Vibration is one of the common problems of synchronous condenser set. During vibration monitoring of off-grid driving and running down of one No.2 synchronous condenser at certain converter station

the vibration velocity of the support system on excitation end at the horizontal direction is up to 12.53 mm/s

higher than the trip value of 11.8 mm/s. In order to ensure the safety of subsequent integrated start-up and grid connection related test

a kind fault diagnosis method combining Fourier transform and frequency response function test is proposed. First

short-time Fourier transform is applied to the vibration signal of rotating machinery to obtain time-frequency diagram. Then

frequency response function test and analysis are performed in accordance with the results of time-frequency diagram. The results show that when the rotor speed is greater than 2 700 r/min

the double frequency component of the vibration has obvious signal characteristics

whichiscausedbytheproximityofforcedvibrationfrequencytothenaturalfrequencyof thesupport system on excitation end. Finally

the change of natural frequency of original support system on excitation end through the separation of emergency oil tank support and bearing seat can

to a certain extent

reduce the horizontal vibration value of bearing seat on excitation end at horizontal direction in the process of running down and off-grid.