Methods of representing the results of voltage fluctuation indices measurements

Voltage variation in power grids is usually described with the use of several measures. One of them is the group of voltage fluctuation indices which concern the δU magnitude and the f rate. Other measures include the maximum and minimum rms voltage values. The paper describes selected methods of representing the results of voltage fluctuation indices measurements. An magnitude-rate chart has been presented which provides the information about magnitude and rates of voltage fluctuations and makes it possible to assess the obnoxiousness of voltage fluctuations. The paper underlines the fact that such a method of evaluating the obnoxiousness is unique among similar measures as it enables the user to estimate the obnoxiousness of voltage fluctuations for different types of powered loads. The next part of the paper includes the representation of measurement results of the voltage fluctuation indices with the use of time plots of δU = f (t) magnitude and f = f (t) rate. It has been shown that the analysis of the voltage fluctuation indices can be supported with the U
_max
maximum and U
_min
minimum rms voltage values. Analysis of time plots revealed periods of time important from the diagnostic point of view. For these periods obnoxiousness of voltage fluctuations has been assessed and δV values along with its rate has been delimited. On the basis of the f = f (δV) histograms, the voltage changes have been grouped within the selected ranges of the δV values. Finally, the rate of δV occurring has been derived for voltage changes grouped in this manner.