ABB Relion 670 Series Applications Manual page 463

1MRK 511 401-UUS F
Circuit breaker manufacturers provide the number of make-break operations possible at various
interrupted currents. An example is shown in figure 215.
100000
50000
20000
10000
5000
2000
1000
500
200
100
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20
10
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IEC12000623 V1 EN-US
Figure 215: 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.
• Breaker interrupts at and below the rated operating current, that is, 2 kA, the remaining life of
the CB is decreased by 1 operation and therefore, 9999 operations remaining at the rated
operating current.
• Breaker interrupts between rated operating current and rated fault current, that is, 10 kA, one
operation at 10kA is equivalent to 10000/900 = 11 operations at the rated current. The
remaining life of the CB would be (10000 – 10) = 9989 at the rated operating current after one
operation at 10 kA.
• Breaker interrupts at and above rated fault current, that is, 50 kA, one operation at 50 kA is
equivalent to 10000/50 = 200 operations at the rated operating current. The remaining life of
Bay control REC670
Application manual
0.2 0.5 1 2 5
Interrupted current (kA)
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P1
P2
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IEC12000623_1_en.vsd
Section 17
Monitoring
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