ABB REC670 Applications Manual page 495

1MRK 511 401-UEN A
Bay control REC670 2.2 IEC
Application manual
Remaining life of circuit breaker
Every time the breaker operates, the circuit breaker life reduces due to wear. The
wear in a breaker depends on the interrupted current. For breaker maintenance or
replacement at the right time, the remaining life of the breaker must be estimated.
The remaining life of a breaker can be estimated using the maintenance curve
provided by the circuit breaker manufacturer.
Circuit breaker manufacturers provide the number of make-break operations
possible at various interrupted currents. An example is shown in figure 210.
100000
50000
20000
10000
5000
2000
1000
500
200
100
50
20
10
0.1 0.2 0.5 1
Interrupted current (kA)
IEC12000623 V1 EN-US
Figure 210: An example for estimating the remaining life of a circuit breaker
Calculation for estimating the remaining life
The graph shows that there are 10000 possible operations at the rated operating
current and 900 operations at 10 kA and 50 operations at rated fault current.
Therefore, if the interrupted current is 10 kA, one operation is equivalent to
10000/900 = 11 operations at the rated current. It is assumed that prior to tripping,
the remaining life of a breaker is 10000 operations. Remaining life calculation for
three different interrupted current conditions is explained below.
P1
2 5 10 20 50
IEC12000623_1_en.vsd
Section 17
Monitoring
P2
100
489