Assessment of Wind Turbine Grounding System

Wind energy is one of the significant contributors of achieving the 2020 energy targets while its penetration is high in most of the electricity markets in Europe. Large majority of wind power plants is erected in high altitude or isolated areas where there is increased lightning activity. The wind turbine lightning protection system which shall comply with IEC61400-24 as minimum includes the internal electrode and the external one which is mainly the foundation grounding and the interconnection of earthing grids between neighboring wind turbines provided that such exist. The grounding system acts as an interface between the wind turbine and the external environment and shall be designed and constructed in compliance with relevant IEC and IEEE standards, national standards and shall ensure smooth and reliable operation of the power production unit. Furthermore, it shall allow dissipation of both lightning and earth fault current and shall ensure the safety of human beings. In the current paper is investigated with the use of ATP-EMTP software, the transient behavior of a wind turbine grounding system considering several scenarios, soil conditions and lightning parameters. The assessment is implemented via simulations which assess apart from the reliability of the system itself and ways of improvement, also the safety of live beings. The simulation results show that any earthing system add-ons decrease the noticed overvoltages while any interconnection does not contribute to further reduction of occurred overvoltages. The derived results by the study can be used by wind power plant owners in order to evaluate the plant overall design, to ensure a safe working environment for the personnel and reliable operation of the whole wind installation. Apart from this, the results can be also considered as basis for future similar projects with equivalent lightning conditions and/or environmental conditions.