Structural Health Monitoring of Wind Turbine Blades

Abstract

Wind Turbine blade failures can occur in several modes, which may depend on the type of construction and load history. Cracking and delamination are two typical modes of blade failure (Fig. 1). A structural health monitoring (SHM) system can help to better understand warranty costs and warranty periods for the blades in wind turbines and predict imminent failure before it occurs. Currently, industry best practices are to increase the number of physical inspections when blades are approaching the end of their fatigue lives. Implementation of an in situ monitoring system would eliminate or greatly reduce the need for such physical inspections. Another benefit of such a monitoring system is that the life of any given component could be extended since real conditions would be monitored. The SHM system is designed to operate while the wind turbine is in service. This means that wireless communication options will be implemented. Because blade failures occur due to cyclic stresses in the blade material, the sensing system will focus on monitoring strain at various points. This paper describes a design and implementation scheme for a real time structural health monitoring system in order to better understand when blade replacement is necessary. Although not described in this research, the same concepts can also be applied to gearbox damage detection.