1.12
SEL-421 Relay Instruction Manual Date Code 20171021
Introduction and Specifications
Product Characteristics
Product Characteristics
Each SEL-400 series relay shares common features, but has unique characteris-
tics. The following table summarizes the unique characteristics of the SEL-421.
Permissive Underreaching
Transfer Tripping (PUTT)
schemes
Supported by POTT logic
Time-step distance backup protection
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 dis-
tance elements
Time-step distance backup protection
Direct Transfer Tripping
(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
Serial DNP3
Optional protocols: Ethernet, IEC 61850, DNP3 (Ethernet),
FTP, Telnet
Customized protection and
automation schemes
Separate protection and automation SEL
OGIC control equa-
tion programming areas
Use timers and counters in expanded SEL
OGIC control equa-
tions 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 as many as 12 current and 8
voltage synchronized measurements, as many as 60 messages
per second (on a 60 Hz nominal power system). Five unique
data streams, three choices of filter response, settable angle
correction, and a choice of numeric representation makes the
data usable for a variety of synchrophasor applications.
SEL Fast Operate commands are available on the synchropha-
sor communications ports, allowing control actions initiated
by the synchrophasor processor.
Records as much as 120 seconds of C37.118 synchrophasor
data based on a trigger. Recorded files follow the C37.232 file
naming convention.
SEL Fast Message Synchrophasor format is also available as
legacy, with as many as four current and four voltage synchro-
nized measurements.
Table 1.1 Application Highlights (Sheet 2 of 2)
Application Key Features
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