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15.4
SEL-400 Series Relays
Instruction Manual
Date Code 20171006
Communications Interfaces
Serial Communication
The +5 V serial port supply that is common to all three rear serial ports is moni-
tored by the relay. If the +5 V supply is overloaded, the relay issues an
HALARM warning (pulses HALARM bit for 5 seconds) and displays a port
overload message in the relay status report. The serial port keeps working,
regardless of this condition.
EIA-232 Communications Cables
For most installations, you can obtain information on the proper EIA-232 cable
configuration from the SEL-5801 Cable Selector Program. Using the SEL-5801
software, you can choose a cable by application. The software provides the SEL
cable number with wiring and construction information, so you can order the
appropriate cable from SEL or construct one. If you do not see information for
your application, please contact SEL and we will assist you. You can obtain a
copy of the SEL-5801 software by contacting SEL or from selinc.com.
Severe power and ground problems can occur on the communications ports of
this equipment as a result of using non-SEL cables. Never use standard null-
modem cables with this equipment.
You can connect to a standard 9-pin computer port with an SEL-C234A cable for
relay configuration and programming with a terminal program or with the
AC
SEL
ERATOR
QuickSet SEL-5030 software.
Fiber-Optic Interface
You can add transceivers to the EIA-232 ports to use fiber-optic cables to connect
devices. We strongly recommend that you use fiber-optic cables to connect
devices within a substation. Power equipment and control circuit switching can
cause substantial interference with communications circuits. You can also experi-
ence significant ground potential differences during fault conditions that can
interfere with communications and damage equipment. Fiber-optic cables pro-
vide electrical isolation that increases safety and equipment protection.
Use the SEL-2800 product family transceivers for multimode or single-mode
fiber-optic communications. All of these transceivers are port powered, require
no settings, and operate automatically over a broad range of data rates. SEL-2800
series transceivers operate over the same wide temperature ranges as SEL relays,
providing reliable operations in extreme conditions.
EIA-485
There is no EIA-485 port integral to the relay. You can install an SEL-2885 or
SEL-2886 transceiver to convert one of the rear-panel EIA-232 ports (
PORT 1
–
PORT 3
) on the relay to an EIA-485 port. The SEL-2885 and SEL-2886 are pow-
ered by the +5 Vdc output on Pin 1. These transceivers offer transformer isolation
not found on most EIA-232-to-EIA-485 transceivers. See the transceiver product
fliers for more information.
The SEL-2885 offers the SEL Distributed Port Switch Protocol (LMD). With this
protocol you can selectively communicate with multiple devices on an EIA-485
network. You can communicate with other network nodes including EIA-232
devices with an SEL-2885 and SEL devices having integral EIA-485 ports. You
can find more information about using SEL LMD in
Summary of Contents for SEL-421-4
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