Provided is a method of diagnosing at least one winding set of a stator of a generator during operation, the winding set having plural wires for plural phases, the method including: obtaining, for each of the plural wires of the winding set, an individual strength of an individual power output from the respective wire of the plural wires of the winding set; obtaining a sum strength of power; forming, for each considered wire of the plural wires of the winding set, an individual ratio between the individual strength of the considered wire and the sum strength; forming, for each considered wire of the plural wires of the winding set, a diagnostic value by subtracting from an individual ratio not corresponding to the considered wire a term depending on the individual ratio corresponding to the considered wire; diagnosing at least one wire based on comparing the diagnostic values.