5.28
SEL-751 Relay Instruction Manual Date Code 20170927
Metering and Monitoring
Breaker Monitor
Breaker
Monitor Output
When the breaker maintenance curve for a particular phase (A, B, or C)
reaches the 100 percent wear level (see Figure 5.25), a corresponding Relay
Word bit (BCWA, BCWB, or BCWC) asserts.
EXAMPLE 5.1 Example Applications
These logic outputs can be used to alarm:
OUT
xxx
= BCW
or drive the relay to lockout the next time the relay trips:
79DTL = TRIP AND BCW
View or Reset
Breaker Monitor
Information
Accumulated breaker wear/operations data are retained if the relay loses
power or the breaker monitor is disabled (setting EBMON := N). The
accumulated data can only be reset if the BRE R command is executed (see
the following discussion on the BRE R command).
Via Serial Port
See Section 7: Communications. The BRE command displays the following
information:
➤ Accumulated number of relay initiated trips
➤ Accumulated interrupted current from relay initiated trips
➤ Accumulated number of externally initiated trips
➤ Accumulated interrupted current from externally initiated trips
➤ Percent circuit breaker contact wear for each phase
➤ Date when the preceding items were last reset (via the BRE R
command)
See Section 7: Communications. The BRE W command allows the trip
counters, accumulated values, and percent breaker wear to be preloaded for
each individual phase.
The BRE R command resets the accumulated values and the percent wear for
all three phases. For example, if breaker contact wear has reached the 100
percent wear level for A-phase, the corresponding Relay Word bit BCWA
asserts (BCWA = logical 1). Execution of the BRE R command resets the
wear levels for all three phases back to 0 percent and consequently causes
Relay Word bit BCWA to deassert (BCWA = logical 0).
Via Front Panel
The information and reset functions available via the previously discussed
serial port commands BRE and BRE R are also available via the front panel.
See Section 8: Front-Panel Operations for details.
Relay Word Bits Definition
BCWA A-Phase breaker contact wear has reached the 100 percent wear level
BCWB B-Phase breaker contact wear has reached the 100 percent wear level
BCWC C-Phase breaker contact wear has reached the 100 percent wear level
BCW BCWA or BCWB or BCWC
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