Analytical Surveys of Transient and Frequency-Dependent Grounding Characteristics of a Wind Turbine Generator System on the Basis of Field Tests

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.