直流电压下环氧浇注绝缘子的表面电场分析
Surface Electric Fields for Epoxy Cast Insulator Under DC Voltage

针对直流气体绝缘设备电场分析及结构设计时气体侧模型的选择问题,以高压直流气体绝缘穿墙套管用环氧浇注绝缘子为研究对象,建立了直流电压下环氧浇注绝缘子的电场计算模型。其中,对气体侧分别采用离子迁移模型和线性模型,在直流电压下对环氧浇注绝缘子的表面电场进行了计算及分析。研究了不同气体电离率、外施电压、体积电导率等条件下两种模型对计算结果的影响及相互替换的条件,给出了直流电压下气体侧模型的选择建议。结果表明:离子迁移模型得到的绝缘子表面电场计算结果受气体中空间电荷不均匀分布的影响,随场强的变化呈现出较强的非线性;线性模型用以匹配离子迁移模型计算结果的气体电导率取值与气体电离率成正比,与外施电压等级成反比;当外施电压等级较高、绝缘子体积电导率较大时,固体侧电流在绝缘子表面电荷积聚过程中起主要作用,离子迁移模型与线性模型得到的计算结果差异较小。这时,线性模型计算时间更短,更适用于环氧浇注绝缘子的结构优化设计。
Aiming at the issue of gas model selection of DC gas？？insulated device in electric？？field analysis and design, a model for electric？？field evaluation is established for an epoxy cast insulator installed in HVDC gas？？insulated wall bushing. Ion？？drift model and linear model are considered for gas domain respectively. Calculating and analyzing the surface electric fields under DC voltage, the influences of two models on calculated results for different gas ionization rate, applied voltage level, bulk conductivity as well as the alternative conditions under DC voltage are investigated and the suggestions for gas model selection are proposed. The results show that the calculated results of ion？？drift model depend on electric？？field strength and are affected by the uneven space charges with gas nonlinearity. The gas conductivity in linear model matching ion？？drift model is proportional to gas ionization rate and inversely proportional to applied voltage level. In the case of higher voltage level and larger bulk conductivity of insulator, the bulk current dominates the surface charge accumulation and calculated result for ion？？drift model slightly differs from that for linear model. The linear model is more applicable to optimal design for epoxy cast insulator with shorter calculating time