Enhanced Interpolated DFT Based Fault Waveform Analysis for the Primary and Secondary Fusion Switch

In order to meet the special requirements of the primary and secondary fusion of the ground fault test signals of the switch, this paper proposes an enhanced three-point interpolated DFT algorithm to achieve high-precision frequency estimation under the very few cycles. In the firstl, the interference of spectral leakage of image component is analyzed based on the classical three-point interpolation DFT. Then, the spectrum containing image component is constructed by using the spectral characteristics of the Maximum Sidelobe Decay Window (MSDW). Finally, an enhanced three-point interpolated DFT algorithm that considers image component interference is proposed to achieve high-precision frequency estimation under short time sampling, and the standard deviation of the algorithm is derived according to the interpolation formula. Furthermore, the algorithm is applied to the frequency estimation of the measured ground fault waveform, and the results show that the algorithm can effectively and accurately estimate the frequency of signal in very short records.