Influence of the −10 °C isotherm altitudes on winter lightning incidence at wind turbines in coastal areas of the Sea of Japan

Abstract

Winter lightning poses the greatest threat to wind turbines in coastal areas of the Sea of Japan. The lower altitude of winter thunderclouds initiates an upward lightning leader. The number of lightning discharges striking wind turbines directly during the winter lightning season (WLS) was significantly larger than in seasons other than winter (SOW). Winter lightning also has more energy which causes catastrophic damage to wind turbines. The characteristics of lightning discharges detected near wind turbines in coastal areas of the Sea of Japan were investigated using the Japanese Lightning Detection Network (JLDN). The JLDN detected 46% and 9% of all lightning discharges near wind turbines during the WLS and SOW, respectively. Most of the lightning discharges during the WLS were upward lightning. The probability of lightning discharges striking tall structures such as wind turbines increases as the −10 °C isotherm altitude drops. The characteristics of the winter lightning observed at Nikaho in Akita, Japan were compared to those worldwide. Winter lightning initiated from tall structures in Japan and at the Gaisberg Tower in Austria differed from those initiated in other regions. In locations exposed to similar winter lightning occurring in coastal areas of the Sea of Japan, lightning protection design for wind turbines should consider huge charge transfers of a lightning flash.