ABB RELION REX640 Technical Manual page 1272

Section 7
Condition monitoring functions
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GUID-9DE07F40-F38D-498A-8E88-A76EF3886614 V1 EN
Figure 694: 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:
1MRS759142 C
REX640
Technical Manual