R.7.36
SEL-421 Relay Reference Manual Date Code 20111215
Synchrophasors
SEL Fast Message Synchrophasor Protocol
Some observations from Table 7.28:
➤ A serial port set with SPEED := 38400 or 57600 can handle any
size message at any data rate.
➤ A serial port set with SPEED := 19200 can handle a single-
synchrophasor or four-synchrophasor message at any data rate,
and any size message up to 10 messages per second.
➤ A serial port set with SPEED := 9600 can handle a single-
synchrophasor message at any data rate, a four-synchrophasor
message at up to 10 messages per second, and any size message
at up to 5 messages per second.
➤ A serial port set with SPEED := 300 cannot be used for Fast
Message synchrophasors.
Protocol Operation
The SEL-421 will only transmit synchrophasor messages over serial ports that
have setting PROTO := PMU. The connected device will typically be a
synchrophasor processor, such as the SEL-3306. The synchrophasor processor
controls the PMU functions of the SEL-421, with SEL Fast Message
commands, including commands to start and stop synchrophasor data
transmission, and commands to request a configuration block from the relay,
so the synchrophasor processor determine the correct configuration for storing
the synchrophasor data.
Transmit Mode Control
The SEL-421 will not begin transmitting synchrophasors until an enable
message is received from the synchrophasor processor. The relay will stop
synchrophasor transmission on a particular serial port when the disable
command is received from the synchrophasor processor, or when the relay
settings for that port are changed. The SEL-421 will stop synchrophasor
transmission on all serial ports when any Global settings change is made.
The SEL-421 will respond to configuration block request messages regardless
of the present transmit status, waiting only as long as it takes for any partially-
sent messages to be completely transmitted.
The SEL-421 will respond to a Ping request immediately upon receipt,
terminating any partially sent messages.
Independent Ports
Each serial port with the PROTO := PMU setting is independently configured
and enabled for synchrophasor and Fast Operate commands. For example, if
there are two serial ports set to PROTO := PMU, the status of one port has no
effect on the other port. One port might be commanded to start transmitting
synchrophasor messages, while the other port is idle, responding to a
configuration block or Fast Operate request, or transmitting synchrophasors.
The ports are not required to have the same SPEED setting, although the
SPEED setting on each PROTO := PMU port will affect the minimum
synchrophasor message data period that can be used on that port.
To Next Page
Loading...
