Abstract
Accidents caused by natural phenomena such as lightning are serious problems for the diffusions of wind power generations. Those problems affect the safety and reliability of wind turbine generator systems. Most of the breakdowns and malfunctions of the electrical and control systems inside wind turbines are caused by a rise in ground potential due to lightning. To solve those problems, the field tests have been carried out so far. In this paper, new measurements of transient grounding characteristics have been carried out at a wind turbine in the vicinity of the Sea of Japan, and new data of the transient characteristics have been obvious.