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The definition and the method to characterize a rapid voltage change (RVC) are defined in the standard IEC 61000-4-30. Other standards, such as IEC 61000-3-7, IEC 61000-2-12 or EN 50160, limit the number and magnitude of RVCs for compatibility level or for planning levels in medium and low voltage public supply systems. Those limits control the effect of RVCs on light flicker. This work analyses the...
Rapid voltage changes are a type of power quality disturbance that has not received sufficient attention in the international power quality standards. IEC 61000-4-30, Ed. 3, will introduce a precise method for their detection and analysis. This paper reviews the definitions and the international regulations on RVCs reports some of the results obtained in the measurement of RVCs in different power...
A simple method for real-time synchronization of power quality measurements in low-voltage supply systems is presented. Proper synchronization between the data acquisition window and the power system frequency is necessary to accurately measure the harmonic distortion. The proposed method is based on the use of the standard Discrete Fourier Transform method using a 10-cycle width rectangular window...
Wavelet transform is, at present, one of the most useful digital signal processing tools for time-frequency analysis of power quality disturbances in power systems. This paper presents a review of the applications of wavelet transforms in the measurement and analysis of harmonic distortion in power systems, discussing the performance, advantages and limitations of the different methods proposed in...
The performance of three-phase induction motors can be severely affected by poor power quality supply, decreasing their efficiency and their life expectancy. Voltage unbalance, voltage magnitude deviation and voltage distortion are the electrical power quality disturbances that most affect the performance of these motors. This paper presents a low-cost virtual measurement instrument for on-line monitoring...
This paper presents the structure and the performance of a low-cost VI-based measurement instrument for assessment of voltage unbalance in a low-voltage distribution system. The system enables the continuous monitoring of the magnitude of the three phase-to-phase voltages and the voltage unbalance factor, as well as their statistical analysis. The instrument developed can be used as a protection scheme...
This paper presents a low-cost virtual instrument for detection and analysis of voltage notches in voltage supply using wavelets. A simple wavelet decomposition tree has been used for detection and analysis of the two main features of voltage notching: the transients associated with the beginning and the end of the commutation notches and the stationary high-frequency components of the spectrum of...
This paper presents a real-time implementation of wavelet transforms for detection and analysis of power quality disturbances in power systems. The paper describes the method used for the implementation of the discrete or packet wavelet transforms in a virtual measurement instrument. The system developed allows the selection of the mother wavelet, the sampling frequency and the decomposition tree...
This paper presents the results of the monitoring of subharmonic voltages in a low-voltage distribution network using an IEC harmonic measurement instrument. The time evolution and the statistical analysis of the r.m.s. voltage magnitude of the subharmonic group and subgroup, defined as grouping of the output bins of an IEC harmonic measurement instrument below 50 Hz, are investigated in a low-voltage...
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