Breaker Boards

Visual and Mechanical Inspection

1. Inspect physical, electrical, and mechanical condition including evidence of moisture or corona.

2. Inspect anchorage, alignment, grounding, and required area clearances.

3. Prior to cleaning the unit, perform as-found tests, if required.

4. Clean the unit.

5. Verify that fuse and/or circuit breaker sizes and types correspond to drawings and coordination study as well as to the circuit breaker's address for microprocessor-communication packages.

6. Verify that current and voltage transformer ratios correspond to drawings.

7. Inspect bolted electrical connections for high resistance using one of the following methods:

1. Use of low-resistance ohmmeter .

2. Verify tightness of accessible bolted electrical connections by calibrated torque-wrench method in accordance with manufacturer's published data.

3. Perform thermographic survey .

8. Confirm correct operation and sequencing of electrical and mechanical interlock systems.

1. Attempt closure on locked-open devices. Attempt to open locked-closed devices.

2. Make key exchange with devices operated in off‑normal positions.

9. Lubrication requirements

1. Use appropriate lubrication on moving current-carrying parts.

2. Use appropriate lubrication on moving and sliding surfaces.

10. Perform as-left tests.

11. Inspect insulators for evidence of physical damage or contaminated surfaces.

12. Verify correct barrier and shutter installation and operation.

13. Exercise all active components.

14. Inspect mechanical indicating devices for correct operation.

15. Verify that filters are in place and/or vents are clear.

16. Perform visual and mechanical inspection of instrument transformers.

17. Inspect control power transformers.

1. Inspect for physical damage, cracked insulation, broken leads, tightness of connections, defective wiring, and overall general condition.

2. Verify that primary and secondary fuse ratings or circuit breakers match drawings.

3. Verify correct functioning of drawout disconnecting and grounding contacts and interlocks.

2. Electrical Tests

1. Perform electrical tests on instrument transformers in accordance.

2. Perform ground‑resistance tests.

3. Perform resistance measurements through bolted electrical connections with a low-resistance ohmmeter.

4. Perform insulation‑resistance tests on each bus section, phase‑to‑phase and phase‑to‑ground, for one minute.

MV Only *5. Perform an overpotential test on each bus section, each phase to ground with phases not under test grounded, in accordance with manufacturer's published data. The test voltage shall be applied for one minute.

*6. Perform insulation-resistance tests on control wiring with respect to ground. 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. For units with solid-state components or control devices that can not tolerate the applied voltage, follow manufacturer's recommendation.

7. Perform system function tests.

8. Control Power Transformers

1. Perform insulation‑resistance tests. Perform measurements from winding‑to‑winding and each winding‑to‑ground.

2. Verify correct function of control transfer relays located in switchgear with multiple power sources.

9. Voltage Transformers

1. Perform insulation‑resistance tests. Perform measurements from winding‑to‑winding and each winding‑to‑ground.

2. Verify secondary voltages.

10. Verify operation of switchgear/switchboard heaters.

3. Test Values

1. Compare bus connection resistances to values of similar connections.

2. Bolt‑torque levels should be in accordance with specs by manufacturer.

3. Microhm or 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 any values which deviate from similar bus by more than 50 percent of the lowest value.

4. Insulation‑resistance values for bus ,and control power transformers shall be in accordance with manufacturer's published data. Values of insulation resistance less than this table or manufacturer's minimum should be investigated. Overpotential tests should not proceed until insulation‑resistance levels are raised above minimum values.

5. Bus insulation shall withstand the overpotential test voltage applied.

6. Control wiring minimum insulation-resistance values should be comparable to previously obtained results but not less than two megohms.