Nexans Begins 525 kV XLPE Subsea Cable Production for LanWin2 — What the Qualification-to-Delivery Transition Actually Changes

Nexans' 16 October 2026 announcement that it has begun industrial-scale production of 525 kV HVDC XLPE subsea cable at Halden, Norway, reads like a routine project milestone. It is more than that. The distinction between a qualified cable design and a cable that can be extruded, degassed, sheathed, tested and loaded out at industrial rate is where most offshore grid programmes actually slip. LanWin2 is the project where Nexans is converting that capability into serial output — and the frame agreement it sits under means the same lines are meant to feed BalWin3 and LanWin4 next.

The substance of the milestone

Reported facts, from Nexans' release and trade press:

• Production of 525 kV HVDC XLPE subsea cable has started at Halden; Nexans describes it as the first industrial-scale production of its 525 kV HVDC XLPE subsea technology (company characterisation).
• The project agreement for LanWin2, worth approximately €1 billion, was signed in January 2025 under a framework agreement with TenneT concluded in May 2023.
• Scope is EPCI of roughly 250 km of 525 kV HVDC onshore and offshore export cable systems for a 2 GW connection landing in the Heide region of Schleswig-Holstein.
• The converter platform is being delivered by the Siemens Energy–Dragados Offshore consortium; first steel was cut in September 2025, with blocks fabricated at Cimolai (Italy) and Eversendai (UAE) for integration at Algeciras (Spain).
• Commissioning is now stated as 2031 by both Nexans and TenneT.

One discrepancy is worth flagging rather than smoothing over: Nexans' January 2025 release said commissioning was expected in 2030. The current figure is 2031. The shift may reflect schedule re-baselining on either the cable or platform side, or simply a more conservative view once engineering firmed up; the sources do not say. Either way, the delivery window is long — roughly four to five years between first cable extrusion and energisation — which is a useful reminder that starting production early is not the same as being on the critical path last.

Why 525 kV extruded insulation matters

Until recently, HVDC submarine links at these voltage levels used mass-impregnated (MI) paper-insulated cable. MI is a mature, well-understood technology, but it is slow to manufacture, requires impregnation and metal-sheathing steps that limit line speed, and offers little headroom for further voltage scaling.

XLPE (cross-linked polyethylene) insulation was already standard for HVAC and for lower-voltage HVDC. Scaling it to 525 kV DC is hard because DC fields are governed by space charge accumulation and conductivity that varies with temperature and field, not by the capacitative grading logic of AC design. The practical consequences are demanding: exceptionally clean compounding and extrusion, very tight concentricity control, long degassing periods to drive out methane by-products, and type/prequalification testing regimes that run for a year or more. CIGRE's Technical Brochure 852 (2021) sets out the testing recommendations for extruded DC systems up to 800 kV, and explicitly addresses the 500 kV-plus class where 525 kV sits.

The payoff is manufacturing throughput. Extruded insulation is a continuous, high-speed process compared with MI, and it permits longer, heavier continuous lengths — fewer factory joints and fewer offshore splices, which is where subsea cable installation risk and cost concentrate. Halden's 2024 expansion, which added a second 153 m extrusion tower and more than doubled HVDC extruded capacity, was built for precisely this throughput problem: four cables insulated simultaneously on two lines.

Analysis: the competitive advantage 525 kV XLPE confers is not primarily a technical specification win — it is a delivery-rate advantage. Europe's offshore grid build-out is now constrained less by demand for 2 GW links than by the number of extrusion lines that can produce qualified 525 kV cable. That is a narrow bottleneck, globally.

The frame agreement is the real story

The LanWin2 award is one call-off under a May 2023 TenneT frame agreement covering three German North Sea connections — BalWin3, LanWin4 and LanWin2 — with an initial value of €1.7 billion and a full EPCI scope exceeding 2,160 km of subsea and land cable across the three projects.

That structure explains the announcement's forward-looking language: Nexans explicitly ties the qualification milestone to readiness for BalWin3, where cable installation in the Wadden Sea and nearshore areas is planned for 2027. In other words, LanWin2 is the proving ground; the production learning curve established here is meant to carry the next two projects.

This is the operational logic TenneT's Matthias Mensing pointed to in describing the shift "from planning and qualification into industrial-scale delivery" and the supply-chain capacity and planning certainty that long-term partnerships provide. For a TSO sequencing a multi-gigawatt programme, a frame agreement converts a series of separate, sequentially tendered cable contracts into a reserved manufacturing slot — which is worth more than any individual price negotiation.

Where the industrial footprint actually sits

The cable work is spread across three countries, and the distinction matters for anyone tracking where value and capacity sit:

The offshore cable itself is Norwegian; French and Belgian sites contribute onshore cable, accessories and test capability. Readers who saw France listed in the project metadata should not conclude that subsea cable is being made there — it is not.

What to watch

Three things will determine whether this milestone translates into programme-level delivery:

1. Halden throughput under serial load. The plant now has to run LanWin2 alongside commitments to other TenneT projects and third-party customers. The rate at which qualified 525 kV lengths leave the factory — not the announcement date — is the real supply indicator.
2. Installation, not manufacture, as the next constraint. Cable installation vessels are a scarcer resource than extrusion lines in the 2027–2030 window, and the BalWin3 nearshore/Wadden Sea campaign planned for 2027 will be an early test of that.
3. The 2030-to-2031 schedule revision. If the platform and cable tracks are converging as intended, TenneT should be able to hold 2031. Any further slippage would signal that the bottleneck has moved from cable supply to system integration.

For the wider market, the significance is straightforward: 525 kV XLPE subsea cable has crossed from a qualified technology into an industrially manufactured product. That reduces one of the more binding constraints on European offshore grid expansion — but only at the rate Halden and its peers can actually extrude.