Time-frequency analyses of disturbances in power distribution systems
Keywords:power quality, time-frequency analyses, short-time Fourier transform, continuous Wavelet transform, Wigner-Ville distribution, Hilbert-Huang transform
AbstractFuture smart distribution grids will apart from a large number of measurement instruments, communication infrastructure, intelligent software etc., also require the appropriate techniques for analysis of the available signals. Various disturbances of different intensities constantly occur in real distribution systems. Many of them are just temporary while others cause the tripping of protection devices and the suspension of electricity supply. For distribution network operators, timely identification and adequate analysis of disturbances represent a very important segment of operation of electricity distribution networks. In this paper, the disturbance registered in the real distribution system of Bosnia and Herzegovina is analysed using four different time-frequency analysis techniques (Short-Time Fourier Transform (STFT), Continuous Wavelet Transform (CWT), Wigner-Ville Distribution (WVD) and Hilbert-Huang Transform (HHT)). The results show that all the applied techniques successfully identified the disturbance which is reflected in changes in frequency during the observed time period. These techniques could be suitable to be applied as a part of power quality monitoring systems, which provide the required measurement signals. The utilization of these techniques can provide distribution system operators with additional, a very important information about the distribution system.
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