The gas-insulated metal closed transmission line can be used as an effective alternative to overhead line, cable, and wall casing in the process of long-distance transmission because of its small footprint, high reliability, and adaptability to harsh climate environments. AC GIL has been in operation for many years. However, compared with AC GIL, DC GIL has poor long-term operation stability. The reason is that the epoxy insulator is under the action of a unipolar DC electric field for a long time and accumulates a large amount of surface charge on its surface, resulting in local distortion of the electric field at the gas-solid interface. The insulation performance is reduced and the reliability of the power system is affected. The surface plasma modification of epoxy resin can improve the insulation performance and flashover voltage of insulators. In this paper, based on micron alumina/epoxy resin composite insulation material, the transient field simulation model of gas-solid composite insulation was constructed. The ion transport equation was used to simulate the generation, recombination, and migration behavior of charged particles in the gas. The constitutive relationship between interface characteristics, charge dynamic behavior and insulation characteristics were studied in the electric field environment by combining the intrinsic conduction of materials and the surface conduction of the gas-solid interface. In this paper, the research idea of experiment-simulation-experiment was adopted. Based on the previous project experience and research basis of the research group, the sample of micron alumina/epoxy resin material was prepared by referring to the basin insulator used in GIS/GIL. The electrical characteristics of the material sample were tested to obtain the key characteristic parameters required by simulation calculation. The key parameters of the experiment were input into the simulation model, and the consistency between the simulation results and the experimental results was evaluated to obtain the gas-solid composite transient field simulation model which can accurately calculate the insulation characteristics of micron alumina/epoxy resin materials. Through iteration and optimization, the insulation properties of composites with different characteristic parameter Settings were quickly calculated, and the simulation results were compared and screened to obtain the best interface characteristic parameters. Giving full play to the guiding role of the simulation model for the experiment, the sample modification scheme was developed, and the plasma surface etching method was used to construct the high-performance epoxy resin surface, to avoid a large number of redundant exploratory experiments, simplify the experimental exploration steps and accelerate the experimental cycle. The following conclusions can be drawn from the study: (1) Increasing the surface conductivity of micron alumina/epoxy resin composites will change the dominant mechanism of surface charge accumulation. (2) The increase of surface conductivity leads to the gradual increase of surface conduction current, and the accumulation of the same polar surface charge at the three binding points increases, resulting in the distortion of the field intensity and the reduction of the maximum field intensity. (3) Appropriately increasing the surface conductivity of insulating materials can accelerate the accumulation and dissipation of charge, reduce the maximum field intensity at the three binding points, reduce the electric field distortion rate, and thus increase the flashover voltage value. However, when the surface conductivity is too large, the leakage current increases and the power loss increases. The excessive charge mobility causes the electric field distortion to rise sharply, but reduces the flashover voltage and threatens the insulation of the system. The experimental results are consistent with the simulation results, which proves the rationality of the experimental design and the effectiveness of the simulation calculation. © 2023 Chinese Machine Press. All rights reserved.
