Modular Offshore Grid (MOG)

Challenge

Elia Asset NV (part of the Elia Group which encompasses two major transmission system operators) is developing a modular, subsea high-voltage grid, largely to connect four planned offshore wind farms in the Belgian sector of the North Sea with the onshore, high-voltage grid on the mainland at Zeebrugge. 
A turnkey contract for the submarine power cables has been awarded for the so-called ‘Modular Offshore Grid’ (MOG), which includes the design, engineering, procurement, manufacturing, installation, testing and commissioning of the cables.
Power from the four wind farms will be concentrated in one offshore point at the Offshore Switch Yard (OSY), and then it will be transmitted from the OSY to the onshore grid through a number of submarine cables. The four wind farms are being constructed by their respective owners in line with their individual development schedules. Hence, the offshore grid has a modular concept, to facilitate the project’s realisation in multiple phases. 

Our solution

 

In a broad scope of works, DEME’s solution includes:
•    The Pre-Lay Grapnel Run operation and Out of Service Removal;
•    Transport of submarine power cables from the cable supplier’s facilities in Greece to the MOG site;
•    Installation of two submarine power cables (2 x 40 km) between the OSY Platform and the beach of Zeebrugge
•    Installation of one submarine power cable (5 km) between the OSY Platform and the Rentel Offshore Substation, as well as 2 repair joints;

•    Pre- & Post-trenching works: pre-sweeping of sand dunes, pre-lay trenching, backfilling & post-lay burial of cables in intertidal zone;
•    Termination works: 2 beach pull-ins & 4 platform pull-ins;
•    Rock installation: 4 pre-lay and post-lay crossings (2 power cables, 1 telecom & 1 gas pipeline) & 2 post-lay repair joints;
•    Quality Control Survey over the cable routes.

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