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6.3
Date Code 20171021
Instruction Manual
SEL-421 Relay
Protection Applications Examples
230 kV Overhead Distribution Line Example
➤
Inverse-time directional zero-sequence overcurrent backup
protection
➤
Switch-onto-fault (SOTF) protection, fast tripping when the circuit
breaker closes
Relay settings that are not mentioned in these examples do not apply to this appli-
cation 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)
You can enter as many as 40 characters per identification setting.
SID :=
HARVARD — 230 kV
.
Station Identifier (40 characters)
RID := SEL-421
Relay
.
Relay Identifier (40 characters)
Configure the SEL-421 for one circuit breaker.
NUMBK :=
1
.
Number of Breakers in Scheme (1, 2)
BID1 :=
Circuit Breaker 1
.
Breaker 1 Identifier (40 characters)
You can select both nominal frequency and phase rotation for the relay.
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 one circuit breaker. The relay
derives the line current source from current input IW when you set ESS to N.
ESS :=
N
.
Current and Voltage Source Selection (Y, N, 1, 2, 3, 4)
illustrates the current and voltage sources for this particular applica-
tion. The relay uses potential input VY and current input IW for line relaying;
potential input VAZ is for synchronism check.
Synchronism Check on page 5.158
describes how to apply the synchronism-check function.
Figure 6.2
Circuit Breaker Arrangement at Station S
SEL-421
VAZ
IW
VY
BK1
3
1
3
34
5 kV Bus
Summary of Contents for SEL-421-4
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