Three-dimensional equivalent circuit analysis of water tree

It is widely recognized that degradation by water tree of electrical power cables would cause serious problems. Therefore, many methods have been studied in order to detect water tree at the early stages. The loss current analysis is one of the methods which can detect water tree, since the degradation of CV cable by water tree gives rise to harmonics in the loss current. Many researches by simulation and experiment have been carried out for the purpose of the elucidation of the mechanism of the harmonics in the loss current generation. In the present study, a polyethylene sample where water tree was generated was replaced by the equivalent circuit composed of a lot of resistance, capacitor and voltage dependent resistance. These elements were united like the network. It will be possible to consider not only length of water tree but also shape of water tree by this method. From the simulation results, it has been understood that the characteristics of loss current vary greatly depending on not only the length of water tree but also the shape of water tree.