Wide scope of infrared

Published:  20 June, 2014

Andrew Baker, sales and marketing manager, FLIR Systems UK, takes a look at the wide scope of infrared in wind energy generation.

As much as 25% of the total cost of producing electricity from a wind turbine can be attributed to maintenance. And the lionís share of turbine failures is caused by poor electrical connections and components. Electrical steering and rotor blade faults are also cited. So efficient and reliable methods to monitor and assure predictable turbine performance are vital to the economics of this source of renewable energy.

Thermal imaging is playing an increasingly important role in this regard both in terms of predictive maintenance of electro-mechanical components and in the detection of surface defects in composite structures.

Predictive maintenance

The safe operation of a wind turbine is of paramount importance and its braking mechanism and gearbox are two of the most critical components as they control rotation speed. The load on the blade tips increases with speed and if left unchecked the blade will ultimately fracture from the rotor, propelled by an enormous amount of kinetic energy and momentum. And this can be life threatening.

The predictive maintenance of these components and the entire electrical system that powers them is the perfect application for thermal imaging. An abnormal heat profile is a sure sign of a fault such as a worn bearing or a bad connection. The technology also pinpoints the location of the problem so swift remedial action can be taken.

The wide choice of camera models available provides the means for wind turbine maintenance crews to perform non-contact, non-destructive testing at close range or over a considerable distance with a high-resolution model. Cameras are designed to be as compact and lightweight as possible and also easy to use. Both are important qualities when the operator has to climb up many metres to conduct the inspection.

Another important factor is the lens. A wide-angle lens allows larger pieces of equipment to be imaged in one go and also at close range. And various software features speed up the inspection process.

Non-destructive testing

Electro-mechanical infrared inspection falls into the category of passive thermography, which can be applied to every component that produces heat during operation. As well as the driveline itís ideal for monitoring the health of critical electrical components such as a high voltage transformer or a cooling fan in the nacelle.

But what about components that donít produce any heat - such as a rotor blade Ė can thermal imaging help here? The answer is yes and the proven method is active or pulse thermography.

This technology is mainly employed to see defects on a qualitative basis. As the structure doesnít produce heat itself an external heat source is applied enabling the thermal imaging camera to obtain a radiometric reading.

In the field of wind energy pulse thermography is commonly used to detect areas of delamination on GRP rotor blades. A correctly laminated composite material structure will have relatively uniform thermal characteristics. Once a disbond or delamination has occurred, the thermal pattern within the composite will be altered and detected by the camera.

Thermal imaging has proved its ability to reduce the time and effort involved in scanning large scale objects and allows the detection of defects instantaneously, on site, without having to disassemble the blade.

For further information please visit: www.flir.com

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