Schweitzer Engineering SEL-351P, Quick Start Manual

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Date Code 990430 Breaker/Recloser Monitor, Battery System Monitor, 8-9
Metering, and Load Profile Functions
SEL-351P Manual Técnico
See Figure SECTION 8: .8 and accompanying text for more information on setting BKMON.
The operation of the breaker monitor maintenance curve, when new current values are read in, is
explained in the following example.
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 SECTION
8: .4 through Figure SECTION 8: .7. Also, presume that the circuit breaker interrupting
contacts have no wear at first (brand new or recent maintenance performed).
Note in each of the following four figures (Figure SECTION 8: .4 through Figure SECTION 8:
.7) that the interrupted current is the same magnitude for all the interruptions (e.g., in
Figure SECTION 8: .5, 2.5 kA is interrupted 290 times). This is not realistic but helps to
demonstrate the operation of the breaker maintenance curve and how it integrates for various
current levels.
0% to 10% Breaker Wear
Refer to Figure SECTION 8: .4. 7.0 kA is interrupted 20 times (20 close/open operations = 20 -
0), integrating the contact wear curve from 0% 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 SECTION 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 SECTION 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.