Sel SEL-421 - Features

U.1.2
SEL-421/SEL-421-1 Relay User’s Guide Date Code 20020501
Introduction and Specifications
Features
Features
The SEL-421 Relay contains many protection, automation, and control
features. Figure 1.1 presents a simplified functional overview of the relay.
Figure 1.1 SEL-421 Relay Functional Overview.
SEL-421 Relay features include the following:
Superior Protection. Combine five zones of phase distance and ground
distance 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 Element™ optimizes directional element
performance and eliminates many settings. Additional logic prevents
Zone 1 overreach on series-compensated lines.
High-Speed Tripping. The SEL-421 Relay uses the HSDPS (High-Speed
Directional and Phase Selection) element and high-speed distance
elements for subcycle detection of power system faults.
Reclosing Control. Incorporate programmable single-pole and three-pole
tripping and reclosing of one and two circuit breakers into an
integrated substation control system. Synchronism and voltage checks
from multiple sources provide complete bay control.
Breaker Failure. The SEL-421 Relay incorporates CT subsidence detection
to produce element dropout in 5/8 cycle. Included is the necessary
logic for single-pole and three-pole breaker failure retrip and initiation
of transfer tripping.
• 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
• DNP and / or UCA Protocol
• High-Accuracy Metering
• M
IRRORED BITS™ Communications
• Remote and Local Control
Switches
• Advanced Local Display
• Fault Locator
• CCVT Transient Overreach and
Load Encroachment Supervision
Bus
Bus
Line
SEL-421 Relay
21
50BF
68
67
50
51
79
25
3
1
3
1
3
Phase &
Ground
Distance
Directional
Overcurrent
Out-of-Step
Trip and / or
Block
Dual Circuit
Breaker Failure
Synchronism
Check
Single- /
Three-Pole
Reclosing
Time-
Overcurrent
Instantaneous
Overcurrent
52
52
NOTE: The SEL-421-1 Relay does not
provide series-compensated line
protection logic.
NOTE: The SEL-421-1 Relay does not
provide high-speed directional
elements and high-speed distance
elements.