2.23
Date Code 20170927 Instruction Manual SEL-751 Relay
Installation
Relay Connections
Power Connections
The POWER terminals on the rear panel (A01(+/H) and A02(—/N)) must connect
to 110–240 Vac, 110–250 Vdc, or 24–48 Vdc (see Power Supply on page 1.13
for complete power input specifications). The POWER terminals are isolated
from chassis ground. Use 14 AWG (2.1 mm
2
) to 16 AWG (1.3 mm
2
) size wire
to connect to the POWER terminals.
For compliance with IEC 60947-1 and IEC 60947-3, place a suitable external
switch or circuit breaker in the power leads for the SEL-751; this device
should interrupt both the hot (+/H) and neutral (—/N) power leads. The maxi-
mum current rating for the power disconnect circuit breaker or optional over-
current device (fuse) should be 20 A.
Operational power is internally fused by a power supply fuse. See Field Ser-
viceability on page 2.50 for details. Be sure to use fuses that comply with
IEC 60127-2.
Grounding (Earthing)
Connections
You must connect the ground terminal labeled GND on the rear panel to a rack
frame or switchgear ground for proper safety and performance. Use 14 AWG
(2.1 mm
2
) wire less than 2 m (6.6 feet) in length for the ground connection.
Serial Ports
Because all ports (F, 2, 3, and 4) are independent, you can communicate to any
combination simultaneously. Although serial Port 4 on the optional communi-
cations card consists of an EIA-485 (4A) and an EIA-232 (4C) port, only one
port is available at a time. Use the Port 4 communications interface COM-
MINF setting to select between EIA-485 and EIA-232.
The serial port EIA-485 plug-in connector accepts wire size AWG 24 through
AWG 12. Strip the wires 8 mm (0.31 inches) and install with a small slotted
screwdriver. All EIA-232 ports accept 9-pin D-subminiature male connectors.
For connecting devices at distances farther than 100 feet, where metallic cable
is not appropriate, SEL offers fiber-optic transceivers or the fiber-optic port.
The SEL-2800 family of transceivers provides fiber-optic links between
devices for electrical isolation and long-distance signal transmission. Contact
SEL for further information on these products.
IRIG-B Time-Code Input
The SEL-751 accepts a demodulated IRIG-B time signal to synchronize the
internal clock with an external source. Three options for IRIG-B signal input
are given, but you should use only one at a time. You can use IRIG-B (B01 and
B02) inputs or an SEL communications processor via EIA-232 serial Port 3.
The available communications processors are the SEL-2032, SEL-2030,
SEL-2020, and the SEL-2100 Logic Processor. You can also use the
SEL-3530 Real-Time Automation Controller (RTAC) to provide IRIG-B
input.
The models with fiber-optic Ethernet and dual copper Ethernet do not have
the terminals B01 and B02 for IRIG-B but have IRIG-B input via EIA-232
Port 3. The third option for IRIG-B is via fiber-optic serial Port 2. Use an
SEL-2812MT Transceiver to connect to the SEL-2030, SEL-2032, or
SEL-3530 RTAC and bring the IRIG-B signal with the EIA-232 input. Use a
fiber-optic cable pair with ST connectors (SEL-C805 or SEL-C807) to con-
nect to Port 2 on the SEL-751. Refer to Section 7: Communications for details
on IRIG-B connections examples and on SEL-2401/2407/2404 for time
source.
Contact with instrument terminals can
cause electrical shock that can result
in injury or death.
Equipment components are sensitive
to electrostatic discharge (ESD).
Undetectable permanent damage can
result if you do not use proper ESD
procedures. Ground yourself, your
work surface, and this equipment
before removing any cover from this
equipment. If your facility is not
equipped to work with these
components, contact SEL about
returning this device and related SEL
equipment for service.
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