Direct-drive Wind Turbine Bearing Vibration Monitoring And Fault Diagnosis

As the fossil fuel consumption caused severe haze weather, which brought serious disasters to the people’s life of our country. In this case, wind energy as a renewable energy has got unprecedented attention by the government of other countries. Then the manufacturing technology of large wind turbine has been mature, especially direct-drive wind turbine is a new trend in the development of the wind turbine, which has obtained the widespread application in the wind turbine industry. However, wind turbine is restricted by the work environment, the failure rate is rather high, and then affects its reliability.Wind turbine bearing as the key part of the drive system of wind turbine, its fault has own characteristics. Main-shaft bearing easily brings about fatigue damage because of its long time inhomogeneous stress; the yaw and pitch bearings directly exposed to the air environment, which were easily influenced by bad environment air, the bad weather usually causes the huge overturning moment in the nacelles and blades, and then the inner and outer rings and rolling bodies of the yaw and pitch bearings will carry huge contact stress, and resulting in bearing internal deformation. The harsh environment, such as the sand、dust and moisture, is easy to cause the bearing wear and corrosion failures. So it is necessary to monitor wind turbine bearing fault,which have important practical significance to understand the mechanism of bearing fault, the bearing maintenance, the prevention of bearing fault and reduce the bearing fault caused economical losses.This paper makes a deepening research on the wind turbine bearings from the following aspects.(1) Through the operation status and stress condition of wind turbines, we analyzed structure characteristics, fault type, fault condition and reason of the fault of the wind turbine bearing. What the vibration test system of wind turbines bearing fault is built is the foundation of the mechanism of vibration, the frequency and signal characteristics for rolling bearing fault.(2) Through the fault characteristics of wind turbine bearings were diagnosed, the conclusion is that the Cepstrum is able to effectively identify the modulation side frequency component that is from the main characteristic frequency of the wind turbine bearing fault. The generalized Cepstrum can effectively diagnose about wind turbine bearing fault in the case of the strong noise interference. The envelope spectrum by demodulating can extract modulated information of bearing fault, which can identify the fault characteristic frequency, harmonic frequency and modulation side-frequency components from the wind turbine bearing fault.(3) Through the comparison analysis of the two kinds of circumstance between the normal and the fault wind turbine main-shaft and yaw bearing can verify the effectiveness of above analysis methods. The comparison analysis of vibration characteristics, operating property, signal characteristics and fault location of the normal and fault bearing, the conclusion is that the Cepstrum method and envelope method have certain limitations in the yaw bearing or the main-shaft bearing fault diagnosis. The Cepstrum method shows diagnosis results more clear and accurate than the envelope spectrum in the main-shaft bearing fault diagnosis. The envelope spectrum method is more powerful than the Cepstrum method function in the yaw bearing fault diagnosis.