www.ecn.nl

Load measurements of bladesFibre Optics, ready for implementation?

Theo VerbruggenWind Turbine Condition Monitoring Workshop, October 8-9, 2009

2 16-10-2009

Contents

• Applications• Principles• Suppliers• Tests• Hardware developments• Software developments• Conclusions

3 16-10-2009

Applications of blade load measurments

• Load measurements for certification

• Turbine control• Blade monitoring• Operation and

maintenance

Blade load measurements can be used for :

4 16-10-2009

Principles of FBG-based measurements

5 16-10-2009

Principles

TDM: Time Division multiplexing

WDM: Wavelength Division Multiplexing

6 16-10-2009

Suppliers

• Smart Fibres TDM

• Insensys TDM

• HBM WDM

• (Micron Optics) WDM

7 16-10-2009

User experienceWhat is demonstrated…

8 16-10-2009

User experienceOr even more...

9 16-10-2009

User experienceAnd this are the details….

10 16-10-2009

User experience

•Inaccuracies in strain•Large differences foropposite locations

•Spikes / missing data•Strain modulation on temperature measurements

•Unreliable instrumentation•Complex repair due to required skills and tools

•Long installation time Still promising!But how to proceed?

11 16-10-2009

Still promising!

But how to proceed?

• Selection of reliable interrogator which meets requirements for in house developments and on site testing

• Development of user friendly sensor assembly, suitable for on site installation

• Development of user friendly data processing and interface

12 16-10-2009

Selection of interrogator

• Accuracy / resolution / long term stability

• Thermal sensitivity• Acceleration / environmental

conditions• Stability during operation /

polarization effects• Reliability / robustness

Reference grating (AOS)

13 16-10-2009

Accuracy / resolution

Single micro strain simulator

14 16-10-2009

Thermal sensitivity

Climate room

15 16-10-2009

Acceleration

16 16-10-2009

Polarization

17 16-10-2009

Remarks interrogator • Required accuracy not ensured• Long term stability not ensured• Thermal effects found• Acceleration effects minimal• Polarization effects (Strong!)• Reliability / robustness• Strong sensitivity for Bragg grating properties• Strong effects due to attenuation

But we made our choice for our sensor development

18 16-10-2009

Sensor developments

• Complicated installation- Skilled personnel / not certified- Special tools

• Time consuming- Gluing process- Curing time and fixation

• Result- Not robust- Prone to damage

Experience:

• Inaccuracies- Strain- Temperature

19 16-10-2009

Sensors development

Requirements: • Life time > 20 years• Easy installation• No drift• Temperature compensation• No (re-)calibration• Easy replaceable• Robust

These requirements are met by the ECN sensor development

20 16-10-2009

Software development (Blade monitoring)

Purpose• Fully automatic• Very limited data to be

stored• Robust to measurement

faults• Applicable for various

platforms• Applicable for various

turbines• Auto-reporting / warning• Friendly user interface

21 16-10-2009

Conclusions

• Load measurements are essential for various wind applications

• Fibre Bragg grating is still promising and still expensive

• Users friendly components still required• Data processing / reduction essential for

monitoring applications

22 16-10-2009

Thank you for your attention!