Research On The Location Method Of Partial Discharge In Power Cable

In recent years,with rapid development of manufacturing technology of power cable at home and abroad,the amount of operation circuit is growing fast. In order to ensure the safety of transmission network, The detection technique of power cable causes the attention of many experts from home to abroad. Therefore, one of the hot researches is the one on the online detection of power cable partial discharge and its location technology.This paper studies and analyzes the transmission characteristics of its discharge mechanism and PD signals. It builds cable model with skin effect and applies MATLAB to the simulation analysis. The result of simulation analysis is that the factors affecting discharge are the length of cable, the equivalent inductance and equivalent capacitance. With those values increasing, PD amplitude attenuates badly and high frequency component attenuates faster than the low one and the time-delay is longer.Through the theoretical analysis of correlation function, applying the calculation method of related time-delay estimation to the location technology in power cable PD, it proposes the method of direct and related time-delay estimation. The result of applying MATLAB to the simulation analysis shows the calculation method of direct and related time-delay estimation is simple and intuitive. When snr is -3dB, this method can estimate the time delay of PD signals with different lengths of cable. When snr reduced,the value of this method time-delay estimation is not high or even can not estimated. Therefore, locating the power cable PD with this method has great interference effect and the resolution is not high and stable.In order to cancel the restricted conditions of this method and improve precision of power cable PD, this paper carries out the simulating calculation with applying wavelet Packet transform to direct and related time-delay estimation.The result shows when snr is -10dB, the method based on wavelet Packet transform can relocate precisely the short or long power cable PD in its detection, showing the little effect on signal attenuation. It can be applied to the detection of power cable PD relocation, but its time-delay estimation is growing worse and worse.