Sel SEL-421 - Example Four: Input Selection of Leader

R.2.22
SEL-421 Relay Reference Manual Date Code 20111215
Auto-Reclosing and Synchronism Check
Two-Circuit-Breaker Auto-Reclosing
BK2 closes as the follower when BK1 successfully closes (after timer
TBBKD).
Lockout State
Circuit Breaker BK1 must close before Circuit Breaker BK2. If Circuit
Breaker BK1 fails to close and goes to lockout, then Circuit Breaker BK2 goes
to lockout as well because BK2 cannot close as the follower and cannot
dynamically become the leader. Table 2.16 defines the logical state of the
auto-reclose logic for this example following the unsuccessful reclose attempt.
Example Four: Input Selection of Leader
Figure 2.4 illustrates a circuit breaker-and-a half configuration for this
particular example. The leader and follower selection settings are shown in
Tab le 2.17. Circuit Breaker BK1 is out of service for maintenance and
Disconnect Switch 1 is open.
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 2 of 2)
Relay Word Bit Description Logical State
Table 2.16 Example Three: Lockout State, BK1
Relay Word Bit Description Logical State
NBK0 No Active Breakers in Reclose Scheme 1
NBK1 One Breaker Active in Reclose Scheme 0
NBK2 Two Active Breakers in Reclose Scheme 0
LEADBK0 No Leader Breaker 1
LEADBK1 Leader Breaker = Breaker 1 0
LEADBK2 Leader Breaker = Breaker 2 0
FOLBK0 No Follower Breaker 1
FOLBK1 Follower Breaker = Breaker 1 0
FOLBK2 Follower Breaker = Breaker 2 0
Table 2.17 Leader/Follower Selection
Setting Label Setting
SLBK1 IN106 (Disconnect 1 a contacts)
SLBK2 IN107 (Disconnect 2 a contacts)
FBKCEN 0