Abstract It is found that some composite insulators with faults in transmission lines have no defect when they are tested in the laboratory, so there is a certain difference between the laboratory and the actual transmission lines. Accordingly, in this paper, flashover tests of natural iced and contaminated composite insulators were conducted at Xuefeng Mountain Natural Icing Test Base in different natural environments, which overcomes the shortcomings of traditional laboratory simulation test methods. Then, AC failure voltages in 5 natural conditions (Dry, rime ice, pollution in cold fog, glaze-ice without icicles and glaze-ice with icicles) of composite insulators were obtained. In addition, the flashover processes in typical conditions were recorded and analyzed. Finally, withstand voltages with different failure probabilities were calculated. The results indicate that the flashover voltage varies greatly in different environments. The maximum flashover voltage is 2.43 times more than the minimum. Besides, both rime ice and dry flashover voltage and equivalent salt deposit density (ESDD) are independent of each other. But there is a negative power function (NPF) relationship between both pollution and glaze-iced flashover voltage and ESDD in natural environment. What’s more, compared with exponential function, power function is more suitable for fitting function between glaze-ice flashover voltage and glaze-ice weight. Last, the gradient flashover voltage Eα with α% failure probability can be calculated by tested flashover voltages through variable substitution. Further, E10, E5 and E(μ-3σ) were obtained which can provide important guidance for insulation design in different natural environments.

中文翻译：

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结冰污染复合绝缘子在不同自然环境下的交流失效电压

摘要 一些输电线路出现故障的复合绝缘子在实验室进行试验时发现没有缺陷，因此实验室与实际输电线路存在一定的差异。为此，本文在雪峰山自然结冰试验基地对自然结冰和污染复合绝缘子进行了不同自然环境下的闪络试验，克服了传统实验室模拟试验方法的不足。然后，得到了复合绝缘子在5种自然条件下（干、雾冰、冷雾污染、无冰柱釉冰和有冰柱釉冰）下的交流故障电压。此外，还对典型工况下的闪络过程进行了记录和分析。最后，计算了具有不同故障概率的耐受电压。结果表明，不同环境下的闪络电压差异很大。最大闪络电压是最小值的 2.43 倍。此外，雾冰和干闪络电压和等效盐沉积密度（ESDD）是相互独立的。但在自然环境中，污染与釉冰闪络电压和ESDD之间存在负功率函数（NPF）关系。此外，与指数函数相比，幂函数更适合作为釉冰闪络电压与釉冰重量的拟合函数。最后，通过变量代入，通过测试的闪络电压可以计算出故障概率为α%的梯度闪络电压Eα。此外，E10，