Cable production for two offshore grid connections has begun at the LS Cable plant in Donghae (South Korea), according to a report from 21 May. The start of cable production is part of the framework agreement, that the European network operator TenneT concluded last May with the consortium comprising the Jan De Nul Group, LS Cable & Systems and Denys.
The new cables with a voltage of 525 kV raise the transmission capacity for offshore wind energy to a new voltage level. They enable low-loss transmission of 2 GW of direct current over long distances. Previously, 320 kV cables were used for offshore grid connections, as in TenneT's 900 MW projects.
The framework agreement regulates the production and laying of four 525 kV direct current cable systems for the TenneT grid connection projects in the North Sea.
The first DC cables produced by the South Korean cable manufacturer LS Cable are intended for the BalWin4 and LanWin1 grid connection projects.
Laying of a total of 1,650 kilometres of cable planned
In future, an additional cable - a so-called metallic return conductor - will be laid for both grid connections in addition to a positive and negative pole. This will allow the power to continue flowing in the event of maintenance or repairs. An additional communication cable supplements these three cables.
A total of 1,650 kilometres of cable will be produced for the BalWin4 and LanWin1 projects (route length per project: 275 km, of which 165 km are submarine cables and 110 km are land cables). The inner conductor is made of copper. Due to its weight, the submarine cables alone weigh around 76 kg per metre. In each individual project, the total weight of the submarine cable (plus/minus pole) is approx. 25,000 tonnes.
Start of construction in 2026
The last cables are scheduled to roll off the production line in 2028, with laying at sea expected to begin in mid-2026. The extra-large cable-laying vessel ‘Fleeming Jenkin’ from the Jan De Nul Group will be used to transport and lay the cables. It is specially designed for transporting and laying the 525 kV DC cables on the seabed.
The laying of the land cable by the construction company Denys is also scheduled to begin in the second half of 2026. Both the open construction method with a cable trench and the closed construction method using horizontal drilling (to cross bodies of water and existing infrastructure) will be used.
BalWin4 is scheduled to go into operation in 2029, LanWin1 in 2030.
