Schweitzer Engineering Laboratories SEL-421-4 - Figure 6.38 Partial Circuit Breaker-And-A-Half Arrangement at Station S, Line

6.143
Date Code 20171021 Instruction Manual SEL-421 Relay
Protection Applications Examples
Autoreclose and Synchronism-Check Example
Autoreclose Solution
Autoreclose Conditions
The relay initiates single-pole autoreclose if a Zone 1 trip or a communications-
assisted trip occurs for a single phase-to-ground fault. The relay initiates three-
pole autoreclose if a Zone 1 trip or a communications-assisted trip occurs for a
multiphase fault.
Circuit Breaker 1 can attempt a reclose if Bus 1 is hot and the line is dead. Circuit
Breaker 2 can attempt a reclose if the synchronism check is successful or if Cir-
cuit Breaker 1 is out of service and the line is dead and Bus 2 is hot.
Block autoreclose if any of the following events occur:
➤ Manual trip
➤ Time-delayed trip
➤ Bus trip
➤ Circuit breaker failure trip
If the SEL-421 detects a loss-of-potential condition, the autoreclose logic drives
the autoreclose function to lockout.
Autoreclose Relay Settings
Select the autoreclose relay settings for this application example.
Relay Configuration
Enable reclosing.
E79 := Y. Reclosing (Y, Y1, N)
Selection Y1 can be used in circumstances where CB2 can be tripped externally,
yet the SEL-421 is to be able to autoreclose.
Figure 6.38 Partial Circuit Breaker-and-a-Half Arrangement at Station S,
Line 1
BUS 1
VY
Follower
Line Disconnect
Leader
VBZVAZ
SEL-421 Relay
from BUS 2
CB1 CB2
3
1
1