Surface Charge Distribution on DC Basin-Type Insulator

Surface charge accumulation on insulators is one of the bottlenecks for the development of DC electric power system. This paper studies a +/- 200 kV DC basin-type insulator designed for GIL (Gas-insulated Transmission Line). A surface charge measurement device is made consisting of a 3-dimension, 4-axes manipulating device, a HV shielding conductor installation system and data acquisition system. A new scaling method of the probe with an inversion algorithm using Cholesky decomposition method is proposed to obtain charge density distribution. The dynamic process of surface charge accumulation and dissipation are studied under DC voltages with different polarities, amplitudes and time durations. Charge distributions are obtained and theoretically analyzed. A novel gas-side normal electric field model is proposed for regular charge distribution and methods of suppressing surface charge are suggested, including a recommended ratio of surface and volume electric conductivity of the insulator at 1 similar to 10, structure design, and direct fluorination of the surface.