
Date Code 20001006
Breaker Monitor, Metering, and Load Profile Functions
8-7
SEL-351 Instruction Manual
Breaker Monitor Operation Example
As stated earlier, each phase (A, B, and C) has its own breaker maintenance curve. For this
example, presume that the interrupted current values occur on a single phase in Figure 8.4 through
Figure 8.7. Also, presume that the circuit breaker interrupting contacts have no wear at first
(brand new or recent maintenance performed).
Note in the following four figures (Figure 8.4through Figure 8.7) that the interrupted current in a
given figure is the same magnitude for all the interruptions (e.g., in Figure 8.5, 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% to 10% Breaker Wear
Refer to Figure 8.4. 7.0 kA is interrupted 20 times (20 close/open operations = 20 - 0), pushing
the breaker maintenance curve from the 0% wear level to the 10% wear level.
Compare the 100% and 10% curves and note that for a given current value, the 10% curve has
only 1/10 of the close/open operations of the 100% curve.
10% to 25% 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% wear level to the 25% wear level.
Compare the 100% and 25% curves and note that for a given current value, the 25% curve has
only 1/4 of the close/open operations of the 100% curve.
25% to 50% 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%
wear level to the 50% wear level.
Compare the 100% and 50% curves and note that for a given current value, the 50% curve has
only 1/2 of the close/open operations of the 100% curve.
50% to 100% 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% wear level to the 100% wear level.
When the breaker maintenance curve reaches 100% for a particular phase, the percentage wear
remains at 100% (even if additional current is interrupted), until reset by the BRE R command (see
View or Reset Breaker Monitor Information
that follows later). But the current and trip counts
continue to be accumulated, until reset by the BRE R command.
Additionally, logic outputs assert for alarm or other control applications – see the following
discussion.
Содержание SEL-351
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