R.5.8
SEL-421 Relay Reference Manual Date Code 20111215
SEL Communications Protocols
Protocol Active When Setting PROTO := SEL
Automatic Messages
If you enable automatic messages, AUTO = Y, the SEL-421 issues a message
any time the relay powers up, asserts a self-test, changes to another settings
group, or triggers an event. For virtual ports, the relay issues automatic
messages only if the connection is active. Automatic messages contain the
following information:
➤ Power up: On power up, the message provides the terminal ID
and the present date and time.
➤ Self-test failure: When the relay detects an internal failure, the
automatic message is the same as the relay response to the
STATUS command.
➤ Group switch: Whenever a settings group change occurs, the
message contains the relay ID, terminal ID, present date and
time, and the selected settings group.
➤ Events: When the relay triggers an event, the automatic
message is the same as the relay response to the SUMMARY
command.
Timeout
Use the TIMEOUT setting to set the idle time for each port. Idle time is the
period when no ASCII characters are transmitted and received (interleaved
fast messages do not affect the idle time). When the idle time exceeds the
TIMEOUT setting, the following takes place:
➤ The access level changes to Access Level 0.
➤ The front-panel targets reset to TAR 0 if the port had previously
remapped the targets.
➤ Virtual connections are disconnected.
➤ The software flow control state changes to XON.
When set to OFF, the port never times out.
SEL Fast Meter, Fast
Operate, and Fast SER
Messages
SEL Fast Meter is a binary message that you solicit with binary commands.
Fast Operate is a binary message for control. The relay can also send
unsolicited Fast SER messages automatically. If the relay is connected to an
SEL communications processor, these messages provide the mechanism that
the communications processor uses for SCADA or DCS functions that occur
simultaneously with ASCII interaction. Reference the section, Interleaved
ASCII and Binary Messages on page R.5.7 and Section 6: SEL
Communications Processor Applications in the Applications Handbook.
This section summarizes the binary commands and messages and includes our
recommendation for using Fast Commands and Compressed ASCII
configuration information to communicate with the relay. You need this
information to develop or specify the software an external device uses to
communicate using Fast Messages with the SEL-421. To support this type of
development, you will also need to contact SEL for Fast Message protocol
details.
Tab le 5.5 lists the two-byte Fast Commands and the actions the relay takes in
response to each command.
NOTE: Starting with firmware
revision R112, synchrophasor data in
the SEL Fast Message format is no
longer available when PROTO:= SEL.
See Section 7: Synchrophasors for
details.
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