BHEL Breaker presentation

EHV CIRCUIT BREAKERS

SWITCHGEAR DIVISION, HYD - 032. 1

SWITCHGEAR DIVISION, HYD - 032.

1. EHV breaker manufacturing operations Started in 1969.

2. Pioneer in high voltage breaker in the country with more

than 15,000 (including MOCBs) breakers in the grid with

more than four decades of experience.

3. About 35% ( more than 700 nos.) population of 400kV

breaker in Indian grid.

4. Complete range of manufacturing and test facilities for

breakers upto 800kV.

ABOUT SWITCHGEAR

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Product range

• SF6 gas circuit breaker– Type 3AT4/5 550kV to 800kV– Type 3AT2/3 420kV– Type 3AV1 245kV– Type 3AR1EG 145kV


CIRCUIT BREAKER

• A circuit breaker is defined as a mechanical device capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specific time and breaking currents under specific abnormal circuit conditions such as those of short circuit.

• The main functions of HV circuit-breakers can be categorized into four functions:

• Switching-off operating currents

• Switching-on operating currents

• Short-circuit current interruption

• Secure open and closed position

.


Power plant

Transformer Transformer Local distribution net work

Transmission

line

Switch

Yards

Switch

Yard


Power Transmission system

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CIRCUIT BREAKER

• Physical requirements of EHV CB:

• Behave as a good conductor during a closed position.

Good isolator during an open position.

• Do not generate overvoltage's during switching.

• Keep high reliability during operation

.


CLASIFICATION OF CIRCUIT BREAKERS

Based on VoltageLow -less than 1kVMedium - 1kV to 52kVHigh/Extra High- 66kV to 765kVUltra High -above 765kV

Based on locationIndoor Outdoor

�Based on External designdead tank Live tank

�Based on Interrupting mediaAir breakAir blastBulk oilMinimum oilSF6 gas insulatedvacuum


Circuit Breakers

• Important standards

• IEC

• 62271-1General and definitions• 62271-100 Classification, Design and construction,

Type and routine testing, Selection of circuit breakers for service, Information in enquiries, tenders and orders.


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Circuit Breakers

• ANSI(American National Standards Institute)

• C3704–1979 Rating structure

• C3706–1979 Preferred ratings

• C3709–1979 Test procedure

• C3710–1979 Application guide

• C3711–1979 Application guide for transient recovery voltage

• C3712–1979 Capacitance current switching


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MAIN COMPONENTES 42OKV EHV CB


INTERRUPTER UNIT

INSULATOR COLUMN

CONTROL UNIT

DRIVE UNIT

BELL CRANK HOUSING

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800kV Type 3AT4/5 SF6 Gas BreakerPole Assembly


CIRCUIT BREAKER

• Components of HV circuit-breakers regarding basic functions

can be divided into five groups:

a). Insulation:

Electric insulation of HV CB is Gaseous, liquid and solid

dielectric materials. Ex. Interrupter.

b). Current carrying:

The current carrying parts are significant components that

assure the flowing of current in the closed position.

The failure of these parts can lead to catastrophic events.

Ex. Guide tube.


CIRCUIT BREAKER

c). Switching:

HV circuit-breakers subjected to electrical, thermal and

mechanical stresses.

It is required that they should be able to make and break large

amount of power without causing failures.

.


CIRCUIT BREAKER

d). Operating mechanism:

The operating mechanism is a part used to move contacts

from open to closed position or inversely.

Ex. Hydraulic Mechanism.

e). Control and auxiliary functions: The signal is sent to the coil to move a latch or open a valve leading to energy release of a mechanical drive.

.


Classification of BreakersClassification of Breakers


DEAD TANK TYPE LIVE TANK TYPE

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Classification of BreakersClassification of Breakers

Indoor Switchgear (GIS) Outdoor breakers (AIS)


SF6 GAS PROPERTIESSF6 GAS PROPERTIES


ARC INTERRUPTION



BREAKER'S OPERATION TIMES

• Basic oprns of the CB is "CLOSE" when joining, and "TRIP" when parting the contacts.• In most of the cases it has to execute on demand a combination of the basic operations, called cycles. The most popular are the following:

1."TRIP FREE", (C-O): simulates a trip on short circuit after a "CLOSE". 2."RECLOSE", (O-C): simulates a fast close after short circuit trip to reestablish the current.3."RECLOSE-OPEN", (O-0.3s-C-O): Simulates a "RECLOSE" on short circuit. The breaker should clear the fault successfully.


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BREAKER'S OPERATION TIMES

4. (C-O)-15 sec-(C-O)-15-sec-(C-O): simulates a multiple close after short circuit trips in purpose of re-establishing the current, hoping that the short circuit is disappeared. This cycle is mostly used in the Medium voltage appls.

5. The times measured, for the different cycles starting from the coil energizing until the switching of the main contacts are called the Breaker's mechanical times of operations.


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Arc interruption in duel flow conducting nozzle interrupter


Arc-quenching in duel flow conducting nozzle interrupter


Arc-quenching in insulated nozzle interrupter

1. Terminal plate 5. Nozzle2. Contact carrier 6. Contact cylinder3. Main contact 7. Base4. Arcing contact 8. Terminal plate


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Blast cylinder assemblySWITCHGEAR DIVISION, HYD - 032.

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OPERATION OF CLOSING RESISTOROPERATION OF CLOSING RESISTOR



Spring operated mechanisms


Pneumatic mechanism


COMPARISON OF ELECTROHYDRAULIC - PNEUMATIC - SPRING MECHANISMS

Electro Hydraulic Pneumatic Spring

1. No compressor is required – Hydraulic pump ismaintenance free and directly coupled to motor.

Compressor is required, which needs routinemaintenance (at least once a year). Compressors arenormally coupled to motor by belt, which is a weaklink. Also intake air filters of compressors requirefrequent change (Every Six months in pollutedatmosphere)

No compressor is required – Hence no associatedmaintenance problems.

2. All parts permanently immersed in oil - No scope forinternal corrosion or rusting.

All parts exposed to atmosphere. In addition,atmospheric air is compressed and releasedduring closing / opening operation. Duringexpansion, traces of moisture present in air inspiteof purification / drying of air, condense on metalparts of the mechanism causing corrosion andrusting.

All parts exposed to atmosphere Heaters providedto prevent condensation of moisture on parts ofmechanism

3. Minimal piping – Oil flow is through ducts in valveblock assembly – No scope for external leakage –Internal leakage, if any, would only cause morefrequent operation of motor at worst.

Piping is involved - Scope for leakage. No piping - No leakage.

4. No mechanical latches.The differential piston principle used clearly definesthe switching condition and ensures that this ismaintained should there be a fall in pressure and that"creeping" trip out is prevented.

Latches are to be checked for disturbances in settingsafter specified no. of operations

Latches are to be checked for disturbances in settingsafter specified no. of operations.

5. Small in size, compact and robust construction.Reliability very high.

Complex construction with many componentsand moving parts - Reliability very low.

Simple in design and construction. Less componentsand moving parts, hence reliable.

6. Two Close-Open operations are possible after failureof supply to motor.

One Open-Close-Open or Close-Open-Closeoperation is possible after failure of supply to motor.

One Open-Close-Open operation is possible afterfailure of supply to the motor.


COMPARISON OF ELECTROHYDRAULIC - PNEUMATIC - SPRING MECHANISMS

Electro Hydraulic Pneumatic Spring

7 No additional damping system The damping requiredfor both closing and opening is provided by thehydraulics of the operating mechanism.

Additional damping system is required which is to beroutinely checked and maintained.

Additional damping system is required which is to beroutinely checked and maintained.

8 No inter-posing mechanism. The piston systemtransmits the operating energy direct to the operatingrod.

Inter-posing mechanism with linkages is required fortransmission of operating energy to the movingcontact system.

Inter-posing mechanism with linkages is required fortransmission of operating energy to the movingcontact system.

9 Low noise level High noise level Low noise level


145 kV TYPE 3AR1EG BREAKER


145kV hydraulic mechanism operated SF6 gas breaker


245kV TYPE 3AV1 BREAKER



800kV Type 3AT4/5

SF6 gas circuit breaker


Testing of circuit breaker• Type tests

– High power tests• Direct tests• synthetic tests

– Short circuit tests

– Switching performance tests

– High voltage tests

– Mechanical and environmental tests

– Temperature rise test

• Routine tests– Mechanical operations test

– Measurement of contact resistance

– Voltage withstand test on control circuit

– Power frequency withstand test on main circuit

– High pressure test on Hydraulic mechanism

– SF6 gas tightness test

– Pump charging time for operations

– Leak testing hydraulic mechanism

– N2 leak test on accumulatorSWITCHGEAR DIVISION, HYD - 032.

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Thank youThank you

40SWITCHGEAR DIVISION, HYD - 032.

BHEL Breaker presentation

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