A new model for propagation of electrical tree structures in polymeric insulation

A quantitative physical model for propagation of electrical tree structures in polymeric insulation is presented. In the present model the propagation of trees arises from the formation of electrodamage that precedes and surrounds the tree tip during the tree propagation process. Electrical tree propagation is modeled as the growth of a fractal cluster, which consists of submicroscopic trees. The formation and growth of the submicroscopic tree is explained in terms of a thermally activated bond-breakdown mechanism. The main results obtained in this study are a novel electrical tree propagation rate equation and a lifetime formula of electrical tree propagation to failure. It has been shown that the proposed new model can give the predicted electrical growth and insulation lives in good agreement with the experimental data of the CT200 epoxy resin.