复合绝缘子芯棒在表面微电流作用下的水解

Hydrolysis of Composite Insulator Core in Condition of Micro Surface Current

近年来,我国出现了若干起复合绝缘子不明原因异常断裂事故,对超、特高压输电线路的安全稳定运行提出了严峻挑战。为此,从芯棒水解导致复合绝缘子异常断裂的假设出发,进行复合绝缘子芯棒材料在表面微电流作用下的水解试验,对复合绝缘子的这种异常断裂进行了实验室模拟。试验结果表明,模拟试验中的芯棒满足这种断裂现象的4个特征:1)芯棒质地变酥,颜色发生变化,形如朽木,玻璃纤维和树脂破碎;2)在高电压作用下,芯棒机械强度发生大幅下降;3)芯棒机械强度下降过程中,表面出现放电和温升现象;4)芯棒的机械强度下降是在没有外加机械载荷的条件下发生的。经分析,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共5个阶段。复合绝缘子芯棒在表面电流作用下会加速水解:流过绝缘子芯棒表面的电流及芯棒表面的放电强度从水解发生期开始逐渐增大;到失效发生期,复合绝缘子芯棒表面形成明显的碳化通道,电流急剧增大,机械强度大幅下降。

In recent years, some unexplained abnormal fracture of composite insulators presented a great challenge to the safety of UHV/EHV power transmission lines in China. Therefore, assuming that the fractures were induced by hydroly- zation, we simulated the abnormal fracture of composite insulators in laboratory through hydrolyzing experiments of insulator＇s fiber reinforced plastic （FRP） rod influenced by surface discharge. In the experiments, the treated rods possess four features of the abnormal fracture： 1） the rods become crispy, and change in color, looked like decayed wood, and have fracture glass fiber and resin inside; 2） the rods decline greatly in mechanic strength by high voltage; 3） there is dis- charge and temperature rising on the rods during their mechanic strength declining; 4） the decline occurs without influence from additive mechanic loads. After analyzing the development of the decay-like fracture, we divided this process into five periods： incubation period of hydrolyzing, emergence period of hydrolyzing, developing period of hy- drolyzing, developing period of discharging, and period of failure. FRP rods of composite insulators would accelerate hydrolyzation under the influence of surface discharge. Both of the current flows over rod surface and the discharge on rod surface get enhanced gradually since the developing period of hydrolyzing. When a rod gets into the period of failure, it will have significant carbonized channels on its surface, along with sharply increasing current and greatly decreasing mechanic strength.