Laboratory test of FBG interrogators for wind turbine blade monitoring
Laboratory test of FBG interrogators for wind turbine blade monitoring
Laboratory test of FBG interrogators for wind turbine blade monitoring
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Load measurements <strong>of</strong> <strong>blade</strong>s<br />
Fibre Optics, ready <strong>for</strong> implementation?<br />
Theo Verbruggen<br />
Wind Turbine Condition Monitoring Workshop, October 8-9, 2009<br />
www.ecn.nl
Contents<br />
• Applications<br />
• Principles<br />
• Suppliers<br />
• Tests<br />
• Hardware developments<br />
• S<strong>of</strong>tware developments<br />
• Conclusions<br />
2 16-10-2009
Applications <strong>of</strong> <strong>blade</strong> load measurments<br />
Blade load measurements<br />
can be used <strong>for</strong> :<br />
• Load measurements <strong>for</strong><br />
certification<br />
• Turbine control<br />
• Blade <strong>monitoring</strong><br />
• Operation and<br />
maintenance<br />
3 16-10-2009
4 16-10-2009<br />
Principles <strong>of</strong> <strong>FBG</strong>-based measurements
Principles<br />
WDM: Wavelength Division Multiplexing<br />
TDM: Time Division multiplexing<br />
5 16-10-2009
Suppliers<br />
• Smart Fibres<br />
TDM<br />
• Insensys<br />
TDM<br />
• HBM<br />
WDM<br />
• (Micron Optics)<br />
WDM<br />
6 16-10-2009
User experience<br />
What is demonstrated…<br />
7 16-10-2009
User experience<br />
Or even more...<br />
8 16-10-2009
User experience<br />
And this are the details….<br />
9 16-10-2009
User experience<br />
•Inaccuracies in strain<br />
•Large differences <strong>for</strong><br />
opposite locations<br />
•Spikes / missing data<br />
•Strain modulation on<br />
temperature measurements<br />
•Unreliable instrumentation<br />
•Complex repair due to<br />
required skills and tools<br />
•Long installation time<br />
Still promising!<br />
But how to proceed?<br />
10 16-10-2009
Still promising!<br />
But how to proceed?<br />
• Selection <strong>of</strong> reliable interrogator which meets<br />
requirements <strong>for</strong> in house developments and on site<br />
<strong>test</strong>ing<br />
• Development <strong>of</strong> user friendly sensor assembly, suitable<br />
<strong>for</strong> on site installation<br />
• Development <strong>of</strong> user friendly data processing and<br />
interface<br />
11 16-10-2009
Selection <strong>of</strong> interrogator<br />
• Accuracy / resolution / long<br />
term stability<br />
• Thermal sensitivity<br />
• Acceleration / environmental<br />
conditions<br />
• Stability during operation /<br />
polarization effects<br />
• Reliability / robustness<br />
Reference grating (AOS)<br />
12 16-10-2009
Accuracy / resolution<br />
Single micro strain simulator<br />
13 16-10-2009
Thermal sensitivity<br />
Climate room<br />
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15 16-10-2009<br />
Acceleration
16 16-10-2009<br />
Polarization
Remarks interrogator<br />
• Required accuracy not ensured<br />
• Long term stability not ensured<br />
• Thermal effects found<br />
• Acceleration effects minimal<br />
• Polarization effects (Strong!)<br />
• Reliability / robustness<br />
• Strong sensitivity <strong>for</strong> Bragg grating properties<br />
• Strong effects due to attenuation<br />
But we made our choice <strong>for</strong> our sensor development<br />
17 16-10-2009
Sensor developments<br />
Experience:<br />
• Complicated installation<br />
- Skilled personnel / not certified<br />
- Special tools<br />
• Time consuming<br />
- Gluing process<br />
- Curing time and fixation<br />
• Result<br />
- Not robust<br />
- Prone to damage<br />
• Inaccuracies<br />
-Strain<br />
- Temperature<br />
18 16-10-2009
Sensors development<br />
Requirements:<br />
• Life time > 20 years<br />
• Easy installation<br />
• No drift<br />
• Temperature compensation<br />
• No (re-)calibration<br />
• Easy replaceable<br />
• Robust<br />
These requirements are met by the ECN sensor development<br />
19 16-10-2009
S<strong>of</strong>tware development (Blade <strong>monitoring</strong>)<br />
Purpose<br />
• Fully automatic<br />
• Very limited data to be<br />
stored<br />
• Robust to measurement<br />
faults<br />
• Applicable <strong>for</strong> various<br />
plat<strong>for</strong>ms<br />
• Applicable <strong>for</strong> various<br />
<strong>turbine</strong>s<br />
• Auto-reporting / warning<br />
• Friendly user interface<br />
20 16-10-2009
Conclusions<br />
• Load measurements are essential <strong>for</strong><br />
various <strong>wind</strong> applications<br />
• Fibre Bragg grating is still promising and<br />
still expensive<br />
• Users friendly components still required<br />
• Data processing / reduction essential <strong>for</strong><br />
<strong>monitoring</strong> applications<br />
21 16-10-2009
22 16-10-2009<br />
Thank you <strong>for</strong> your attention!
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