U.1.3
Date Code 20020501
User’s Guide
SEL-421/SEL-421-1 Relay
Introduction and Specifications
Features
Out-of-Step Blocking and Tripping.
Select out-of-step blocking of distance
elements or out-of-step tripping during power swings. The SEL-421
Relay includes multizone elements and logic for detection of an out-
of-step condition.
Switch-Onto-Fault.
Relay switch-onto-fault (SOTF) logic permits specific
protection elements to quickly trip after the circuit breaker closes,
protecting maintenance personnel and substation equipment.
Fault Locator.
Efficiently dispatch line crews to quickly repair line
problems.
Primary Potential Redundancy.
Multiple voltage inputs to the SEL-421
Relay provide primary input redundancy. At loss-of-potential (LOP)
detection, configure the relay to use inputs from an electrically
equivalent source. Protection remains in service without
compromising security.
Dual CT Input.
Connect separate CTs to the relay inputs and combine these
currents inside the relay for protection functions, but keep these CT
currents separately available for protection, monitoring, and station
integration applications.
NOTE:
The SEL-421-1 Relay has only
one 100-line automation programming
block.
Expanded SEL
OGIC
Control Equations.
Modify and set custom relay
applications with PLC–style (programmable logic controller, IEC
61131-3 ST compatible) SEL
OGIC
control equation programming that
includes math and comparison functions. Use counters and
multifunction timers for greater application flexibility. Perform
advanced PLC functions within the relay. The SEL-421 Relay has
separate protection and automation SEL
OGIC
control equation
programming areas. These programming areas provide you with ample
protection programming capability and 10 blocks of 100-line
automation programming capability (1000 lines).
Monitoring.
Schedule breaker maintenance when accumulated breaker
duty (independently monitored for each pole of two circuit breakers)
indicates excessive contact wear. The SEL-421 Relay records
electrical and mechanical operation times for the last operation and for
the average of operations since the monitor function reset. In addition,
the relay alarms for out-of-tolerance conditions that you specify. Use
the two independent battery monitors to detect substation battery
voltage problems even if battery voltage is low only during a trip or
close operation.
Metering.
View metering information for Line, Circuit Breaker 1, and
Circuit Breaker 2. SEL-421 Relay metering includes fundamental and
rms metering, as well as energy import/export, demand, and peak
demand metering data.
Oscillography and Event Reporting.
Record raw voltages and currents at a
sampling rate as great as 8 kHz (8000 samples/second). Investigate
relay internal logic points and power system performance with event
report phasor and harmonic analysis.
Sequential Events Recorder (SER).
Record 1000 system entries, including
settings changes, power-ups, and Relay Word bit elements that you
select. Set element names to easily understood aliases.
High-Accuracy Time Stamping.
Time-tag event reports with real-time
accuracy of 10 µs. You can coordinate time-stamped data to determine
system states at an accuracy of 0.25 electrical degree.
Summary of Contents for SEL-421
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