To exploit high wind conditions, wind turbine generator systems are constructed in places with few tall structures; as a consequence, they are often struck by lightning. This results in breakdown and malfunction of electrical, communications, and control systems inside and adjacent to the wind turbine generator system because of ground potential rise. Impulse tests were conducted on an actual wind turbine generator system and analytical surveys based on field tests were carried out using electromagnetic field analysis. The ground potential rise of the system and that around its foundation was measured and analyzed. The grounding system employed in this study consisted of the foundation, grounding mesh, and foundation feet. The frequency characteristics were calculated using the Laplace transform to get voltage responses for all types of lightning current waveforms.Step and typical lightning current waveforms were used to calculate potential rise responses.

In order to exploit high wind conditions, wind turbine generator systems are often constructed in places where few tall structures exist; therefore, they are often struck by lightning. Much of the damage caused by lightning is from the resulting breakdown and malfunction of the electrical, communication, and control systems inside the wind turbine generator system; these breakdowns can be attributed to a rise in electric potential both within the system and in the surroundings due to lightning. Impulse tests were conducted on a wind turbine generator system at a disposal site where the conductivity of the ground was very low, like that found on the surface of the sea. The rise in ground potential of the system, and around its foundation, was measured. When a wind turbine generator system is constructed at a site where the grounding resistivity is very low, the potential rise at the wave front typically becomes larger than that of the steady state because of the inductivity of the grounding system. Therefore, it is very important that the transient characteristics of the grounding system are well understood. 

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In recent years, the number of lightning damages has been increased with that of lightning flashes. Therefore, it has become important to understand the features of lightning current damaging electrical and electronics equipment. At the sites of wind turbines and tall antenna towers such as TOKYO SKYTREE ® , lightning current waveforms are observed using large-scale Rogowski coils. Data of not only the main current measured by the large-scale Rogowski coils but also the shunt current damaging electrical and electronics equipment are useful to establish lightning protection methodologies. In this paper, we present the developed system using a Rogowski coil to measure such shunt current.

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