8-18 Breaker Monitor, Metering, and Load Profile Functions Date Code 20020426
SEL-351-5, -6, -7 Instruction Manual
Timer output SV4T is from the bottom of Figure 8.10. When dc voltage falls below pickup
DCHIP, timer output SV4T drops out (= logical 0), driving the relay to lockout:
79DTL = !SV4T + ... = NOT(SV4T) + ... = NOT(logical 0) + ... = logical 1
Circuit breaker tripping and closing requires station dc battery energy. If the station dc batteries
are having a problem and the station dc battery voltage is declining, the relay should not reclose
after a trip—there might not be enough dc battery energy to trip a second time after a reclose.
View Station DC Battery Voltage
Via Serial Port
See MET Command (Metering Data)—Instantaneous Metering in Section 10: Serial Port
Communications and Commands. The MET command displays the station dc battery voltage
(labeled VDC).
Via Front Panel
The information available via the previously discussed MET serial port command is also
available via the front-panel OTHER pushbutton. See Figure 11.3 in Section 11: Front-Panel
Interface.
Analyze Station DC Battery Voltage
See Standard 15/30-Cycle Event Reports in Section 12: Standard Event Reports, Sag/Swell,
Interruption Report, and SER. The station dc battery voltage is displayed in column Vdc in the
example event report in Figure 12.2. 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 12.
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 5.1). For example, output contact OUT101 is set to trip:
OUT101 = TRIP
Anytime output contact OUT101 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, make connections similar to Figure 8.8 and
program optoisolated input IN106 (monitoring the trip bus) in the SEL
OGIC control equation
event report generation setting:
e.g., ER = /IN106 + ...
Anytime the trip bus is energized, any dip in station dc battery voltage can be observed in column
Vdc in the event report.
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