Sel SEL-421 - Compressed ASCII Message Format; Compressed ASCII Commands

R.5.5
Date Code 20111215 Reference Manual SEL-421 Relay
SEL Communications Protocols
Protocol Active When Setting PROTO := SEL
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
characters than conventional SEL ASCII reports, because the compressed
reports reduce blanks, tabs, and other white space between data fields to a
single comma.
Compressed ASCII Message Format
Each message begins with the start-of-transmission character, STX, and ends
with the end-of-transmission character, ETX:
<STX><MESSAGE LINE 1><CR><LF>
<MESSAGE LINE 2><CR><LF>
...
<LAST MESSAGE LINE><CR><LF><ETX>
Each line in the message consists of one or more data fields, a checksum field,
and a CRLF. Commas separate adjacent fields. Each field is either a number or
a string. Number fields contain base-10 numbers using the ASCII characters
0–9, plus (+), minus (-), and period (.). String fields begin and end with quote
marks and contain standard ASCII characters. Hexadecimal numbers are
contained in string fields.
The checksum consists of four ASCII characters that are the hexadecimal
representation of the two-byte binary checksum. The checksum value is the
sum of the first byte on a line (first byte following <STX>, <CR>, or
<CR><LF>) through the comma preceding the checksum.
If you request data with a Compressed ASCII command and these data are not
available, (in the case of an empty history buffer or invalid event request), the
relay responds with the following Compressed ASCII format message:
<STX>“No Data Available”“0668”<CR><ETX>
Tab le 5.4 lists the Compressed ASCII commands and contents of the
command responses. The Compressed ASCII commands are described in
Section 9: ASCII Command Reference in the Reference Manual.
where:
No Data Available
is a text string field.
0668 is the checksum field, which is a hexadecimal
number represented by a character string.
Table 5.4 Compressed ASCII Commands (Sheet 1 of 2)
Command Response Access Level
BNAME ASCII names of Fast Meter status bits 0
CASCII Configuration data of all Compressed ASCII com-
mands available at access levels > 0
0
CBREAKER Circuit breaker data 1
CEVENT Event report 1
CHISTORY List of events 1
CSER Sequential Events Recorder report 1
CSTATUS Self-diagnostic status 1
CSUMMARY Summary of an event report 1
DNAME ASCII names of digital I/O reported in Fast Meter 0