A Framework for the Reliability Analysis of Wind Turbines against Windstorms and Non-Standard Inflow Definitions

Abstract

The development and application of design standards has been a critical element in raising the level of reliability across the entire wind energy industry. Designs have an objective set of criteria against which they can be judged and entire fleets of turbines can be manufactured to a common set of criteria. Each wind power development is then left with the task of assessing whether or not a particular turbine designed for a standards-driven class is appropriate for a particular site. There are increasing numbers of turbines deployed in sites that possess unusual wind speed and turbulence characteristics, perhaps driven by complex terrain or other special features. The effects of atmospheric stability and stratification can also lead to off-design loadings. A unified approach to dealing with the risks using an event tree framework is applied to identify and organize the critical assessments needed to fill out the risk portfolio. This approach is applied to normal operation as well as to the variants or off-standard atmospheric conditions that could be encountered including extreme atmospheric events. Many of the characteristics of extreme atmospheric events that impact typical wind turbine systems are yet to be characterized in ways that drive aeroelastic loads and design criteria. Hurricanes, thunderstorms, and tornadoes have well-studied influences on buildings, bridges, etc., but the coherence structure and turbulence kinetics at the spatial scale of wind turbine rotors are not as well documented. This study examines the aeroelastic response of a wind turbine to example offstandard and extreme atmospheric conditions and maps out site criteria that provide direction in conducting a risk assessment.