Sel SEL-421 - Example One: no Follower; Reset State and 79 CY3 Cycle State

R.2.18
SEL-421 Relay Reference Manual Date Code 20111215
Auto-Reclosing and Synchronism Check
Two-Circuit-Breaker Auto-Reclosing
The following examples help illustrate how the SEL-421 auto-reclose logic
dynamically determines the leader and follower circuit breakers. These
examples describe a two circuit breaker scheme (such as used in a circuit
breaker-and-a-half arrangement) as shown in Figure 2.3.
Example One: No Follower
This example describes recloser states when Circuit Breaker BK1 fails to
reclose following the first three-pole open interval delay. Set the FBKCEN
SEL
OGIC control equation to prevent Circuit Breaker BK2 from closing as the
follower. The leader and follower selection settings are shown in Table 2.6.
Figure 2.3 Multiple Circuit Breaker Arrangement
Reset State and 79CY3 Cycle State
Prior to receiving initiation for a three-phase fault, the auto-reclose logic
resets for both circuit breakers. Tabl e 2.7 defines the logical state of the auto-
reclose logic for this example prior to the initiation of an auto-reclose cycle.
Table 2.6 Leader/Follower Selection
Setting Label Value
SLBK1 1
SLBK2 0
FBKCEN 0
Bus 1
(Leader) (Follower)
Line
Three-phase fault
Bus 2
BK2 BK1
Table 2.7 Example One: Reset and 79CY3 States
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