Analysis on stator circulating current characteristics under eccentricity faults of turbo-generator

Abstract

The air gap eccentricity fault is one of the main mechanical faults of turbo-generators. The stator wingding parallel branches circulating current characteristics under normal condition and the fault were analyzed in order to monitor and diagnose the fault, and a diagnosis method for the fault based on the circulating current characteristics was put forward. Firstly, the turbo-generator parameters were analyzed under normal condition and the fault, viz. air-gap magnetomotive force, the magnetic permeability, the magnetic flux density. Secondly, three types of eccentricities, i.e. static eccentricity, dynamic eccentricity, and mixed eccentricity faults were studied. Moreover, the instantaneous electric potential equation of each stator parallel branch and the instantaneous electric potential difference between the two stator parallel branches were further deduced. Then, the circulating current characteristics were investigated under the fault. The results show that the first harmonic circulating current increases when the air gap eccentricity fault occurs. Finally, the circulating current of a type SDF-9 generator with the air gap eccentricity fault was measured in laboratory to verify the theoretical analysis presented above.