Workscope: MVCB On-Site Maintenance

• The circuit breaker will be 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/Phase barriers will be removed and interrupters will be inspected for erosion and damage
  

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

• Contacts will be cleaned and inspected for proper wipe and signs of deterioration
  

  -	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 frame and mechanism will be cleaned and inspected
  

  -	The frame and mechanism will be cleaned with rags and solvent.
  -	The mechanism will be inspected for proper operation and binding of moving components.

• The operating mechanism will be lubricated with extended life lubricant
  

  -	Where possible, all bearings and sliding surfaces will be lubricated with the appropriate extended life lubricants.

• Mechanical adjustments will be checked and adjusted as required
  

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

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

  -	Each circuit breaker will be electrically operated in its respective cubicle via system control power to assure proper operation (If applicable).
  -	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.

• 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.

• The switchgear will be cleaned, lubricated, and inspected for worn and missing parts
  

  -	The circuit breaker cubicle will be cleaned with a vacuum solvent and rags as appropriate.
  -	The circuit breaker racking mechanism will be inspected and lubricated.
  -	Shutter assemblies will be inspected for proper operations and lubricated as necessary.

• 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
• Motor starters
• Substation maintenance
• Protective relays
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