18.25
Date Code 20171006 Instruction Manual SEL-400 Series Relays
Synchrophasors
C37.118 Synchrophasor Protocol
Referring to Table 18.13 and Table 18.14, it is clear that the lower SPEED set-
tings are very restrictive.
The smallest practical synchrophasor message would be comprised of one syn-
chrophasor and one digital status word, and this message would consume
between 26 and 34 bytes, depending on the numeric format settings. This type of
message could be sent at any message rate (MRATE) when SPEED := 38400 or
57600, as fast as MRATE := 50 or 30 when SPEED := 19200, and as fast as
MRATE := 25 or 20 when SPEED := 9600.
Another example application has messages comprised of eight synchrophasors,
one digital status word, and two analog values. This type of message would con-
sume between 62 and 98 bytes, depending on the numeric format settings. The
62-byte version, using integer numeric representation, could be sent at any mes-
sage rate (MRATE) when SPEED := 57600. The 98-byte version, using floating-
point numeric representation, could be sent at as fast as MRATE := 30 when
SPEED := 57600, as fast as MRATE := 25 when SPEED := 38400, and as fast as
MRATE := 12 when SPEED := 19200.
Protocol Operation
The relay will only transmit synchrophasor messages over serial ports that have
setting PROTO := PMU. The connected device will typically be a synchrophasor
processor. The synchrophasor processor controls the PMU functions of the relay,
with IEEE C37.118 commands, including commands to start and stop synchro-
phasor data transmission, and commands to request a configuration block from
the relay, so the synchrophasor processor can automatically build a database
structure.
Transmit Mode Control
The relay will not begin transmitting synchrophasors until an enable message is
received from the synchrophasor processor. The relay will stop synchrophasor
transmission when the appropriate command is received from the synchrophasor
processor. The relay can also indicate when a configuration change occurs, so the
synchrophasor processor can request a new configuration block and keep its data-
base up-to-date.
The relay will only respond to configuration block request messages when it is in
the nontransmitting mode.
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 syn-
chrophasor messages, while the other port is idle, responding to a configuration
block or Fast Operate request, or transmitting synchrophasors. The ports are not
30 (60 Hz only) 22 45 90 136
50 (50 Hz only) 27 54 81
60 (60 Hz only) 22 45 68
Table 18.14 Serial Port Bandwidth for Synchrophasors (in Bytes) (Sheet 2 of 2)
Global Setting
MRATE
Port Setting SPEED
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