4.18
SEL-734 Meter Instruction Manual Date Code 20090730
Metering
Crest Factor Metering
27P1P, Undervoltage Pickup Percent: Phase undervoltage elements, 27A,
27B, 27C, operate using the minimum of the measured phase voltage
magnitudes, operating if any single-phase measurement falls below the set
threshold percent.
Crest Factor Metering
Along with total harmonic distortion, crest factor is an indication of power
quality. A sinusoidal waveform crest factor is 1.414 and a square wave crest
factor is 1.0. The SEL-734 records the maximum and minimum crest factor
metering values.
The SEL-734 uses the equation shown in Equation 4.2 to calculate crest factor
values every second.
Equation 4.2
View or Reset Crest Factor Metering Information
Via Serial Port
See MET CF (Crest Factor Metering) on page 10.19. Use the MET CF
command to display crest factor metering for the following values:
Use the MET R CF command to reset the crest factor metering values.
Via Front Panel
The metering and reset functions available via serial port commands MET CF
and MET R CF are also available via the front-panel pushbuttons. See
Figure 11.3.
Crest Factor Metering
Update and Storage
The crest factor metering function is intended to reflect normal load variations
rather than fault conditions or outages. Therefore, crest factor values are only
updated if the following conditions are met:
➤ DFAULT is deasserted (= logical 0).
➤ For Form 9 voltage values V
A,B,C
or Form 5 voltage values
V
AB,BC,CA
, the voltage is above the corresponding 25.0 V
secondary threshold.
NOTE: Meter Word bit FAULT and
DFAULT also control other Meter
functions.
➤ For current values I
A,B,C,N
, the current is above the
corresponding 0.05 A secondary threshold.
The SEL-734 stores crest factor values the same as maximum/minimum
values.
Crest Factor
Peak Value
RMS Value
----------------------------=
Currents I
A,B,C,N
Input currents (A primary)
Voltages V
A,B,C
Input voltages (kV primary, Form 9 voltage only)
V
AB,BC,CA
Input voltages (kV primary, Form 5 voltage only)
Reset Time Last time the maximum/minimum meter was reset
Courtesy of NationalSwitchgear.com
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