5.18
SEL-751 Relay Instruction Manual Date Code 20170927
Metering and Monitoring
Station DC Battery Monitor
Analyze Station DC
Battery Voltage
The station dc battery voltage is displayed in column Vdc in the example
event report in Figure 10.3. Changes in station dc battery voltage for an event
(e.g., circuit breaker tripping) can be observed. Use the EVE command to
retrieve event reports as discussed in Section 10: Analyzing Events.
Station DC Battery Voltage Dips During Circuit Breaker Tripping
Event reports are automatically generated when the TRIP Relay Word bit
asserts (TRIP is the logic output of
Figure 4.79). For example, output
contact OUT103 is set to trip:
OUT103 = TRIP
Anytime output contact OUT103 closes and energizes the circuit breaker trip
coil, any dip in station dc battery voltage can be observed in column Vdc in
the event report.
To generate an event report for external trips, program an optoisolated input
INxyz (monitoring the trip bus) in the SEL
OGIC control equation event report
generation setting:
ER = R_TRIG(INxyz) OR…
Anytime the trip bus is energized, any dip in station dc battery voltage can be
observed in column Vdc in the event report.
Station DC Battery Voltage Dips During Circuit Breaker Closing
To generate an event report when the SEL-751 closes the circuit breaker, make
the SEL
OGIC control equation event report generation setting:
ER = R_TRIG(OUT102) OR…
In this example, output contact OUT102 is set to close:
OUT102 = CLOSE (CLOSE is the logic output of Figure 4.80)
Anytime output contact OUT102 closes and energizes the circuit breaker close
coil, any dip in station dc battery voltage can be observed in column Vdc in
the event report.
This event report generation setting (ER := R_TRIG(OUT102) OR …) might
be made just as a testing setting. Generate several event reports when doing
circuit breaker close testing and observe the “signature” of the station dc
battery voltage in column Vdc in the event reports.
Station DC Battery Voltage Dips Anytime
To generate an event report anytime there is a station dc battery voltage dip,
set the dc voltage element directly in the SEL
OGIC control equation event
report generation setting:
ER = F_TRIG(SVnT) OR …
Timer output SVnT is an example dc voltage element from the bottom of
Figure 5.18. Anytime dc voltage falls below pickup DCHIP, timer output
SV4T drops out (logical 1 to logical 0 transition), creating a falling-edge
condition that generates an event report. Also, you can use the Sequential
Event Recorder (SER) report to time-tag station dc battery voltage dips.
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