• Breaker interrupts at and below the rated operating current, that is, 2 kA, theremaining life of the CB is decreased by 1 operation and therefore, 9999operations remaining at the rated operating current.• Breaker interrupts between rated operating current and rated fault current, thatis, 10 kA, one operation at 10kA is equivalent to 10000/900 = 11 operations atthe rated current. The remaining life of the CB would be (10000 – 10) = 9989at the rated operating current after one operation at 10 kA.• Breaker interrupts at and above rated fault current, that is, 50 kA, oneoperation at 50 kA is equivalent to 10000/50 = 200 operations at the ratedoperating current. The remaining life of the CB would become (10000 – 200)= 9800 operations at the rated operating current after one operation at 50 kA.Accumulated energyMonitoring the contact erosion and interrupter wear has a direct influence on therequired maintenance frequency. Therefore, it is necessary to accurately estimatethe erosion of the contacts and condition of interrupters using cumulativesummation of Iy. The factor "y" depends on the type of circuit breaker. The energyvalues were accumulated using the current value and exponent factor for CBcontact opening duration. When the next CB opening operation is started, theenergy is accumulated from the previous value. The accumulated energy value canbe reset to initial accumulation energy value by using the Reset accumulatingenergy input, RSTIPOW.Circuit breaker operation cyclesRoutine breaker maintenance like lubricating breaker mechanism is based on thenumber of operations. A suitable threshold setting helps in preventive maintenance.This can also be used to indicate the requirement for oil sampling for dielectrictesting in case of an oil circuit breaker.Circuit breaker operation monitoringBy monitoring the activity of the number of operations, it is possible to calculatethe number of days the breaker has been inactive. Long periods of inactivitydegrade the reliability for the protection system.Circuit breaker spring charge monitoringFor normal circuit breaker operation, the circuit breaker spring should be chargedwithin a specified time. Detecting a long spring charging time indicates the time forcircuit breaker maintenance. The last value of the spring charging time can begiven as a service value.Circuit breaker gas pressure indicationFor proper arc extinction by the compressed gas in the circuit breaker, the pressureof the gas must be adequate. Binary input available from the pressure sensor isbased on the pressure levels inside the arc chamber. When the pressure becomestoo low compared to the required value, the circuit breaker operation is blocked.Section 13 1MRK 504 169-UEN AMonitoring282 Transformer protection RET650 2.2 IECApplication manual
