A Novel Distributed Sensor Network to Assess Wind Turbine Blade Acoustics for Structural Health Monitoring

ABSTRACT To reduce the need for scheduled wind turbine blade inspections and large‐scale repairs, a novel distributed acoustic sensing system for monitoring the structural health of wind turbine blades is proposed. This integral passive monitoring system utilizes a sparse array of in‐blade multimodal sensors and a single blade‐external downtower sensor, working together to monitor the naturally occurring acoustic environment generated by an operational wind turbine. This paper overviews the system‐level design approach, the controlled laboratory benchmark testing conducted, the deployment process exercised in the field, and test results revealing baseline healthy and aberrated acoustic radiation by operational turbines. A comprehensive test campaign was conducted using two different operational utility‐scale wind turbines in the field for more than 6 months each. Results from the first field test at the National Renewable Energy Laboratory helped establish an acoustic baseline that shows distinct mechanical acoustic tones mostly concentrated below 2 kHz with a 3 dB to 13 dB sound pressure level prominence relative to the spectral floor. Results from a second test campaign, conducted in a different location, demonstrate how the multimodal sensing approach allows, for the first time, the correlation of acoustic radiation at its source to blade position and the compartmentalization of various operational and environmental based acoustic events to specific blades and blade cavities.