U.2.17
Date Code 20020501 User’s Guide SEL-421/SEL-421-1 Relay
Installation
Jumpers
Jumpers
The SEL-421 Relay contains jumpers that configure the relay for certain
operating modes. The jumpers are located on the main board (the top board)
and the I/O interface boards (one or two boards located immediately below the
main board).
Main Board Jumpers
The jumpers on the main board of the SEL-421 Relay perform these
functions:
➤ Temporary/emergency password disable
➤ Circuit breaker control enable
➤ Rear serial port +5 Vdc source enable
Figure 2.13 on page 2.18 shows the positions of the main board jumpers. The
main board jumpers are in two locations. The password disable jumper and
circuit breaker control jumper are at the front of the main board. The serial
port jumpers are near the rear-panel serial ports; each serial port jumper is
directly in front of the serial port that it controls.
Password and Circuit Breaker Jumpers
You can access the password disable jumper and circuit breaker control
jumper without removing the main board from the relay cabinet. Remove the
SEL-421 Relay front cover to view these jumpers (use appropriate ESD
precautions). The password and circuit breaker jumpers are on jumper header
J18 on the front of the main board, located immediately left of Power
connector J17 (see Figure 2.13).
CAUTION: Do not install a jumper
on positions A or D of the main board
J18 header. Relay misoperation can
result if you install jumpers on
positions J18A and J18D.
The J18 header is denoted A, B, C, and D from right to left (position A is on
the right). Position B is the password disable jumper; position C is the circuit
breaker control enable jumper. Positions A and D are not used. Figure 2.14 on
page 2.19 shows the jumper header with the circuit breaker/control jumper in
the ON position and the password jumper in the OFF position; these are the
normal jumper positions for an in-service relay. Table 2.3 on page 2.19 lists
the J18 jumper positions and functions.
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