Offshore installation company Jan De Nul has completed a cable reburial project at Eneco’s Luchterduinen wind farm in the Dutch North Sea.
The wind farm, located 23 kilometers off the coast of Noordwijk and Zandvoort, has been operational since 2015. The 43 Vestas V112 offshore wind turbines at the wind farm, produce a combined capacity of 129 MW. From the Offshore High Voltage Station (OHVS) one 150 kV export cable of 25 kilometers directs the current to the shore.
Jan De Nul said Thursday Eneco had recently requested it to rebury a section of an existing export cable at the wind farm.
"Due to morphological changes the export cable burial was over the last few years decreasing in depth within the nearshore section. To guarantee the cable will at all times remain sufficiently buried and thus protected, a reburial campaign was requested by Eneco," Jan De Nul explained.
For this project, Jan De Nul modified its in-house designed and built intertidal trencher Sunfish and successfully reburied the nearshore section of the cable to a minimum depth of 2.5 meters below the seabed.
Since the section of decreased burial depth was located in the nearshore zone, it was not accessible with typical offshore trenching vehicles nor could it be easily accessed from the beach, the offshore services firm said.
"Jan De Nul offered Eneco the solution by mobilizing its intertidal trencher Sunfish. The Sunfish successfully lowered the nearshore part of the cable working up to 1 kilometer offshore and a water depth of 8.5 meters," the company said.
Tom Baguet, Project Manager at Jan De Nul Group: “Deepening the live export cable in a challenging intertidal zone with our unique in-house designed trenching vehicle Sunfish proves our expertise in various operational fields. We look back to an excellent cooperation with our client Eneco, the municipality of Noordwijk, KNRM and all local stakeholders.”
Ernest Diepstraten, Project Manager at Eneco: “Eneco greatly appreciated working together with Jan De Nul constructively in delivering this project in time and in budget. We are pleased that, thanks to the work of Jan De Nul Group, the cable to our Eneco Luchterduinen wind farm is buried deep enough again so that the wind farm can continue to supply power to our customers.”
The Sunfish, which was initially designed as a plowing machine suitable for working in tidal areas, was modified to a suitable post-lay jet-trenching vehicle with 2 water pumps delivering each 1250 m³/hr jet water and 3.5 m long jet swords and has successfully completed the Eneco Luchterduinen export cable reburial in jetting configuration by using water under high pressure.
Also, according to Jan De Nul, to accurately locate the cable, the Sunfish was further equipped with two sets of cable tracker sensors of SMD’s innovative tracking system ‘Artemis’ using the live tone of the cable. As a result, Eneco did not have to switch off the wind farm during the entire campaign.
Lee Carden, SMD Head of Sales for Artemis: “SMD very much appreciated this opportunity to continue to trial our Artemis cable tracking technology on live projects. Following a robust series of offshore trials, this project enabled live cable reburial operations to be completed without turning off windfarm power. SMD very much looks forward to continuing our collaborative relationship with Jan De Nul, who have a great history of innovative approaches to their operations.”