Numerical simulation of the effect of wind removing the corona space charge over grounded structures under thunderstorm conditions

Different types of tall structures are severely exposed to lightning discharges, including power lines, communication towers, buildings and wind turbines all over the world. The present paper focuses on the numerical modelling and simulation of the effect of wind on the electric field developed over a grounded object under thunderstorm conditions. The electric field created by the charge distribution in the thundercloud above the object, which is in first place enhanced by its geometry, leads to the generation and secondly upward propagation of charge from the object. Recent investigations underline that the effect of the removal of the corona space charge by the wind leads to a higher field strength at the grounded object and, therefore, it becomes easier for it to initiate an upward connecting leader compared to a situation where the space charge is present. In this work, a simplified space charge drift model quantifies the difference between static towers and rotating wind turbines which are influenced by different resultant wind velocities. The voltage distribution and ion drift velocities in the vicinity of the grounded structures are illustrated. The results show a higher voltage gradient at the side of the object facing the wind, leading to a higher probability of lightning attachment.