Reliability analysis for the load-carrying parts of horizontal axis wind turbines

摘要

Presently, wind turbines are being designed in accordance with deterministic design rules. These rules concern the design of main components and the safety systems. They neither facilitate the quantification of the degree of conservatism in the applied safety margins nor explicitly address the reliability and availability of the wind turbine. By a case study of the Lagerwey LW 15/75 wind turbine design, it has been demonstrated that the wind turbine industry can take advantage of the safety and reliability practices applied in e.g. aerospace, nuclear and offshore industry. Qualitative methods for System Reliability, such as a Thorough System Description, State Diagram, Failure Mode, Effect, and Criticality Analysis (FMECA), Event Tree and Fault Tree Analysis, can be implemented immediatly in the design process of wind turbines. Quantitative analysis methods can be applied during the useful life period, where failures are random. System reliability is a strong and systematical method to improve and assess the safety and reliability of a wind turbine and to feedback operational experience. To reduce the early failures which are quite often the result of unknown phenomena during rare events, load measurement programmes and operation monitoring must be performed during the burn-in period of a wind turbine. The collection of data for the LW 15/75 turbines under study has shown limitations in the current practice. Not all types of data required for reliability purposes were recorded. Despite of the shortcomings of data collection, both qualitative and quantitative information has been derived from the available operational experience. This information is helpful to plan and optimize maintenance and inspection procedures. Recommendations are given to improve data collection and analysis possibly by means of a computerized system. The feasibility and applicability of Structural Reliability in wind turbine engineering has been demonstrated.