N-Sea sends off pontoon for Gwynt y Môr cable repair project

Multi-purpose pontoon NP459 is en route to the Gwynt y Môr offshore wind farm where it will work on repairing one of the project’s export cables.

The 82.5-meter long pontoon passed N-Sea Group’s head office yesterday, 17 May, through the river Oude Maas in Dordrecht on its way to the Gwynt y Môr project.

N-Sea has been awarded a contract for a preemptive repair to one of the four export cables that serve the wind farm.

Gwynt Y Mor, located some 13 kilometers off the coast of North Wales, was put into operation in 2015. That same year the project encountered its first issues with the export cable, which then underwent repair.

Five years later, an O&M contractor performing a routine test of the fibers in the spare fiber optic cable (FOC) discovered that all fibers within the spare FOC within subsea export cable 3 (SSEC3) had failed. This initial FOC break was located close to the location where the repair was undertaken in 2015.

Between February and September 2020, the project’s offshore transmission system owner carried out further tests to check for any degradation of the power cores and to improve the accuracy of the location of the break.

On 15 October 2020, Gwynt y Môr OFTO plc, a consortium comprising Balfour Beatty and Equitix, discovered a second break on the spare FOC within SSEC3, in whose vicinity the main power core of the cable section failed. This second FOC break was located approximately 1.5 kilometers from the initial FOC failure.

Gwynt y Môr OFTO reported the Transmission Services Reduction to Ofgem and filed the Exceptional Event claim, which Ofgem accepted in February 2021.

In May last year, Sumitomo Electric Industries reported that it had won a contract to supply the export cable for the 576 MW offshore wind farm.

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