Fiber-optical grating sensors for wind turbine blades: a review

Abstract

Abstract. With the rapid growth of wind turbines and focus on maintenance costs structural measurements are becoming essential. Fiberoptical sensors have physical properties that make them suitable for embedding in wind turbine blades, such as small size and immunity to electrical interferences. Fiber-optical grating sensors can be utilized to provide important information regarding strain, temperature, and curvature of the blades, which can be applied in condition-monitoring to detect fatigue failure and furthermore for optimization of the production from the wind turbine. We provide an overview of the current status and a discussion on research and implementation of fiber Bragg gratings and long-period gratings in wind turbine blade sensors. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Long-period gratings in special geometry fibers for high-resolution and selective sensors

“…LPGs are sensitive to temperature and strain, which must be taken into consideration for a given application; however, the sensitivity can be suppressed by the fiber and grating composition. 4 For example, considering the D-shaped fiber, the germanium doped core can expand more in one direction compared to a symmetrical fiber affecting the sensitivity to strain and temperature.…”

“…It has been demonstrated that LPGs are suitable for structural health monitoring, especially for large structures such as wind turbines, as they can provide directional bend sensing of the blades, due to the fiber geometry. 4 These sensors can also provide the possibility for direct compensation of temperature drift. The utilization in D-shaped fibers provides a good access to the surroundings while retaining sufficient robustness; therefore, they are also ideal for several other evanescent field applications.…”

“…In particular, fiber Bragg gratings (FBGs) have been utilized in numerous applications as they have narrow bandwidths and are sensitive to strain and temperature. UVwritten long-period gratings (LPGs) were demonstrated in optical fibers by Vengsarkar et al 3 Compared to FBGs, the bandwidth of the LPG resonance is very broad, typically about 20 nm, 4 which results in limited effective resolution for interrogating their resonant dip and shift. However, it is possible to utilize the general principle of interaction between a particle and two consecutive oscillatory fields, developed originally by Ramsey,5 where identical LPGs in an optical fiber act as a Mach-Zehnder (MZ) device in transmission, 6 which provides narrow resonances for high-resolution detection of the sensing parameter and reduces noise.…”

Drug-Induced T-Wave Morphology Changesn

“…The chapter is mainly based on the work presented in the publication "Fibre-optical grating sensors for wind turbine blades: a review" [18]. This paper provides review of this field and describes the current status of utilization fibre optical gratings technology as wind turbine blade load sensors.…”

Damage Sensing in Blades

“…FBGs are local sensors with high sensitivity and reliability, allowing the possibility to multiplex several FBG sensors in a single optical fibre. In recent years, most of the investigations about fibre optic applications have been related to FBGs due to the variety of advantages that they offer (Choi et al 2012;Glavind et al 2013;Kim et al 2013Kim et al , 2014. FBGs are periodic variations in the refractive index of the core of the optical fibre.…”