Robust Time Delay Estimation Method for Locating UHF Signals of Partial Discharge in Substation

Partial-discharging (PD) test is one of the most effective methods for insulation diagnosis. Because of the advantages of ultra-high frequency (UHF) electromagnetic wave, UHF signals radiated by PD have been widely used to locate faults on power equipment. Time delay estimation is not only on the basis of the PD localization algorithm, but is also the key in determining the localization accuracy. Currently, common methods are the threshold value method, energy accumulation method, and the cross-correlation analysis method, etc. However, field signals always include a variety of unknown noises, so common methods cannot be effective enough. This paper proposes time delay estimation algorithms based on four-order cumulant and bispectrum, and gives their computational realization. These algorithms have a prominent advantage of being insensitive to Gaussian noises with unknown correlation properties. The time delay of simulated UHF signals with Gaussian noises and fixed-frequency interference is estimated by the given algorithms. Numerical robustness of the algorithms is verified. Finally, time delays of field UHF signals received by UHF antennas are estimated, and then substituting the sequence of time delay estimations into the localization equations based on the time difference and 3-D coordinate of the PD source can be calculated accurately. The effectiveness and practicability of this algorithm are verified.