Fiber optic load monitoring of wind turbine blades
Condition based maintenance is increasingly being used in the control of operation and maintenance costs of wind turbines, especially those offshore where site visits and maintenance tasks are particularly expensive.
However, traditional techniques such as SCADA data, drive train monitoring, inspection of oil samples etc. all have one thing in common. That is they all start providing data before degradation of the components really starts to occur.
Since the wear on components and assemblies is related to the loads acting on the structure, ECN has developed a “Fiber Optic Blade Load Monitoring” (FOBM) system. Since most of the loads are introduced via the rotor blades, this development has focussed on a method of monitoring the blade root bending moments. The data is used by the turbine operators to decide if and when maintenance action is required or to postpone or prioritise visits.
A fiber optic based sensor technology was selected over traditional electric strain gauges, to ensure less drift over time, a longer lifetime and to provide reproducible data. FBGS draw tower gratings were chosen over traditional FBG’s to ensure the sensor was sufficiently robust to operate in a harsh environment over the lifetime of the structure.