O & M Of CIRCUIT BREAKER

K N Srinivasan

Breaker Chamber Drive Mechanism

Breaker

Air,oil,SF6

Driving Mechanism

Tests
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

Classical Maintenance Thinking

Conditional probability of failure

Bath Tub Curve

Infant mortality
Design, Reliability and manufacturing

Useful life period

Preventive and Condition based maintenance

Phase out period

RLA

Age

ROUTINE TESTS

THE ROUTINE TESTS ARE TO BE COSIDERED AS ACCEPTANCE TESTS

Routine tests S. No. 1 2 3 4 5 Dielectric test on main circuit Dielectric test on auxiliary & control circuit Design identification test Mechanical operating test Measurement of resistance of main circuit

TYPE TESTS IEC: 62271-100]

1 2 3 4 5 6 7 8

Dielectric tests Radio Interference voltage test Resistance of the main circuit Temp. rise test Short-time withstand current & peak withstand current Mechanical operation test at ambient temp. Short-circuit current making/ breaking tests Capacitive current charging tests: -Line charging current breaking tests -Cable charging current breaking tests

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

Types of Faults Random

Non-observable

Time Induced
observable Non-observable

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

MAINTENANCE TERMINOLOGIES

Swedish Standard SS-EN 13306, 2001

BREAKDOWN MAINTENANCE
Equipment Productivity
High downtime Frequent failures Poor quality Reduced safety

Employee Productivity
High work time High waiting time Low morale

PREVENTIVE MAINTENANCE
Planned Maintenance based on periodicity Advantages Disadvantages
Reduction in failures Enables planning

Over maintenance Human intervention in equipment technology

PREDICTIVE MAINTENANCE
Maintenance based on machine condition Advantages
Better availability Reduced maintenance costs Safety and quality Operation and maintenance planning Design Improvements

CONDITION MONITORING
CONDITION MONITORING SUBJECTIVE (70%) OBJECTIVE (30%)

SIMPLE AIDS

INSTRUMENTAL TECHNIQUES

Symmetry & Asymmetry

Switch On V peak - No asymmetry

Steady Operation -no asymmetry

Fault MVA = 3 x VL x IL VL= Line voltage IL = Line current

Contact separation

400kV CB

420 kV SF6 With Pneumatic Mechanism

INTERRUPTER DESIGN

Internal Details of Interrupter

Contact Configuration

PIR ASSEMBLY FAILURES MECHANICAL BLASTING OF CB DUE

BREAKAGE OF PTFE ROD

TO PIR PROBLEM

OVERHAULING OF CBs

Ratings

Types

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 Resistor

420 kV 800 kV 300-450 Ohms 300-40 0 Ohms

Types of CB Mechanisms
Spring operating Pneumatic Hydraulic
All store potential energy in elastic medium and facilitate fast release

Rated Voltage (kV)

Rated Short Circuit Breaking current (kA)

Rated normal current (Amp)

630 630 630

36

8 12.5 16 25 40

1250 1250 1250 1250

1600 1600 1600

2500 2500

72.5

12.5 16 20 31.5 12.5 20 25 40

800 800

1250 1250 1250 1250 1250 1250

1600 1600 1600 1600 1600

2000 2000 2000 2000 2000

123

800

145

12.5 20 25 31.5 40

800

1250 1250 1250 1250

1600 1600 1600 1600

2000 2000 2000 2000

3150

Rated Voltag e (kV)

Rated Short Circuit Breaking current (kA)

Rated normal current (Amp) 1250 1250

245

20 31.5 40

1600 1600

2000 2000

3150

420

31.5 40 50 63 40

1600 1600

2000 2000 2000

3150 3150 3150 3150

4000 4000

800

2000

Reasons of CB Failures
MECHANICAL 74% (OPERATING COMPONENTS FAILURES) ELECTRICAL (DIELECTRIC FAILURE) DRIVEs etc. 16% 10%

Static contact resistance measurement

DYNAMIC CONTACT RESISTANCE MEASUREMENT (DCRM) CONTACT RESISTANCE MEASUREMENT DURING CLOSING AND 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 PROBLEM IN ARCING AND MAIN CONTACTS.

Basic connection arrangement for DCRM Measurement

DCRM CONNECTION ARRANGEMENT

Typical DCRM Signature

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

SF6 gas quality testing purity & dew point . recycling.

SF6is easily recycled for reuse Standards established gas handling equipment is readily available Contamination
Gas handling Leakage Desorption from surfaces Decomposition by electrical discharges Secondary reactions Mechanical generation of dust particles Effects Health risk Corrosion Insulation performance of gas gaps Insulation performance of insulator surfaces Switching capability Heat transfer

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/Particles polymer carbonization and mechanical wear 1 micrometer pore size filters in gas handling equipment Oil From pumps and lubrication IEC 480 is being revised to provide an international standard for purity levels

Minimize leakage rate Gas monitoring

Reclaim Quality Checks Air and CF4:speed of sound or thermal conductivity Humidity: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: CaSO4 CaF2 These are naturally minerals used in construction and toothpaste

CONDITION ASSESSMENT TECHNIQUES

1.

ON LINE CONDITION MONITORING TECHNIQUES OFF LINE CONDITION ASSESSMENT TECHNIQUES

2.

ON LINE CONDITION MONITORING TECHNIQUES

1. SF6 GAS PRESSURE MONITORING 2. TRIP COIL SUPERVISON 3. AUXILIARY CONTACTS OPERATING

TIMINGS 4. CONTACT SPEED MEASUREMENT BY INSTALLING TRANSDUCERS 5. LINE CURRENT AND CUMULATIVE FAULT CURRENT USING EXTERNAL CT- UNDER EVALUATION

OFF LINE CONDITION ASSESSMENT TECHNIQUES

1. 2. 3. 4. 5. 6. 7. 8.

OPERATING TIMINGS OF MAIN AND AUXILIARY CONTACTS-1 Y TRIP/CLOSE COIL CURRENTS MEASUREMENT-1Y STATIC CONTACT RESISTANCE MEASUREMENT-2Y VIBRATION MEASUREMENT UNDER EVALUATION STAGE CONTACT TRAVEL MEASUREMENT-3Y DEW POINT MEASUREMENT OF SF6 GAS-2Y DYNAMIC CONTACT RESISTANCE MEASUREMENT-3Y TAN DELTA MEASUREMENT OF GRADING CAPACITORS- 3Y

Breaker Operation Checks(

From CBIP Manual )

1 2 3 4 5 6 7 8 9

CB Operating timings (Main,PIR,Aux) Static contact resistance measurements DCRM Checking of Pole discrepancy relay Functional checks, Duty cycle operation including SF6 density monitor Checking of all operational lock-outs including SF6 density monitor Checking of all interlocks Checking of pressure settings Cleaning of breaker interrupter, support insulrs,PIRs & grading Cs

Y 2Y 2Y Y Y Y Y Y

Accptable Norms