The diagnosis method of generator rotor winding inter-turn short circuit fault based on excitation current harmonies

The early diagnosis of rotor winding inter-turn short circuit fault is one of the most difficult problems in the operation of large synchronous generator, and a diagnosis method based on excitation current harmonics is described. Through analyzing air-gap electromagnetism characteristic on the fault, it is got that armature reaction magnetic field non-synchronously rotates with rotor when harmonics' times and the poles' pairs of generator satisfy a certain relation, so additional harmonic current is induced in rotor winding, and gives the additional harmonic equation, which is the function of air-gap excitation magnetic field harmonic frequency, poles' pairs of generator and rotor mechanical revolution. Finally, practically acquires the excitation current of MJF-30-6 generator on the rotor winding inter-turn short circuit fault, the results of verification show that the theory analysis is right, and points out that the amplitude of additional excitation harmonic current can reflect the rotor inter-turn short circuit fault extent.