Study on short time charge behavior in pulsed residual charge method for water tree diagnostics of XLPE cables

Water tree generated in insulation parts of the XLPE (Cross Linked Polyethylene) cable is concerned as one of the causes of deterioration or breakdown. For the stable supply of electric power, the facilitated and accurate diagnosis technique is important to measure the deterioration of power cable. In our previous study, we proposed a residual charge measurement method using pulse voltage (charge larder method) and suggested that this method makes it possible the degradation position to measure more accurately than conventional methods. In this method, the deterioration signal is detected when the charge trapped at the tip of water tree is depolarized by the short time pulse voltage. However, quantitative evaluations have not been studied yet. In this paper, we investigated the residual charge behavior around the water tree under pulse voltage application and performed the numerical analysis using Maxwell-Wagner model.