DPP-BOTDA Based Wind Turbine Blade Fatigue Monitoring Technique And Evaluation Method

Fatigue is a critical issue for the safety of wind turbine blade. Blade failureleads to system invalidation, even hit the tower and cause the progressive collapseof the whole wind power generation system. Due to the cumulative fatigue damage,it’s very hard for wind power system to satisfy the standard20years designservicelife. It is highly important to conduct a health monitoring system for windturbine blade to ensure system safety, reliability and maintainability.Up to now, there is no qualified online fatigue monitoring technique for thewind turbine blade due to the harsh working environment, aerodynamic requirement,long service life and large scale. In this paper, a novel wind turbine blade onlinefatigue monitoring system was developed using Differential Pulse-width PairBrillouin Optical Time Domain Analysis (DPP-BOTDA) technique. Characteristicsof DPP-BOTDA monitoring system and DPP-BOTDA based wind turbine bladefatigue monitoring technique were studied. A novel fatigue damage evaluationmethod base on the Brillouin gain spectra was proposed. The specific contents are asfollows:1：A DPP-BOTDA monitoring system was set up, system characteristics,especially signal characteristics and spatial resolution impact, were studied.2：A500W small wind turbine blade static test was conducted to studyDPP-BOTDA based wind turbine blade full scale strain monitoring technique,including layout of the optic fiber, temperature compensation method, signalpositioning method, measuring accuracy, signal distortion processing method andBrillouin gain spectrum characteristics of the crack area.3：A500W small wind turbine blade fatigue test was conducted using linearoscillating mass method. DPP-BOTDA based wind turbine blade fatigue monitoringtechnique were studied. Layout optimization of the optic fiber was studied. Bladefatigue damage model was found. DPP-BOTDA signal characteristics of differentfatigue damage model were studied. Damage identification approach based onDPP-BOTDA signal was proposed.4：A novel fatigue damage evaluation method base on the Brillouin gain spectrawas proposed. The fatigue damage index was defined. the fatigue damage indexdistribution on the whole wind turbine blade was calculated and the relationshipbetween fatigue damage index and load cycle was given.