Abstract: As the core equipment of a power plant, the health status of the rotor winding of a generator directly affects the safe and stable operation of the unit. During the maintenance and pre-test period of a generator in a certain power plant, the RSO (repetitive pulse) test data indicated that there might be an inter-turn short circuit fault in the rotor winding. However, subsequent multiple supplementary test data contradicted this diagnostic conclusion. This paper elaborates on the entire process of the abnormal data investigation and discusses the limitations of the RSO test in diagnosing inter-turn short circuits in rotor windings and the comprehensive judgment methods. The investigation approach and handling experience presented in this paper can provide important references for the fault diagnosis of rotor windings in similar generators and have practical guiding significance for ensuring the safe and economic operation of the units.