Fugro Finishes DOB Survey on Greater Gabbard Export Cables (UK)

Fugro has successfully completed 2 positional and depth of burial surveys on export cables for SSE’s 500MW Greater Gabbard offshore wind farm off the Suffolk coast on behalf of installation contractor Fluor.

The main objective is to provide a final report with the final position including depth of bury of the L2 export cable and Galloper interconnector to enable the installation of the export L1 cable.

Our challenge in completing this work was twofold, the prevailing high current, shallow water in the area to be inspected and locating an energised power cable. Currently most ROV operators have to work around the tidal coastal areas by only working slack waters in-between tides, however Fugro has developed a crawler base allowing conventional ROVs to operate 24 hours a day in currents up to 7 kts.

Cable detection can usually be performed by tone injection or magnetising a cable pre-installation, however neither of these options were available and existing cable detection systems (TSS440) often became incapacitated by the energised cable (carrying 500KVac at up to 300A) creating fluctuating flux levels produced by a wind farm export cable. Therefore selection of detection equipment capable of locating such an energised export cable at up to 2 mtrs burial to accuracies of 10mm, Fugro worked with Innovatum in the selection and use of their Smart track 9 system.

Project Manager John Freeland said “this has been a difficult project with many unexpected underwater obstacles including unexploded WW2 bombs and soft seabed conditions, this has been a real test for the new tracked skid system”.

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Source: rovtech, October 26, 2011