The production of TenneT’s new cables that can transmit up to 2 GW of offshore wind capacity has started at LS Cable in Donghae, South Korea.
The new cables with a voltage of 525 kV make it possible to transmit 2 GW of direct current (DC) over long distances with low losses, said the Dutch-German transmission system operator (TSO) TenneT. Up to now, 320 kV cables have been used for offshore grid connections, for example in TenneT’s 900 MW projects.
The start of cable production is part of the framework agreement that TenneT concluded with the consortium consisting of the Jan De Nul Group, LS Cable & Systems, and Denys in May 2023.
The contract covers the production and installation of four 525 kV DC 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.
In addition to a positive and negative pole, an additional cable (so-called metallic return conductor) will be laid for both grid connections in the future, which will ensure that electricity can continue to flow in the event of maintenance or repair work, said TenneT. The three cables will be supplemented by an additional communication cable.
A total of 1,650 kilometres of cable will be produced for the BalWin4 and LanWin1 projects (route length per project: 275 kilometres, of which 165 kilometres are submarine cables and 110 kilometres are land cables). The total weight of the submarine cable is around 25,000 tonnes.
Production of the cables is planned to be completed in 2028 while cable-laying at sea is expected to begin in the second half of 2026.
The transport and the laying of the 525 kV DC cables on the seabed will be performed by Jan De Nul Group’s extra-large cable-laying vessel Fleeming Jenkin .
The construction of the land cable is also scheduled to start in the second half of 2026 by Denys, with work being carried out using the open trench method with a cable trench and the closed trench method using horizontal drilling.
The cable systems of the two grid connections coming from the offshore converter stations will cross the Wadden Sea and be connected to the extra-high voltage grid in Unterweser.
BalWin4 and LanWin1 are scheduled to go into operation in 2029 and 2030, respectively. The grid connections will enable renewable electricity from offshore wind farms with a total transmission capacity of 4 GW to be fed into the German grid.