Types of electrical trees in solid insulation under electrical and mechanical energy basis

Abstract

The shape of electrical trees is critical in determining the life of electrical insulation subject to this type of degradation. This paper identifies a physical basis for determining tree shape. 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. A kinetic model for the electrical tree structures in solid polymeric insulation is developed, that allows for combined electrical and mechanical stresses. Also present an energy balance analysis during the tree growth process, and present results which show that the proposed model can give predicted tree shape type which in a good agreement with the experimental data of the tree growth subjected to a combined electrical and mechanical stress.