Establishment of Evaluation Method of Electrical Insulating Characteristics of External Interface and Discussion of Its Application to Field

研究了聚合物绝缘子典型界面--硅橡胶-空气外界面的电绝缘特性。主要研究结果如下：1.水滴在硅橡胶上的行为。利用光学系统和高速摄像机在交流电压下进行了一系列实验。研究了水滴振动对绝缘性能的影响。(1)随着外加电压的增加，水滴的振动变得更加剧烈。沿电场方向扩展后，最终发生沿液滴方向的闪络。(2)不带电水滴的振动频率是所施加电压频率的两倍。相反，在人工带电液滴的情况下，这与施加电压的情况相同。(3)在本研究的范围内，对于每种尺寸的水滴，振动具有三个机械共振频率。目视观察到三种共振模式。(4)研究结果表明，当水滴在机械共振频率下剧烈振动时，闪络电压比非共振时降低了65%.污秽和潮湿条件下硅橡胶表面漏电流的测量：（1）搭建了测量系统并进行了工作验证。该系统能够分别和同时测量泄漏电流的导电、干带电弧和局部放电分量。(2)加速盐雾试验结果表明，泄漏电流的累积电荷按导电成分、干带电弧成分和局部放电成分的顺序排列。(3)与棒状硅橡胶相比，片状硅橡胶的制备工艺更为简单，通过对硅橡胶和电极形状的研究，建立了片状硅橡胶的盐雾试验规范。

Electrical insulation characteristics of external interface between silicone rubber and air were studied, which was a typical interface of polymer insulators. Main results obtained are as follows.1. Behavior of water droplet on silicone rubber. A series of experiments were carried out under ac voltage application by using an optical system and a high-speed camera. The effect of water droplet vibration on electrical insulation capability was also investigated.(1) Water droplet became to vibrate more severely with increasing applied voltage. After it was extended in the direction of applied electric field, flashover occurred finally through the droplet.(2) Vibration frequency of an uncharged water droplet was double the frequency of the applied voltage. On the contrary, in the case of an artificially charged droplet, it was the same with that of the applied voltage.(3) The vibration had three mechanical resonance frequencies for each size of the water droplet in the range of the present study. Three modes of resonance were visually observed.(4) It was confirmed that flashover voltage was decreased as 65% as that at non-resonance when a water droplet vibrated severely at the mechanical resonance frequency.2. Measurement of leakage current flowing on silicone rubber surface under contaminated and wet conditions :(1) A measuring system was constructed and operation was confirmed. The system enabled measurement of conductive, dry-band arc and partial discharge components of leakage current separately and simultaneously.(2) Results of the accelerated salt fog tests showed that cumulative charge of leakage current was large in the order of conductive, dry-band arc and partial discharge components.(3) Specifications of salt fog test for silicone rubber sheet, which was able to be prepared more easily compared with rod-shaped silicone rubber, werer established by paying attention to the shapes of silicone rubber and electrodes.