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1.4
SEL-421 Relay
Instruction Manual
Date Code 20171021
Introduction and Specifications
Features
High-Accuracy Time Stamping.
Time-tag binary COMTRADE event reports
with real-time accuracy of better than 10 µs. View system state information
to an accuracy of better than 1/4 of an electrical degree.
Digital Relay-to-Relay Communication.
Enhanced M
IRRORED
B
ITS
communi-
cations to monitor internal element conditions between relays within a sta-
tion, or between stations, using SEL fiber-optic transceivers. Send digital,
analog, and virtual terminal data over the same M
IRRORED
B
ITS
channel.
Parallel Redundancy Protocol (PRP).
Provide seamless recovery from any sin-
gle Ethernet network failure with this protocol, in accordance with IEC
62439-3. The Ethernet network and all traffic are fully duplicated with both
copies operating in parallel.
Ethernet Access.
Access all relay functions with the optional Ethernet card.
Interconnect with automation systems using IEC 61850 or DNP3 LAN/
WAN protocols directly or DNP3 through an SEL-2032 Communications
Processor or SEL-3530 RTAC. Use file transfer protocol (FTP) for high-
speed data collection.
Increased Security.
The SEL-421 divides control and settings into seven relay
access levels; the relay has separate breaker, protection, automation, and out-
put access levels, among others. Set unique passwords for each access level.
Rules-Based Settings Editor.
Communicate with and set the relay using an
ASCII terminal, or use the PC-based QuickSet Software to configure the
SEL-421 and analyze fault records with relay element response. View real-
time phasors.
Settings Reduction.
Internal relay programming shows only the settings for
the functions and elements you have enabled.
Thermal Overload Modeling.
Use the SEL-421 with the SEL-2600 RTD Mod-
ule for dynamic overload protection using SEL
OGIC
control equations. For
more information, see SEL Application Guide AG2003-06,
Implementation
of the SEL-49 Relay Line Thermal Protection Using the SEL-421 Relay
SEL
OGIC
Equations
.
Bay Control.
The SEL-421 provides bay control functionality with status indi-
cation and control of as many as ten disconnects. The relay features control
for as many as two breakers and status indication of as many as three break-
ers. Numerous pre-defined user-selectable mimic displays are available; the
selected mimic is displayed on the front-panel screen in one-line diagram
format. The one-line diagram includes user-configurable labels for discon-
nect switches, breakers, bay name, and display for as many as six analog
quantities. The SEL-421 features SEL
OGIC
programmable local control
supervision of breaker and disconnect switch operations. See
Section 5:
Control in the SEL-400 Series Relays Instruction Manual
for more informa-
tion.
Alias Settings.
Use as many as 200 aliases to rename any digital or analog
quantity in the relay. The aliases are now available for use in customized pro-
gramming, making the initial programming and maintenance much easier.
Auxiliary TRIP/CLOSE Pushbuttons.
The part number indicates whether the
relay has auxiliary
TRIP
and
CLOSE
pushbuttons. These pushbuttons are shown
Figure 4.2 on page 4.2 in the SEL-400 Instruction Manual
. These features
are electrically isolated from the rest of the relay. They function inde-
pendently from the relay and do not need relay power.
Summary of Contents for SEL-421-4
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