Application of Oil Debris Monitoring For Wind Turbine Gearbox Prognostics and Health Management

Experience has shown that premature gearbox failures are a leading maintenance cost driver that can easily lower the profit margin from a wind turbine operation. Prognostics and Health Management (PHM) techniques offer the potential of effectively managing gearbox health problems by detecting early damage, tracking the severity of damage, estimating the time to reach pre-defined damage limits, and providing key information for proactive maintenance decisions. Experience has revealed that major damage modes of wind turbine gearboxes are bearing spall and gear teeth pitting, both of which release metallic debris particles in the oil lubrication system. Oil debris monitoring is thus well suited to provide an early indication and quantification of internal damage to bearings and gears of a wind turbine gearbox.This paper reviews the application of oil debris monitoring as an effective PHM solution for wind turbine gearboxes. The paper describes the principle of operation of the oil debris monitoring technology and the principle of application for effective PHM of wind turbine gearboxes. The paper explains the common surface fatigue damage mode of bearing and gear rolling elements and the characteristics of the destructive debris that result from this damage mode. The paper outlines a simple means of deriving accumulated debris count damage limits based upon basic gearbox component geometry and the use of moving averages for estimating rates of debris generation as a simple yet effective damage data-driven propagation model. Finally, the application of oil debris monitoring as an effective PHM technology for wind turbine gearboxes is illustrated by presenting actual data obtained from seeded fault bearing and gear tests and fielded gearbox applications.