experimental investigation, whose most important segments are described in this paper, should enable a better understanding of this phenomenon. The tests were conducted in the ICMET Craiova high-voltage laboratory, applying the up-and-down method for determination of the 50 % flashover standard switching voltage. The impulse voltage waves were applied between the specially designed arching electrode and the blades of a reduced-size wind turbine model, driven by a frequency controlled motor. A lightning protection system in the form of receptors on the tips of the blades was examined. According to the theory of similarity the paper discusses the characteristics of direct atmospheric discharges for several typical rotational speeds of the wind turbine. It was concluded that the number of direct lightning strikes in the zone of the air termination system on the blades is decreasing due to the rotation of the blades.

Keywords: Air-termination system, Arching electrode, Blades, Flashover voltage, Lightning protection, Wind turbine