Abstract: The rotor mass imbalance has a big effect on the safe and stable operation of the wind turbine generators, the traditional diagnosis technologies which are based on the vibration monitoring require a large number of sensors mounting on wind turbines, it costs a lot and the reliability is also poor. The experiment researches have been made using the diagnosis technologies based on the electrical signals in recent years, but it has not provide theory understanding for the diagnosis technologies. Based on the description of the mechanism of the fault, then in theory, derive the impact of the fault on the generator power, finally establish the simulink model under the fault which contains the rotor model, the drive train model and the generator model, and obtained the generator power signal which has detected the 1st frequency of the rotor under the fault, with the imbalance increases, the amplitude of 1st frequency increases too, it’s consistent with the experiment results of the ISET, the simulation results reveal the severity of the fault qualitatively, this method can be applied to the fault diagnosis system to determine the size of the imbalance mass.

Key words: Fault diagnosis, Fault modeling, Mass imbalance, Wind turbines