I.13
Date Code 20170927 Instruction Manual SEL-751 Relay
Synchrophasors
View Synchrophasors Using the MET PM Command
The Relay Word bit PMDOK indicates that the phasor measurement data are
acceptable and asserts under the following conditions.
For the SEL-751 models with the voltage option:
➤ The relay is enabled
➤ EPMU = Y
➤ IRIGOK = 1
➤ TSOK = 1
➤ The synchrophasor filter buffers are fully primed
➤ The magnitude of the positive-sequence voltage, |V1| > 10 V
➤ The frequency is 40–70 Hz
For the SEL-751 models with the currents only option:
➤ The relay is enabled
➤ EPMU = Y
➤ IRIGOK = 1
➤ TSOK = 1
➤ The synchrophasor filter buffers are fully primed
➤ The magnitude of the positive-sequence current,
|I1| > 0.1 • I
NOM
(I
NOM
=1A or 5A)
➤ The frequency is 40–70 Hz
PMDOK takes 15 seconds to assert when the relay is first powered, after any
of the settings in Table I .1 are changed, or when an IRIG-B time signal is first
connected. This is due to the delay in time qualification (TSOK to assert).
View Synchrophasors Using the MET PM Command
You can use the MET PM serial port ASCII command to view the SEL-751
synchrophasor measurements. See MET Command (Metering Data) on
page 7.42 for general information on the MET command.
There are multiple ways to use the MET PM command:
➤ As a test tool, to verify connections, phase rotation, and scaling
➤ As an analytical tool, to capture synchrophasor data at an exact
time and to compare it with similar data captured in other
phasor measurement unit(s) at the same time
➤ As a method of periodically gathering synchrophasor data
through a communications processor
The MET PM command displays the same set of analog synchrophasor
information, regardless of the Global settings PHDATAV and PHDATAI. The
MET PM command can function even when no serial ports are sending
synchrophasor data—it is unaffected by serial port setting PROTO.
The MET PM command only operates when the SEL-751 is in the IRIG
timekeeping mode, as indicated by Relay Word bit TSOK = logical 1.
NOTE: To have the MET PM xx:yy:zz
response transmitted from a serial
port, the corresponding port must
have the AUTO setting set to Y (YES).
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