Condition Monitoring of Rotor Blades:Damages, ICe, Overload

摘要

Rotor blades are among the most highly stressed components of wind turbines.And if damaged they are also one of the most expensive parts to replace.The currently executed monitoring of rotor blades by visual inspections on a period basis with long intervals in-between can be problematic,because a small and easily rectifiable defect can grow to become a serious problem.Besides damages particular environmental conditions such as icing and overloads can also influence the operational state of the rotor blades and therefore the entire wind turbine.Since these phenomena are of temporary nature they can only the detected by a continuous surveillance of the blades.An introduction is provided to the analysis of a rotor blade's natural frequencies as the bases of a continuously operating condition monitoring system.The blade oscillations are measured with accelerometers mounted inside the rotor blades.The analysis of the spectra is done by comparing the measured frequencies to reference data.Severe and light damages can be securely distinguished from their appearance in the frequency spectrum.Examples show the correlation between damage and frequency deviations.1Ce formation as additional blade mass can be determined directly from the measurable frequency shift with an accuracy of up t0 0.004％of the blade mass which will be shown with examples.The method measures during shutdown periods as long as wind blows,thus enabling automatic restarting of the turbine without on-site inspection after ice has shed.Further,the experience of combined 750 0perational years of rotor blade monitoring is summarized.