6.21
Date Code 20171021 Instruction Manual SEL-421 Relay
Protection Applications Examples
500 kV Parallel Transmission Lines With Mutual Coupling Example
Global Settings
General Global Settings
The SEL-421 has settings for identification. These settings allow you to identify
the following:
➤ Station (SID)
➤ Relay (RID)
➤ Circuit Breaker 1 (BID1)
➤ Circuit Breaker 2 (BID2)
You can enter as many as 40 characters per identification setting.
SID := MOSCOW — 500 kV. Station Identifier (40 characters)
RID := SEL-421 Relay. Relay Identifier (40 characters)
Configure the SEL-421 for two circuit breakers. This particular application uses
two circuit breakers because the terminal is a circuit breaker-and-a-half configu-
ration.
NUMBK := 2. Number of Breakers in Scheme (1, 2)
BID1 := Circuit Breaker 1. Breaker 1 Identifier (40 characters)
BID2 := Circuit Breaker 2. Breaker 2 Identifier (40 characters)
You can select both the nominal frequency and phase rotation.
NFREQ := 60. Nominal System Frequency (50, 60 Hz)
PHROT := ABC. System Phase Rotation (ABC, ACB)
Current and Voltage Source Selection
The voltage and current source selection is for two circuit breakers in a circuit
breaker-and-a-half configuration. Set ESS to 3.
ESS := 3. Current and Voltage Source Selection (Y, N, 1, 2, 3, 4)
After you select 3 for setting ESS, the relay automatically sets LINEI, BK1I, and
BK2I as follows:
LINEI := COMB. Line Current Source (IW, COMB)
BK1I := IW. Breaker 1 Current Source (IW, IX, NA)
BK2I := IX. Breaker 2 Current Source (IW, IX, NA)
In this application example Circuit Breaker BK1A is Breaker 1 in the relay set-
tings and BK1B is Breaker 2 in the relay settings.
Figure 6.4 illustrates the current and voltage sources for this particular applica-
tion. The relay uses potential input VY and the combination of current inputs IW
and IX for line relaying; potential input VAZ is for synchronism check. Autore-
close and Synchronism Check Example on page 6.141 describes how to apply the
synchronism-check function.
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