Nexans Moves 525 kV XLPE From Qualification to Volume — and TenneT's German 2 GW Programme Into Delivery

Nexans has begun manufacturing 525 kV HVDC XLPE subsea cable for TenneT's LanWin2 grid connection at its Halden plant in Norway. The company presents this as the first industrial-scale production of its 525 kV XLPE subsea system, following qualification of the technology. That framing is the more consequential part of the announcement: what has changed is not the design but the manufacturing regime — the shift from type-tested prototype and prequalification loops to a continuous extrusion and delivery programme against a firm date.

The commercial frame is already established. Nexans booked the LanWin2 call-off in January 2025 at roughly EUR 1 billion, under a framework agreement signed with TenneT in May 2023 that covered three German North Sea projects — BalWin3, LanWin4 and LanWin2 — with an initial value of EUR 1.7 billion and additional subcontracted works to be added at call-off. LanWin2's scope is EPCI of about 250 km of onshore and offshore 525 kV export cable systems for a 2 GW connection landing at Heide in Schleswig-Holstein.

Why volume production matters more than the qualification

A type test proves a design; it does not prove a factory. 525 kV extruded DC insulation is sensitive to cleanliness, degassing dwell time and the consistency of the cross-linking process across long lengths, and CIGRE TB 852 (2021), which extended qualification guidance for extruded DC systems up to 800 kV, added tests such as by-product measurement and thermal-stability testing precisely because those are process-dependent rather than design-dependent properties. Running that discipline at serial scale — on 250 km of cable, in two insulation lines, with joints and terminations — is where cost, yield and schedule risk now sit.

The accessory side is equally load-bearing. Nexans has type-tested SF6-free 525 kV DC terminations at its Calais laboratory against CIGRE TB 852 and IEC 62895, and claims the elimination of SF6 cuts termination-related global-warming potential by 99% or more. For a project landing in Germany, where SF6 handling and reporting obligations are tightening, that is a genuine procurement advantage rather than an environmental footnote. It is also worth keeping the insulation technologies distinct: Nexans' separate ±525 kV mass-impregnated (MI) system, type-tested for 3,000 m water depth in work presented to CIGRE in 2026, is a different product for a different duty. The LanWin2 milestone rests on the XLPE line, not the MI line.

Halden is the real supply constraint

The Halden site's 34,000 m² expansion, completed in June 2024, added a second extrusion tower — at 152.89 m, described as Norway's tallest structure — allowing four cables to be insulated simultaneously across two lines for products up to 525 kV HVDC and 420 kV HVAC. That expansion is the enabling asset for the TenneT programme; without it, the German framework could not have been scheduled.

This matters for how the rest of the programme should be read. Nexans' frame obligations to TenneT extend to more than 2,160 km of subsea and land cable across the three projects, delivering 6 GW. LanWin2 alone is about 250 km; BalWin3 and LanWin4 will compete for the same tower time. On the disclosed figures, the EUR 1 billion LanWin2 call-off equals roughly 59% of the initial EUR 1.7 billion framework value, which confirms that the headline number is an EPCI price — including marine installation, vessels and land works — and not a cable-supply rate. It follows that the binding constraint on TenneT's 2 GW programme is not order backlog but extrusion and installation slots at Halden.

A schedule that has quietly moved

The January 2025 Nexans release stated commissioning was expected in 2030. The October 2026 announcement, attributed to both Nexans and TenneT, gives 2031 — consistent with the original May 2023 framework language of projects becoming operational between 2029 and 2031. The same October release says the projects "remain on schedule."

Both statements can be true only if the baseline has been rebased. Read plainly, the current commissioning expectation for LanWin2 is 2031, one year later than the figure published when the contract was awarded. For an industry planning electrolysers, hydrogen offtake or grid reinforcement around German North Sea connection dates, that distinction matters more than the language used to smooth it.

The cable is one leg of a three-legged project

LanWin2's critical path runs through the offshore converter platform as much as through Halden. The Siemens Energy and Dragados Offshore consortium cut first steel in September 2025, with block fabrication split between Cimolai in Italy and Eversendai in the UAE and integration at Dragados' Algeciras yard; KCI has since been engaged on the jacket substructure design. Fabricating, outfitting, transporting and commissioning a 2 GW HVDC topside is a multi-year sequence that has to converge with cable laydown and land-section civil works at Heide.

The practical consequence: the start of cable extrusion in late 2026 is a necessary milestone but not evidence of programme-level de-risking. Cables produced early must be stored, jointed and protected onshore for years before energisation, which carries its own handling and quality-assurance burden. On the evidence available, the more useful reading of this announcement is that Nexans has cleared its technology gate and entered the phase in which execution — tower availability, degassing throughput, jointing crews, vessel scheduling — becomes the dominant variable. TenneT's supply-chain certainty, which its project manager cites as the rationale for long-term partnerships, is now dependent on a single Norwegian site performing at serial yield.

What to watch

• Halden throughput: any indication that cable production for BalWin3 and LanWin4 is being sequenced around LanWin2 will signal where TenneT's 2 GW programme really stands.
• Accessory qualification for the as-built system: onshore and submarine cables in the same voltage class typically require separate type-test evidence; ENTSO-E's consultation work on 525 kV land and submarine systems points to that asymmetry.
• Platform integration at Algeciras: the convergence of topside completion with cable delivery is the likeliest source of further schedule slippage.
• Competitive response: with 525 kV XLPE subsea now in serial production at Halden, the pressure shifts to whether rival European capacity can match qualification status and tower time, not merely price.