A Statistical Analysis of Wind Turbine Grounding Systems: a Study Focused on the Surge Impedance

The surge impedance of a grounding grid is a mandatory parameter to be considered in the project of a Lightning Protection Systems (LPS). As these parameter determinates de proper design and ensure the reliable operation of the associated grounding structure, its practical understanding is required. In this context, based on in situ measurements, the present work investigates if the surge impedance of a wind turbine (WT) grounding system presents significant values differences in two distinct situations: (i) when only the grounding grid and WT foundation were built and (ii) after the complete construction of the WT including the tower, nacelle and blades. The investigation is based on a statistical study supported by Analysis of Variance (ANOVA). Considerations about the measurement procedures are presented and experimental data are discussed. Preliminary results indicate that there is no significative difference between values from both scenarios. Moreover, recommendations are proposed in order to improve the data reliability to further investigations.