Surface charge accumulation on the cone-type insulator under DC voltage

Surface charge accumulation on cone-type insulators is a remarkable phenomenon in Gas Insulated Line (GIL), especially under DC voltage. It may lead to a considerable reduction of the flashover voltage of insulators. For this respect, this paper focuses on the surface charge distribution on the real insulator after applying DC voltage. In order to study this phenomenon, a set of device for measuring surface voltages on the insulator is designed, base on the electrostatic probe method. After applying different DC voltage amplitudes to the cone-type insulator, the surface voltage distributions, which reflect charge distributions to some extent, are measured by an electrostatic probe in SF ₆ gas. Despite of the axial symmetry of the insulator, the measurement results show that the charge distribution is nonaxisymmetrical. The negative charge accumulates mostly under positive DC voltage. On the other hand, no apparent positive charge accumulation is observed on the surface. In areas which are close to electrode, the measured voltage amplitudes are much higher than outer areas.