Schweitzer Engineering Laboratories SEL-421-4 - Figure 6.35 Circuit Breaker Arrangement at Station

6.138
SEL-421 Relay Instruction Manual Date Code 20171021
Protection Applications Examples
Autoreclose Example
Solution
Autoreclose Conditions
The relay initiates three-pole autoreclosing if a Zone 1 trip occurs because of a
multiphase fault.
Circuit Breaker1 attempts the three-pole reclose if Bus 1 is hot and the line is
dead. For this application example, 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 an LOP condition, the autoreclose logic drives the autore-
close function to lockout.
Relay Settings
Select the relay settings for this application example.
Relay Configuration
NOTE: Setting E79 := Y1 is intended
for certain double circuit breaker
applications. Use E79 := Y for a single
circuit breaker.
Enable reclosing:
E79 := Y. Reclosing (Y, Y1, N)
Recloser Closing
Select one shot of three-pole autoreclose.
N3PSHOT := 1. Number of Three-Pole Reclosures (N, 1–4)
Use an external switch to select when Circuit Breaker 1 is enabled for three-pole
autoreclose.
E3PR1 := IN106. Three-Pole Reclose Enable -BK1 (SELOGIC Equation)
If Circuit Breaker 1 fails to close within 10 seconds after the reclose command is
received, the autoreclose logic goes to lockout.
BKCFD := 600. Breaker Close Failure Delay (1–99999 cycles)
Figure 6.35 Circuit Breaker Arrangement at Station S
SEL-421
VAZ
IW
VY
BK1
3
1 3
345 kV Bus