Schweitzer Engineering Laboratories SEL-421-4 - Page 35

1.5
Date Code 20171021 Instruction Manual SEL-421 Relay
Introduction and Specifications
Models and Options
Part numbers 0421xxxxxxxxxx3Axxxxx, 0421xxxxxxxxxx7Axxxxx,
0421xxxxxxxxxx3Bxxxxx, and 0421xxxxxxxxxx7Bxxxxx designate relays with
the auxiliary TRIP and CLOSE pushbuttons.
The lowercase xs in the above part numbers represent fields that contain
other values that are not important in determining the operator controls of the
relay. Refer to the SEL-421 Model Option Table for complete part number
details. These tables are available on the SEL website or from the factory.
Models and Options
Consider the following options when ordering and configuring the SEL-421.
➤ Chassis size
➢ 3U, 4U, and 5U
(U is one rack unit—1.75 inches or 44.45 mm)
➤ Main board I/O
➢ Main Board:
Contact inputs: 5 independent and 2 common inputs (level sensi-
tive and optoisolated);
Contact outputs: 2 standard Form A, 3 standard Form C, and 3
high-current interrupting Form A outputs
➤ Additional I/O board (for 4U and 5U chassis)
➢ INT1:
Contact inputs: 8 independent inputs (programmable pickup
threshold);
Contact outputs: 13 standard Form A and 2 standard Form C
outputs
➢ INT2:
Contact inputs: 8 independent inputs (level sensitive and
optoisolated);
Contact outputs: 13 standard Form A and 2 standard Form C
outputs
➢ INT3:
Contact inputs: 18 common (2 groups of 9) and 6 independent
inputs (level sensitive and optoisolated);
Contact outputs: 4 high-current interrupting
Form A outputs
➢ INT4:
Contact inputs: 18 common (2 groups of 9) and 6 independent
inputs (level sensitive and optoisolated);
Contact outputs: 6 high-speed, high-current interrupting Form A
and 2 standard Form A outputs
➢ INT5:
Contact inputs: 8 independent inputs (programmable pickup
threshold);
Contact outputs: 8 high-speed, high-current interrupting Form A
outputs
NOTE: When used in TiDL
applications, the relay is only
available in the 4U chassis.