Schweitzer Engineering SEL-387-0, Instruction Manual

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5.12
SEL-387-0, -5, -6 Relay Instruction Manual Date Code 20170601
Metering and Monitoring
Breaker Monitor
calculated by the first equation. For B n KAP2 < I < B n KAP3, O(I) is
calculated by the second equation. For I > B n KAP3, O(I) = 0 and contact wear
= 100 percent.
Since the breaker monitor calculates and accumulates current by phase, the
wear for each pole of the breaker is calculated separately, using the same wear
curve as a basis. Thus, over time, the cumulative percent wear for each of the
three poles will be different. If a breaker already has some estimated wear
when the relay is first applied, the user can preload a separate amount of wear
for each pole of the breaker using the serial port command
BRE W n (or
BRE n W ). Integer values of percent wear up to 100 percent are accepted by
the relay. The incremental wear for the next interruption, and all subsequent
interruptions, is added to the prestored value for a total wear value.
When the cumulative wear on any breaker pole reaches 100 percent, Relay
Word bits are set to one for the particular pole, as well as for the breaker
containing that pole. For example, for Breaker “
n ” the Relay Word bits for the
three poles are designated BCWA n , BCWB n , and BCWC n ; for the breaker
itself, Relay Word bit BCW n is set to one if any of the individual pole bits are
set to one. These bits may be used for alarm or display purposes to alert the
user that breaker inspection and maintenance may be required.
After breaker maintenance is performed or a new breaker installed, the breaker
monitor operation counters, cumulative interrupted currents by pole, and
percent wear by pole should be reset to zero. This can be done via the
BRE R
n (or BRE n R ) serial port command or from the front panel via the {OTHER}
pushbutton menu.
Both the BRE W n and BRE R n commands can be executed from
Access Level B or 2.
Breaker Wear
Example
A breaker having the wear curve of Figure 5.5 experiences a fault current
interruption of 17,000 A. Previous accumulated wear is 44 percent.
The fault current falls between B n KAP2 (8 kA) and B n KAP3 (20 kA). The
second equation is used to calculate O(I).
Equation 5.7
Incremental Percent Wear = 100/18.81 = 5.32%
Cumulative Percent Wear = 44 + 5.32 = 49.32% (which appears as 49%
in BRE listing)
Breaker Monitor
Report Function
(BRE Command)
The accumulators for each breaker can be reviewed either by a serial port
command
BRE or via the front-panel display, using the {OTHER} pushbutton
menu.
The report lists all breakers, giving the number of internal and external trips
for each breaker, the total accumulated rms current by phase, and the Percent
Wear by pole. The operation accumulators for each trip type have a maximum
value of 65,000 trips. The current accumulators for each trip type have a
maximum value of 99,999.00 kA rms. Percent Wear never exceeds
100 percent. The accumulators can be reset by the serial port command
BRE n R or via the {OTHER} front-panel pushbutton menu. The serial port
report format is shown below.
O(I) 46,284 17
2.756
–
• =
46,284 0.00041
• =
18.81
=