温度梯度下直流套管绝缘子表面电荷积聚特性与电场调控

Charge accumulation on the surface of insulator is an important reason for surface discharge which may cause electrical failue to DC bushings. The temperature gradient formed by the current heating of DC bushing internal conductor, can affect not only the properties of the surface charge accumulation, but also the electric field variation. But the mechanism is still unclear. Therefore, the researches on DC bushing insulator are to be carried out as follows: 1) to investigate temperature and electric field affecting the nonlinear conductance characteristics of epoxy resins through measuring and analyzing a variety of dielectric properties; 2) to establish the system of surface potential measurement under temperature gradient condition, to measure and simulate the surface potential distributions of insulators under a variety of conditions, and to reveal the influence mechanism of temperature gradient to the surface charge accumulation and electric field distortion; 3) to develop the electric field model of gas/solid insulation system, to simulate the eletro-thermal coupling fields based on multi-objective optimization, and to propose a method to optimize the insulation structure and to improve the electric field distribution on the basis of the properties of surface charge accumulation and electric field variation under temperature gradient condition. This study may provide a design and theoretical basis for China domestic UHVDC SF6 gas-insulatedwallbushing. It may have important engineering application value for improving the reliability of bushings.

绝缘子表面电荷积聚是引发闪络事故，造成直流套管电气故障的重要原因。套管中心导杆在运行时载流发热所形成的温度梯度，会影响绝缘子表面电荷积聚特性和电场变化规律，其作用机理尚不明确。因此，本项目以直流套管绝缘子为研究对象，开展如下科学问题研究：1）通过多种介电性能的测量和分析，研究温度、场强对环氧复合材料非线性电导特性的影响机制；2）搭建温度梯度下表面电位测量系统，开展不同条件下绝缘子表面电位分布的测量和仿真，揭示温度梯度对表面电荷积聚方式和电场畸变的影响机理；3）建立气/固绝缘系统电场模型，结合温度梯度下表面电荷的积聚特性和电场变化规律，开展基于多目标优化的电热耦合场数值仿真，提出优化绝缘结构、改善电场分布的方法。本研究可为我国特高压直流SF6气体绝缘穿墙套管提供设计和理论依据，对提高套管运行可靠性具有重要的工程应用价值。

特高压直流SF6 气体绝缘穿墙套管支撑绝缘子表面所存在的电荷积聚现象，是畸变电场分布，引发闪络事故，造成套管电气故障的重要原因。套管中心导杆在运行时载流发热所形成的的温度梯度，会对绝缘子表面电荷积聚方式和电场变化规律产生较大影响，但目前相关研究仅限于少量仿真分析，缺乏实验观测以及系统性的研究。本项目通过对环氧复合材料的宽频介电谱数据和不同温度、电场条件下的极化/去极化电流等进行拟合分析，实现了对环氧复合材料内部不同介电驰豫过程的辨别和分解，获得了不同温度下环氧复合材料的电流密度-场强（J-E）关系曲线，综合考虑了导电聚合物复合材料以及经典电介质的相关电导理论，揭示了温度、场强对环氧复合材料非线性电导特性的影响机理。开展了支撑绝缘子试样表面在不同温度、温度梯度，不同电压幅值，不同极性以及不同作用时间等条件下的电位分布测量，分析了电荷来源、电荷极性、电荷积聚量、气体侧电流密度、电场分布、场强畸变因子等参数随温度、温度梯度等因素的变化规律，揭示了温度梯度对环氧支撑绝缘子表面电荷积聚方式与电场畸变的影响机理。研究成果为我国特高压直流SF6气体绝缘穿墙套管提供设计和理论依据，对提高套管运行可靠性具有重要的工程应用价值。