Schweitzer Engineering Laboratories SEL-751 - Table C.1 Supported Serial Command Sets; Appendix C: SEL Communications Processors; SEL Communications Protocols

Date Code 20170927 Instruction Manual SEL-751 Relay
Appendix C
SEL Communications Processors
SEL Communications Protocols
The SEL-751 Feeder Protection Relay supports SEL protocols and command
sets shown in Table C.1.
SEL ASCII Commands
We originally designed SEL ASCII commands for communication between
the relay and a human operator via a keyboard and monitor or a printing
terminal. A computer with a serial port can also use the SEL ASCII protocol
to communicate with the relay, collect data, and issue commands.
SEL Compressed
ASCII Commands
The relay supports a subset of SEL ASCII commands identified as
Compressed ASCII commands. Each of these commands results in a comma-
delimited message that includes a checksum field. Most spreadsheet and
database programs can directly import comma-delimited files. Devices with
embedded processors connected to the relay can execute software to parse and
interpret comma-delimited messages without expending the customization
and maintenance labor necessary to interpret nondelimited messages. The
relay calculates a checksum for each line by numerically summing all of the
bytes that precede the checksum field in the message. The program that uses
the data can detect transmission errors in the message by summing the
characters of the received message and comparing this sum to the received
checksum.
Most commands are available only in SEL ASCII or Compressed ASCII
format. Selected commands have versions in both standard SEL ASCII and
Compressed ASCII formats. Compressed ASCII reports generally have fewer
Table C.1 Supported Serial Command Sets
Command Set Description
SEL ASCII Use this protocol to send ASCII commands and receive ASCII
responses that are human readable with an appropriate termi-
nal emulation program.
SEL Compressed ASCII Use this protocol to send ASCII commands and receive Com-
pressed ASCII responses that are comma-delimited for use
with spreadsheet and database programs or for use by intelli-
gent electronic devices.
SEL Fast Meter Use this protocol to send binary commands and receive binary
meter and target responses.
SEL Fast Operate Use this protocol to receive binary control commands.
SEL Fast SER Use this protocol to receive binary Sequential Events Recorder
unsolicited responses.
SEL Fast Message Use this protocol to write Remote Analog data via unsolicited
writes.