Every time the breaker operates, the life of the circuit breaker reduces due to wearing. The wearing in the breaker depends on the tripping current, and the remaining life of the breaker is estimated from the circuit breaker trip curve provided by the manufacturer. The remaining life is decremented at least with one when the circuit breaker is opened.
The operation of the remaining life of the circuit breaker subfunction can be described with a module diagram. All the modules in the diagram are explained in the next sections.
CB life estimator
CB life estimator module calculates the remaining life of the circuit breaker. The Op number rated and Op number fault parameters set the number of operations the breaker can perform at the rated current and at the rated fault current. If the tripping current is lower than the rated operating current set with the Rated Op current setting, the remaining operation of the breaker reduces by one operation. If the tripping current is higher than the rated fault current set with the Rated fault current setting, the remaining operation of the breaker reduces by Op number rated divided by Op number fault. The remaining life reduction of the tripping current in between these two values is calculated based on the trip curve given by the manufacturer.
The remaining life is calculated separately for all three phases and it is available as a monitored data value CB_LIFE_A (_B,_C). The values can be cleared by setting the parameter SSCBR1 rem.life in the Clear menu from LHMI.
Alarm limit check
When the remaining life of any phase drops below the Life alarm level threshold setting, the corresponding circuit breaker life alarm CB_LIFE_ALM is activated.
It is possible to deactivate the CB_LIFE_ALM alarm signal by activating the binary input BLOCK. The old circuit breaker operation counter value can be taken into use by writing the value to the Initial CB Rmn life parameter and resetting the value via the Clear menu from LHMI.