Wind Turbines

Wind turbines incorporate many different electrical and mechanical components. Like all other equipment these components are susceptible to wear and can break down. This can cause costly downtime as well as dangerous accidents.

A common cause for these accidents is a failure in either the brake mechanism or in the gearbox. The gearbox and the brakes prevent the blades from turning too quickly. If either of these components fail then the turbine is allowed to revolve at many times its normal speed, which imposes loads on the blades well in excess of what they were designed for.

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Cyclic mechanical loading of rotor blades

Heavy wind and air pressure changes have a great impact onto the laminated rotor blade material. Especially the continuous influence of cyclic loadings will affect the material, cracks will appear and an ongoing degradation process will affect the blades.

Frequently changing of the loads, will produce temperature differences in the blades during the rotation indicating high stress or stress release in different areas of the blade (Image below).

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                                      The rotor while it is moving. The bright areas are warmer and show the heat production due to mechanical loading(blue arrows).

 

Beside the stress distribution, small cracks and dry laminate will produce heat by friction due to the cyclic excitation (Image below, red arrows).

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                                                              The bright areas indicate delaminations produced by heat due to the friction of micro cracks.

 

Check the internal structure of the blades

In the picture below is a panorama view composed of four different thermal images taken in a cold winter night, shortly after sunset. Most of the important inner structures of the blades can be seen, as the glued rim at the trailing edge indicated by the arrows or the twin main spars marked by the rectangle. A repaired area can be seen only very faintly as weak white shadow which is circled for better visibility.

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Thermal image of the rotor blade showing important structures like the gluing at the trailing edge (arrows), the twin main spars (rectangular) and a repaired area (circle).

 

Check the entire system

Thermal imaging cameras can be used to inspect the electrical components such as transformers, connectors, controllers yaw motors and such. Thermal imaging is the only technology that allows you to inspect all electrical and mechanical components of the wind turbine and of the surrounding electrical system.

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