Method for cleaning a generator of a wind turbine

A method for cleaning a generator of a wind turbine, wherein the wind turbine comprises a tower, a nacelle rotatably mounted to the tower, a wind turbine rotor with at least one rotor blade, the wind turbine rotor being rotatably mounted to the nacelle around an essentially horizontal rotational axis, and an electric generator drivable by the wind turbine rotor, the electric generator including a fixed housing and a rotating housing, a generator rotor having magnetic elements, a stator having windings, and a cooling device attached to an opening of the fixed housing, the method comprising:

• locking the wind turbine rotor and shutting off the electric generator;
• removing the cooling device such that the opening is accessible for maintenance purposes;
• inserting a cleaning agent into the opening such that the cleaning agent gets at least partially in effective contact with a winding and/or with a magnetic element;
• at least partially removing the cleaning agent from the electric generator;
• mounting the cooling device to the opening;
• and
• releasing the wind turbine rotor,
• wherein the cleaning agent is or comprises a grease remover, and wherein the grease remover is non-water-soluble and is a fluid liquid such that the electric generator of the wind turbine can be partially flushed with the grease remover, has a density larger than 0.6 g/cm3 and lower than 0.85 g/cm3, has a kinematic viscosity larger than 1.3 mm2/s and lower than 2.5 mm2/s, and comprises N-Paraffins and hydrocarbons.