Turbine generator(13.8 kV, 137.5 MW) has high bearing vibration at rotation speed. Shorted turns in generator rotor windings have strong correlation with increased field current which is thus related to increase in bearing vibration. The recurrent surge oscillograph (RSO) test is performed on the rotor winding in turbine generator to detect shorted turns. The result of the RSO test indicates that shorted turns of rotor winding are generated in two locations. The RSO test was capable of identifying the presence, number, and location of shorted turns in generator rotor windings.