Power Quality Logger
Instrument and Logging Setup
31
Rapid Voltage Changes
Rapid voltage changes (RVC) are quick transitions of the RMS
voltage between two steady states. Rapid voltage changes are
captured based on RVC threshold. RVC threshold are set as
percentage of the nominal voltage and the threshold level is calculated
over the preceding 100/120
U
rms(1/2)
values. (100/120 is defined as
100 values for 50 Hz nominal or 120 values for 60 Hz nominal.) An
RVC Event is detected when the arithmetic mean of 100/120
U
rms(1/2)
values falls outside the an RVC threshold. When a voltage change
crosses the dip or swell thresholds, it is considered a dip or swell and
not a rapid voltage change. The event list shows the voltage step,
transition time, and Vmax. See Figure 12.
Parameters to configure:
•
Trigger on/off
•
Limit
The voltage Threshold limit value is defined as % of nominal
voltage. The values is typically in the range of 1% to 6%. The RVC
hysteresis shall be less than the RVC threshold and is typically
50 % of the RVC.
Waveform Deviation
The Waveform Deviation trigger monitors the differences in the
waveforms of consecutive voltage cycles. Each sample magnitude of
the last cycle is compared with the sample magnitude of the actual
cycle. The trigger starts when the difference exceeds the configured
limit and ends when the difference is lower than the threshold minus
the hysteresis. If a waveform deviation triggers starts within one
second after the previous waveform deviation trigger ended, it is
combined to one event.
