, Volume 95, Issue 4, pp 331-340
Date: 16 Nov 2012

A novel way to quantify the magnitude of voltage sag

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Abstract

The magnitude of the voltage sag is accepted as one of the most important parameters for its characterization, classification, and the detection. Hence, the selection of most suitable method to quantify the magnitude of voltage sag is a basic requirement of the power quality (PQ) monitoring. This paper first discusses the three different existing methods, namely root mean square (RMS), peak, and fundamental voltage component methods, to determine the magnitude of the voltage sag. Here, these three methods are applied on test waveform, as provided by the PQ event characterization working groups, to assess the various characteristics of the voltage sag. Further, these characteristics have been compared to highlight the shortfalls of method applied. Additionally, an attempt has been made to propose a hybrid method to quantify the magnitude of the voltage sag. The proposed hybrid method is tested on the same test waveform and compared with the three existing methods available to quantify the magnitude of voltage sag. The results of comparisons show that the proposed hybrid concept reduces the overestimation in sag duration at high-threshold voltage and gives precise detection of overshoot just after the event. The effects of sampling frequency and the length of sliding window to determine the magnitude of the voltage sag are also investigated and the results are discussed in terms of depth, duration, and oscillation. Furthermore, the effect of sampling frequency on phase angle jump is discussed and minimum number of samples per cycle and minimum length of window for proper characterization of the voltage sag are suggested.