Observation of lightning flashes to wind turbines

An observation of winter lightning flashes striking wind turbines has been conducted at Nikaho Kougen Wind Farm in the coastal area of the Sea of Japan. We measured the current waveforms of the lightning flashes using wide-frequency-band Rogowski coils and observed the features of lightning flash striking the wind blades with still cameras and a CCTV camera. 128 flashes were captured from 2005 to 2006 and result of measurement was reported in previous papers [1]. We obtained 150 flashes in following season from 2007 to 2008 and 278 flashes were recorded totally. This paper reports overall result of measurement from 2005 to 2008. The median values of the duration, current peak, and charge transfer of bipolar flashes were larger than those of negative and positive flashes. Most of the flashes were initiated by an upward lightning leader. Furthermore, 30% of the flashes are multiple termination strokes to the wind turbines in winter.