Sel 421 - Page 64

U.2.2
SEL-421 Relay User’s Guide Date Code 20090715
Installation
Shared Configuration Attributes
horizontal and vertical relay orientations; dashed lines denote the pocket
areas. Refer to the instructions included in the Configurable Label kit for
information on reconfiguring front-panel LED and pushbutton labels.
Rear Panels
Rear panels are identical for the horizontal and the vertical configurations of
the relay. Figure 2.2 is an example of a rear panel for a 3U relay with fixed
terminal block analog inputs. Figure 2.3 shows a rear panel for a 3U relay
with Connectorized
®
analog inputs. See Rear-Panel Layout on page U.2.32
for representative 3U, 4U, and 5U relay rear panels (large drawings are in
Figure 2.28, Figure 2.29, Figure 2.30, and Figure 2.33).
Connector Types
Screw Terminal Connectors—I/O and Monitor/Power
Connect to the relay I/O and Monitor/Power terminals on the rear panel
through screw terminal connectors. You can remove the entire screw terminal
connector from the back of the relay to disconnect relay I/O, dc battery
monitor, and power without removing each wire connection. The screw
terminal connectors are keyed (see Figure 2.37), so you can replace the screw
terminal connector on the rear panel only at the location from which you
removed the screw terminal connector. In addition, the receptacle key prevents
you from inverting the screw terminal connector, making removal and
replacement easier.
Secondary Circuit Connectors
Fixed Terminal Blocks
Connect PT and CT inputs to the fixed terminal blocks in the bottom row of
the relay rear panel.
You cannot remove these terminal blocks from the relay rear panel. These
terminals offer a secure high-reliability connection for PT and CT
secondaries.
Connectorized
The Connectorized SEL-421 features receptacles that accept plug-in/plug-out
connectors for terminating PT and CT inputs; this requires ordering a wiring
harness (SEL-WA0421) with mating plugs and wire leads. Figure 2.3 shows
the relay 3U chassis with Connectorized CT and PT analog inputs (see
Connectorized on page U.2.42 for more information).
Courtesy of NationalSwitchgear.com