Abstract：The inter-turn short circuit fault and thermal imbalance fault of the generator rotor winding will both

cause a positive correlation phenomenon between rotor vibration and excitation current. In order to improve the

efficiency and accuracy of fault diagnosis，the research was conducted on the characteristics of the positive

correlation phenomenon for different types of faults. The relationship between the electromagnetic force and

excitation current of the rotor with inter-turn short circuit fault，the time-domain expression of the excitation

winding temperature，and the thermal expansion difference of the rotor components were analyzed. It has been

demonstrated that the method of comparing the correlation between vibration and excitation current in different

directions of excitation current variation can be used to determine the type of fault. Two generator sets were

diagnosed on site，and the dismantling situation after returning to the factory demonstrated the accuracy of the

analysis method.

      Key words：inter-turn short circuit；thermal imbalance；rotor vibration；excitation current；positive correlation