Workscope: Oil Circuit Breaker Basic Preventive Maintenance

• Before work can begin, a PCB oil sample must be taken to ensure the unit is not PCB contaminated
  

  -	The customer is responsible for supplying GE with an oil sample report verifying the level of PCB contamination within the OCB.
  -	If so desired, GE can take the sample and send it to the oil test lab for analysis.
  -	A comprehensive analysis can also be completed on the condition of the circuit breaker oil.

• The circuit breaker will be inspected for worn, damaged and missing components
  

  -	A visual inspection of the entire circuit breaker will be completed.
  -	The breaker anchorage, alignment and grounding will be inspected.
  -	All gasketed covers and seals will be checked for weather tight condition.
  -	Any item found damaged will be recorded and a suitable replacement identified.

• The frame and mechanism will be cleaned and inspected
  

  -	The frame will be inspected for signs of rust and deterioration.
  -	The mechanism will be inspected for proper operation and binding.
  -	Any item found damaged will be recorded and a suitable replacement identified.

• Mechanical adjustments will be checked
  

  -	Measure and record primary and secondary wipe and gap, adjustments will be made as required.
  -	Perform mechanical operation and contact alignment tests on breaker and mechanism.

• Interlocks, mechanical and electrical, will be checked for proper operation
• Breaker electrical accessory devices will be tested for proper operation (if applicable).Adjustments will be made as necessary
  

  -	Under voltage device
  -	Shunt trip
  -	Close coil
  -	Auxiliary switch
  -	Other devices

• Each circuit breaker will be electrically operated using system control power to assure proper operation (if applicable)
  

  -	The circuit breaker will be isolated from the distribution system (if applicable), and the protective relays will be used to simulate a fault trip signal.
  -	The circuit breaker will be inspected for proper operation.

• Final electrical tests will be performed, as applicable
  

  -	Contact resistance tests - A digital low resistance ohmmeter will be used to record the contact resistance and compare it to the manufacturer's specifications. High resistance in the contact structure can cause excessive heat in the breaker and prematurely dry out the lubrication.
  -	Insulation resistance tests - A 1,000-volt megger will be used to determine the condition of the circuit breaker's insulation to the ground and across phases.
  -	Functional operational tests (electrical and manual) - The breaker will be operated manually and electrically to verify proper operation.
  -	Power factor test (optional) - If requested, the circuit breaker primary bushings will be power factor tested and the results compared to industry standards of acceptability.
  -	Time motion analysis (optional) - If requested, the circuit breaker opening and closing time and speed will be verified and compared with the manufacturer's specifications.
  -	High potential tests (optional) - If requested, the circuit breaker will be high potential tested according to manufacturer's specifications.

• The switchgear will be inspected for worn and missing parts.
  

  -	The circuit breaker auxiliary cabinets will be inspected for worn or missing components.
  -	Any item found damaged will be recorded and a suitable replacement identified.

• Test data will be included as part of the final customer report.
  

  -	All test data received will be included with the circuit breaker test report. The test report will be shipped with the equipment.

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Related Information

• Low/med voltage circuit breakers
• High voltage circuit breakers
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• Substation maintenance
• Protective relays
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