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2.26
SEL-421 Relay
Instruction Manual
Date Code 20171021
Installation
Connection
Rear-Panel Layout
through
show available SEL-421 rear panels.
All relay versions have screw-terminal connectors for I/O, power, and battery
monitor. You can order the relay with fixed terminal blocks for the CT and PT
connections, or you can order SEL Connectorized rear-panel configurations that
feature plug-in/plug-out PT connectors and shorting CT connectors for relay ana-
log inputs.
shows the Connectorized 3U horizontal configuration of
the SEL-421.
The screw-terminal connections for the INT1 (or INT2) and the INT6 (or INT7)
I/O interface boards are the same. The INT5 (or INT8) I/O interface board has
control output terminals grouped in threes, with the fourth terminal as a blank
additional separator (terminals 4, 8, 12, 16, 20, 24, 28, and 32). The INT3, INT4,
and INT5 (or INT8) I/O interface boards both contain high-speed, high-current
interrupting control outputs, but use a different terminal layout—see
for details.
For more information on the main board control inputs and control outputs, see
. For more information on the I/O interface board
control inputs and control outputs, see
I/O Interface Board Jumpers on
Figure 2.23
3U Rear Panel, Main Board
Figure 2.24
3U Rear Panel, Main Board, Connectorized
Summary of Contents for SEL-421-4
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