Measures Against Lightning Damage on Power Distribution Lines by One-phase Lightning Protection System

Abstract:
Since distribution substations in Japan are composed of ungrounded systems, based on the idea that one-phase ground faults will naturally extinguish the arc, lightning damage countermeasures that installing two-phase lightning protection devices are often taken. In this study, further developing this idea, the effectiveness of lightning protection using a onephase lightning protection system (strengthening the insulation strength of the middle phase, which is the least susceptible to dielectric breakdown, and installing lightning protection devices on one of the remaining two phases) that is set a disparity in the dielectric strength of each phase of the distribution line, was analysed. As a result, it was shown that in the one-phase lightning protection system, the higher the dielectric strength of the medium-phase insulator and the lower the grounding resistance of the concrete pole, the less likely it is that a direct lightning hit will cause more than twophase breakdown and these measures was found to be effective.