输电线路的外绝缘故障，特别是绝缘子污秽闪络是影响电网可靠运行的主要因素之一。由于不同地区的绝缘子表面可溶盐成分存在差异，相同等值盐密的自然积污绝缘子污闪电压差异很大，使得基于等值盐密的输变电设备外绝缘配置裕度不足或过高。为了提出自然污秽可溶盐成分的修正方法，本文研究了绝缘表面污层的受潮特性，通过比较绝缘子饱和受潮时和等值盐密测量时表面污秽中可溶盐的溶解量，提出了基于表面电导率的自然污秽试验盐密的修正方法并研制了相应的测量装置。首先，本文提出了一种基于表面电导率的绝缘子表面污层附水量的测量方法。在此基础上研究了污层在受潮过程中的附水量变化，分析了绝缘子表面饱和附水量和污秽灰密、倾斜角度之间的的关系。为了研究绝缘子的温差受潮特性，测量了绝缘表面在不同初始温差下的泄漏电流，分析了温差作用期间绝缘表面污层附水量的变化。研究发现，在较低湿度下，绝缘子表面污层的附水量和温差成正比，温差引起的污层附水量的变化可以定量计算。通过测量不同比例微溶盐和易溶盐的污层在饱和受潮条件下的表面电导率，分析了污层表面电导率与等值盐密、可溶盐成分的关系，通过分析受潮过程中表面水珠盐度和污层表面电导率的变化，研究了憎水性对污层可溶盐溶解特性的影响。最后，本文提出了一种基于表面电导率的自然污秽试验盐密的修正方法并研制了适用于现场的测量装置。通过测量绝缘子的局部等值盐密和局部表面电导率，可以得到污秽可溶盐成分修正系数ke，该系数ke可以将绝缘子的等值盐密修正到试验盐密。本方法中局部表面电导率的测量成本较低、方法简单，有较强的工程应用价值。
External insulation failure of transmission lines, especially pollution flashover, is one of the main factors affecting the reliability of power grid. The difference in component of natural contamination leads to the dispersion of the pollution flashover voltage with the same ESDD, which makes the insufficient or excessive external insulation configuration of power equipment. In order to put forward the correction method for soluble salt components on the insulators, the wetting characteristics of the contamination layers was studied by measuring the surface conductivity of contamination layers during the wetting process. On this basis, the dissolution amounts of soluble salts during ESDD measurement and under the saturated moisture condition were studied and a method for the analysis of soluble salt components based on surface conductivity was proposed. Firstly, a method to analyze the saturated water absorption of the contamination layer based on the surface conductivity was proposed. Based on this method, the saturated water absorption of contamination layer on the specimen surface was measured and the influence of non-soluble deposit density (NSDD) and the inclination angle of specimen on the saturated water absorption of the contamination layers were analyzed.To figure out the effects of the temperature difference on the wetting process of the pollution layers quantitatively, the leakage current on the insulators with different initial temperature difference was measured, and the relationship between temperature difference and water absorption of contamination layer on insulator surface was analyzed. The results reveal that under medium humidity, the water absorption of the polluted layer is directly proportional to the temperature difference. The water absorption in a certain period caused by the temperature difference can be calculated.The relationship between ESDD, contamination components and surface conductivity under saturated moisture was analyzed. By measuring the changes of water droplet salinity and surface conductivity of hydrophobic surface, the wetting characteristics of artificial contamination on the surface of composite insulators and dissolving characteristics of soluble salts were analyzed in depth.Finally, a method for correcting the soluble salt components of natural contamination was proposed and a device, which was applicable to actual engineering applications, was developed. By measuring the local ESDD and local surface conductivity, the coefficient ke can be obtained, and the ESDD of insulators in this area can be corrected to SDD by the coefficient. The local surface conductivity analysis is much simpler, less costly, and has a more explicit relationship with the actual contamination flashover of insulator surface. Therefore, it is worthy of further popularization.
