Evaluation of Flashover Rate on Distribution Lines Taking into Account Insulation-covered Conductor

In Japanese distribution lines, insulation-covered conductor is generally used. Flashover characteristics of an insulator with the insulation-covered conductor are different from that with a bare conductor. However, flashover characteristics of an insulator with the insulation-covered conductor have not been well studied. To improve the accuracy of a lightning outage rate calculation method of medium-voltage distribution lines, it is important to develop an accurate flashover model of an insulator with insulation-covered conductor. In this paper, first, we experimentally examine the flashover characteristic of an insulator with a insulation-covered conductor against a short-wave-tail lightning impulse voltage. Next, we propose a flashover model of the insulator taking into account the influence of the insulation-covered conductor. Finally, we evaluate the influence of the insulation-covered conductor on the flashover rate of the insulator using the proposed flashover model. As a results, we clarify that the flashover rate on distribution lines can be up to 50% lower by taking into account the influence of the insulation-covered conductor.