8-2
Breaker Monitor and Metering Functions
Date Code 20010625
SEL-311L Instruction Manual
Table 8.1: Breaker Maintenance Information
for an Example Circuit Breaker
Current
Interruption
Level (kA)
Permissible Number
of Close/Open
Operations*
0.00–1.20 10,000
2.00 3,700
3.00 1,500
5.00 400
8.00 150
10.00
85
20.00
12
* The action of a circuit breaker closing and then later opening is counted as one
close/open operation.
The breaker maintenance information in Table 8.1 is plotted in Figure 8.1.
Connect the plotted points in Figure 8.1 for a breaker maintenance curve. To estimate this
breaker maintenance curve in the SEL-311L Relay breaker monitor, three set points are entered:
Set Point 1
maximum number of close/open operations with corresponding current
interruption level.
Set Point 2
number of close/open operations that correspond to some midpoint
current interruption level.
Set Point 3
number of close/open operations that correspond to the maximum
current interruption level.
These three points are entered with the settings in Table 8.2.
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