Observed Characteristics of Lightning Attachment to the Wind Turbines and Its Magnetic Field

In the present study, we analysed lightning flash strokes attached on the wind turbines. The data was simultaneously measured through a comprehensive lightning observation system in the Zhangbei wind farm in 2017 located in northwest of China. The camera and the related time-synchronized magnetic field are included in the present study. Based on magnetic field data, optical images, and data from the lightning location system, it is shown that the flashes demonstrated a noticeably large number of return strokes for strokes to the wind turbines in Zhangbei wind farm, with an average number of 8. The arithmetic mean and geometric mean of the time interval of all return strokes were 63.38 ms and 45.06 ms, respectively. The distance between the striking point and the observational site ranged from 7 km to 9 km. The current of each return stroke ranged from 3.8 kA to 62.9 kA. The median value of 50% of the current peak is 19.2 kA. The magnetic field waveforms all behave as microsecond-scale fast variations, and the magnetic field waveforms were all similar in shape. The 10-90% risetime ranged from 0.6 μs to 2.2 μs, the arithmetic mean and geometric mean are 1.1 μs and 1.0 μs. The half-peak width ranged from from 1.2 μs to 6.3 μs, the arithmetic mean and geometric mean are 3.4 μs and 3.3 μs, respectively. Furthermore, comparing peak value of magnetic field and lightning current, the magnetic field is approximately linear with the current as expected.