Experienced owners and original equipment manufacturers with a large fleet of wind turbines expect some failures due to random strength exceedances. As with infant failures, it is prohibitively expensive to overdesign wind turbine components to survive all likely random, extreme failures. The rate of a random failure is constant regardless of the equipment age. These failures are caused mostly by an unlikely string of preceding events, which can be an overload event like a 50 year extreme gust or a lightning strike. Random failures are expected to appear throughout the wind turbine life cycle. Premature failures can impact a small or a large portion of an aging turbine population and these failures often disrupt operations like a “bump in the road,” or in extreme cases may be like a “fall from a small cliff.” Corrosion is another premature failure seen on wind turbine components. Axial cracks are a common premature failure of wind turbine gearbox bearings. Premature failures are often detected after some period of operation and may progress to show signs of degradation and wear before functional failures. Premature failures include those events due to a latent defect in the design, manufacturing process, or application (including maintenance activities). Performing life data analysis on infant failures provides the wind turbine owners with a way to measure the quality management of the supplier and to understand the value of a supplier warranty. For wind project owners, the majority of infant failures are mitigated by a supplier warranty. The allowable defect rate is a function of the manufacturer’s quality management and risk assessment. Preventing all infant failures is prohibitively expensive and every turbine manufacturer must allow some defect rate for each component. These types of failures are more likely to occur early in life and have a decreasing incidence rate with age. Infant failures are those events mostly due to wear-in problems or quality defects from the material manufacturing process. Wind turbine components commonly suffer from four types of failures: infant, premature, random, and wear out. Ĭomponent life cycle reliability needs to consider all independent failure modes of the component. Figurative chain of dependability showing the relationship of major equipment in a wind turbine.