Pre-Commissioning check for indoor vacuum circuit breaker

Breaker Contact Resistance Test

Testing and commissioning of indoor Vacuum circuit breaker

Physical Inspection and Mechanical checks:-

  1. Check the circuit breaker, vacuum bottle and insulators for cracks or other signs of physical damage.
  2. Check the tightness of connections, including flexible connection between vacuum bottle and busbar.
  3. Switch off control power to the breaker of disconnect the control plug. Discharge the closing and tripping springs- this done by first tripping the breaker (if it is closed), then closing the breaker, then tripping it again. Open the cover of the mechanism box. Check for damage, check tightness of push-on lugs at closing and tripping solenoids-if not tight, use a nose plier ti tighten the same,close the cover.
  4. Manually charge the closing spring,using the spring charging handle. Manually close the circuit breaker then manually trip it. Charge the spring again to confirm that it is OK after closing and tripping was done.
  5. DO a vacuum check on the vacuum bottle. This is done by de-coupling the moving contact of the bottle from the insulated coupling rod and physically checking the pressure with which the moving contact pushes against the fixed contact. This is just a qualitative test,done at site to ensure that the vacuum is OK.
  6. Check for erosion of the contacts of the vacuum bottle.

Breaker IR Values :-  

Breaker Insulation Resistance (IR) test open condition Breaker Insulation Resistance (IR) test close condition

With the Circuit breaker in closed condition, check IR values of each phase to earth and between phases. With the breaker in ope condition , check IR values across each vacuum bottle.

Special Tests:-

  1. Contact resistance :   Breaker Contact Resistance Test With the circuit breaker in closed position, use a micro-ohmme ductor tester to measure the contract resistance cross each pole of the breaker.

  2. Breaker Timing Test : Breaker Timing Test

    Note:-DC supply to breaker closing coil for closing timing
    Dc supply to breaker tripping coil for tripping timing

    Measure the closing time and the tripping time of the circuit breaker.To the time interval between the operation of the close / trip command contact and the instant when the main contacts of the breaker close / open. This can be measured connecting a close / trip command spare contact to the “start” input of an electronic timer and the breaker main contacts “Stop” input of the timer.