R.7.9
Date Code 20111215 Reference Manual SEL-421 Relay
Synchrophasors
Settings for Synchrophasors
Accuracy
The listed SEL-421 phasor measurement accuracy is valid when frequency-
based phasor compensation is enabled (Global setting PHCOMP := Y), and
when the phasor measurement application setting is in the narrow bandwidth
mode (Global setting PMAPP := N).
See IEEE C37.118 for an explanation of total vector error and for accuracy
definitions and conditions.
The SEL-421 synchrophasor measurement accuracy is:
TVE (total vector error) 1% for one or more of the following influence
quantities:
➤ Signal Frequency Range: ±5 Hz of nominal (50Hz or 60Hz)
➤ Voltage Magnitude Range: 30 V – 150 V
➤ Current Magnitude Range: (0.1 - 2) • I
nom
, (I
nom
= 1A or 5A)
➤ Phase Angle Range: –179.99 to 180°
➤ Harmonic distortion 10% (any harmonic)
➤ Out of band interfering signals 10%
The out of band interfering signal frequency (f
i
) must satisfy:
| f
i
– NFREQ | > MRATE/2,
where NFREQ is nominal system frequency and MRATE is the message rate,
as defined in IEEE C37.118.
Settings for Synchrophasors
The phasor measurement unit (PMU) settings are listed in Table 7.1. Make
these settings when you want to use the C37.118 synchrophasor protocol, or if
you want to use synchrophasor analog quantities.
The Global enable setting EPMU must be set to Y before the remaining
SEL-421 synchrophasor settings are available. No synchrophasor data
collection can take place when EPMU := N.
You must make the serial port settings in Table 7. 3 to transmit data with a
synchrophasor protocol. It is possible to set EPMU := Y without using any
serial ports for synchrophasor protocols. For example, the serial port
MET PM ASCII command can still be used.
The Global settings for the SEL Fast Message synchrophasor protocol are a
subset of the Table 7.1 settings, and are listed separately, see SEL Fast
Message Synchrophasor Protocol on page R.7.31.
NOTE: When the SEL-421 is in the
fast response mode (Global setting
PMAPP := F), the TVE is within
specified limits only when the out of
band interfering signals influence
quantity is not included.
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