Vibration Characteristics of a Hydroelectric Generating System During the Load Rejection Process

Abstract

Forces and moments increase rapidly in complex interactions while maintaining stability of the shaft for the hydroelectric generating system in the load rejection process. These interactions caused by factors such as the unbalanced hydraulic fault give rise to vibration patterns, which are of interest for fault identification and diagnosis. In this work, the vibration characteristics of the generating system are investigated in the load rejection process. The first is a novel-established model based on the interaction effect of the mechanical–electrical forces and the pressure pulsation solved by method of characteristics in the penstock. In the second analysis, the shaft displacement is compared with experimental data in order to verify the correctness of the established model. Transient radial displacements are conducted in different load rejection conditions and then mechanical and electrical factors are analyzed to investigate the shaft vibration characteristics. The results of this study suggest that the excretion coefficient of the runner inlet, the initial position angle of the turbine blade, the up guide bearing, and the mass of the generator rotor have the ability in decreasing the shaft vibration, while decreasing the mass eccentricity reduces the shaft vibration and ensure the structural reliability of the generating system.