Finite element analysis of electric field distribution in water treed XLPE cable insulation (1): The influence of geometrical configuration of water electrode for accelerated water treeing test

Water trees are localized degraded zones that can be found in the polymeric insulation of service-aged underground cables, and observed as microchannels or chains of microcavities in the bulk of a solid dielectric material. Since water trees have microscale local structures, some phenomena related to them can be understood and analyzed in detail only when using numerical analysis methods such as finite element method (FEM). For the artificial accelerated growth of water trees, water electrodes in needle form or with conical structure are often utilized, and then some unexpected initiation positions and shapes of water trees have frequently been observed. This paper deals with the investigation of the influence of the geometrical configuration of water electrodes on water tree initiation and its shape, on the basis of numerical experiment results using the FEM and accelerated water treeing test data.