一种覆冰污秽绝缘子闪络电压的理论计算模型

将覆冰视为一种特殊的污秽形式,其电阻可用冰体电阻与冰面水膜电阻的并联电阻来等效.将基于Obenaus概念和污秽均匀分布平板模型得出的闪络电压与电弧常数、泄漏距离及单位长度污层电阻的关系式用于覆冰污秽绝缘子,推导出了一个描述闪络电压与覆冰量、融冰水电导率、绝缘子泄漏距离等多个参数之间关系的理论计算模型.利用该模型分析计算了多组覆冰污秽绝缘子串(3片/串～21片/串)的交流闪络电压,计算值与试验值基本吻合.还利用该理论模型解释了经验公式,并较为准确地计算出了经验公式中的系数和指数的具体数值.

A THEORETICAL CALCULATION MODEL FOR FLASHOVER VOLTAGE OF ICE-COATED AND POLLUTED INSULATORS

The authors regard the ice coated on insulator as a special pollution form and hold that the resistance of the ice- coating can be equivalent to that of the ice body resistance in parallel with the water film resistance on the surface of ice body. Applying the relational expression among flashover voltage, arc constant, leakage distance and resistance of unit length pollutant layer, which is obtained from Obenaus concept and plate model with uniformly distributed pollution, to ice coated insulator, a theoretical calculation model describing the parameter correlativity of flashover voltage with the amount of coated ice, conductivity of molten ice and leakage distance of insulator, etc., is deduced. Using this model the AC flashover voltages of multi ice coated insulator strings, namely from 3 pieces of insulators per string to 21 pieces of insulators per string, are analyzed and calculated. The calculated results are in reasonable agreement with testing results. Besides, the presented theoretical model is applied to the explanation of empirical formula, and the concrete values of the coefficient and index in empirical formula are accurately calculated.