A network model of water tree

A computer model simulating the electrical properties of water trees has been developed. Tree-like patterns of various sizes, grown from a needle electrode, were generated by a random walk process on a rectangular grid of electrical impedances. The rate of change of the total impedance of the grid versus the size of the tree pattern was examined. This was compared with the experimental results of J.D. Cross and J.Y. Koo (1984). The computer model confirms that water in a water tree cluster is contained in a dispersed form. It is shown that, if water tree branches form interconnected, hollow channels, the number of unfilled voids in these channels must be greater than 30% for the changes in the admittance to be comparable with the changes in electric signal recorded by Cross and Koo. The quantity of water must be even smaller if polyethylene, instead of unfilled voids, separates microdrops of water