ABB Relion 650 Series Applications Manual page 215

1MRK 505 287-UUS B
Calculation of Directional Coefficient
The directional coefficient is calculated according to the formula:
Directional Coef
A070794 V2 EN-US
I
r
I
f
A
B
Calculation for estimating the remaining life
The trip curve shows that there are 30,000 possible operations at the rated operating current of
630 A and 20 operations at the rated fault current 16 kA. Therefore, if the tripping current is 10 kA,
one operation at 10 kA is equivalent to 30,000/58=517 operations at the rated current. It is also
assumed that prior to this tripping, the remaining life of the circuit breaker is 15,000 operations.
Therefore, after one operation of 10 kA, the remaining life of the circuit breaker is
15,000-517=14,483 at the rated operating current.
Spring charging time indication
For normal circuit breaker operation, the circuit breaker spring should be charged within a
specified time. Therefore, detecting long spring charging time indicates the time for circuit
breaker maintenance. The last value of the spring charging time can be given as a service value.
Gas pressure supervision
The gas pressure supervision monitors the gas pressure inside the arc chamber. When the
pressure becomes too low compared to the required value, the circuit breaker operations are
locked. A binary input is available based on the pressure levels in the function, and alarms are
generated based on these inputs.
Busbar protection REB650
Application manual
 
B
log  
 
A
= = −
. 2 2609
 
I
f
 
log
I
 
r
Rated operating current = 630 A
Rated fault current = 16 kA
Op number rated = 30000
Op number fault = 20
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Section 12
Monitoring
(Equation 30)
209