Protection for wind power station

A wind power station (1) comprises a wind rotor (3); a transmission (8) mechanically coupled to the wind rotor (3); an asynchronous generator (10) having a generator rotor (11) mechanically coupled to the transmission, and a generator stator (12) electrically coupled to a power grid (2); and a protection unit (14,15) protecting the generator and the transmission against accidental breakdowns of an alternating voltage provided by the power grid. The Protection unit (14,15) includes at least one choke (14) electrically arranged between the power grid and the generator stator, and a synchronous electrical machine (15) electrically coupled to the choke.