Schweitzer Engineering Laboratories SEL-421-4, Instruction Manual

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6.13
Date Code 20171006 Instruction Manual SEL-400 Series Relays
Autoreclosing
Two-Circuit-Breaker Autoreclosing
before the recloser can proceed to timing 3POID1. If the supervisory condition is
not met within the duration of timer 3POISD (Three-Pole Open Interval Supervi-
sion Delay), the recloser goes to lockout.
After three-pole open interval time 3POID or 3PFOID expires.
➤
and E79 := Y, the recloser attempts to close the leader breaker, as
discussed below (first checking the supervisory condition 3P
n CLS).
➤
and E79 := Y1, the recloser checks if the leader breaker is open. If
open, it attempts to close the leader breaker, as discussed below (first
checking the supervisory condition 3P
n CLS). If the leader breaker is
closed (it never opened at the outset), the recloser skips the leader
breaker close logic and attempts to close the follower breaker, as
discussed further below (first checking for two active breakers and an
open follower breaker, before starting timer TBBKD [Time Between
Breakers for ARC]).
The recloser closes the leader if supervisory condition 3P n CLS (Three-Pole BK n
Reclose Supervision) is satisfied within the duration of timer BK n CLSD (BK n
Reclose Supervision Delay).
At the leader close command, the recloser starts timer BKCFD (Breaker Close
Failure Delay). If the leader fails to close, the recloser sends the leader to lockout
BK
n LO after timer BKCFD expires. If the leader closes within the BKCFD time,
the recloser goes to 3PRCD (Three-Pole Reclaim Time Delay) reclaim timing if
NBK1 is asserted, or prepares to close the follower circuit breaker if NBK2 is
asserted.
To close the follower circuit breaker, the recloser checks for two active circuit
breakers in the scheme. If NBK2 is asserted, the recloser checks for a three-pole
open on the follower and starts timer TBBKD (Time Between Breakers For
ARC). When TBBKD expires, the recloser closes the follower breaker if FBK-
CEN (Follower Breaker Closing Enable) is asserted and supervisory condition
3P
n CLS is satisfied within the duration of timer BK n CLSD. At the follower
close command, the recloser starts timer BKCFD (Breaker Close Failure Delay).
If the follower fails to close, the recloser sends the follower to lockout after timer
BKCFD expires. If the leader circuit breaker is not in lockout, the recloser begins
timing 3PRCD reclaim time for the leader.
If the follower breaker closes successfully, the recloser starts the 3PRCD (Three-
Pole Reclaim Time Delay) timer if 79BRCT (Block Reclaim Timer) is not asserted.
3PRCD Reclaim Timing
The recloser determines subsequent state transitions during reclaim timing
according to the status of Relay Word bit 3PLSHT (Three-Pole Reclose Last Shot).
3PLSHT Deasserted (Three-Pole Shot Remains)
The recloser exhibits two possible state transitions when 3PLSHT is not asserted:
➤
If no further trip conditions occur and timer 3PRCD expires, the
recloser returns to the reset states BK
n RS.
➤
If a fault occurs while the 3PRCD reclaim timer is timing, then the
recloser asserts 3PARC if all three-pole initiate conditions are
satisfied and goes to the beginning of the 79CY3 cycle. The recloser
then recalculates and freezes the number of active circuit breakers,
the leader, and the follower. The recloser then increments the shot
counter and begins the next open interval timer.