Date Code 20011026
Communications
3-1
SEL-321/321-1 Instruction Manual
SECTION 3: COMMUNICATIONS
I
NTRODUCTION
This section explains the communications protocol. It also gives examples of commands and
front-panel operations for the SEL-321 Relay.
You set and operate the SEL-321 Relay via front-panel controls and serial communications
interfaces. The serial interfaces may be connected to a computer terminal and/or modem. Relay
communication serves these purposes:
•
The relay responds to commands spanning all functions, (e.g., setting, metering, and control
operations).
•
The relay generates an event record for TRIP output assertions, for an event triggering
command, or for the pickup of any relay element that triggers an event record.
•
The relay transmits messages in response to changes in system status, e.g., self-test warning.
•
No priority is set for communications ports. The last settings saved supersede all other
settings. The relay avoids race conditions when two ports are addressed simultaneously.
Note:
In this manual, commands you type appear in bold/uppercase:
OTTER
. Keys you press
appear in bold/uppercase/brackets:
<ENTER>
.
Relay output appears boxed and in the following format:
EXAMPLE: BUS B, BREAKER 3 Date: 02/01/93 Time: 00:03:25.180
C
OMMUNICATIONS
P
ROTOCOL
The communications protocol consists of hardware and software features.
Software Protocol
The following software protocol is designed for manual and automatic communications.
1. All commands received by the relay must be of the form:
<command><CR> or <command><CR><LF>
A command transmitted to the relay should consist of the following:
•
A command followed by either a carriage return or a carriage return and line feed.
•
You may truncate commands to the first three characters.
EVENT 1 <ENTER
>
would become
EVE 1 <ENTER>
.
•
Upper and lower case characters may be used without distinction, except in passwords.
Note
: The ENTER key on most keyboards is configured to send the ASCII character 13
(^M) for a carriage return. This manual instructs you to press the ENTER key after
commands, which should send the proper ASCII code to the relay.
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