Date Code 20080918 Instruction Manual SEL-749M Relay
Section 7
Communications
Overview
A communications interface and protocol are required for communicating
with the SEL-749M Motor Protection Relay.
A communications interface is the physical connection on a device. Serial
ports that conform to the EIA-232 standard (often called RS-232) use DB-9 or
DB-25 connectors as the physical interface.
Once you have established a physical connection, you must use a
communications protocol to interact with the relay. A communications
protocol is a language used to perform relay operations and collect data.
The first part of this section describes communications interfaces and
protocols available with the relay, including communication interface
connections. The remainder of the section describes the ASCII commands
used with the EIA-232 serial port(s).
Communications Interfaces
The SEL-749M physical interfaces are shown in Table 7.1. Several optional
SEL devices are available to provide alternative physical interfaces, including
EIA-485 and fiber-optic cable.
Ta b l e 7.1 S E L -74 9 M P o r t In te r f ac e s
Port Serial Port Interface
PORT 1 Reserved
PORT 2 Rear fiber-optic port RTD MODULE RX
This port receives the RTD measurement information from the optional
external SEL-2600 RTD Module RTD module. Refer to the SEL-2600
RTD Module Instruction Manual for information on the fiber-optic inter-
face.
PORT 3 EIA-232
PORT 4
(Optional)
Option 1: EIA-232 or EIA-485
Option 2: DeviceNet
Rear-panel DeviceNet port (available only with the optional DeviceNet
protocol card). Refer to Appendix E: DeviceNet for information on the
DeviceNet communications card.
PORT F EIA-232
Courtesy of NationalSwitchgear.com
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