8.15
Date Code 20171006 Instruction Manual SEL-400 Series Relays
Monitoring
Circuit Breaker Monitor
Note that the relay provides a time out of approximately 200 ms after the trip or
300 ms after the close threshold to end detection of pole scatter alarms.
Pole Discrepancy
The relay continuously monitors the status of each circuit breaker pole to detect
open or close deviations among the three poles. In addition, at tripping and clos-
ing, the relay measures the differences in operating times during the auxiliary cir-
cuit breaker (52A) contact status changes or open-phase logic operation. The
relay triggers an alarm Relay Word bit, B1PDAL, if the status of any pole com-
pared to another pole exceeds the time window setting B1PDD for the circuit
breaker.
NOTE: Pole discrepancy applies only
to single-pole mechanism circuit
breakers (BK1TYP := 1). These circuit
breakers have an auxiliary circuit
breaker (52A) contact output for each
phase.
You can set the relay to use the current flowing through the circuit breaker to
supervise pole discrepancy timing of the auxiliary circuit breaker (52A) contacts.
Enable this supervision by setting E1PDCS to Y for Circuit Breaker 1.
Pole discrepancy setting B1PDD should be longer than the single-pole reclosing
dead time.
B1PDD := (SPOID + circuit breaker pole operating time + contact latency) • 1.2
Equation 8.4
where:
SPOID is the single-pole open interval time and the factor 1.2 is a safety factor.
Round this time to the next higher hundreds of milliseconds value to give the pole
discrepancy setting.
Figure 8.8 shows a Circuit Breaker 1 operation where Pole B closes first, fol-
lowed by Pole C; Pole A closes slowly. If the time from a change in 52AB1 to the
change in 52AA1 exceeds the pole discrepancy time threshold setting B1PDD,
then the relay asserts the B1PDAL alarm. Once activated, the relay asserts the
pole discrepancy alarm for five seconds.
If any of the pole-open times (TAB, TBC, and TCA in Figure 8.7) exceed
4 ms, or if any of the pole close times exceed 6 ms, the relay asserts the
Relay Word bit B1PSAL. Assertion of B1PSAL indicates any one of the fol-
lowing four conditions:
➤ The pole scatter time for trip operation exceeds the alarm setting
time (4 ms)
➤ The pole scatter time for close operation exceeds the alarm
setting time (6 ms)
➤ One phase auxiliary circuit breaker (52A) contact status change
exceeds B1PSTRT plus approximately 5 ms after the trip
initiation
➤ One phase auxiliary circuit breaker (52A) contact status change
exceeds B1PSCLT plus approximately 5 ms after the close
initiation
Example 8.7 Pole Scatter Settings (Continued)
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