ABB REF615 Applications Manual page 209

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