A safe and cost-effective design of a wind turbine generator (WTG) grounding system requires accurate modeling of local soil resistivity, particularly when wind turbines are spatially distributed across a wide area with different soil types and features. In this paper, three locations at an Australian wind farm were modeled based on measured data. Four soil resistivity models were considered: uniform, multilayer horizontal, vertical, and exponential variation with depth. Full-wave electromagnetic simulations were performed at different lightning discharge current frequencies to find the expected ground potential rise and WTG earthing impedance in the event of a lightning strike. Furthermore, the effect of frequency dependent soil parameters on the WTG earthing was analyzed, along with the effect of foundation rebar on the grounding impedance. Our results show that an accurate soil resistivity model is critical in the design of a WTG earthing system. INDEX TERMS Wind turbine generator, lightning protection, soil resistivity, grounding system, grounding impedance, ground potential rise. The recent proliferation of wind farms as a source of clean energy production calls for an effective design of the grounding system to ensure their safe and reliable operation over their entire life span [1]. Wind turbine generators (WTGs) are extremely vulnerable to lightning strikes due to their size, shape, and location, which is usually in mountainous sites with very high soil resistivity [2], [3]. Moreover, it is worth noting that, according to recent studies [4], elevated terrain can further increase the value of grounding resistance. When lightning strikes a WTG, electrical and electronic components embedded in the WTG are prone to failure and damage as a result of the ground potential rise (GPR) caused by electrical surges [2]. Consequently, WTGs should be provided with a low impedance grounding system to ensure safe and reliable operation. Recommendations for effective grounding and lightning protection of WTGs and wind power systems are provided by IEC 61400-24 [5]. The associate editor coordinating the review of this manuscript and approving it for publication was Huiqing Wen.
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