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This is an excerpt from the Second Quarter 2012 edition of the Wind Program R&D Newsletter.

Premature gearbox failures have a significant impact on the cost of wind farm operations. In 2007, the Energy Department's National Renewable Energy Laboratory (NREL) initiated the Gearbox Reliability Collaborative (GRC). The project combines analysis, field testing, dynamometer testing, condition monitoring, and the development and population of a gearbox failure database in a multipronged approach to determine why many wind turbine gearboxes do not achieve their expected design life—the time period that manufacturers expect them to last.

The collaborative of manufacturers, owners, researchers, and consultants focuses on gearbox modeling and testing and the development of a gearbox failure database. Members of the collaborative also investigate gearbox condition-monitoring techniques. Data gained from the GRC will enable designers, developers, and manufacturers to improve gearbox designs and testing standards and create more robust modeling tools. The Gearbox Reliability Collaborative (GRC) website offers wind turbine manufacturers and researchers accessible information on the latest results and reports by the collaborative.

The GRC project instrumented two identical, representative gearboxes. Knowledge gained from the field and dynamometer tests conducted on these gearboxes builds an understanding of how the selected loads and events translate into bearing and gear response. The GRC also investigates condition-monitoring methods to improve turbine availability; evaluates current wind turbine gearbox gear and bearing analytical tools and models; develops new tools and models; and recommends improvements to design and certification standards.

Information gained from the various projects within the GRC led to the development of the GRC Failure Database. This database provides the means for multiple partners to document root cause analyses in a tool that identifies key failure trends. Once identified, the trends allow researchers to focus on the solution to gearbox challenges, and the database provides a method to measure improvements.

NREL and its GRC partners have been able to identify shortcomings in the design, testing, and operation of wind turbines that contribute to reduced gearbox reliability. In contrast to private investigations of these problems, GRC findings are quickly shared among GRC participants, including many wind turbine manufacturers and equipment suppliers. The GRC website makes the findings public for use throughout the wind industry.

In February, the GRC members met at NREL in Golden, Colorado, to discuss the completion of Phase 2 testing, which included hundreds of hours of steady state and dynamic loads testing. Selected data sets have been released to the GRC partners to aid in data validation and modeling assumption convergence. The February meeting included planning of Phase 3 modeling, analysis, and testing activities to be conducted in the remainder of 2012 and in 2013. Condition-monitoring data were collected and disseminated into a recently completed condition-monitoring round-robin analysis by GRC condition-monitoring partners.

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