Schweitzer Engineering Laboratories SEL-421-4 - Figure 6.4 Circuit Breaker-And-A-Half Arrangement: Station S, Line 1

6.22
SEL-421 Relay Instruction Manual Date Code 20171021
Protection Applications Examples
500 kV Parallel Transmission Lines With Mutual Coupling Example
Breaker Monitor
Circuit Breaker Configuration
Set the relay to indicate that both circuit breakers are single-pole trip type.
BK1TYP := 1. Breaker 1 Trip Type (Single-Pole = 1, Three-Pole = 3)
BK2TYP := 1. Breaker 2 Trip Type (Single-Pole = 1, Three-Pole = 3)
Circuit Breaker 1 Inputs
The SEL-421 uses normally open auxiliary contacts from the circuit breakers to
determine whether each pole is opened or closed.
52AA1 := IN101. A-Phase N/O Contact Input—BK1 (SELOGIC Equation)
52AB1 := IN102. B-Phase N/O Contact Input—BK1 (SELOGIC Equation)
52AC1 := IN103. C-Phase N/O Contact Input—BK1 (SELOGIC Equation)
Circuit Breaker 2 Inputs
52AA2 := IN104. A-Phase N/O Contact Input—BK2 (SELOGIC Equation)
52AB2 := IN105. B-Phase N/O Contact Input—BK2 (SELOGIC Equation)
52AC2 := IN106. C-Phase N/O Contact Input—BK2 (SELOGIC Equation)
Group Settings
Line Configuration
The SEL-421 has four transformer turns ratio settings that convert the secondary
potentials and currents that the relay measures to the corresponding primary val-
ues. These settings are the potential transformer and current transformer ratios
PTRY, PTRZ, CTRW, and CTRX. Use the Y potential input for line relaying and
the Z potential input for synchronism checks. Enable the voltage and current
source selection so you can combine W and X current inputs for the line current.
VNOMY and VNOMZ specify the nominal secondary line-to-line voltage of the
potential transformers (see Figure 6.4).
Figure 6.4 Circuit Breaker-and-a-Half Arrangement: Station S, Line 1
VY
C
ir
cu
i
t
1
VAZ
IX
IW
BK1A
BK1B
S
EL-42
1
1
3
3
3