TenneT Advances Offshore Grid Expansion with New Cable Production in South Korea

TenneT has commenced production of high-performance 525 kV cables for its 2 GW grid connection systems. This milestone marks the beginning of a new era in offshore grid connection technology, with the first cables being manufactured by LS Cable in Donghae.


These advanced cables, capable of transmitting two gigawatts (GW) of direct current over long distances with minimal losses, represent a significant upgrade from the previously used 320 kV cables. The enhanced transmission capacity is expected to bolster the efficiency and reliability of offshore wind energy projects.

The cable production is part of a framework agreement TenneT signed in May 2023 with a consortium that includes the Jan De Nul Group, LS Cable & Systems, and Denys. This contract encompasses the production and installation of four 525 kV DC cable systems for TenneT’s North Sea grid connection projects. The initial cables produced will serve the BalWin4 and LanWin1 projects.

Each grid connection will feature a positive and negative pole, along with a metallic return conductor to maintain electricity flow during maintenance or repairs. Additionally, a communication cable will be integrated into the system. In total, 1,650 kilometers of cable will be produced, with each project requiring 275 kilometers of route length, including 165 kilometers of submarine cables and 110 kilometers of land cables.

The copper inner conductor of these cables makes them particularly heavy, with submarine cables weighing approximately 76 kilograms per meter. The total weight for each project’s submarine cables amounts to around 25,000 tonnes, presenting a substantial logistical challenge.

Production is expected to be completed by 2028, with cable laying at sea slated to begin in the second half of 2026. The Jan De Nul Group will employ the specialized vessel ‘Fleeming Jenkin’ for this task. Land cable construction, also starting in the latter half of 2026, will be executed by Denys using both open trench and horizontal drilling methods to navigate water bodies and existing infrastructure.

BalWin4 is projected to become operational in 2029, followed by LanWin1 in 2030, marking a significant advancement in TenneT’s offshore grid expansion efforts.

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