U.4.3
Date Code 20020501
User’s Guide
SEL-421/SEL-421-1 Relay
Basic Relay Operations
Inspecting a New Relay
shows a serial number label for an SEL-421 Relay with standard
I/O in a 3U horizontal chassis. This example serial number label is for a
5 A-per-phase secondary current transformer input relay. For information on
CT and PT inputs, see
Secondary Circuits on page U.2.5 in the User’s Guide
.
The power supply specification in
indicates that this relay is
equipped with a power supply that accepts a nominal 125/250 Vdc input. This
power supply also accepts a 120/230 Vac input. Other power supply options
include nominal 24/48 Vdc, and 48/125 Vdc power supplies. The 48/125 Vdc
power supply also accepts a 120 Vac input. Refer to the serial number label
affixed to the back of your relay to determine the power supply voltage you
should apply to the relay power supply input terminals. As this label indicates,
the voltage source should be capable of providing at least 35 W for dc inputs
and 120 VA for ac inputs. See
Power Supply on page U.1.11 in the User’s
for more information on power supply specifications.
The serial number label does not call out power system phase rotation and
frequency ratings, because you can use relay settings to configure these
parameters. The factory defaults are ABC phase rotation and 60 Hz nominal
frequency. See
Making Settings Changes: Initial Global Settings on page 4.19
for details on setting these parameters.
The serial number label does not list a control input (logic input) level because
the SEL-421 Relay uses an advanced A/D input converter circuit that accepts
inputs over a wide range. For more information on control inputs, see
Inputs on page U.2.6 in the User’s Guide
.
Summary of Contents for SEL-421
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