Shaft mis-alignment induced vibration of a hydraulic turbine generating system considering parametric uncertainties

Shaft mis-alignment is one of the most common faults in rotating machineries. Most existing approaches that establish mathematical models address the complex forces acting on the shafting of the hydraulic turbine generating system, and fail to comprehensively consider the impact of the coupling hydro-mechanical-electrical factors on the vibration of the shafting. In this paper, a novel model is developed, considering the coupling relationship of the penstock (hydraulic system), the power grid (electrical system) and the guide vane device (mechanical system). Global sensitivity analysis is performed to investigate the effect of parametric uncertainty on the shaft vibration, and the novel model is verified compared with the numerical results of the FEW model and measured data from monitoring system of Nazixia hydropower station. Furthermore, the effects of the coupling hydro-mechanical-electrical factors are analyzed in detail when the mis-alignment distance is set as different values. The results show the synchronous dynamic evolutions of the hydraulic turbine flow, the guide vane opening, the rotational speed and the amplitudes of the shafting centroid. Moreover, the relationship between the mis-alignment distance and centroid amplitudes is investigated, and a stable operation interval is obtained regarding the coupling mis-alignment distance on the basis of the criteria of the coupling mis-alignment in rotating machineries. Finally, these results offer a useful insight into the vibration diagnosis of hydropower stations.