Unusual voltage sag event detection in power systems

Abstract

Abstract-This paper is organized in twelve sections. In the second section the features extracted from sag waveforms are described. Next, we present the registers of voltage sags. In the fourth to sixth sections, PCA, FA and DA are briefly explained. Later, in the seventh to ninth sections, the results of each technique are shown. Finally, comparison results, conclusion and future works are discussed. II. FEATURES OF VOLTAGE SAGSWe have extracted, from the sags waveforms, a set of features useful to describe duration, magnitude and unbalance degree of sags. They are summarized in Table I This is a new feature we propose in this paper. Gain of zero sequence voltage corresponds as the integral of the RMS zero sequence voltage during the event. It has been computed using the equation 2:(2) 4) I ratio : Ratio between the fundamental frequency component of the currents during and before of voltage sag event. It was previously defined in [6]. 5) T:Voltage sag event duration measured in samples. 6) N seg :Nseg/2 corresponds to number of sag transitory states.Duration, magnitude and unbalanced grade were selected as sag characteristics in order to determine this unusualness. III. DESCRIPTION OF VOLTAGE SAGS:The study has been carried out with 69 registers of sags. All the registers contain 40 cycles, sampled at 128 samples per cycle (50Hz).