A new optical method for physical characterization of water trees in polyethylene

To understand the influence of water treeing on the dielectric strength of polyethylene, an investigation of all the physically relevant parameters of the water tree (WT) controlling the inception of electrical breakdown is necessary. Usually only the water tree length is taken into account. The author proposes that the optical absorbance of the water tree, which is correlated with the water concentration, be measured. The principle of this method is explained, and it is shown that the optical absorbance of the water tree is related to the initiation of electrical trees in its vicinity in polyethylene samples