U.2.30
SEL-421 Relay
User’s Guide
Date Code 20090715
Installation
Relay Placement
Relay Placement
Proper placement of the SEL-421 helps make certain that you receive years of
trouble-free power system protection. Use the following guidelines for proper
physical installation of the SEL-421.
Physical Location
You can mount the SEL-421 in a sheltered indoor environment (a building or
an enclosed cabinet) that does not exceed the temperature and humidity
ratings for the relay.
The relay is IEC EN61010-1 rated at Installation/Overvoltage Category II and
Pollution Degree 2. This rating allows mounting the relay indoors or in an
outdoor (extended) enclosure where the relay is protected against exposure to
direct sunlight, precipitation, and full wind pressure, but neither temperature
nor humidity are controlled.
You can place the relay in extreme temperature and humidity locations. The
temperature range over which the relay operates is –40
°
to +185
°
F (–40
°
to
+85
°
C, see
Operating Temperature on page U.1.15
). The relay operates in a
humidity range from 5 percent to 95 percent, no condensation. For EN61010
certification, the SEL-421 rating is 2000 m (6560 feet) above mean sea level.
Rack Mounting
When mounting the SEL-421 in a rack, use the reversible front flanges to
either semiflush-mount or projection mount the relay.
The semiflush mount gives a small panel protrusion from the relay rack rails
of approximately 1.1 in. or 27.9 mm. The projection mount places the front
panel approximately 3.5 in. or 88.9 mm in front of the relay rack rails.
for exact mounting dimensions for both the horizontal and
vertical rack-mount relays. Use four screws of the appropriate size for your
rack.
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