8.2
SEL-311C Relay Instruction Manual Date Code 20060320
Breaker Monitor and Metering Functions
Breaker Monitor
Breaker Monitor
The breaker monitor in the SEL-311C helps in scheduling circuit breaker
maintenance. The breaker monitor is enabled with the enable setting:
EBMON = Y
The breaker monitor settings in Table 8.2 are available via the SET G and
SET L commands (see Tab le 9.1 and also Breaker Monitor Settings (See
Breaker Monitor on page 8.2) on page SET.23). Also refer to BRE Command
(Breaker Monitor Data) on page 10.15 and BRE n Command (Preload/Reset
Breaker Wear) on page 10.34.
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. Table 8.1 provides an example of breaker maintenance
information for an example circuit breaker.
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-311C 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.
Table 8.1 Breaker Maintenance Information for an Example 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
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