The numerical modelling and experimental validation of a partial discharge within an air-filled cavity bound in oil impregnated paper

A numerical model to simulate a partial discharge within a bound cavity is presented in this paper. The partial discharge inception voltage and current pulse characteristics are established numerically and compared against experimental tests. The defect geometry used in this work is associated with a high voltage transformer bushing, namely a cavity formed between a punctured aluminium grading foil layer and the surrounding oil impregnated paper insulation. In the simulations, hydrodynamic drift-diffusion formulation is used to transport electron, positive and negative ion concentrations under the influence of an electric field; the movement of species is translated into an external current pulse. Experimentally, a high speed oscilloscope is used to capture the current pulse during a discharge. The numerical technique, defect sample preparation and high voltage laboratory setup, are discussed in detail. The results show a good agreement between numerical and experimental methods.