Sel 751A - Figure 5.22 Breaker Monitor Accumulates 50 Percent Wear

5.22
SEL-751A Relay Instruction Manual Date Code 20100129
Metering and Monitoring
Breaker Monitor
25 Percent to 50 Percent Breaker Wear
Refer to Figure 5.22. The current value changes from 2.5 kA to 12.0 kA. 12.0
kA is interrupted 11 times (11 close/open operations = 24 – 13), pushing the
breaker maintenance curve from the 25 percent wear level to the 50 percent
wear level.
Compare the 100 percent and 50 percent curves and note that for a given
current value, the 50 percent curve has only 1/2 of the close/open operations
of the 100 percent curve.
Figure 5.22 Breaker Monitor Accumulates 50 Percent Wear
10,000
100%
1000
2
3
4
5
6
7
8
9
100
2
3
4
5
6
7
8
9
10
2
3
4
5
6
7
8
9
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50
40
30
20
10
.5
Number of Close/Open Operations
kA Interrupted per Operation
25%
50%