The dielectric breakdown model is generalized and adapted to describe electric discharge propagation in inhomogeneous insulators. The influences of the injected space charge, inclusions and barriers with different dielectric permittivities and conductivities are investigated. The growth of bush, dendrite and skeleton types of discharge structure as well as transformations from one type to another are simulated.

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Electrical treeing in an epoxy resin under an ac voltage for a point-to-plane gap configuration has been investigated using a phase-resolved partial discharge measurement system and shadow survey and light emission registration techniques. A self-consistent model based on the concepts of energy and electric field has been developed and used for quantitative description the temporal-spatial and electric characteristics of electrical treeing obtained in experiment. The electrical treeing is considered to be a phenomenon of self-organized criticality.

A model of partial discharge development in electrical tree strnctures is presented. The model considers channel conductivity, charge transport, and electric field redistribution during propagation of the discharge along the channels. It has been used for numerical investigation of temporal-spatial and electric characteristics of the partial discharges in capillaries and electrical trees exposed to ac voltage in a needle-plane geometry. The simulation results have been compared with experimental data given in the literature.

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