Fundamentals of Circuit Breaker Maintenance. AVO Training Institute, Inc. 2018

Transcription

1 Fundamentals of Circuit Breaker Maintenance 1 AVO Training Institute, Inc. 2018

2 Moderator n Ron Spataro AVO Training Institute Marketing Manager 2

3 Q&A n Send us your questions and comments during the presentation 3

4 Today s Presenter Mike Carter AVO Training Institute, Senior Instructor and Curriculum Advisor 4

5 Definition and Purpose of Circuit Breakers Definition A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by excess current from an overload or short circuit. Its basic function is to interrupt current flow after a fault is detected. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. 5

6 Definition and Purpose of Circuit Breakers Definition Circuit breakers are made in varying sizes, from small devices that protect low-current circuits or individual household appliance, up to large switchgear designed to protect high voltage circuits feeding an entire city. The generic function of a circuit breaker, RCD or a fuse, as an automatic means of removing power from a faulty system is often abbreviated as OCPD (Over Current Protection Device). 6

7 Definition and Purpose of Circuit Breakers 7 Purpose Interconnection of multiple generator sources into an electrical grid required development of circuit breakers with increasing voltage ratings and increased ability to safely interrupt the increasing short-circuit currents produced by networks. Simple air-break manual switches produced hazardous arcs when interrupting high voltages; these gave way to oilenclosed contacts, and various forms using directed flow of pressurized air, or of pressurized oil, to cool and interrupt the arc.

8 Definition and Purpose of Circuit Breakers Purpose All circuit breaker systems have common features in their operation, but details vary substantially depending on the voltage class, current rating and type of the circuit breaker. The circuit breaker must first detect a fault condition. In small mains and low voltage circuit breakers, this is usually done within the device itself. Circuit breakers for large currents or high voltages are usually arranged with protective relay pilot devices to sense a fault condition and to operate the opening mechanism. 8

9 Definition and Purpose of Circuit Breakers Purpose These typically require a separate power source, such as a battery, although some high-voltage circuit breakers are selfcontained with current transformers, protective relays, and an internal control power source. Once a fault is detected, the circuit breaker contacts must open to interrupt the circuit; this is commonly done using mechanically stored energy contained within the breaker, such as a spring or compressed air to separate the contacts. 9

10 Definition and Purpose of Circuit Breakers Purpose Circuit breakers may also use the higher current caused by the fault to separate the contacts, such as thermal expansion or a magnetic field. Small circuit breakers typically have a manual control lever to switch off the load or reset a tripped breaker, while larger units use solenoids to trip the mechanism, and electric motors to restore energy to the springs. 10

11 Definition and Purpose of Circuit Breakers Purpose The circuit breaker contacts must carry the load current without excessive heating, and must also withstand the heat of the arc produced when interrupting (opening) the circuit. Contacts are made of copper or copper alloys, silver alloys and other highly conductive materials. Service life of the contacts is limited by the erosion of contact material due to arcing while interrupting the current. 11

12 12 Air, Low- Voltage Power Circuit Breakers

13 Air, Low- Voltage Power Circuit Breakers 13 Visual and Mechanical Inspection Inspect physical and mechanical condition. Inspect anchorage, alignment, and grounding. Verify that all maintenance devices are available for servicing and operating the breaker. Prior to cleaning the unit, perform as-found tests, if required. Clean the unit. Inspect arc chutes. Inspect moving and stationary contacts for condition, wear, and alignment.

14 Air, Low- Voltage Power Circuit Breakers Visual and Mechanical Inspection Verify that primary and secondary contact wipe and other dimensions vital to satisfactory operation of the breaker are correct. Perform all mechanical operator and contact alignment tests on both the breaker and its operating mechanism in accordance with manufacturer s published data. 14

15 Air, Low- Voltage Power Circuit Breakers Visual and Mechanical Inspection Inspect bolted electrical connections for high resistance using one or more of the following methods: Use of a low-resistance ohmmeter Verify tightness of accessible bolted electrical connections by calibrated torque-wrench method in accordance with manufacturer s published data or Neta Table Perform a thermographic survey 15

16 Air, Low- Voltage Power Circuit Breakers Visual and Mechanical Inspection Verify cell fit and element alignment. Verify racking mechanism operation. Use appropriate lubrication on moving current-carrying parts and on moving and sliding surfaces. Perform adjustments for final protective device settings in accordance with coordination study provided by end user. Perform as-left tests. Record as-found and as-left operation counter readings. 16

17 Air, Low- Voltage Power Circuit Breakers Electrical Test Perform resistance measurements through bolted connections with a low-resistance ohmmeter. Perform insulation-resistance tests for one minute on each pole, phase-to-phase and phase-to-ground with the circuit breaker closed, and across each open pole. Apply voltage in accordance with manufacturer s published data. In the absence of manufacturer s published data, use Neta Table

18 Air, Low- Voltage Power Circuit Breakers Electrical Test Perform a contact/pole-resistance test. (Optional) Perform insulation-resistance tests on all control wiring with respect to ground. The applied potential shall be 500 volts dc for 300-volt rated cable and 1000 volts dc for 600-volt rated cable. Test duration shall be one minute Determine long-time pickup and delay, short-time pickup and delay, ground-fault pickup and delay and instantaneous pickup current by primary current injection. 18

19 Air, Low- Voltage Power Circuit Breakers Electrical Test (Optional)Test functions of the trip unit by means of secondary injection. Perform minimum pickup voltage test on shunt trip and close coils in accordance with Neta Table Verify correct operation of auxiliary features such as trip and pickup indicators, zone interlocking, electrical close and trip operation, trip-free, antipump function, and trip unit battery condition. 19

20 Air, Low- Voltage Power Circuit Breakers Electrical Test Reset all trip logs and indicators. Verify operation of charging mechanism. Test Values Visual and Mechanical Compare bolted connection resistance values to values of similar connections. Investigate values which deviate from those of similar bolted connections by more than 50 percent of the lowest value. 20

21 Air, Low- Voltage Power Circuit Breakers Test Values Visual and Mechanical Bolt-torque levels should be in accordance with manufacturer s published data. In the absence of manufacturer s published data, use Neta Table Results of the thermographic survey. Settings shall comply with coordination study recommendations. Operations counter should advance one digit per close-open cycle. 21

22 Air, Low- Voltage Power Circuit Breakers Test Values Electrical Compare bolted connection resistance values to values of similar connections. Investigate values which deviate from those of similar bolted connections by more than 50 percent of the lowest value. Insulation-resistance values of breakers should be in accordance with manufacturer s published data. In the absence of manufacturer s published data, use Neta Table Values of insulation resistance less than this table or manufacturer s recommendations should be investigated. 22

23 Air, Low- Voltage Power Circuit Breakers Test Values Electrical Microhm or dc millivolt drop values should not exceed the high levels of the normal range as indicated in the manufacturer s published data. If manufacturer s data is not available, investigate values that deviate from adjacent poles or similar breakers by more than 50 percent of the lowest value. Insulation-resistance values of control wiring should be comparable to previously obtained results but not less than two megohms. 23

24 Air, Low- Voltage Power Circuit Breakers Test Values Electrical Pickup values and trip characteristic should be as specified and within manufacturer s published tolerances. Minimum pickup voltage on shunt trip and close coils should be in accordance with manufacturer s published data. In the absence of manufacturer s published data, refer to Neta Table Auxiliary features should operate in accordance with manufacturer s published data. 24

25 25 Circuit Breakers, Air, Medium-Voltage

26 Circuit Breakers, Air, Medium-Voltage Visual and Mechanical Inspection Inspect physical and mechanical condition. Verify that all maintenance devices are available for servicing and operating the breaker. Perform operator analysis (first-trip) test. Prior to cleaning the unit, perform as-found tests, if required. Inspect arc chutes. Inspect moving and stationary contacts for condition, wear, and alignment. 26

27 Circuit Breakers, Air, Medium-Voltage Visual and Mechanical Inspection If recommended by manufacturer, slow close/open breaker and check for binding, friction, contact alignment, contact sequence, and penetration. Verify that contact sequence is in accordance with manufacturer s published data. Perform all mechanical operation tests on the operating mechanism in accordance with manufacturer s published data. 27

28 Circuit Breakers, Air, Medium-Voltage Visual and Mechanical Inspection Inspect bolted electrical connections for high resistance using one or more of the following methods: Use of a low-resistance ohmmeter, verify tightness of accessible bolted electrical connections by calibrated torque-wrench or perform a thermographic survey. Verify cell fit and element alignment. Verify racking mechanism operation. 28

29 Circuit Breakers, Air, Medium-Voltage Visual and Mechanical Inspection Inspect puffer operation. Use appropriate lubrication on moving current-carrying parts and on moving and sliding surfaces. (Optional) Perform time-travel analysis. Perform as-left tests. Record as-found and as-left operation-counter readings. 29

30 Circuit Breakers, Air, Medium-Voltage Electrical Tests Perform resistance measurements through bolted connections with a low-resistance ohmmeter. Perform insulation-resistance tests for one minute on each pole, phase-to-phase and phase-to-ground with the circuit breaker closed, and across each open pole. Apply voltage in accordance with manufacturer s published data. In the absence of manufacturer s published data, use Table

31 Circuit Breakers, Air, Medium-Voltage Electrical Tests Perform a contact/pole-resistance test. With the breaker in a test position, perform the following tests: Trip and close breaker with the control switch. Trip breaker by operating each of its protective relays. Verify mechanism charge, trip-free, and antipump functions. (Optional)Perform minimum pickup voltage tests on trip and close coils 31

32 Circuit Breakers, Air, Medium-Voltage Electrical Tests (Optional) Perform power-factor or dissipation-factor tests with breaker in both the open and closed positions and each bushing equipped with a power-factor/capacitance tap. In the absence of a power-factor/ capacitance tap, perform hotcollar tests. (Optional) Perform a dielectric withstand voltage test on each phase with the circuit breaker closed and the poles not under test grounded. Test voltage should be in accordance with manufacturer s published data or Neta Table

33 Circuit Breakers, Air, Medium-Voltage Electrical Tests Verify blowout coil circuit continuity. Verify operation of cubicle space heaters. Test Values Visual and Mechanical Compare first-trip operation time and trip-coil current waveform to manufacturer s published data. In the absence of manufacturer's published data, compare first-trip operation time and trip coil current waveform to previously obtained results. 33

34 Circuit Breakers, Air, Medium-Voltage Test Values Visual and Mechanical Compare bolted connection resistance values to values of similar connections. Investigate values which deviate from those of similar bolted connections by more than 50 percent of the lowest value. Bolt-torque levels should be in accordance with manufacturer s published data. Results of the thermographic survey. Compare travel and velocity values to manufacturer s published data and previous test data. 34

35 Circuit Breakers, Air, Medium-Voltage Test Values Visual and Mechanical Operations counter should advance one digit per close-open cycle. Test Values Electrical Compare bolted connection resistance values to values of similar connections. Investigate values which deviate from those of similar bolted connections by more than 50 percent of the lowest value. 35

36 Circuit Breakers, Air, Medium-Voltage 36 Test Values Electrical Insulation-resistance values of circuit breakers should be in accordance with manufacturer s published data. In the absence of manufacturer s published data, use Neta Table Values of insulation resistance less than this table or manufacturer s recommendations should be investigated. Microhm or dc millivolt drop values shall not exceed the high levels of the normal range as indicated in the manufacturer s published data. If manufacturer s data is not available, investigate values that deviate from adjacent poles or similar breakers by more than 50 percent of the lowest value.

37 Circuit Breakers, Air, Medium-Voltage Test Values Electrical Breaker mechanism charge, close, open, trip, trip-free, and antipump features shall function as designed. Minimum pickup for trip and close coils shall be in accordance with manufacturer s published data. Power-factor or dissipation-factor values shall be compared with previous test results of similar breakers or manufacturer s published data. 37

38 Circuit Breakers, Air, Medium-Voltage Test Values Electrical Power-factor or dissipation-factor and capacitance values should be within ten percent of nameplate rating for bushings. Hot collar tests are evaluated on a milliampere/ milliwatt loss basis, and the results should be compared to values of similar bushings. If no evidence of distress or insulation failure is observed by the end of the total time of voltage application during the dielectric withstand voltage test, the circuit breaker is considered to have passed the test. 38

39 Circuit Breakers, Air, Medium-Voltage Test Values Electrical The blowout coil circuit should exhibit continuity. Cubicle space heaters should be operational. 39

40 40 Circuit Breakers, Vacuum, Medium-Voltage

41 Circuit Breakers, Vacuum, Medium-Voltage Visual and Mechanical Inspection Inspect physical and mechanical condition. Inspect anchorage, alignment, and grounding. Verify that all maintenance devices are available for servicing and operating the breaker (Optional)Perform operator analysis (first-trip) test. Prior to cleaning the unit, perform as-found tests, if required. Clean the unit. Inspect vacuum bottle assemblies. 41

42 Circuit Breakers, Vacuum, Medium-Voltage Visual and Mechanical Inspection Measure critical distances such as contact gap as recommended by the manufacturer. If recommended by the manufacturer, slow close/open the breaker and check for binding, friction, contact alignment, contact sequence, and penetration. Perform all mechanical operation tests on the operating mechanism in accordance with manufacturer s published data. 42

43 Circuit Breakers, Vacuum, Medium-Voltage Visual and Mechanical Inspection Inspect bolted electrical connections for high resistance using one or more of the following methods: 1. Use of a low-resistance ohmmeter. 2. Verify tightness of accessible bolted electrical connections by calibrated torque-wrench method in accordance with manufacturer s published data. In the absence of manufacturer s published data, use Neta Table Perform a thermographic survey 43

44 Circuit Breakers, Vacuum, Medium-Voltage Visual and Mechanical Inspection Verify cell fit and element alignment. Verify racking mechanism operation. Inspect vacuum bellows operation. Use appropriate lubrication on moving current-carrying parts and on moving and sliding surfaces. Perform time-travel analysis. Perform as-left tests. Record as-found and as-left operation counter readings. 44

45 Circuit Breakers, Vacuum, Medium-Voltage Electrical Test Perform resistance measurements through bolted connections with a low-resistance ohmmeter. Perform insulation-resistance tests for one minute on each pole, phase-to-phase and phase-to-ground with circuit breaker closed and across each pole with the breaker open. Apply voltage in accordance with manufacturer s published data. In the absence of manufacturer s published data, use Table

46 Circuit Breakers, Vacuum, Medium-Voltage Electrical Test (Optional)Perform insulation-resistance tests on all control wiring with respect to ground. Perform a contact/pole-resistance test. With breaker in a test position, perform the following tests: 1. Trip and close breaker with the control switch. 2. Trip breaker by operating each of its protective relays. 3. Verify mechanism charge, trip-free, and antipump functions. 46

47 Circuit Breakers, Vacuum, Medium-Voltage Electrical Test (Optional) Perform minimum pickup voltage tests on trip and close coils. (Optional) Perform power-factor or dissipation-factor tests on each pole with the breaker open and each phase with the breaker closed. (Optional) Perform power-factor or dissipation-factor tests on each bushing equipped with a power-factor/capacitance tap. In the absence of a power-factor/ capacitance tap, perform hot-collar tests. 47

48 Circuit Breakers, Vacuum, Medium-Voltage Electrical Test Perform a vacuum bottle integrity (dielectric withstand voltage) test across each vacuum bottle with the breaker in the open position in strict accordance with manufacturer s published data. (Optional) Perform a dielectric withstand voltage test on each phase with the circuit breaker closed and the poles not under test grounded. Test voltage should be in accordance with manufacturer s published data. In the absence of manufacturer s published data, use Neta Table

49 Circuit Breakers, Vacuum, Medium-Voltage Test Values Visual and Mechanical Compare first-trip operation time and trip-coil current waveform to manufacturer s published data. In the absence of manufacturer's published data, compare first-trip operation time and trip coil current waveform to previously obtained results. Mechanical operation and contact alignment should be in accordance with manufacturer s published data. Compare bolted connection resistance values to values of similar connections. Investigate values which deviate from those of similar bolted connections by more than 50 percent of the lowest value. 49

50 Circuit Breakers, Vacuum, Medium-Voltage Test Values Visual and Mechanical Bolt-torque levels should be in accordance with manufacturer s published data. In the absence of manufacturer s published data, use Neta Table Results of the thermographic survey. Compare travel and velocity values to manufacturer s published data and previous test data. Operation counter should advance one digit per close-open cycle. 50

51 Circuit Breakers, Vacuum, Medium-Voltage Test Values Electrical Compare bolted connection resistance values to values of similar connections. Investigate values which deviate from those of similar bolted connections by more than 50 percent of the lowest value. Insulation-resistance values of circuit breakers should be in accordance with manufacturer s published data. In the absence of manufacturer s published data, use Table

52 Circuit Breakers, Vacuum, Medium-Voltage Test Values Electrical Microhm or dc millivolt drop values shall not exceed the high levels of the normal range as indicated in the manufacturer s published data. If manufacturer s data is not available, investigate values that deviate from adjacent poles or similar breakers by more than 50 percent of the lowest value. Breaker mechanism charge, close, open, trip, trip-free, and antipump features shall function as designed. 52

53 Circuit Breakers, Vacuum, Medium-Voltage Test Values Electrical Minimum pickup for trip and close coils shall be in accordance with manufacturer s published data. In the absence of data use NetaTable Power-factor or dissipation-factor values shall be compared to manufacturer s published data. In the absence of manufacturer s published data the comparison shall be made to similar breakers. 53

54 Circuit Breakers, Vacuum, Medium-Voltage Test Values Electrical Power-factor or dissipation-factor and capacitance values should be within ten percent of nameplate rating for bushings. Hot collar tests are evaluated on a milliampere/ milliwatt loss basis, and the results should be compared to values of similar bushings. If no evidence of distress or insulation failure is observed by the end of the total time of voltage application during the vacuum bottle integrity test, the test specimen is considered to have passed the test. 54

55 Circuit Breakers, Vacuum, Medium-Voltage Test Values Electrical If no evidence of distress or insulation failure is observed by the end of the total time of voltage application during the dielectric withstand voltage test, the test specimen is considered to have passed the test. Heaters should be operational. 55

56 Summary We discussed the definition and history of circuit breakers. We addressed the Neta MTS maintenance standards for the following circuit breaker types: Low voltage air circuit breakers. Medium voltage air circuit breakers. Medium voltage vacuum breakers. In future we will discuss oil circuit breakers of all voltage classes as well as SF6 gas breakers. 56

57 Save the Date for Our Next Webinar Tuesday September 18, 2018 at 1pm 2pm CDT Title: Vacuum Interrupter Technology Presented by: Greg Richmond AVO Training Specialist - Instructor 57

58 n DLRO A micro ohmmeter Smooth DC output Programmable ramp up, time on, ramp down, and output current Battery and line operated Megger Recommended Equipment n CABA Win Interfaces with EGIL, TM1600, TM1700, and TM1800 Detailed CB analysis and comparison to historical tests Simple consistent testing Fully customizable testing with Test Plan Editor (TPE) n EGIL For substations 245kV and below Vacuum CBs, OCBs, and gang operated SF 6 CBs CBs with 1 break per phase and 1 operating mechanism (gang op) 58 n TM kV substations and below Can be used on all circuit breakers 16 main and 16 Resistor contacts per phase Gang operated or IPO OCBs, SF 6, Vacuum, GIS, Airblast Dualground testing

59 Questions? After more than 50 years, AVO Training remains a global leader in safety and maintenance training for the electrical industry. We deliver an engaging, hands-on experience for our clients in a professional, real-world environment. We strive to provide industry relevant courses in a practical and flexible learning environment through an ongoing commitment to quality service, integrity, instruction, and client satisfaction. Our goal is to convey practical job skills and career development for our clients and students by saving lives through a world-class learning experience. 59 AVO Training Institute, Inc. 2018