Measurement of motion on floating wind turbine foundation

Highly specialised measurement tasks are one of Geopartner Inspections’ core areas of expertise. One example of such a task was a monitoring task we performed over a longer period of time on behalf of Siemens Gamesa on a floating wind turbine foundation (TetraSpar) that is manufactured by Stiesdal. The foundation was assembled at the harbour in Grenaa and was then tugged out to a location 10 km off the coast at Karmøy in Norway for testing.

The project involved keeping track of the motion of the floating foundation over time during the installation of the wind turbine’s column, nacelle (the turbine’s “control room” – i.e. the unit the blades are attached to) and the rotor.

The project was very demanding of the equipment that would be used as the requirements for accuracy and precision were extremely high. It was therefore necessary to fabricate special prism mounts for the task. The prisms were placed on the parts of the turbine foundation for which Siemens required motion data. The prisms that would be used as measurement points were installed while taking safety very seriously indeed.

During the task, equipment was also used that was able to autonomously measure distances to the prisms that had been fitted approximately once a minute. This allowed the motion of the wind turbine to be tracked in real time from the office.

Siemens compared the actual measurements of the foundation’s motion with the theoretical/modelled motion for the individual components. This made it possible to keep a constant eye on whether motion deviated from what was expected, so it would be possible to intervene on time if problems arose.

Siemens will be able to use what was learned from the monitoring in future installations of wind turbines onto floating foundations for the floating marine wind turbines of the future.

The project was carried out in close collaboration with the Kynde og Toft engineering workshop, who fabricated the prism mounts for the monitoring points on the various wind turbine components and the fixed benchmark points that were used as reference points for the measurements.