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1MRK 506 369-UEN B
Line distance protection REL670 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 393.
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 393:
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 18
Monitoring
P2
100
779
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