直流GIS/GIL局部放电导致绝缘子表面电荷积聚与影响因素及抑制方法研究

Surface charge accumulation of insulator at DC voltage is very serious, leading to a great decrease of its surface withstanding performance, which becomes a difficult problem to affect the safety operation of DC gas-insulated switchgear (GIS) and gas-insulated transmission line (GIL). Moreover, because the understanding about surface charge accumulation generated by partial discharges in GIS/GIL is not clear, the existent methods for charge suppression cannot fully solve practical problems. Based on a self-constructed measurement platform, the charges on insulator surfaces will be overall measured, which results from three typical micro-defects, i.e. micro-protrusion from high-voltage conductor, surface roughness of the insulator, and metallic micro-particles adsorbing on insulator surface. With considering the influences of temperature, gas pressure and trace water, initiation conditions and distributed characters of surface charge accumulation through electric conduction within gas volume will be obtained. In terms of these results, the internal relationship between surface charge accumulation and partial discharges will be explored. Besides, nonlinear conductance character of SiC epoxy composites, as well as surface conductance character of coated insulator, will be measured. Based on this, physical simulation models about surface charge accumulation and dissipation processes will be established, which employs the current continuity equation. Moreover, mechanisms of charge accumulation and dissipation on insulator surface after nonlinear conductance material coated will be revealed. After the optimization of coating formulation and coating method, a method aiming to reduce charge accumulation and speed up insulator surface charge dissipation could be proposed. This project will provide theoretical and technical supports for scientific design and security operation of DC GIS/GIL.

直流下绝缘子表面电荷积聚严重，导致其沿面耐受能力大为降低，成为影响气体绝缘组合电器(GIS)和封闭输电线路(GIL)安全使用的一大难题。由于对GIS/GIL内部局部放电导致绝缘子表面电荷积聚特性与影响因素认识不清，现有电荷抑制方法还不能满足工程实际。本项目拟在自建的绝缘子表面电荷测量平台上，对高压导体微突物、绝缘子表面粗糙和吸附金属微粒三种微缺陷在绝缘子表面产生的电荷积聚进行全覆盖测量，获取温度、气压及微水等影响因素引起表面电荷积聚的起始条件和分布特点，探索绝缘子表面电荷积聚与局部放电的关联规律，研究SiC环氧基复合材料非线性电导特性及涂覆绝缘子后的表面电导特性，构建基于电流连续性方程的绝缘子表面电荷积聚与消散过程仿真模型，揭示非线性电导材料涂覆绝缘子后表面电荷聚散机理，优化涂料配方和涂覆方式，提出抑制电荷积聚并加快电荷消散的措施，为直流GIS/GIL科学设计与安全运行提供理论与技术支撑。

直流下绝缘子表面电荷积聚是导致沿面耐受能力降低的主要原因，已成为影响气体绝缘组合电器(GIS)和封闭输电线路(GIL)安全使用的一大难题。本项目搭建了一套基于有源静电探头的表面电位测量平台，并针对现有维纳滤波算法无法准确获取反演滤波系数的问题，开发了一套基于约束最小二乘方滤波器的表面电荷反演算法，在实现滤波系数自适应选取的同时提升反演计算精度，可满足于平移不变系统中的电荷反演需求。测量了SF6中不同电压幅值和电压极性、金属导杆突出物缺陷、不同绝缘子表面电导率以及不同压强下的表面电荷积聚特性。通过对不同条件下电荷特征分布的提取，分析了表面电荷积聚的主导途径，总结出了表面电荷主导积聚途径转变的现象。以共混法为基础研发了适用于环氧基复合材料的绝缘子表面均匀涂覆工艺，实现了SiC/epoxy复合材料在任意绝缘形状表面的均匀涂覆效果。采用了电极-绝缘子直接压接与电极-绝缘子紧密贴合两种充电方式，对含涂层绝缘子的表面电荷积聚与消散特性进行了系统评估。不同充电方式将带来不同的电荷主导积聚途径，最终导致不同的电荷分布模式。另外，直接压接充电方式中发现电荷积聚总量将随SiC含量上升而减小，且高浓度试样还会观察到加压过程中电荷密度积聚减少的现象。结合电场计算对测量结果进行了分析，将电荷积聚过程的抑制效果归因于涂层非线性电导特性的作用。另外，发现来自于不同放电强度的电荷源积聚于绝缘子表面后将呈现出不同的消散规律。通过对电荷消散过程的观测已经表面电荷自建电场分布特性的计算理清了不同充电方式下的电荷消散主导路径。