Oscillations in turbogenerator sets, which consist of a synchronous generator, a hydraulic turbine, and an automatic speed regulator, are investigated. This study was motivated by the emergency that took place at the Sayano-Shushenskaya Hydroelectric Power Station in 2009. During modeling of the parameters of turbogenerator sets of the Sayano-Shushenskaya Hydroelectric Power Station, the ranges corresponding to undesired oscillation regimes were determined. These ranges agree with the results of the full-scale tests of the hydropower units of the Sayano-Shushenskaya Hydroelectric Power Station performed in 1988.