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1.2
SEL-421 Relay
Instruction Manual
Date Code 20171021
Introduction and Specifications
Features
Features
The SEL-421 contains many protection, automation, and control features.
presents a simplified functional overview of the relay.
SEL-421 features include the following:
NOTE:
The SEL-421-4 does not
provide series-compensated line
protection logic.
Superior Protection.
Combine five zones of phase-distance and ground-dis-
tance elements with directional overcurrent elements. Patented Coupling
Capacitor Voltage Transformer (CCVT) transient overreach logic enhances
Zone 1 distance element security. The Best Choice Ground Directional Ele-
ment optimizes directional element performance and eliminates many set-
tings. Additional logic prevents Zone 1 overreach on series-compensated
lines.
NOTE:
The SEL-421-4 does not
provide high-speed directional
elements and high-speed distance
elements.
High-Speed Tripping.
The SEL-421 uses the HSDPS (High-Speed Directional
and Phase Selection) element and high-speed distance elements for subcycle
detection of power system faults.
Reclosing.
Incorporate programmable single-pole and three-pole tripping and
reclosing of one and two circuit breakers into an integrated substation con-
trol system. Synchronism and voltage checks from multiple sources provide
complete bay control.
Breaker Failure.
The SEL-421 incorporates CT subsidence detection to pro-
duce element dropout in 5/8 cycle. Apply the SEL-421 to supply three-pole
breaker failure for one or two breakers. Included is the necessary logic for
single-pole and three-pole breaker failure retrip and initiation of transfer trip-
ping.
Figure 1.1
SEL-421 Functional Overview
➤
Password Separation of Protection and Automation
➤
Expanded SEL
OGIC
Control Equations
➤
Event Reports and Oscillography
➤
Sequential Events Recorder
➤
Dual Breaker Condition Monitor
➤
Station Battery Monitor
➤
DNP3
➤
IEC 61850 (Optional Feature)
➤
High-Accuracy Metering
➤
M
IRRORED
B
ITS
Communications
➤
Synchrophasors
➤
Fault Locator
➤
CCVT Transient Overreach and Load Encroach-
ment Supervision
➤
Remote and Local Control Switches
➤
Advanced Local Display
➤
Time-Domain Link Remote Data Acquisition
SEL-2600
Bus
3
Line
Bus
3
3
1
SEL-2800
1
ENV
21
25
50BF
51
50
50BF
51
50
67
68
79
81
O
U
SEL-421
27
59
4
EIA-232
2
Ethernet
1
*
1
IRIG-B
Summary of Contents for SEL-421-4
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