抄録
This paper presents the results of an investigation of the contamination flashover voltage characteristics of cylindrical polymer insulators with different core diameters under simulated rain. The specimens had the same or very similar shed profiles but different core diameters. On the contrary to the results obtained under heavy fog conditions, flashover voltages of transmission line insulator with the smallest core diameter were not significantly higher compared with those of station insulators having larger core diameters, such as station post insulators and bushing shells. The dominant flashover mechanism of hydrophobic polymer insulators under contaminated and rain conditions is water streaming along the insulator surface and the bridging between the adjacent shed tips by dripping water irrespective of core diameter. So, the flashover voltage of a contaminated cylindrical polymer insulator is not significantly influenced by its core diameter under rain conditions. Based on our investigation results, combined with the results obtained under heavy fog conditions reported in our companion paper (part I), it can be said that contamination flashover/withstand voltage tests may be conducted only under heavy fog conditions for evaluating polymer insulators having larger core diameters, while tests under simulated rain conditions as well as under heavy fog conditions may be necessary for evaluating transmission line polymer insulators having the smallest core diameter. The investigation results of flashover voltage characteristics of hydrophobic polymer insulators presented in this paper will be helpful in the selection, design and maintenance of polymer insulators for contamination areas.
