having superior characteristics achieves more uniform speed of operation.

Torque

Speed

Speed

DISCONNECTOR TYPE SGF (FEATURE) FLEXIBILITY IN AUXILIARY SWITCH Option to change contact configuration at site by --Changing contact condition(NO NC) --Altering setting angle with respect to MAIN ARM Rupturing capacity is independent of SPEED of switching(operation) of motor/hand drive

© ABB Ltd., India - 219

Also most suitable for most modern protection scheme like SCADA or SPACOM where switching angle should be accurate & repeatable

CONVENTIONAL APPROACH

ABB PHILOSOPHY / FEATURES

PAINTING OF DRIVE BOXES Drive housing of painted steel sheet calls for routine touch-up in long run to avoid rusting.

Drive housing of Aluminum sheet with Polyester Powder Coating. High aesthetic value.

INSULATOR VERTICAL ALIGNMENT Extreme variation in insulator as per IEC, cause major problem in alignment as no

© ABB Ltd., India - 220

adjustment possible.

Complete flexibility for right alignment.

DISCONNECTOR TYPE SGF (FEATURE) CONVENTIONAL APPROACH

ABB PHILOSOPHY/FEATURE

CURRENT TRANSFER IN ARMS Bolted joint between rotary head and main arm.

Main arm welded with rotary head.

SPHERICAL BUSH FOR LINKAGE For inter-pole connections normally

© ABB Ltd., India - 221

metallic bush bearings are used which requires accurate alignment and frequent maintenance.

Inter-pole rods are having corrosion free end type bearing with self alignment capability of 30 degree. Bearing has Teflon lining(non-corrosive, smooth, long life).

DISCONNECTOR TYPE SGF (FEATURE) CONVENTIONAL APPROACH

ABB PHILOSOPHY / FEATURES

SEALED BOTTOM THRUST BEARING Normally exposed bush bearing is used at bottom of rotary system which calls for frequent maintenance.

Totally protected and sealed-for-life. Double ball bearings are used to achieve trouble-free operation.

CURRENT TRANSFER IN CONNECTION HEAD

© ABB Ltd., India - 222

Rotary head has limited freedom of rotation endangering accuracy at initial location and also exerts tortional moment on the terminal due to laminated strip conductor.

Rotary head can rotate through 360 degree and no undue stress as tulip contacts are provided for current transfer.

Interfacing Equipment/System How the product is placed in the system „

The product is invariably needed in any generating/switching station.

„

This equipment is used mainly for isolation of a part or complete network for maintenance or long shutdown.

„

Present trend is that customer demand package order in which disconnector is a part.

Other Equipment/System with which the product is interfaced and that can affect the Product Performance „

Normally performance of this product is not influenced by other outdoor products except overvoltages

© ABB Ltd., India - 227

that can affect the Product Performance

© ABB Ltd., India - 229

Drives - Manual and Motorised

© ABB Ltd., India - 230

HCB Disconnector Type SGF

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Vertical Mounting

© ABB Ltd., India - 232

PARALLEL ARRANGEMENT

PARALLEL ARRANGEMENT

© ABB Ltd., India - 233

Series Arrangement

© ABB Ltd., India - 234

Tandem Arrangement