Evaluation of Wind Turbine Earthing System

The majority of the wind farms are constructed in high altitudes and isolated areas which put in risk the wind turbines due to their exposure to lightning activity and their high total height. Wind turbine earthing system is part of its lightning protection design according to IEC61400-24 and shall ensure a safe path for the lightning current hitting the wind turbine and a safe working environment for the live beings. The earthing system contributes also in earth fault current dissipation and is considered in the electrical studies. In the current paper, the performance of a wind turbine earthing system of an existing wind farm with medium soil resistivity is discussed, based on simulations in ATP-EMTP which is suitable for steady-state and transient studies. Two cases (Case A and Case B) were examined relatively to the lightning current, i.e. 5 kA and 150 kA for the same concrete and soil resistivity, applied at the base and the top of the tower, respectively. In Case A, two occasions were considered by using or not an extra vertical rod placed at the base of the tower. In Case B, two scenarios were assumed by considering or not the ionization effect. It was noticed the reduction of the voltages and currents, when the ionization effect was regarded. The results can be used to evaluate the earthing system performance and the need for improvement to ensure a reliable operation of the whole asset mitigating the operational risk for the equipment.