Collaborative Optimization of Conductivity and Permittivity on GIL Spacer Surface for Electric Field Regulation Under DC Superimposed Impulse Voltages

Abstract

The gas-solid interface electric field distortion is an essential factor leading to surface insulation failure. This study proposes the conductivity and permittivity-graded coating layer (ε/γ-layer) method, aiming at regulating surface charge and electric field distribution on GIL spacers under DC/ DC superimposed impulse voltages. The iteration optimization algorithm is developed to obtain the optimal conductivity and permittivity distribution of the ε/γ-layer. The surface charge and electric field behavior on GIL spacers with the ε/γ-layer are investigated through the numerical simulation approach. The polarity of the accumulated surface charges reverses on both the convex and concave sides as the conductivity of the ε/γ-layer increases under DC voltages, indicating the dominant mechanism changing from the bulk conductivity model to the surface conductivity model. The electric field distribution is also improved with the ε/γ-layer at the optimal permittivity and conductivity distribution. Compared with the raw spacer, the maximum electric field strength with ε/γ-layer is reduced by about 31.97% under DC, 20.56% under DC superimposed positive impulse (DC+Po.Im), 42.68% under DC superimposed negative impulse (DC+Ne.Im) on the convex surface, about 64.22% under DC, 21.37% under DC+Po.Im, 36.46% under DC+Ne.Im on the concave surface, correspondingly. It is hoped that the results of this study could spark off novel ideas for the optimal design of DC GIL spacers.