Schweitzer Engineering Laboratories SEL-351A - Page 285

8.7
Date Code 20080213 Instruction Manual SEL-351A Relay
Breaker Monitor and Metering
Breaker Monitor
0 Percent to 10 Percent Breaker Wear
Refer to Figure 8.4. Seven 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.
10 Percent to 25 Percent Breaker Wear
Refer to Figure 8.5. The current value changes from 7.0 kA to 2.5 kA. 2.5 kA
is interrupted 290 times (290 close/open operations = 480 – 190), pushing the
breaker maintenance curve from the 10 percent wear level to the 25 percent
wear level.
Compare the 100 percent and 25 percent curves and note that for a given
current value, the 25 percent curve has only 1/4 of the close/open operations
of the 100 percent curve.
25 Percent to 50 Percent Breaker Wear
Refer to Figure 8.6. 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.
50 Percent to 100 Percent Breaker Wear
Refer to Figure 8.7. The current value changes from 12.0 kA to 1.5 kA. 1.5 kA
is interrupted 3000 times (3000 close/open operations = 6000 – 3000),
pushing the breaker maintenance curve from the 50 percent wear level to the
100 percent wear level.
When the breaker maintenance curve reaches 100 percent for a particular
phase, the percentage wear remains at 100 percent (even if additional current
is interrupted), until reset by the BRE R command (see View or Reset Breaker
Monitor Information on page 8.12). However, the current and trip counts
continue to be accumulated, until reset by the BRE R command.
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