含污秽薄层的高压复合绝缘子表面电场计算新方法

Novel Method for Electric Field Calculation Considering the Thickness of Contaminant Layer on the Surface of Composite Insulator

为研究复合绝缘子污闪机理,需对含污层的复合绝缘子进行电场分析,然而绝缘子表面污秽层厚度数量级达10?4m,甚至更小,远远小于绝缘子的尺寸。目前现有的有限元及边界元电场计算方法都无法解决此类多空间尺度的场域分析问题。为此,提出一种基于数字图像处理的污秽绝缘子表面电场计算新方法,该方法首先应用图像处理技术对m×n大小绝缘子图像二值化处理,利用像素单元实现区域的网格剖分,同时在像素单元基础上建立阻抗数学模型;然后形成(m×n)×(m×n)大小的节点导纳矩阵,采取节点电压法对其进行电网络分析,得到污秽绝缘子表面电场分布。实例计算表明,与其他算法相比,该方法对于含污层的复合绝缘子电场计算具有明显优势,为复合绝缘子表面污闪机理的研究提供了新的有效的电场计算方法。

To study the mechanism of composite insulator pollution flashover, electric field analysis of the polluted composite insulators is required. However, the thickness of the contamination layer is only a fraction of millimeter that is much smaller than the size of insulator itself. Consequently, neither the finite element method nor boundary element method can solve such field problems with multiple scales at present. Therefore, This paper proposes a new method to calculate the surface electric field of polluted insulator based on the digital image processing. First, binary image processing is applied to the image of insulator with size m×n, and regional meshing is realized at each the pixel unit. Meanwhile, a mathematical model of impedance is established based on pixel unit. Then the node admittance matrix of size（m×n）×（m×n） is formed. The distribution of surface electric field of polluted insulator is calculated by electrical network analysis using node voltage method. The example shows that, compared with the existing algorithms, this method has significant advantages and improved effectiveness for modeling filthy layer which revealed contamination mechanism of composite insulator surface flashover, corona discharge, etc.