Increasing the reliability of industrial multi-MW wind turbines

Although wind turbine gearboxes are designed to remain in-service for 20-25 years, this is not the case since a large number of failures have been reported to occur prematurely. A large number of gearboxes fail after 7 to 8-years in-service. In offshore wind farms gearbox failures have been reported as early as only 1 to 2 years in-service. Hence, wind turbine gearboxes are currently a source of significant reliability issue resulting in noteworthy loss of production and downtime for wind farm operators. Within this paper the quality of the materials used for manufacturing gears and bearings used in industrial wind turbine gearboxes has been evaluated. In addition, the damage mechanisms affecting gears and bearings have been investigated based on metallographic analysis of failed samples removed from in-service industrial wind turbines. Finite Element Analysis (FEA) has been carried out in order to simulate damage initiation and propagation in gear and bearing materials under inservice conditions. The results have been compared with those obtained from the failed samples retrieved from the field. Finally, an integrated condition monitoring methodology based on the use of online oil sensors coupled with vibration analysis and acoustic emission for the reliable evaluation of wind turbine gearboxes is presented.