Multiple Lightning Discharges in Wind Turbines Associated with Nearby Cloud-to-Ground Lightning

This paper presents the analysis of five events where simultaneous lightning currents were registered in different wind turbines of a wind farm with lightning monitoring equipment installed. Measurements from current monitoring devices installed at the wind turbines and observations from auto-triggering video cameras were correlated with data from the U.S. National Lighting Detection Network. In all five events, the correlation showed that a cloud-to-ground (CG) lightning stroke with high peak current struck the ground within 10 km of the affected turbines at the time of the currents in the wind turbines. The polarity of the CG discharges was negative in two events and positive in the three remaining events, which were also accompanied by small intracloud pulses. According to the analysis of the data for each event, the simultaneous discharges at the wind turbines are most likely caused by the nearby CG strokes, involving mechanisms that vary depending on the polarity of the associated CG stroke. The analysis also suggests that the event of upward lightning from wind turbines triggered by nearby lightning activity occurs very often and therefore it should be considered carefully in the processes of assessing the lightning exposure of the wind turbines, designing the lightning protection, and defining validation tests.