U.2.45
Date Code 20090715
User’s Guide
SEL-421 Relay
Installation
Connection
!
WARNING
!
WARNING
Auxiliary {TRIP}/
{CLOSE} Pushbuttons
and OPEN/CLOSED
LEDs (select models
only)
Select relay models feature auxiliary
{TRIP}
and
{CLOSE}
pushbuttons and
OPEN
and
CLOSED
LED indicators. These features are electrically isolated from the
rest of the relay. They function independently from the relay and do not need
relay power.
The pushbuttons and LEDs can be hard-wired into a substation trip and close
control circuit and operate the same as a separate installation of external trip/
close switches and LED indicators.
shows example trip and close
circuit connections for a control scheme configuration with a dc substation
voltage source. The pushbutton switches come set from the factory for dc
operation (arc suppression enabled). To use an ac trip or close potential, the
arc suppression must be disabled for one or both pushbuttons (see
).
The voltage operating ranges of the LEDs are selected by jumpers (see
).
SEL-421 features such as Hot Line Tag
and Synchronism Check do not
supervise the auxiliary close
pushbutton.
Since the trip and close buttons are functionally separate from the relay, a
manual trip or close cannot be distinguished from an external protection or
automation-initiated operation. Unless provisions are made in the control
wiring, the action of the close pushbutton is unsupervised.
TIME Input
Connections
IRIG-B Input Connection
The SEL-421 accepts a demodulated IRIG-B signal through two types of rear-
panel connectors. These
IRIG-B
inputs are through the BNC connector labeled
TIME IRIG-B
or through Pin
4
(+) and Pin
6
(–) of the rear-panel 9-pin D-
subminiature connector
PORT 1 (
see
Communications Ports Connections on
for other DB-9 connector pinouts and additional details).
These inputs accept the dc shift time code generator output (demodulated)
IRIG-B signal with positive edge on the time mark. For more information on
IRIG-B and the SEL-421, see
.
The
PORT 1 IRIG-B
input circuit connects to a 330
Ω
resistor in series with an
optocoupler input diode. The optocoupler input diode forward voltage drop is
about 1.5 V. Driver circuits should source approximately 10 mA through the
circuit for the ON state. When you are using the
PORT 1
input, ensure that you
connect Pins
4
and
6
with the proper polarity.
Where distance between the SEL-421 and the IRIG-B sending device exceeds
the cable length recommended for conventional EIA-232 metallic conductor
cables, you can use transceivers to provide isolation and to establish
communication to remote locations.
Conventional fiber-optic and telephone modems do not support IRIG-B signal
transmission. Use the SEL-2810 transceiver to provide long distance delivery
of the IRIG-B signal to the SEL-421. The SEL-2810 includes a channel for
the IRIG-B time code. These transceivers enable you to synchronize time
precisely from IRIG-B time code generators (such as the SEL-2032
Communications Processor) over a fiber-optic communications link.
Use the IRIG-B BNC connector for synchrophasor and high-accuracy
timekeeping applications—see
Configuring High-Accuracy Timekeeping on
. Make the connection using a 50
Ω
coaxial cable assembly with a
male BNC connector.
NOTE:
The position of the IRIG-B
BNC connector changed when
SEL-421 firmware version R112 was
released. See
for details.
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