ABB REF615 - Page 209

A071114 V2 EN
Figure 103: 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:
DirectionalCoef
B
A
I
I
f
r
=












= −
log
log
.2 2609
A070794 V1 EN (Equation 12)
I
r
Rated operating current = 630 A
I
f
Rated fault current = 16 kA
A Op number rated = 30000
B Op number fault = 20
Calculation for estimating the remaining life
1MRS756378 D Section 8
Condition monitoring functions
REF615 203
Application Manual