Workscope: MVCB Basic Preventive Maintenance

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

  -	A visual inspection of the entire circuit breaker will be done specially for items such as damaged wiring, bent secondary contacts, rusted frame, etc.
  -	Any item found damaged will be recorded and a suitable replacement identified.

• Box barriers and arc chutes will be removed (as required), cleaned, and inspected for erosion and damage
  

  -	Arc chutes will be inspected for excessive carbon in the throat area of the arc chute, cracks and other defects.
  -	Box barriers will be inspected for damaged insulators and components.
  -	Any item found damaged will be recorded and a suitable replacement identified.

• The circuit breaker will be functionally and operationally tested to determine any additional work required
  

  -	The breaker will be operated and inspected for binding in the moving components.
  -	Individual electrical components will be tested as required.
  -	The circuit breaker will be inspected for applicable manufacturer updates.
  -	Any additional work required will be quoted separately.

• Primary bushings will be inspected for signs of corona tracking and damage
  

  -	The bushings will be inspected for damaged insulation and tracking.
  -	The bushings and breaker frame will be inspected for signs of stationary primary disconnects leaking compound.
  -	Any item found damaged will be recorded and a suitable replacement identified

• The circuit breaker's contact assemblies and mechanism will be cleaned and inspected
  

  -	The contacts will be inspected for excessive wear, burning or pitting.
  -	Pivot points will be inspected for dried and/or missing lubrication.
  -	The contact assemblies will be cleaned in place.
  -	All silver-plated components will be inspected for wear.
  -	The mechanism will be inspected for proper operation.

• The circuit breaker will be lubricated with extended life lubricant
  

  -	Where possible, all bearings and sliding surfaces will be lubricated with the appropriate extended life lubricants.
  -	Main contact surfaces will be lubricated with a light coat of grease.

• Mechanical adjustments will be checked and adjusted in accordance with the manufacturer's specifications
  

  -	Wipe and gap measurements will be taken and adjusted as required.
  -	Mechanism adjustments, such as trip latch and release latch wipes, will be completed as per manufacturer's specification.

• Interlocks, mechanical and electrical, will be checked and adjusted for proper operation, if necessary
• Arc chutes and box barriers will be installed
• Final electrical tests will be performed
  

  -	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.

• 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.

• GE recommended equipment upgrades, if applicable, will be quoted separately.
• Option (on-site only): The circuit breaker will be functionally tripped, utilizing test couplers, via its associated protective relays
  

  -	The circuit breaker will be placed in the test position, and the protective relays will be used to simulate a fault trip signal.
  -	The circuit breaker will be inspected for proper operation.

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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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