R.7.31
Date Code 20111215 Reference Manual SEL-421 Relay
Synchrophasors
SEL Fast Message Synchrophasor Protocol
SEL Fast Message Synchrophasor Protocol
SEL Fast Message Unsolicited Write (synchrophasor) messages are general
Fast Messages (A546h) that transport measured synchrophasor information.
The SEL-421 can send unsolicited write messages as fast as every 50 ms on a
60 Hz system, and 100 ms on a 50 Hz system. Use Global settings PHDATAV,
PHDATAI, and PHCURR to select the voltage and current data to include in
the Fast Message. Table 7.22 and Table 7.23 list analog quantities included in
the Fast Message for various Global settings (frequency is included in all
messages). Not all messages are supported at all data speeds. If the selected
data rate is not sufficient for the given message length, the relay responds with
an error message.
Tab le 7.20 lists the Synchrophasor Fast Message Write function codes and the
actions the relay takes in response to each command.
See SEL Application Guide AG2002-08 for more information on the SEL Fast
Message Synchrophasor protocol. This application guide refers to previous
SEL-421 firmware versions, and the relay-specific portions (pages 1 and 2)
should be disregarded.
Differences in New
SEL-421 Fast Message
Synchrophasor
Implementation
One of the differences between the C37.118 and SEL Fast Message formats
relates to data transmission speed. When the C37.118 format is used, Global
Setting MRATE determines the message rate—the synchrophasor processor
cannot request a data rate via the enable message.
In the SEL Fast Message format, the synchrophasor processor must request a
particular data message period, which is embedded in the enable message. If
the requested message period can be supported, the SEL-421 will
acknowledge the request (if an acknowledge was requested) and begin
transmitting synchrophasors. If the requested message period is not permitted,
the SEL-421 will respond with a bad data message (if an acknowledge was
requested), and will not transmit any synchrophasor data.
Table 7.20 Fast Message Command Function Codes for Synchrophasor
Fas t Wr ite
Function Code (Hex) Function Relay Action
00h Fast message
definition block
request
Relay transmits Fast Message definition
request acknowledge (Function Code 80)
01h Enable unsolicited
transfer
Relay transmits Fast Message command
acknowledged message (Function
Code 81). Relay transmits Synchropha-
sor Measured Quantities (function to
enable: Unsolicited Write broadcast,
Function Code 20)
02h Disable unsolicited
transfer
Relay sends Fast Message command
acknowledge message (Function
Code 82) and discontinues transferring
unsolicited synchrophasor messages
(function to disable: Unsolicited Write
broadcast, Function Code 20)
05h Ping: determine if
channel is operable
Relay aborts unsolicited message in
progress and transmits ping acknowledge
message (Function Code 85)
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