Charge accumulation has always been a problem for the safe operation of gas insulated switchgear (GIS)/gas insulated transmission line (GIL) both under AC and DC. It is of great significance to investigate the behaviour of surface charge under high voltage. In this study, the charge distribution characteristics and accumulation mechanism on insulator surface in air and heptafluorobutyronitrile/carbon dioxide (C 4 F 7 N/CO 2 ) mixtures under AC voltage are studied via the means of surface potential measurement and inversion algorithm, combined with the improved method of controlling the truncated phase of AC voltage. The results show that under the needle–plate electrode structure, charge distribution on the insulator surface presents a three-tier concentric circle structure both in air and C 4 F 7 N/CO 2 gas mixtures, and the charge composition of the innermost circle is closely related to the truncated phase of AC voltage. Under the same amplitude of voltage, the range of charge distribution on insulator surface in C 4 F 7 N/CO 2 mixtures is smaller than that in air, with the negative charges domination. It is suggested that the characteristic of charge distribution in C 4 F 7 N/CO 2 mixtures is related to the larger electron attachment cross-section of C 4 F 7 N gas in a wide range of electron energy distribution.

中文翻译：

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空气和C4F7N / CO2混合物在交流电压下聚合物绝缘子表面的电荷累积特性

电荷累积一直是气体绝缘开关设备（GIS）/气体绝缘传输线（GIL）在AC和DC下安全运行的问题。研究高压下的表面电荷行为具有重要意义。通过表面电势测量和反演算法，研究了交流电压下空气和七氟丁腈/二氧化碳（C 4 F 7 N / CO 2）混合物中绝缘子在空气中的电荷分布特征和累积机理。控制交流电压截断相位的改进方法。结果表明，在针板式电极结构下，绝缘体表面的电荷分布在空气和C 4 F 7 N / CO 2气体混合物中均呈现出三层同心圆结构，最内圈的电荷组成与交流电压的截断相位密切相关。在相同电压幅度下，C 4 F 7 N / CO 2混合物在绝缘子表面的电荷分布范围小于空气中的电荷分布范围，负电荷占主导地位。这表明在广泛的电子能量分布范围内，C 4 F 7 N / CO 2混合物中电荷分布的特征与C 4 F 7 N气体的较大电子附着截面有关。