Schweitzer Engineering Laboratories SEL-421-4 - Page 1020

6.44
SEL-400 Series Relays Instruction Manual Date Code 20171006
Autoreclosing
Voltage Checks for Autoreclosing and Manual Closing
Note that the lead breaker and follower breaker supervision (Relay Word bits
LEADBKn and FOLBKn, respectively) provides dynamic control for reclose
supervision. One, but not both, of the breakers can reclose for a dead line/live bus
condition (lead breaker), while the other then closes for a synchronism-check
condition (follower breaker).
Supervising Manual Closing
Voltage checks can also be used to supervise manual closing. For example, pre-
sume that manual closing of breaker BK1 (Figure 6.18) should not be allowed if
the respective bus is dead (dead line/dead bus or live line/dead bus condition):
BK1MCL := NOT(DLDB1 OR AND LLDB1) AND (…)
Figure 6.18 Voltage Check Element Applications
Bus 2
V
S1
(Bus 1 Potential)
V
S2
(Bus 2 Potential)
BK1 BK2
1 1
3
V
P
(Line Potential)
Dead Line/
Live Bus 2
(DLLB2)
Dead Line/
Dead Bus 2
(DLDB2)
Live Line/
Dead Bus 2
(LLDB2)
Dead Line/
Live Bus 1
(DLLB1)
Dead Line/
Dead Bus 1
(DLDB1)
Live Line/
Dead Bus 1
(LLDB1)
Bus 1
Line