5-10
Metering and Monitoring
Date Code 20020129
SEL-387E Instruction Manual
*22'
)$,/
)$,/
:$51
:$51
9'&
'&3
'&3
'&3
'&3
':*0
Figure 5.3: Undervoltage and Overvoltage Warning and Alarm Regions
From Figure 5.2 and Figure 5.3, you can see that no warning or alarm triggers so long as the
battery dc voltage neither exceeds DC3P nor falls below DC2P. The relay triggers a warning for
voltages exceeding DC3P or falling below DC2P. The relay triggers a failure alarm for voltages
exceeding DC4P or falling below DC1P. For example, if the battery voltage exceeds the DC3P
threshold, but falls below the DC4P threshold, the Relay Word bit DC3 asserts and the relay
triggers a warning.
Detection of Voltage Dips in Event Reports
You can also use the battery monitor voltage threshold settings to detect momentary supply
voltage fluctuations during periods of high demand on the station battery and charger system.
The digital event report lists assertion of Relay Word bits DC1 through DC4. View this listing
with the
EVE D
serial port command. To trigger an event report, include these bits in the
SEL
OGIC
control equation ER (event report trigger setting). Use the
CEV
command to retrieve a
compressed event report containing the value of the station dc battery voltage during the event.
B
REAKER
M
ONITOR
The SEL-387E Relay breaker monitoring function captures information on the number of
operations and total interrupted current for as many as three breakers. These data are used to
estimate the amount of contact wear per pole, based on wear curve information the user derives
from breaker manufacturer maintenance curves and enters into the relay. Separate settings for
each breaker determine under what conditions the monitoring function initiates for that breaker.
The breaker monitoring function is capable of differentiating between an internal trip, generated
by units associated with the winding where the breaker is applied, and an external trip, initiated
by another winding’s units, another relay, or control contact. This information will assist the
user in determining when to schedule maintenance of the breakers.
Breaker Monitor Description and Initiation Setting
The breaker monitor function has one initiation setting for each breaker. The BKMON1 through
BKMON3 settings, in the Global/Relay Settings area, are SEL
OGIC
control equations, using
Relay Word bits to initiate the monitor. The BKMONn settings look for rising edges (transition
from logical 0 to logical 1) as an indication to read in current values. Currents are read 1.5
cycles after initiation, as symmetrical RMS current, and sent to the monitor IA, IB, and IC
