固-气界面电荷消散特性及其动力学过程

Charge accumulation on a solid insulator under dc field will lead to the local field distortion along the gas-solid interface and decrease the insulation level of the system. To study the surface charge dissipation characteristics will provide an important basis for the development of HVDC gas-insulated equipment. In this paper, the needle-to-plate electrode was used to inject charges onto the surface of insulating material, and the charge dissipation was studied under different conditions. The electrostatic probe method was used to measure the potential distribution on the sample surface, from which charge density distribution was obtained by the inversion calculation. Results show that surface charge on an epoxy resin insulator in the gas is mainly dissipated by neutralization with gas ions, and the process is related to the electric field distribution in the gas. For the charged sample in a free volume, electric field is more concentrated where the surface charge density is the maximum. As a result, more hetero-charges migrate to this area, leading to faster charge decay. Finally, a crater-shaped charge distribution forms. Based on the three ways for the surface charge decay, i.e. bulk conduction, surface conduction, and neutralization with gas ions, a kinetic model was built and the charge dissipation characteristics through the three mechanisms were studied separately. It reveals that surface charge of materials with bulk conductivity less than 10^-15S/m is mainly dissipated by neutralization with gas ions; for bulk conductivity larger than 10^-14S/m, surface charges are mainly dissipated through bulk conduction with almost the same dissipation rate on the surface; an insulating material without special treatment has a small surface conductivity, which has limited effect on charge decay.