Integration of a distributed fiber optic current sensor setup for lightning detection in wind turbines

With increasing height and rated power of wind turbines (WTs), the potential number of lightning strikes rises to the square of the height as well as the average lightning current peak value [1]. To prevent consequential damages due to lightning on such structures, lightning impact should be monitored. Therefore a new method for lightning measurements on WTs using fiber optic current sensors (FOCS) has been developed. FOCS are robust with respect to electromagnetic interference (EMI), as the magnetic field produced by the lightning current is directly converted into an optical signal in a device with small dimensions. Another advantage is the broad bandwidth, allowing the transducer to measure high current steepness. Furthermore, the sensor cannot be damaged by over-current coming from an unexpected surge caused by a lightning stroke. However, the accuracy of current measurements with FOCS is affected by the environmental perturbations, such as mechanical vibration and temperature changes. To prove the feasibility and accuracy of the new fiber optic measurement system for WT application, simulations and practical experiments were undertaken and are presented in this paper.