ABB REQ650 Applications Manual page 286

Section 12
Monitoring
280
Remaining life of the breaker
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.
Example for estimating the remaining life of a circuit breaker
A071114 V3 EN
Figure 107: Trip Curves for a typical 12 kV, 630 A, 16 kA vacuum interrupter
Nr the number of closing-opening operations allowed for the circuit breaker
Ia the current at the time of tripping of the circuit breaker
Calculation of Directional Coefficient
1MRK 505 291-UEN A
Application manual