ABB Relion REC670 Applications Manual page 393

1MRK 511 358-UEN A
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IEC12000623 V1 EN-US
Figure 190: 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 the CB would become (10000 – 200) = 9800 operations at the rated operating
current after one operation at 50 kA.
Accumulated energy
Monitoring the contact erosion and interrupter wear has a direct influence on the required
maintenance frequency. Therefore, it is necessary to accurately estimate the erosion of the
contacts and condition of interrupters using cumulative summation of I
Application manual
0.2 0.5 1 2 5
Interrupted current (kA)
P1
P2
10 20 50 100
IEC12000623_1_en.vsd
Section 16
Monitoring
y
. The factor "y"
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