6.89
Date Code 20171021
Instruction Manual
SEL-421 Relay
Protection Applications Examples
EHV Parallel 230 kV Underground Cables Example
Application Summary
This particular example is for a single circuit breaker, three-pole tripping applica-
tion with the following functions:
➤
POTT (permissive overreaching transfer trip) scheme
➤
Three zones of phase (mho) and ground (quadrilateral) distance
protection
➢
Zone 1—forward-looking, provides instantaneous
underreaching protection
➢
Zone 2—forward-looking, provides communications-assisted
and time-delayed tripping
➢
Zone 3—reverse-looking, prevents unwanted tripping during
current reversals
➤
Two levels of negative-sequence directional overcurrent protection
➢
Level 2—forward-looking, provides communications-assisted
high-speed tripping
➢
Level 3—reverse-looking, prevents unwanted tripping during
current reversals
➤
Inverse-time directional negative-sequence overcurrent backup
protection
➤
SOTF protection (fast tripping when the circuit breaker closes)
Relay settings that are not mentioned in this example do not apply to this applica-
tion 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 :=
LEWISTON -- 230 kV
.
Station Identifier (40 characters)
RID :=
SEL-421 Relay
.
Relay Identifier (40 characters)
Configure the SEL-421 for the one circuit breaker that this particular application
uses:
NUMBK :=
1
.
Number of Breakers in Scheme (1, 2)
BID1 :=
Circuit Breaker 1
.
Breaker 1 Identifier (40 characters)
Set the relay for nominal frequency and phase rotation.
NFREQ :=
60
.
Nominal System Frequency (50, 60 Hz)
PHROT :=
ABC
.
System Phase Rotation (ABC, ACB)
Summary of Contents for SEL-421-4
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