Abstract-A new method for voltage dips and swells analysis is presented in this paper. This method is based on the space vector representation in the complex plane and the zero-sequence voltage. Indeed, in the case of nonfaulted system voltages, the space vector follows a circle in the complex plane with a radius equal to the nominal voltage. It follows the same shape for balanced dips, but with a smaller radius. For unbalanced dips, this shape becomes an ellipse with parameters depending on the phase(s) in drop, dip magnitude and phase angle shift. For swells the space vector shape is not modified, though the zero-sequence voltage presents significant changes in its phase and magnitude and can be used for swells analysis. The changes in the space vector and the zero-sequence voltage are used to determine the dip/swell time occurrence, to classify and finally characterize the measured power-quality disturbance. Algorithms are developed for each step of this automatic voltage dips and swells analysis (segmentation, classification, and characterization) and are validated on real measurement data.
A new method is presented to identify and to characterize voltage dips measurements from power quality survey. This method is based on the space vector transformation, which describes the three power system voltages by one complex variable-the space vector. Its representation in the complex plane is used to classify voltage dips. Indeed, for a not disturbed system voltages, the space vector represents a circle in the complex plane with a radius equal to the nominal voltage. It follows the same shape for balanced dips, but with a smaller radius. For unbalanced dips, this shape becomes an ellipse with parameters depending on the phase(s) in drop, dip severity and phase angle shift. Further, space vector characteristics and zero sequence voltage are used for a more precise determination of the voltage dip type. The developed algorithm for voltage dips classification is validated by EMTP simulations and measurement data.
Power Quality surveys and studies show that the major part of end users has limited knowledge on power quality and its possible impact on equipment and installation. Even when power quality monitoring systems are in place, end users have difficulties to follow, understand, analyze and exploit power quality measurements. The purpose of this paper is to introduce simple green-yellow-red indicators for each power quality problem. Easy to understand and integrate in a power quality monitoring system, they are based on recognized power quality standards and statistical analysis. This paper introduces as well a Power Quality Index, summarizing the global power quality level.
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