The development of the way of measuring the leakage current to evaluate the deterioration of the insulation material in the snowy cold region

本研究的目的是通过测量泄漏电流来评估聚合物绝缘材料在下雪寒冷条件下使用时的劣化。潮湿污秽条件下的泄漏电流大小是评价户外绝缘子运行期间电气性能的重要指标之一。然而，由于导电电流和放电电流在聚合物绝缘体的表面上交替地和间歇地流动，因此这些幅度变化严重。因此，很难仅通过该水平来评估绝缘子的劣化。看来，除了泄漏电流的大小，波形的形状，即高频分量，也可以提供有用的信息的状态的聚合物绝缘体表面。在本研究中，我们采用IEC 587测试来测量漏电流。在-20 ℃ +25℃的实验室中进行了测试。在此测试的早期阶段，聚合物表面抗润湿，并允许极低的泄漏电流。此时，微小的辉光放电散布在材料表面上。随着测试持续时间的延长，聚合物表面逐渐变湿并允许漏电流发展。对于这种放电，聚合物绝缘材料最终会产生跟踪劣化。此时，泄漏电流具有高频分量。该谐波分量表明聚合物绝缘材料即将发生失效，当硅橡胶受到放电损伤时，失效的类型不再是跟踪击穿，而是腐蚀。腐蚀不仅使其失去硅橡胶的绝缘功能，而且破坏其结构。当漏电流中断一次时，硅橡胶会出现腐蚀。

This research was done for the purpose of evaluating the deterioration of the polymeric insulation material used under snowy cold condition by the measurement of leakage current. Leakage current magnitude in wet and contaminated condition is one of significant indicators to assess electrical performances of outdoor insulators during operation.. However, because conductive current and discharge current flow alternately and intermittently on the surface of the polymeric insulator, therefore these magnitudes change seriously. So it is difficult to evaluate the deterioration of the insulator only by that level. It seems that apart from the leakage current magnitudes, the shape of the waveform, namely high frequency components, also can provide useful information the state of the polymeric insulator surface. In this research we employ IEC587 test for measuring leakage current. Tests have been carried out under -20〜+25℃ in a laboratory chamber.Early stage of this test, polymer surfaces resist being wetted and allow extremely low leakage current. At this time minute glow discharges are scattered on the surface of the material. With the test duration, the polymer surfaces gradually transfer to wet and allow leakage current to develop. As for this discharge, polymeric insulation material does final tracking deterioration. Leakage current has high frequency components at this time. This harmonic component shows that failure of the polymeric insulation material will happen soon.When silicon rubber suffers the damage of the discharge, the type of the failure is not tracking breakdown, and becomes erosion. Not only erosion makes it lose the insulation function of the silicon rubber but also its structure is destroyed. When leakage current is interrupted once, erosion will appear on the silicon rubber.