A fault location method for power cables using time-frequency analysis

The pulse radar method is one of the fault location methods for power cables. It locates the breakdown point by measuring the delay time of the echo or the discharge signal coming from the breakdown point. The equipment for the pulse radar method is more compact compared to the Murray loop bridge, and its operation is simpler because sensitive adjustments to the proportions are not needed. However, the signal propagating through the cable may be distorted, depending on the distance and frequency, leading to poor location accuracy. In this report, signal processing in the timefrequency domain is proposed to resolve this problem. The pulse waveforms received at two different terminals of the cable were extracted by a window function, and subsequently Fourier-transformed in order to calculate the phase difference at an appropriate frequency. Special care was taken for unwrapping the folded phase spectrum. The phase difference was interpreted as the time lag at an identical frequency. The technique was applied to fault location for a full-size XPLE cable line. (c) 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 182(1): 1017, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22323