近年来，高压输电线路中出现了一种新的复合绝缘子机械断裂形式，对电力系统危害很大，但目前国内外针对这种断裂所开展的研究工作非常罕见。本论文通过对这种复合绝缘子机械断裂事故一般特征的总结和分析，将其命名为复合绝缘子的酥朽断裂，并首次将其作为一类独特的复合绝缘子机械断裂形式进行研究。研究主要包括复合绝缘子酥朽断裂机理、离子溶液渗透穿过护套使芯棒表面受潮的过程以及表面微弱放电对复合绝缘子护套性能的影响等方面。通过对10起现场复合绝缘子酥朽断裂事故的分析，归纳出复合绝缘子酥朽断裂的主要特征。复合绝缘子酥朽断裂的断裂处芯棒质地变酥，形如朽木。芯棒表面粉化，玻璃纤维与树脂分离，颜色变为棕色和白色，并存在黑色放电烧蚀痕迹。复合绝缘子通常断裂形式和脆性断裂形式的机理均无法解释酥朽断裂发生的原因。用于防止复合绝缘子脆性断裂的耐酸芯棒也无法防止此类事故的发生。针对酥朽断裂复合绝缘子存在芯棒表面电流升高的现象，研究了潮湿环境下的表面电流增大对复合绝缘子芯棒性能的影响，并在实验室中成功进行了复合绝缘子芯棒酥朽断裂的模拟试验。经过模拟试验作用，复合绝缘子芯棒试品表面出现了与现场酥朽断裂复合绝缘子一致的现象和主要特征。提出了复合绝缘子酥朽断裂发生的原因和过程，将复合绝缘子芯棒的酥朽断裂起始和发展过程分为水解潜伏期、水解发生期、水解发展期、放电发展期和失效发生期五个阶段。发现了复合绝缘子芯棒在表面电流作用下加速水解的现象，并提出了复合绝缘子酥朽断裂两种不同类型的划分方法。通过碱性品红乙醇溶液、硝酸和乙酸在高温硫化硅橡胶试片中的渗透试验，阐明了离子溶液在有无电场作用下渗透通过完好的硅橡胶护套进入到复合绝缘子芯棒表面的可能性和渗透机理。解释了复合绝缘子酥朽断裂中芯棒表面受潮的可能原因和酥朽断裂中复合绝缘子护套上出现击穿孔的一个可能原因。针对复合绝缘子酥朽断裂均出现在高电压等级输电线路的现象，进行了电晕放电对高温硫化硅橡胶性能影响的研究，研究了高温硫化硅橡胶在电晕放电处理前后电气性能、机械性能和憎水性的变化规律，并通过官能团分析与元素分析阐释了变化的机理。试验结果有助于对复合绝缘子酥朽断裂过程有更深入的理解。结合各部分研究结果，提出了防止运行中芯棒发生酥朽断裂的几个注意事项。
In recent years, a new type of composite insulator mechanical fracture appearred in high votage transmission lines, which is a type of severe accident for power system, but only few studies on it has been carried out at home and abroad. In this thesis, this type of fracture was named Decay-like Fracture by summarizing and analyzing the general characteristics, and decay-like fracture of composite insulator was treated and studied as a type of individual composite insulator mechanical failure for the first time. Systematic experiment on decay-like fracture mechanisms, damping process of fiber reinforced plastic (FRP) rod which lead to decay-like fracture and influence of surface weak discharge on sheath properties of composite insulator were carried out.By analyzing 10 field-failed composite insulators which sufferred decay-like fractures, main properties of decay-like fracture were then summarized. The fracture place of decay-like fractured insulator became crisp and looked like decayed wood. Chalking as well as separation of glass fiber and resin appeared on the surface of FRP rod, and the colour of the rod turned to brown and white. At the same time, black trace caused by surface discharge could also be found on the surface of FRP rod. The mechanisms of the normal fracture and brittle fracture of composite insulator could not explain this type of fracture, and boron-free FRP rod which was used to prevent brittle fracture could not prevent decay-like fracture.Focusing on the phenomena of current increase over FRP rod surface, the influence of surface current increasing on composite insulator properties in wet environment was carried out, and main characteristics of decay-like fracture had been reproduced successfully in laboratory. After the reproduce test treatment, black trace caused by surface discharge could be found on the surface of FRP rod specimens. Meanwhile, chalking, colour changing as well as the separation of glass fiber and resin appeared. These phenomena were in accordance with field failed decay-like fracture insulators.Mechanism of causes and developing process of decay-like fracture was put forward. The developing process of decay-like fracture could be divided into five periods – incubation period of hydrolyzing, emergence period of hydrolyzing, developing period of hydrolyzing, developing period of discharging, and period of failure. With the combined action of current and moisture, hydrolyzing would appear on the surface of fiber reinforced plastic rod. Classification criterion for the two different types of decay-like fracture was then put forward.Ionic solution could pass through undamaged silicone rubber sheath and arrived at rod surface with or without E-field affecting. This process and the mechanisms had been clarified by adopting the diffusion solution of fuchsine solution, nitric acid and acetic acid into HTV silicone rubber. The surface damping of FRP rod surface as while as the puncture holes in insulator sheath in decay-like fracture was then explained.Because all the discovered decay-like fractures of composite insulator happened in EHV transmission line, a multi-needle electrode was used to assess the influence of corona discharge on the properties of HTV silicone rubber. Electrical properties, mechanical properties as well as hydrophobic of HTV silicone rubber were studied before and after exposure under corona discharge. FTIR analyzing and XPS analyzing were used to explain the mechanism of these changes. The results could help to understand the developing process of decay-like fracture.Matters need attentions were put forward to prevent decay-like fracture of composite insulator.
