ABB RER615 - Page 562

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
Figure 290: 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 Coef
The directional coefficient is calculated according to the formula:
Directional Coef
B
A
I
I
f
r
=












= −
log
log
.2 2609
(Equation 66)
I
r
Rated operating current = 630 A
I
f
Rated fault current = 16 kA
A Op number rated = 30000
B Op number fault = 20
Condition monitoring functions 1MRS758755 C
562 REC615 & RER615
Technical Manual