Revision of IEC PT61400 -12-1 Power performance measurements on electricity producing wind turbines TC88 meeting March

1. Revision of IECPT61400-12-1Power performance measurements on electricity producing wind turbinesTC88 meeting March 2010 Troels Friis Pedersen

2. Status, MCR basis for revision • First version of IEC61400-12-1 December 2005 • Revision based on MCR 88/319 • Main topics in revision are inclusion of wind shear and turbulence in performance measurements • Other issues comprise: air density correction, site calibration, generic versus site specific power curves, obstacle model, topography requirements, lightning protection, lattice tower flow distortion and anemometer classification

3. Status, Maintenance team • MT was supplemented with additional experts in LIDAR and SODAR technology • MT has 41 members, about 25 members participate in meetings • Meetings have been held January, May, October 2009 and February 2010 • Two major sub-groups established, one on performance methods, and one on measurement methods (LIDAR, SODAR, mast) • Seven minor sub-groups on other issues

4. Status, shear • Shear problems has been documented. Shear has a significant influence on power performance measurements in special cases (up to 5% on AEP) • In special cases shears are non-power law profiles, and these may vary very differently above and below hub height • A concept of a shear equivalent wind speed has been introduced for analysis • A shear normalised hub height wind speed has also been presented (requires a reference shear)

5. Status, turbulence • A turbulence normalisation method (published 2008) has been tested by several members • The turbulence normalisation method primarily changes the power curve at low wind speeds and around power regulation • The turbulence normalisation method did not seem to reduce scatter of data

6. Status, LIDAR • LIDAR’s are appropriate instruments for measurement of shear • LIDAR’s are sold in larger numbers (50-100) • LIDAR comparisons to met masts (verification measurements) are made systematically on most systems • Procedures for comparison of individual LIDAR’s to met masts are considered a necessary part of the standard

7. Status, LIDAR • LIDAR’s can be positioned right next to met masts • LIDAR’shave been tested for performance measurements, but at present stage they must be supplemented by met masts, perhaps not all the way to hub height (traceability) • Traceability and uncertainty important issues

8. Status, SODAR • SODAR’s are also potential instruments for measurements of shear • A new generation of SODAR’s are sold in larger numbers (50-100) • SODAR’s are used regularly for siting (US) • SODAR’s cannot be positioned close to masts • Requirements will preferably be based on technical requirements rather than on type of instrument

9. Status, Time schedule • Present target date April 2010 • Meetings planned for June 2010, October 2010 and January 2011 • Expected target date April 2011 • MT requests TC88 to postpone target date to April 2011