Analysis and Treatment of the Trip Accident Caused by Bearing Vibration of the 300Mvar Synchronous Condenser
With the development of UHVDC transmission system,large capacity synchronous condensers are installed in power grid to supply dynamic reactive power compensation and prevent commutation failure.During the start-up and commissioning of the synchronous condenser in a converter station,the bearing vibration of the synchronous condenser on excitation end at X-direction exceeded the standard level,which led to a trip accident.Combined with the Bode diagram and the waterfall diagram of the vibration,it was found that the reason was that the double-frequency resonance occurred when the synchronous condenser passed through the third-order sub-critical rotating speed of the rotor during the acceleration process,and the resonant frequency was close to a certain natural frequency of the bearing system,resulting in mechanical resonance.Then the stiffness of the bearing system was adjusted step by step and the bearing seat was replaced to avoid the double-frequency resonance frequency of the rotor and to enhance the damping on site.It was found that the problem of bearing vibration has been improved to some extent,but it still exceeded the normal operation requirements after the test.Subsequently,the fixing method of the emergency oil tank at the top of the bearing seat on excitation end was adjusted,and the structure of the emergency oil tank was optimized.It was found that the bearing vibration on excitation end was significantly reduced,and the bearing vibration during start-up and shut-down process of the synchronous condensers reached the requirements of safe operation.
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