Power and Voltage Quality Trainer
AD 2
– MI 3399
199
As sudden changes (such we can
observe) can’t be seen on steady RMS
measurements, the next step is to check minimum and maximum RMS values for each
phase. Note that before observing, the RESET key (F2) should be pressed, in order to
clear all previous values. As can be seen from the figure below, MAX and MIN values
are significantly different from the average value, which clearly indicates that we are
dealing with sudden changes on voltages (similar to dip/swell).
Measured every half cycle
(100 times per second)
Measured over 10 cycle
(5 times per second)
Figure 4-92: Half cycle minimal and maximal Voltage values
In such cases it is best to try to catch disturbance with a waveform recorder. Below is
a WAVEFORM SETUP screen, which was setup according to the measured minimum
voltage from the previous figure.
Figure 4-93: Waveform recorder setup parameters
After the WAFEFORM RECORDER is correctly setup, press the START button (Key
F1). Phase shifting should occur within10 seconds. During the phase shift the RMS
voltage will be changed, which triggers the waveform recorder. The captured waveform
can be observed in the figure below, where disturbance can be seen. By carefully
observing the waveform shape, we can
notice that the waveform shape before and after the disturbance is not the same. This
indicates that we have a problematic switching event where the phase sequence is
changed.
Summary of Contents for MI 3399
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Page 46: ...Electrical Installation Safety Trainer AD 1 MI 3399 46 3 Exit settings...
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