U.1.12
SEL-421 Relay User’s Guide Date Code 20090715
Introduction and Specifications
Applications
Directional Comparison
Blocking Trip (DCB)
schemes
Current reversal guard logic
Carrier coordinating timers
Carrier send and receive extend logic
Zone 3 latch eliminates the need for offset three-phase
distance elements
Time-step distance backup protection
Direct Transfer Trip-
ping (DTT) schemes
SEL
OGIC control equations program the elements that key
direct tripping
SCADA applications Analog and digital data acquisition for station wide functions
Communications
capability
SEL ASCII
Enhanced M
IRRORED BITS communications
SEL Fast Meter, SEL Fast Operate, SEL Fast SER
SEL Compressed ASCII
Phasor Measurement Unit (PMU) protocols
RTD
Optional Serial DNP3
Optional protocols: Ethernet, IEC 61850, DNP3 (Ethernet),
FTP, Telnet
Customized protection
and automation schemes
Separate protection and automation SEL
OGIC control
equation programming areas
Use timers and counters in expanded SEL
OGIC control
equations for complete flexibility
Synchrophasors The SEL-421 can function as a phasor measurement unit
(PMU) at the same time as it provides best-in-class protective
relay functions.
C37.118 message format allows up to eight current and four
voltage synchronized measurements, up to 60 messages per
second (on a 60 Hz nominal power system). Two choices of
filter response, settable angle correction, and choice of
numeric representation makes the data usable for a variety of
synchrophasor applications.
SEL Fast Operate commands are available on the
synchrophasor communications ports, allowing control actions
initiated by the synchrophasor processor.
SEL Fast Message Synchrophasor format is also available,
with up to four current and four voltage synchronized
measurements.
Table 1.1 Application Highlights (Sheet 2 of 2)
Application Key Features
NOTE: Starting with SEL-421
firmware version R112,
synchrophasors are available in the
Courtesy of NationalSwitchgear.com
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