Sel 751A - Figure 5.20 Breaker Monitor Accumulates 10 Percent Wear

5.20
SEL-751A Relay Instruction Manual Date Code 20100129
Metering and Monitoring
Breaker Monitor
Note in the following four figures (Figure 5.20–Figure 5.23) that the
interrupted current in a given figure is the same magnitude for all the
interruptions (e.g., in Figure 5.21, 2.5 kA is interrupted 290 times). This is not
realistic, but helps in demonstrating the operation of the breaker maintenance
curve and how it integrates for varying current levels.
0 Percent to 10 Percent Breaker Wear
Refer to Figure 5.20. 7.0 kA is interrupted 20 times (20 close/open operations
= 20 – 0), pushing the breaker maintenance curve from the 0 percent wear
level to the 10 percent wear level.
Compare the 100 percent and 10 percent curves and note that for a given
current value, the 10 percent curve has only 1/10 of the close/open operations
of the 100 percent curve.
Figure 5.20 Breaker Monitor Accumulates 10 Percent Wear
10,000
100%
10%
1000
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100
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10
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50
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10
.5
Number of Close/Open Operations
kA Interrupted per Operation