A time-dependent model of partial discharges in voids

A time-dependent, hydrodynamic, model of partial discharges in voids in dielectrics is presented. The partial discharge is regarded as a space charge dominated electron avalanche. The model incorporates the relevant collisional and radiative processes in the void and at its boundary, and the field distortion due to the presence of space charge and void surface charges. Also the coupling with the external circuit is taken into account. Model simulations show that, as a result of field quenching, the associated charge versus applied field shows saturation above a certain threshold. The threshold field depends on geometry and initial electron number, but is higher than the inception values usually quoted. The saturation charge may deviate by a factor of 2-10 from values obtained with simplified models.