直流GIL中温度对绝缘子表面电荷积聚时变特性影响研究

柱式绝缘子表面电荷积聚是严重影响直流GIL绝缘水平的重要因素之一。本文在综合考虑GIL内部热交换、绝缘子材料电导特性和绝缘气体中正负离子微观机制的基础上,构建了直流GIL柱式绝缘子表面电荷积聚多物理场耦合时变数学模型,仿真分析了柱式绝缘子的温度分布、空间电荷密度分布和表面电荷密度分布。结果表明:在800 kV直流电压作用下,柱式绝缘子温度由极不均匀分布向均匀分布发展,使得绝缘子电导率不断变化;柱式绝缘子内部主要积聚正电荷,随着温度朝着均匀化发展和时间的延长,绝缘子内部空间电荷密度越来越大,并且柱式绝缘子内部最大空间电荷密度位置由初始状态的中心导体附近变为接地电极附近;温度对表面电荷积聚的影响较大,随着温度朝着均匀分布发展,绝缘子表面电荷密度零点不断右移,表面电荷密度峰值越来越大,切向电场强度也越来越大。

Effect of Temperature on Time-varying Characteristics of Surface Charge Accumulation of Insulators in DC-GIL

The surface charge accumulation of column insulators is one of the important factors that seriously affect the insulation level of DC GIL. On the basis of the comprehensive consideration of the internal heat exchange of GIL, the conductance characteristics of insulator materials, and the micro-mechanism of positive and negative ions in insulating gas, a multi-physical field coupling time-varying mathematical model for the surface charge accumulation of DC GIL column insulators was constructed. The distribution of temperature, space charge density, and surface charge density of column insulators were simulated and analyzed. The results show that under the effect of 800 kV DC voltage, the temperature distribution of the column insulator is extremely uneven at first and then become homogeneous, so the conductivity of insulator changes constantly. Electric charge accumulates inside the column insulator is mainly positive,with the temperature distribution getting homogeneous and the extension of time, the internal space charge density of insulator becomes larger and larger, and the location of the maximum space charge density of column insulator changes from nearby the center conductor of initial state to nearby the grounding electrode. Temperature has great influence on the surface charge accumulation, with the temperature distribution getting homogeneous, the zero point of surface charge density of insulator shifts to the right constantly, and the peak value of surface charge density and the tangential electric field strength increase.