P12x/EN T/Eb6 - Schneider - error

P12x/EN AP/Eb6Page 62/78Application GuideMiCOM P120/P121/P122/P12324.2.2 Setting the Number of Operations ThresholdsEvery operation of a circuit breaker results in some degree of wear for its components. Thus,routine maintenance, such as oiling of mechanisms, may be based upon the number ofoperations. Suitable setting of the maintenance threshold will allow an alarm to be raised,indicating when preventative maintenance is due.Should maintenance not be carried out, the relay can be set to lockout the autoreclosefunction on reaching a operations threshold. This prevents further reclosure when the circuitbreaker has not been maintained to the standard demanded by the switchgearmanufacturer’s maintenance instructions.Certain circuit breakers, such as oil circuit breakers (OCB’s) can only perform a certainnumber of fault interruptions before requiring maintenance attention. This is because eachfault interruption causes carbonising of the oil, degrading its dielectric properties.24.2.3 Setting the Operating Time ThresholdsSlow CB operation is also indicative of the need for mechanism maintenance. Therefore,alarm is provided and is settable in the range of 100 ms to 5 s. This time is set in relation tothe specified interrupting time of the circuit breaker.