Pre-commissioning checks or testing on circuit breaker


Circuit breakers are installed indoor and outdoor. indoor in the panels , and outdoor in the panels or standalone. Circuit breaker can be air circuit breaker(ACB) or SF6 circuit breaker or Vacuum Circuit breaker (VCB) before commissioning of the breaker, various tests are carried out in order to check healthiness of the breaker or to integrate in the system . The tests are given below.

  1. Mechanical operation timing check or simply breaker timing test : First and most important thing for a breaker , is the operation . breaker operation is like a switch i.e. On & Off. so in this test, breaker on and off time is measured. generally trip(opening) time is less than closing time. usually time measured is in Milli-seconds(ms). if breaker is single pole means one breaker for each phase, than timing check of each breaker is done.

2. Contact Resistance measurement : contact resistance measurement means ..what you are going to measure , a resistance which the breaker offers when it is in closed position i.e. both the contacts of breaker , fixed and moving contacts are connected to each other. Generally its value is in micro -ohms and the measured value should be less than 50 micro ohms at 20 degree Celsius. first the value of contact resistance is measured at the ambient temperature than the value is calculated on 20 degree Celsius.

3. Trip and closing coil resistance measurement : In this test,resistance of both the closing coil and trip(opening) coil is measured.

4. Tests on the spring charging motor : there is a motor in the breaker to charge the closing spring of the breaker. before commissioning, it is necessary to check the motor also. checks on the motor can be current drawn by the motor and time taken by the motor to fully charge the spring.


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