Upward lightning occurrence on wind turbines: duration characteristics from high-speed cameras

• ICC period corresponds to 96% of an upward flash total duration. • One thunderstorm presents three upward flashes that last more than 1 s. • All return strokes present some continuing current. • Extreme meteorological scenarios play a key role in upward flash durations. Questions regarding the efficiency of the lightning protection systems used in wind turbines are closely related to the knowledge of the physical parameters of lightning flashes. The data indicate that upward lightning flashes from wind turbines present characteristics comparable to those from telecommunication towers, though often influenced by severe meteorological conditions. The present work aims to describe the physical processes involved in the development of upward lightning flashes on wind turbines. A total of 49 upward lightning flashes recorded with high-speed cameras during campaigns carried out between 2021 and 2024 were analyzed. The distribution of the total duration of these flashes is highly asymmetric. The average total duration is 347 ms and the median is 264 ms. The initial continuous current period corresponds to approximately 96% of the total duration. For lightning flashes that exhibited subsequent return stroke, the median total duration (692 ms) was nearly three times longer than the median duration of a flash presenting only an initial continuous current period (230 ms). In addition, several events had durations significantly longer than average, highlighting the vulnerability of wind turbines to extreme events.