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Harmonics generation Due to Multi-Cycle Auto Reclosing on HV Transmission Lines

The technology of auto-reclose has been widely used on overhead HV transmission lines in most of power systems. As most of the faults on a transmission line are transient in nature, the auto-reclose can greatly improve the reliability and stability of the power system. The purpose is to make the fault line re-run after the temporary fault elimination. In this work the generation and nature of harmonics during auto reclosing process is investigated using adopted Fourier series instead of Fourier transform. It is found that subharmonics as well as higher order harmonics of the line frequency are generated depending on the type and durations of the reclosing. Also the amplitude and phase-angle relationships of these harmonic components are calculated for multi-pole multi-cycle auto reclosing. The results were verified using fast Fourier transform. It is found that the adopted Fourier series method gives more accurate and clearer results for the nature of harmonics than those based on simulation techniques such as FFT and discrete Wavelet Transform (DWT).