Single-Event Characteristics for Voltage Dips in Three-Phase Systems

Abstract

This paper compares different methods for voltagedip characterization. Those methods are based on earlier proposed algorithms for extracting three-phase characteristics (dip type, characteristic voltage, and so-called "PN factor"). The difference between the 12 methods being studied in this paper is in the way in which the time variation of those characteristics is treated to result in single-event characteristics. The methods are applied to 259 measured voltage dips and the performance of the different methods is compared. It is found that small differences in method can result in big difference in results. From the comparison, two methods are selected and recommended for inclusion in international standards.

An Adaptive Approach for Voltage Sag Automatic Segmentation

“…If transition segments cannot be detected, it would result in the wrong result (more than 3% unbalance instead of 1%). The impacts of segmentation on other characteristics can be found in some published works, where segmentation is considered to be an unsolved problem [9,10]. In general, the inaccuracy of segmentation sometimes may result in an unacceptable error in the characteristics calculation.…”

“…Since most sag events are caused by faults, which are more To improve the characterization method, the magnitude and phase variation with time, as well as the difference between each phase, are taken into consideration. Some characteristics, e.g., "single-event characteristics" and "single-segment characteristics", are introduced in [8][9][10]. Besides magnitude and duration, which are defined in standards [1][2][3][4], additional characteristics are required, e.g., the sag type [9], phase-angle jump [10], point-on-wave [15], unbalance [1,16], etc.…”

“…Some characteristics, e.g., "single-event characteristics" and "single-segment characteristics", are introduced in [8][9][10]. Besides magnitude and duration, which are defined in standards [1][2][3][4], additional characteristics are required, e.g., the sag type [9], phase-angle jump [10], point-on-wave [15], unbalance [1,16], etc. In general, segmentation is a prerequisite process to obtain these characteristics that helps network operators and end-users to analyze sag events completely.…”

“…In response to the above needs, the standard method has been recognized as insufficient, and improved characterization methods have been studied [7][8][9][10][11][12]. Among these methods, one generally accepted method has been proposed by an international working group (CIGRE/CIRED/UIE JWG C4.110).…”

“…However, from a practical standpoint, it does not specify how to divide the recorded waveforms, i.e., automatic segmentation. Although a visual inspection is often implemented in characteristics calculations [9,10], this manual method mainly depends on human experience, and is not practicable for the analysis of enormous volumes of data. Reference [13] is probably the pioneering work in automatic segmentation for voltage sags.…”