5.19
Date Code 20170927 Instruction Manual SEL-751 Relay
Metering and Monitoring
Breaker Monitor
Breaker Monitor
The breaker monitor in the SEL-751 helps in scheduling circuit breaker
maintenance. The breaker monitor is enabled with the enable setting:
EBMON := Y
The breaker monitor settings in Tabl e 5.11 are available via the SET G
commands (see Table 6.3). Also refer to BRE Command (Breaker Monitor
Data) on page 7.24 and BRE Command (Preload/Reset Breaker Wear) on
page 7.24.
The breaker monitor is set with breaker maintenance information provided by
circuit breaker manufacturers. This breaker maintenance information lists the
number of close/open operations that are permitted for a given current
interruption level. The following is an example of breaker maintenance
information for a 25 kV circuit breaker. The breaker maintenance information
in Table 5 . 10 is plotted in Figure 5.19.
Connect the plotted points in Figure 5.19 for a breaker maintenance curve. To
estimate this breaker maintenance curve in the SEL-751 breaker monitor,
three set points are entered:
Table 5.10 Breaker Maintenance Information for a 25 kV Circuit Breaker
Current Interruption Level (kA) Permissible Number of Close/Open Operations
a
a
The action of a circuit breaker closing and then later opening is counted as one close/open
operation.
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
Set Point 1
COSP1
maximum number of close/open operations with
corresponding current interruption level.
Set Point 2
COSP2
number of close/open operations that correspond to
some midpoint current interruption level.
Set Point 3
COSP3
number of close/open operations that correspond to
the maximum current interruption level.
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