Sel SEL-421 - Example Three: BK2 as Conditional Follower; 79 CY3 Cycle State

R.2.21
Date Code 20111215 Reference Manual SEL-421 Relay
Auto-Reclosing and Synchronism Check
Two-Circuit-Breaker Auto-Reclosing
Example Three: BK2 as Conditional Follower
One method to program BK2 for closing only after a successful BK1 close is
to set SLBK1/SLBK2/FBKCEN as in Table 2.13.
Reset State
Prior to receiving initiation for a three-phase fault, the auto-reclose logic
resets for both circuit breakers. Table 2. 14 defines the logical state of the auto-
reclose logic for this example prior to the initiation of an auto-reclose cycle.
79CY3 Cycle State
The SEL-421 auto-reclose logic receives a three-pole initiation. Table 2.15
defines the logical state of the auto-reclose logic for this example during the
three-pole auto-reclose cycle.
FOLBK0 No Follower Breaker 1
FOLBK1 Follower Breaker = Breaker 1 0
FOLBK2 Follower Breaker = Breaker 2 0
Tabl e 2 . 12 Exa m ple Two: Fin a l Re s et S t at e (Sheet 2 of 2)
Relay Word Bit Description Logical State
Table 2.13 Leader/Follower Selection
Setting Label Value
SLBK1 1
SLBK2 0
FBKCEN 52AA1
Tabl e 2 . 14 Exa m pl e Th re e : Rese t St a te
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
Table 2.15 Example Three: Three-Pole Cycle State (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 0
NBK2 Two Active Breakers in Reclose Scheme 1
LEADBK0 No Leader Breaker 0
LEADBK1 Leader Breaker = Breaker 1 1