Research On The Application Of Low Voltage Pulse Method In Cable Fault Location

Power cable fault occurs regularly in power system. Fault location is the precondition to eliminate the fault. Accurate fault location can reduce the time to find out the fault point and the cost of power cable cut. This paper has carried on the low voltage pulse experiment to the cable of different lengths. The law in the cable of low voltage pulse is known well through time-frequently analysis on the data, and the new solution to the problem that appeared in the experiment is put forward. Because of the loss of cable, the traveling wave is distorted and the reflect pulse rise becomes slowly, which don't benefit to the accurate judge of start point of the reflect wave. The curve fit method is proposed to compute the start point of reflection wave, and the least squares method is used to fit the data of reflect pulse rise. The wave cross zero point is the considered as the start point of reflection wave. The conic section method is adopted to revise the result. The results show that the start points of reflect wave can be distinguished accurately. The absolute error is no more than 3 sampling points, so it has more advantages compared with the traditional methods to judge the start point of reflect wave.The real signal often influenced by various kinds of noises, which reduce the SNR of gathering signal and put blight on fault location. The improved wavelet soft-threshold method is presented based on the different propagation property of real signals and white noises under the wavelet transform. It can accelerate the separation of the signal from the noise and get higher SNR for the reconstructed signal.