Analysis of Pulse Propagation Characteristics for Detection of Water Trees in Power Cables

Abstract

In this paper, characteristics of propagated pulse signals are analyzed for detection of water trees in power cables using simulationbased TDR (Time Domain Reflectometry). COMSOL Multiphysics software is used for time-domain simulations of propagated pulse signals with high frequency components. The water trees with various penetration depths and lengths are modeled by axis-symmetry or 3D geometry, depending on the shapes of the water trees considered. The reflected waveforms and RMS values of the applied diagnostic pulse signals are analyzed according to the shapes and lengths of the water tree models and outer conductor conditions. Also, the propagation velocity of the pulse signal is calculated considering the material property of XLPE insulator in the cable, and the location of the water tree is obtained by checking the starting point of the reflected pulse. Furthermore, positional errors with respect to the actual positions of the water trees are calculated.