A Proposed Method for Calculating Earth Electrode Length for a Wind Turbine Generator Grounding System

A safe and reliable grounding system plays a critical role in the design of an effective lightning protection system of a wind turbine generator. An accurate design of grounding electrodes is required to achieve the necessary low impedance of a wind turbine generator earthing system. IEC 61400-24 provides guidelines for selecting the minimum length of an earth electrode, however, this standard cannot be utilized for all types of electrode shapes and buried depths. Moreover, it is important to address the frequency dependency of soil resistivity for the selection of electrode length. This paper proposes a novel method enhancing the IEC 61400-24 standard method. Also, a thorough analysis of existing method with suitable recommendations for the selection of electrode length for various dimension and buried depth to address the frequency dependency issue has been provided. Finally, guidelines for the selection of electrode length for the wind turbine grounding design from the lightning protection view point are proposed.