4 - Running the Test
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display. The tabular data displayed in this window provides a permanent record of the test conditions that
existed at the time of the voltage fluctuations test.
ñThe Measured Values area on the right side of the display provide a record of the test conditions
at the time the voltage fluctuations pre-test was run.
ñThe Output Impedance of the Harmonic/ Flicker Test System is automatically set to the
requirements of IEC 1000-3-3 when testing for Voltage fluctuations. For 230 V/50 Hz power
distribution systems, the reference value is 0.4 + j 0.25 Ω (lumped phase and neutral per IEC
725). This corresponds to 796 µH for the inductive component.
NOTE: The output impedance is set to a minimum during the pre-test. This is done to permit
evaluation of ac source performance under the worst-case loading condition possible for
the equipment under test.
Pre-test Measurements
Pre-test measurement data is collected using the following measurement processes:
Measurement Method Measurement Method
Rms voltage Rms Power factor Watts/VA
Frequency One-shot Voltage THD One-shot
Rms current Rms Current THD One-shot
Peak Current Estimated Voltage harmonics Peak
Real power Average Current waveform One-shot
Apparent power Vrms x Irms
Average, rms, and peak measurements are based on a long-term acquisition process that is
determined by the duration time specified in the Pre-test window. Varying the test duration time
increases the amount of data upon which the measurements are based.
ñAverage measurements are made by acquiring N measurements, totaling the acquired values, and
multiplying by 1/N.
ñRms measurements are made by acquiring N measurements, totaling the square of the values,
multiplying by 1/N, and then taking the square root. Vrms and Irms values returned with the pre-
test data are used to calculate Vrms and Irms over integration periods specified by the pre-test
duration control.
ñPeak method measurements are made by returning the highest value obtained during the
specified integration period.
ñVoltage THD is calculated by:
()THD n
Max harmonic
nto
rms
V
==∑2
240 100
_
*
For voltage harmonics, this is the highest rms value encountered during the pre-test for each
individual voltage harmonic.
ñThe Estimated peak current measurement is implemented by multiplying the integrated Irms
value by the crest factor of the current waveform. Crest factor is calculated by dividing the peak