Study on the Importance of Precise Control of Installation Deviation to the Structural Behavior of the Shaft System of a 1000 MW Hydro-generator Unit

The stable operation of the giant hydro-generator unit's shaft system determines the power station's safety. In this study, the full three-dimensional model of the shaft system of a 1000 MW hydro-generator unit is established to accurately analyze the structural behavior of the shaft system via the finite element method with different boundary conditions. The analysis results show that the installation deviation increases the oil film thickness of the hydraulic bearings and greatly reduces the bearing stiffness of the hydro-generator shaft system. Since the bearings are the most important boundary conditions of the shaft system, the reduction of the bearing stiffness due to installation deviation is 1/10 of the designed bearing stiffness, which significantly changes the eigenmodes and eigenfrequencies of the hydro-generator shaft system. The first eigenfrequency of the hydro-generator shaft system with installation deviations is around 68.8% of the eigenfrequency without installation deviations. The installation deviations negatively affect the safe operation of hydro-generator units. Therefore, it is extremely important to control the shaft system installation deviation with high precision to ensure the stable operation of hydro generator units.