直流电压下聚合物表面电荷测量方法及积聚特性

Measurement Method and Accumulation Characteristics of Surface Charge Distribution on Polymeric Material Under DC Voltage

固体绝缘介质表面电荷积聚现象是研发高压直流气体绝缘装置的重要考虑因素,这些积聚的表面电荷会导致绝缘介质局部电场畸变,大大降低装置的绝缘水平。因此,研究直流电压下聚合物表面电荷积聚现象具有重要意义,如何实现对绝缘子表面电荷分布进行准确的测量,成为该领域一个重要的课题。针对这一问题,采用静电探头法测量缩比气体绝缘输电线路(gas-insulated line,GIL)中圆锥绝缘子的表面电位,研究针对这种"平移改变"系统的表面电荷的反演计算方法。研究采用数值模拟的方法获得了从电荷到电位的传递函数矩阵,应用了基于维纳滤波的数字图像处理技术,对传递函数矩阵的病态特性进行了改善,大大降低了系统噪声,提高了反演计算的稳定性。研究分析了测量结果的空间分辨率和计算精度,发现该系统的空间分辨率可以达到1.8mm。采用该算法,分别研究了空气和SF6中直流电压下绝缘子表面电荷的积聚情况,发现绝缘子表面电荷呈均匀分布的"基本模式"和随机分布的"电荷斑"两种模式。"基本模式"的极性与所加电压极性相同,表明固体侧体电流是电荷积聚的主要来源。

Charge accumulation on a solid insulator surface is one of the critical factors for the development of dc gas-insulated equipment since it will lead to the overstress of polymeric insulation due to local field distortion and enhancement. Therefore, it is significant to study the charge accumulation phenomenon on spacer surface under dc field. However, it remains an important subject to obtain the accurate results of surface charge distribution. Electrostatic probe method was used to measure the surface potential distribution of a cone-shaped spacer in a downsized gas-insulated line （GIL） and the inverse calculation method of the surface charge distribution, especially for this ＂shift-variant＂ configuration, was investigated. Numerical simulation was used to obtain the transfer matrix from charge density to the probe output. By a signal processing technique based on the Wiener filter, the ill-condition problem of the matrix was solved and the stability of the calculation was improved. The study also analyzed the spatial resolution and accuracy of the calculation results, which shows that the spatial resolution of the system can reach 1.8 ram. Based on the above method, we studied the charge accumulation phenomena of the epoxy spacer under dc voltage in air and SF6. The results show that there are two patterns in the charge distribution： ＂dominant uniform charging＂ and random ＂charge speckles＂. The uniform charging was of the same polarity as the applied voltage, which indicates current flow from the solid bulk is the dominate mechanism in surface charging.