Study on the Surface Charge Accumulation and Dispersion Process of Polyimide for New Cables

High voltage cables are key factors that determine the quality and capacity of power transmission. Polyimide has been widely concerned for its excellent thermal stability and electrical insulation properties, and has been used in the development of cable insulation materials. The surface charge of insulating material has an important influence on the performance of the material. It can not only distort the electric field around itself, but also provide a discharge channel for surface discharge, which affects the safe and stable operation of power system. In this paper, the surface of polyimide for new cables is subjected to voltage treatment by needle-plate electrode, the surface potential is measured by electrostatic probe method, and the surface charge is calculated by inverse mathematical method. The surface charge accumulation distribution characteristics of the polyimide under different applied voltage times and amplitudes and the surface charge dissipation distribution characteristics under different dissipation time under DC high voltage are obtained. The experimental results show that increasing the time and amplitude of voltage applied to the polyimide can promote the accumulation of electric charges. The surface electric charges take on the form of charge patterns and are unevenly distributed. On the whole, compared to the edge position of the material, the charge density at the center position is greater, and in this case, the surface electric charge distribution does not have similarity. In the decay process, the surface potential of the center of the material decays faster than the surrounding, forming a bell shape. Under the action of the electric field, the surface charge pattern presents a positive and negative alternating phenomenon.