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Date Code 20171021
Instruction Manual
SEL-421 Relay
Instruction Manual
Instruction Manual
S E C T I O N
7
Metering, Monitoring, and Reporting
The SEL-421 Relay provides extensive capabilities for monitoring substation
components, metering important power system parameters, and reporting on
power system performance. The relay provides the following useful features:
➤
➤
Circuit Breaker Monitor on page 7.7
➤
Station DC Battery System Monitor on page 7.7
➤
Section 7: Metering, Section 8: Monitoring
SEL-400 Series Relays Instruction Manual
for general information. This section
contains details specific to the SEL-421.
Metering
The SEL-421 provides five metering modes for measuring power system operations:
➤
Instantaneous Metering on page 7.2
➤
Maximum/Minimum Metering on page 7.5
➤
➤
➤
Synchrophasor Metering on page 7.7
Monitor present power system operating conditions with instantaneous metering.
Maximum/Minimum metering displays the largest and smallest system devia-
tions since the last reset. Demand metering includes either thermal or rolling
analyses of the power system and peak demand metering. Energy metering dis-
plays the megawatt-hours imported, megawatt-hours exported, and total mega-
watt-hours. Time-synchronized metering displays the line voltage and current
synchrophasors.
The SEL-421 processes three sets of current quantities: LINE, BK1, and BK2
(when configured for two circuit breakers). In one configuration using two circuit
breakers, Terminal W is usually connected as BK1, and Terminal X is generally
connected as BK2. The line voltage from Terminal Y (V
Y) provides the voltage
quantities for LINE. See
Current and Voltage Source Selection on page 5.2
for
more information on configuring the SEL-421 inputs.
Use the
MET
command to access the metering functions. Issuing the
MET
com-
mand with no options returns the fundamental frequency measurement quantities
listed in
. The
MET
command followed by a number,
MET
k
, specifies
the number of times the command will repeat (
k
can range from 1 to 32767). This
is useful for troubleshooting or investigating uncharacteristic power system con-
ditions. With other command options, you can view currents from either circuit
breaker. For example, you can monitor the fundamental currents on Circuit
Summary of Contents for SEL-421-4
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