Diagnosis of Rotor Eccentricities in Two-Pole Synchronous Generators By Spectrum Analysis of Complex Split-Phase Currents

Two-pole synchronous machines (turbogenerators) are high power machines used in generating plants, needing careful monitoring to avoid costly faults. The rotors may fail due to thermal, mechanical, and magnetic problems. Rotor eccentricities make rise unbalances in the stator armature split-phase currents. This paper shows a diagnosis method based on symmetrical components analysis in 2-pole round-rotor machines, and FFT spectral analysis of 4-pole complex sequence currents carried out from split-phase currents. The split-phase current signature analysis is validated in this paper by extensive time-stepping finite-elements simulations of a 600MVA practical turbogenerator, with various fault degrees, voltage levels, and loads. The results show very good agreement between the theoretical previsions and the simulations.