Reliability Analysis and Preventive Maintenance Strategy for Competitive Failure Process of Wind Turbine Blade with Hard Failure-Caused Threshold Variation

Abstract

During the operation of wind turbines, various failure forms are often caused by the interaction of their own performance degradation and external shocks due to the complexity of the operating environment and the form of the load. Whereas these failures are not obvious, improvement of life cycle and reduction of maintenance cost can be realized by identifying potential failures using a sound maintenance strategy and inspecting each system. In this study, we further extend the applicability of the competitive failure model by considering the existence of multiple shock types in the degradation process based on the competitive failure model of threshold variation caused by hard failure. We discuss two different cases of varying failure thresholds due to the multiple shock types. In case 1, cumulative degradation causes the system to fail at less than a predetermined failure threshold and with the presence of multiple shock types. In case 2, the cumulative degradation of the system reaches a predetermined failure threshold but is less than or equal to the set maximum failure threshold under multiple shock types. Finally, the validation is performed by two special cases. A status maintenance model based on preventive maintenance state thresholds is investigated to ensure that the system works properly under different degradation stages and to obtain the optimal preventive replacement threshold based on minimizing the desired cost rate. At last, the feasibility of the method was verified by reliability assessment and sensitivity analysis of wind turbine blade.