A Frequency Sweep Location Method for Soft Faults of Power Cables Based on MUSIC-Pseudospectrum.

Due to the spurious peaks caused by multireflection and the randomness of the cable transfer function, the frequency domain reflectometry (FDR) method based on Fourier transform (FT) is inaccurate, even resulting in misjudging the soft faults of the cable. Thus, in this article, a frequency sweep location method based on multiple signal classification (MUSIC) pseudospectrum is proposed to accurately diagnose and locate the soft faults. The idea of the method is to extend the cable transfer function into an array signal and estimate the MUSIC-pseudospectrum of the transfer function, which can transform the analysis of uncertain signals into the analysis of deterministic functions. Thus, the impact of the spurious peaks and the randomness of the cable transfer function can be eliminated. First, the transfer function of the cable is obtained by frequency sweep. Then, the soft fault information in the transfer function is extracted and reconstructed by variational mode decomposition (VMD), which has a good ability to divide the harmonic frequency band. The MUSIC-pseudospectrum of the reconstructed signal is estimated to locate the cable soft faults. At last, the feasibility and effectiveness of the proposed method were verified by testing on a laboratory cable and field underground cable.