Study On Detection Method And Monitoring System Of Looseness Of Wind Turbine Tower Bolts

As the installed capacity of wind turbines continues to increase,the workload of wind farm operation and maintenance personnel gradually becomes larger,so more and more functional requirements are required for the monitoring system of wind turbines.At present,due to the lack of real-time monitoring of the loosening of the tower bolts and the monitoring of the safety status of the tower in the wind turbine monitoring system,the collapse of the wind turbine tower has occurred from time to time,resulting in greater economic losses.In response to this problem,this thesis proposes a strain detection method and a phase difference detection method for the loosening of the wind turbine tower bolts,and carries out relevant feasibility verification experiments.Finally,a wind turbine tower monitoring system is designed in accordance with actual needs.The use of this monitoring system has a significant practical effect and important practical value for avoiding wind turbine tower collapse accidents.The main research contents are as follows:(1)Aiming at the problem of monitoring the looseness of individual bolts of wind turbine towers,this thesis proposes a Built-in strain detection method.First,the bolt(M39)was simulated using COMSOL software.After obtaining the strain distribution inside the bolt,the placement of the sensor was determined.Then,a multifunctional bolt loosening test platform was designed and built,and the calibration experiment of bolt preload and strain was carried out.The calibration function is obtained.Finally,the verification experiment shows that the error of the calibration function is less than 5%,which meets the basic error condition.(2)Aiming at the problems of the large number of bolts at the flange of the tower of the wind turbine,the difficulty in accurately determining the number and position of loosening,the complicated layout and high cost of the strain detection method,this thesis introduces a phase difference detection method.First,the flange model was modeled and simulated using ANSYS finite element software.It was concluded that when the number of bolts loosened was greater than 50%,the phase difference between the upper and lower flanges would have obvious changes.The feasibility of the method was initially verified,and then designed and built.The flange model test bench was tested for the bolt loosening phase difference detection method.The final experimental results showed that there was a positive correlation between the bolt loosening amount and the phase difference.When the bolt loosening amount was greater than 25%,the phase difference value was greater than30 °.The effect is more obvious.(3)Combining the above bolt detection methods and other monitoring technical methods(vibration,inclination and strain),this thesis designs and develops a wind turbine tower condition monitoring system.Through the demand analysis of tower condition monitoring,system architecture selection and database design,the function of real-time monitoring of tower vibration,inclination,strain and bolt loosening is designed and implemented.