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O & M Of CIRCUIT BREAKER

K N Srinivasan

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Breaker Chamber

Drive Mechanism

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Air,oil,SF6

Breaker

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Driving Mechanism

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Contact timing test Testy

Travel & velocity Test

Contact resistance Test

AC Insulation Test

Oil Dielectric Test

Oil gas analysis Test

Water content Test

SF6 by-products Test

Sf6 mixture percentage Test

Auxiliary circuit

insulation Test

First trip Test

Dynamic resistance contact Test

Vibration Test Test

X Ray Test

Ultrasound(731) Test

Capacitance Test

Air pressure consumption Test

Infrared temperature Test

Tightness Test

Tests

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Age

Cond

itionalprobabilityoffailu

re

Infant mortality Useful life period Phase out period

Classical Maintenance Thinking

Design,

Reliability andmanufacturing

Preventive and Condition based

maintenance

RLA

Bath Tub Curve

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ROUTINE TESTS

S. No.Routine tests

1 Dielectric test on main circuit

2 Dielectric test on auxiliary & control

circuit3 Design identification test

4 Mechanical operating test

5 Measurement of resistance of main circuit

THE ROUTINE TESTS ARE TO BE COSIDERED AS ACCEPTANCE TESTS

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TYPE TESTSIEC: 62271-100]

1 Dielectric tests

2 Radio Interference voltage test

3 Resistance of the main circuit

4 Temp. rise test

5 Short-time withstand current & peak withstandcurrent

6 Mechanical operation test at ambient temp.

7 Short-circuit current making/ breaking tests

8 Capacitive current charging tests:-Line charging current breaking tests

-Cable charging current breaking tests

Switching impulse voltage ( applicable for 420 kV CB and above)

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Types of Faults

Random Time Induced

Non-observable Non-observableobservable

Maintenance Strategies for combating the Above Fault Types

Accept breakdowns Readiness to repair

Improve reliability Design out maintenance

Condition Monitoring Continuous monitoring

Periodic monitoring

Periodic overhauls Periodic replacements

Reconditioning

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Swedish Standard SS-EN 13306, 2001

MAINTENANCE TERMINOLOGIES

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BREAKDOWN MAINTENANCE

Equipment Productivity High downtime

Frequent failures

Poor quality

Reduced safety

Employee Productivity High work time

High waiting time Low morale

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PREVENTIVE MAINTENANCE

Planned Maintenance based on periodicityAdvantages

Reduction in failures

Enables planning

Disadvantages Over maintenance

Human intervention in equipment technology

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PREDICTIVE MAINTENANCE

Maintenance based on machine conditionAdvantages

Better availability

Reduced maintenance costs Safety and quality

Operation and maintenance planning

Design Improvements

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CONDITION MONITORINGCONDITION MONITORING

OBJECTIVE (30%)SUBJECTIVE(70%)

SIMPLE AIDS INSTRUMENTAL

TECHNIQUES

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Symmetry &Asymmetry

Steady Operation -no asymmetry

SwitchOn V peak - No asymmetry

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Fault MVA = 3 x VL x IL

VL= Line voltage

IL = Line current

Contact

separation

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400kV CB

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420 kV SF6 With Pneumatic Mechanism

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INTERRUPTER DESIGN

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Internal Details of Interrupter

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Contact Configuration

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PIR ASSEMBLY FAILURES MECHANICAL

BREAKAGE OF PTFEROD

BLASTING OF CB DUE

TO PIR PROBLEM

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OVERHAULING OF CBs

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TypesTypes

RatingsRatings

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Total Break Time (As Per IEC: 62271-100

72.5 kV

145 kV

245 kV

420 kV

800 kV

60 ms to 100 ms

60 ms to 100 ms

Not exceeding 60 ms

Not exceeding 40 ms

Not exceeding 40 ms

Pre Insertion Resistor420 kV 300-450 Ohms

800 kV 300-40 0 Ohms

Types of CB Mechanisms

Spring operatingPneumatic

Hydraulic

All store potential energy in elastic medium and facilitate fast release

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36 8

12.5

16

25

40

630

630

630

1250

1250

1250

1250

1600

1600

1600

2500

2500

72.5 12.5

16

20

31.5

800

800

1250

1250

1250 1600

1600

2000

2000

123 12.5

20

25

40

800 1250

1250

1250

1600

1600

1600

2000

2000

2000

145 12.5

20

25

31.5

40

800 1250

1250

1250

1250

1600

1600

1600

1600

2000

2000

2000

2000 3150

Rated

Voltage

(kV)

Rated ShortCircuit

Breaking current

(kA)

Rated normal current (Amp)

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245 20

31.5

40

1250

1250 1600

1600

2000

2000 3150

420 31.5

40

5063

1600

1600

2000

2000

2000

3150

31503150

40004000

800 40 2000 3150

Rated

Voltag

e(kV)

Rated Short Circuit

Breaking current

(kA) Rated normal current (Amp)

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Reasons of CB Failures

MECHANICAL - 74%(OPERATING COMPONENTS FAILURES)

ELECTRICAL - 16%(DIELECTRIC FAILURE)

DRIVEs etc. - 10%

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DYNAMIC CONTACT RESISTANCE MEASUREMENT (DCRM)

CONTACT RESISTANCE MEASUREMENT DURING CLOSINGAND TRIPPING OPERATION. C-O DELAY TIME ABOUT 300MS.

100 AMP CURRENT IS INJECTED THROUGH CB CONTACTS.

VOLTAGE DROP AND CURRENT IS MEASURED TO COMPUTE

CONTACT RESISTANCE.

VARIATION IN FINGER PRINT OF DCRM INDICATE PROBLEMIN ARCING AND MAIN CONTACTS.

Static contact resistance measurement

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Basic connection arrangement for DCRMMeasurement

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DCRM CONNECTION ARRANGEMENT

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Typical DCRM Signature

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DCRM can detect

Erosion of Arcing Contact

Erosion of main contact

Contact misalignments

Contact wipe of main and arcing contact Main & arcing contact resistance

Healthiness of damping system

Contact travel & speed

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SF6is easily recycled for reuseStandards establishedgas handling equipment is readily available

ContaminationGas handlingLeakageDesorption from surfacesDecomposition by electrical dischargesSecondary reactions

Mechanical generation of dust particles

EffectsHealth riskCorrosion

Insulation performance of gas gapsInsulation performance of insulator surfacesSwitching capabilityHeat transfer

SF6 gas quality testing purity & dew point . recycling.

Ai d CF4 (fl b )

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Air and CF4 (fluorocarbon )handling and switching arcs

dilution with new SF6gas

SF4, WF6(Tungsten hexafluoride ), SOF4, SOF2, SO2, HF, SO2F2

From arcing, partial discharges, and secondary reactions

absorbants used in gas handling equipment

Solid Decomposition Products: CuF2, WO3, WO2F2, WOF4, AlF3

contact erosion and internal arcing

dust filters of 1 micrometer pore

Carbon and Metal Dust/Particlespolymer carbonization and mechanical wear

1 micrometer pore size filters in gas handling equipment

OilFrom pumps and lubrication

IEC 480 is being revised to provide an international standard for purity levels

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Minimize leakage rate

Gas monitoring

Reclaim

Quality ChecksAir and CF4:speed of sound or thermal conductivityHumidity:electronic hygrometers or dew point instruments

Decomposition Products:chemical reaction tubes with visual indication

Final Disposal

Use a thermal process followed by a calcium hydroxide scrubber to form solid

sulphates and fluorides:CaSO4CaF2

These are naturally minerals used in construction and toothpaste

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CONDITION ASSESSMENT TECHNIQUES

1. ON LINE CONDITION MONITORING

TECHNIQUES

2. OFF LINE CONDITION ASSESSMENT

TECHNIQUES

ON LINE CONDITION MONITORING

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TECHNIQUES

1. SF6 GAS PRESSURE MONITORING

2. TRIP COIL SUPERVISON3. AUXILIARY CONTACTS OPERATING

TIMINGS

4. CONTACT SPEED MEASUREMENT BYINSTALLING TRANSDUCERS

5. LINE CURRENT AND CUMULATIVE FAULTCURRENT USING EXTERNAL CT- UNDER

EVALUATION

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OFF LINE CONDITION ASSESSMENT TECHNIQUES

1. OPERATING TIMINGS OF MAIN AND AUXILIARYCONTACTS-1 Y

2. TRIP/CLOSE COIL CURRENTS MEASUREMENT-1Y

3. STATIC CONTACT RESISTANCE MEASUREMENT-2Y

4. VIBRATION MEASUREMENT UNDER EVALUATION

STAGE5. CONTACT TRAVEL MEASUREMENT-3Y

6. DEW POINT MEASUREMENT OF SF6 GAS-2Y

7. DYNAMIC CONTACT RESISTANCE MEASUREMENT-3Y

8. TAN DELTA MEASUREMENT OF GRADINGCAPACITORS- 3Y

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Breaker Operation Checks(From CBIP Manual )

1 CB Operating timings (Main,PIR,Aux) Y

2 Static contact resistance measurements 2Y

3 DCRM 2Y

4 Checking of Pole discrepancy relay Y

5 Functional checks, Duty cycle operation including SF6 density monitor Y

6 Checking of all operational lock-outs including SF6 density monitor Y

7 Checking of all interlocks Y

8 Checking of pressure settings Y

9 Cleaning of breaker interrupter, support insulrs,PIRs & grading Cs

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A

Accptable Norms

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