18.4
SEL-400 Series Relays Instruction Manual Date Code 20171006
Synchrophasors
Synchrophasor Measurement
After low-pass filtering, the data are decimated to the nominal power system fre-
quency (NFREQ).
If frequency-based phasor compensation is enabled (PHCOMP = Y), the relay
calculates a compensation factor based on the measured synchrophasor fre-
quency (FREQPM) and filter configuration (based on NFREQ, MRATE, and
PMAPP). The PMU then corrects the measured synchrophasors by this factor.
Using the VmCOMP and InCOMP settings, the PMU compensates the voltage
and current synchrophasors for any externally introduced phase angle errors. The
PMU adds the user-entered phase angle to the phase angle of the measured syn-
chrophasor.
The PMU converts the synchrophasor data to primary units by multiplying them
with the respective PT or CT ratios. Note that the resulting data VkmSF and
IknSF is in complex form (A + jB). The PMU calculates the positive-sequence
synchrophasor with the three-phase synchrophasors.
The PMU then converts all synchrophasor data to polar and rectangular quanti-
ties. The data are available as analog quantities as well as for the synchrophasor
data frames. The synchrophasor data are updated at the nominal power system
frequency.
Accuracy
The following phasor measurement accuracy is valid when frequency-based pha-
sor compensation is enabled (Global setting PHCOMP := Y), and when the pha-
sor measurement application setting is in the narrow bandwidth mode (Global
setting PMAPP := N).
NOTE: When the PMU 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.
TVE (total vector error) 1% for one or more of the following influence quantities.
➤ For PMAPP = N Signal Frequency Range: ±5 Hz of nominal
(50 or 60 Hz)
➤ For PMAPP = 1 Signal Frequency Range: ±2 Hz of 60 Hz
➤ Voltage Magnitude Range: 30 V–150 V
➤ Current Magnitude Range: (0.1–2) • I
NOM
, (I
NOM
= 1 A or 5 A)
➤ Phase Angle Range: –179.99° to 180°
➤ Harmonic distortion 10 percent (any harmonic)
➤ Out of band interfering signals 10 percent
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.
It is important to note that the synchrophasors can only be correlated when the
PMU is in HIRIG or HPTP timekeeping mode, which can be verified by monitor-
ing the TSOK Relay Word bit. When TSOK = logical 1, the PMU timekeeping is
synchronized to the high-accuracy IRIG-B signal or PTP time source, and the
synchrophasor data are precisely time-stamped. See Section 11: Time and Date
Management for details.
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