By 31 July 2025, Asso.subsea had been awarded the nearshore cable installation scope for three of TenneT’s 2 GW projects, including BalWin4. Working under main contractor Jan De Nul for TenneT, Asso.subsea will handle transportation and nearshore installation off the northwestern coast of Baltrum Island of a bundled package comprising two HVDC power cables, one metallic return cable, and one fibre optic cable for BalWin4, using the modified CLV Atalanti and specialised beaching and intertidal installation methods.
On 9 June 2025, TenneT and its partners marked the start of block production for the BalWin Delta offshore HVDC platform topside in Batam, Indonesia, signalling a major manufacturing milestone for the BalWin4 grid connection. The consortium of GE Vernova and McDermott is managing construction of the approximately 30,000-tonne topside, with this production phase essential to meeting the planned 2028 North Sea installation and end-2029 commissioning schedule for the 2 GW platform.
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BalWin4 is a ±525 kV HVDC offshore grid connection developed and owned by TenneT to bring up to 2,000 MW of offshore wind energy from the German North Sea to the onshore transmission grid at Unterweser (Lower Saxony). The system comprises an offshore converter station (the BalWin delta platform) ...
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NOR-9-3, BalWin delta
On 3 March 2025, OffshoreWind.biz reported that the first steel had been cut for BalWin4, Germany’s first 2 GW offshore grid connection, at Sangsangin Ship Machinery’s factory in South Korea. This marked the start of fabrication of the foundation for the BalWin4 topside, with steel panels to be produced in South Korea and then shipped to Batam, Indonesia, where McDermott will assemble the offshore converter substation topside.
By around October 2024, Fugro had completed survey work for TenneT’s German 2 GW offshore grid connection projects, which include the BalWin4 offshore grid connection system. The OffshoreWIND.biz item titled “Fugro Completes Surveys for TenneT’s 2 GW Offshore Grid Connection Projects in Germany” indicates that these site investigation surveys were finalised as part of developing the 2 GW transmission links.
On 30 May 2024, TenneT reported that LS Cable & System had started production of high-performance 525 kV DC cables at its Donghae plant in South Korea, with the first cables destined for the BalWin4 and LanWin1 2 GW grid connection projects, marking the beginning of cable manufacturing for these links.
Planning consent application submitted for BalWin4 grid connection.
BNetzA confirmed BalWin4 in Netzentwicklungsplan (NEP) 2037/2045 (2023) on 1 March 2024. This confirmation under §12c EnWG creates the legal basis for the responsible TSO to plan, procure, and construct the offshore grid connection system.
BNetzA confirmed the Netzentwicklungsplan Strom 2037/2045 (2023 edition) on 1 March 2024 under section 12c of the German Energy Industry Act (EnWG). This confirmation creates the legal basis and obligation for the responsible TSO to plan, procure, and construct this offshore grid connection system. For regulated German TSO offshore grid connections, the BNetzA NEP confirmation functions as the de facto Final Investment Decision: unlike merchant or developer-led projects that require a separate board-level investment decision and financial close, the NEP confirmation simultaneously authorises and obligates the TSO to invest. Costs are recovered through the offshore grid levy (Offshore-Netzumlage). The NEP 2037/2045 (2023) schedules 25,980 MW of offshore transmission capacity across 16 grid connection systems for commissioning between 2026 and 2032.
On 5 May 2023, TenneT awarded contracts worth about €5.5 billion to NKT, Nexans, and a consortium of Jan De Nul, LS Cable & System, and Denys for 525 kV HVDC cable systems across several grid connection projects. Under this award, the Jan De Nul–LS Cable–Denys consortium will deliver the cable connections for BalWin4 in Lower Saxony, including cable design, engineering, production, delivery, and onshore, offshore, and nearshore installation to connect BalWin4 to the Unterweser area.
On 30 March 2023, TenneT awarded the GE/McDermott consortium the framework contract for the BalWin4 and LanWin1 2 GW HVDC offshore grid connections. McDermott responsible for design, fabrication, installation and commissioning of the offshore converter substation platforms.
Cable route engineering for BalWin4 completed. Jan De Nul consortium (with LS Cable & Denys) contracted Dec 2023.
In November 2022, TenneT launched a large-scale tender for 525 kV HVDC cable systems covering multiple offshore and onshore grid connection projects, including the BalWin4 offshore grid connection. The procurement notice invited bidders for cable design, engineering, production, delivery, project management, and onshore, offshore, and nearshore installation works for these grid connection systems.
On 10 November 2022, engineering firm G.E.O.S. announced it had been commissioned by grid operator TenneT to carry out planning works for the land cable sections of the NOR-9-3 and NOR-12-1 offshore wind power connection systems, including BalWin4 (NOR-9-3). The contract covers full technical approval planning, project coordination, preliminary subsoil investigations, and surveying for roughly 100 km of onshore cable route from the Baltrum/Dornumersiel landfall area to the grid connection point at the former Unterweser nuclear power plant site.
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