R.2.20
SEL-421 Relay Reference Manual Date Code 20111215
Auto-Reclosing and Synchronism Check
Two-Circuit-Breaker Auto-Reclosing
Example Two: BK2 as Successful Follower and Dynamic Leader
Another example is similar to the first with SLBK1/SLBK2/FBKCEN at 1/0/1
(see Tab le 2.10).
Reset State
Prior to receiving initiation for a three-phase fault, the auto-reclose logic
resets for both circuit breakers. At the start of the reclose cycle, Relay Word
bits LEADBK1, FOLBK2, and NBK2 are asserted (see Table 2.11).
When BK1 successfully recloses, BK2 closes as the follower after timer
TBBKD (Time Between Breakers for ARC).
If BK1 goes to lockout during a reclose cycle (after BKCFD time), then BK2
will close as the follower. After timer 3PRCD (Three-Pole Reclaim Time
Delay) expires, the recloser enters the reset state for BK2 (BK2RS). The
recloser dynamically recalculates the leader and follower circuit breakers.
BK2 becomes the leader with Relay Word bits LEADBK2, FOLBK0, and
NBK1 asserted (see Table 2.12). When BK2 becomes the leader, the recloser
immediately issues the close command to BK2 and does not add any
additional SPOID or 3POID interval time.
Table 2.10 Leader/Follower Selection
Setting Label Value
SLBK1 1
SLBK2 0
FBKCEN 1
Table 2.11 Example Two: Initial Reset State
Relay Word Bit Description Logical State
NBK0 No Active Breakers in Reclose Scheme 0
NBK1 One Breaker Active in Reclose Scheme 0
NBK2 Two Active Breakers in Reclose Scheme 1
LEADBK0 No Leader Breaker 0
LEADBK1 Leader Breaker = Breaker 1 1
LEADBK2 Leader Breaker = Breaker 2 0
FOLBK0 No Follower Breaker 0
FOLBK1 Follower Breaker = Breaker 1 0
FOLBK2 Follower Breaker = Breaker 2 1
Tabl e 2 . 12 Exa m ple Two: Fin a l Re s et S t at e (Sheet 1 of 2)
Relay Word Bit Description Logical State
NBK0 No Active Breakers in Reclose Scheme 0
NBK1 One Breaker Active in Reclose Scheme 1
NBK2 Two Active Breakers in Reclose Scheme 0
LEADBK0 No Leader Breaker 0
LEADBK1 Leader Breaker = Breaker 1 0
LEADBK2 Leader Breaker = Breaker 2 1
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