Simulation of Partial Discharge Influenced by Space Charges in Silicone Rubber

As the fast development of modern city and industry, energy consumption shows an increasing tendency in recent years. More power cables of high-voltage and extra-high-voltage class are widely used to meet the demand of sustainable growth of grid capacity. However, in power cable system, statistics show that above all failures in recent years, the faults of cable accessories can make up more than 70%. One of the main reasons for the high failure rate is the performance degradation of insulating materials, which is strongly influenced by the partial discharge occurrence. Hence, as an effective way to evaluate the performance of insulating dielectrics, modelling of partial discharge is a significant issue to cable accessories. The paper aims to give a simplified model of partial discharge based on space charge transport along the silicone rubber which is adopted as the main insulating material of cable accessories containing one spherical air void, considering partial discharge happens when gas were ionized by charge collision under AC applied voltage. The model contains the physical processes of charge injection and extraction at the interface between electrode and dielectric material, space charge transport along the material, charge exchange at the interface between dielectrics and the spherical void. Additionally, the influence of gas conductivity under various temperature and electric field is also concerned. The parameters of applied voltage and the size of void are analysed in this paper. The simulation results indicate that the range of discharge phase concentrates on the first and third quadrant of one AC cycle where the voltage amplitude ascends. With the increase of applied voltage and the size of void, the magnitude of charge also rises. Higher applied voltage and larger void size contribute to the accumulation of space charges in the void and accelerate gas ionization process. Therefore, the probability of partial discharge in the interior of silicone rubber increases as well. The model which links the partial discharge phenomena with space charge transport along the material and the interface between solid and gas provides the other efficient way to reflect the condition of partial discharges in insulating material.