Water tree mechanism in electrical insulation

A theoretical study of water tree mechanism is described. Microscopic analyses (1),(2) of water trees revealed that they are composed of many water-filled micro-voids which are less than several microns in diameter. The mechanism of the void generation is explained by the thermo-dynamics in which the electric field is considered. Based on this mechanism, the growth of water tree is explained in respect of the effect of frequency, temperature and electric field strength. This corresponds well with the results of experiments made by many researchers. Also given are the characteristics of the start points of the tree and cable containing water tree.