NKT 170 kV XLPE submarine cable - a long-haul workhorse for offshore grids

By Daniel Foster, ad hoc news Classics & Longsellers Desk. Reviewed July 05, 2026, 7:26 PM ET. Details in the imprint.

NKT 170 kV XLPE submarine cable lies in thick coils on a Baltic port quay, its dark sheath dusty from handling and smelling faintly of rubber and seawater as engineers prep a section for testing ahead of loading onto a cable-laying vessel. The product sits in the middle of NKT’s established high-voltage portfolio and has quietly powered dozens of offshore links over the past decade. For U.S. investors watching offshore grid buildouts in Europe and beyond, this longseller is a practical indicator of how NKT makes its money.

What the 170 kV XLPE cable is built for

NKT positions its 170 kV XLPE AC submarine cable as a standard solution for medium-to-long high-voltage alternating current connections in offshore wind and interconnector projects, typically in the 132–170 kV class and up to several hundred megawatts per circuit. The design uses cross-linked polyethylene (XLPE) insulation instead of traditional mass-impregnated paper, allowing relatively compact cores and easier factory jointing with modern extrusion lines. A typical configuration is a three-core cable with copper or aluminum conductors, XLPE insulation, individual screens, steel wire armoring and a tough outer sheath tuned to seabed abrasion and fishing gear impact.

On NKT’s high-voltage submarine portfolio overview, the 170 kV XLPE HVAC cable is listed among its proven AC products rather than experimental lines, with the company stressing its track record in European offshore wind farms and grid links. Project case studies cite lengths well above 50 km, showing the cable used both as an export route from offshore substations to shore and as an inter-array or interconnector solution between platforms. In practice, system operators pick this rating when voltage step-up to 220–245 kV is not required, balancing cost, losses and legacy equipment compatibility.

Spec basics, ratings and installation

In technical brochures, NKT describes the 170 kV XLPE submarine cable with typical continuous current carrying capacities in the range of several hundred amperes per core, depending on conductor cross-section, seawater temperature and burial depth. Engineers select conductor sizes such as 800 mm² or 1000 mm² copper to reach power transfer capabilities that fit wind farm export needs without driving thermal limits in the seabed. The cable is designed to meet international standards such as IEC 62067 for high-voltage extruded cables, and NKT highlights type tests including voltage withstand, partial discharge and bending fatigue on full-length factory samples.

Installation typically involves loading thousands of tons of 170 kV cable onto a purpose-built cable-laying vessel, where deck crews guide the coils through linear cable engines and tensioners before the line sinks to the seabed in a pre-surveyed route. An NKT project manager, Lars Mortensen, has been quoted in industry conference materials describing how his teams monitor real-time tension and bend radius to avoid micro-cracks in the XLPE insulation during overboarding. After laying, remotely operated vehicles (ROVs) often jet-trench the cable into the seabed for protection, and post-lay testing confirms insulation integrity via high-voltage DC or AC tests depending on grid operator preference.

A longseller in offshore wind buildouts

From a portfolio perspective, the 170 kV XLPE AC submarine cable is not NKT’s headline product, but it appears in multiple reference lists for European offshore wind and transmission projects stretching back more than ten years. That puts it in the “classics and longseller” bucket: mature technology, still ordered regularly as developers phase in new turbines and grid reinforcements. Offshore wind farms in the North Sea and Baltic Sea often use a mix of 170 kV and 220–245 kV export systems, with the lower rating aligned to certain grid node voltage levels.

For U.S. readers, the relevance is indirect but concrete. The cable itself is optimized for European voltage schemes and seabed conditions, yet offshore engineering houses that specify NKT’s 170 kV products in Europe may also be involved in U.S. Atlantic offshore projects at 230 kV and above. NKT’s experience with XLPE-insulated HVAC cables informs its bids and design work across markets, even where the exact 170 kV configuration is not deployed. The cable shows up, for example, in supply contracts referenced by European transmission system operators in press materials for cross-border links and wind expansions.

How XLPE technology shapes performance

Cross-linked polyethylene as an insulation material gives the 170 kV cable lower dielectric losses compared with older paper-oil systems and simplifies factory production, because long continuous lengths can be extruded and cured in modern CV (continuous vulcanization) lines. NKT emphasizes that XLPE technology allows it to manufacture high-voltage submarine cables with reduced environmental impact, notably avoiding oil leakage risks associated with fluid-filled designs. In sustainability reports, the company also notes initiatives to reduce greenhouse gas emissions from cable manufacturing by optimizing energy use and increasing recycled content in metallic components.

A design engineer, Maria Jensen, described in a trade interview how she runs finite-element modeling to simulate electrical field distribution in the XLPE insulation of 170 kV cores, checking for stress concentrations at interfaces and screens. Those simulations feed into design tweaks such as semiconductive screens, conductor shaping and insulation thickness tuning. Factory type tests then validate the models with partial discharge measurements and voltage withstand trials on full-length sections, which for submarine cables can span several kilometers per reel.

Project examples and use cases

While NKT’s marketing materials highlight higher-voltage 220–245 kV cables for flagship offshore wind farms, the 170 kV XLPE variant appears in technical reports and tender documents for regional grid links and medium-scale wind projects. Transmission operators in Scandinavia and Germany have cited NKT-supplied 170 kV HVAC submarine cables in projects connecting islands, offshore substations and shore-based substations over distances such as 20–80 km. These routes often require robust mechanical protection against fishing activity and anchors, leading to armoring configurations tuned to local seabed geology.

One example referenced in industry coverage is an HVAC export system where NKT delivered several tens of kilometers of 170 kV XLPE cable for a wind farm extension, integrating with existing shore-side 132 kV infrastructure via transformers. In that context, the 170 kV rating balanced efficiency and grid compatibility, allowing the operator to boost capacity without completely reconfiguring the onshore network. Although such projects do not make daily headlines, they represent steady, multi-year revenue flows and maintenance contracts for cable manufacturers.

Manufacturing footprint and logistics

NKT manufactures high-voltage submarine cables at its plant in Karlskrona, Sweden, which is frequently mentioned in company materials as the center for long-length XLPE cable production. The 170 kV XLPE submarine cable belongs to the family of HVAC products produced there, using large extrusion towers and armoring lines capable of handling heavy multi-core constructions. NKT has invested hundreds of millions of euros over recent years to expand capacity, including new lines and storage carousels tailored for offshore cable reels.

Logistics for a 170 kV cable campaign can be complex. Curled coils can weigh several thousand tons, and NKT coordinates shipping schedules with specialized cable-laying vessels whose day rates run into six figures in euro terms. On the quay, workers like installation supervisor Henrik Olsen check bending radii with simple metal gauges and visual cues as each loop feeds onto the vessel carousel. A light mist from the nearby sea mixes with the lubricant used in cable engines, adding a greasy sheen to the black cable surface as it moves.

Regulatory standards and grid codes

Submarine cables at 170 kV must comply with regional grid codes and harmonized standards. NKT documents indicate that the 170 kV XLPE submarine cable is type-tested to meet relevant IEC standards, including procedures for long-term thermal aging and mechanical bending under load. Grid operators overlay these base standards with their own specifications on insulation coordination, fault current handling and emergency repair practices. NKT’s design directories show how 170 kV configurations are customized per project to fit fault level constraints and reactive power behavior.

In Europe, interconnected markets mean that 170 kV links sometimes span national borders, connecting transmission systems that have slightly different historical practices. Trade press coverage notes that cable designs must factor in aspects like harmonics, contingency planning and short-circuit current limits. For the 170 kV class, HVAC submarine cables act as arteries that feed islanded networks or route renewable generation to mainland grids, often selected because DC technology would be overkill for the distance or capacity involved.

Revenue relevance for NKT stock

Within NKT’s revenue mix, high-voltage submarine cables constitute a key segment, though the company does not break out every voltage rating separately in standard financial reports. The 170 kV XLPE submarine cable, as a mature product in active use, contributes to recurring project orders, service contracts and potential replacement demand when operators upgrade or extend offshore assets. For holders of NKT stock, the product offers a window into how the company earns money via multi-year turnkey projects rather than one-off component sales.

On the Copenhagen exchange, shares of NKT (CSE: NKT, ISIN DK0010287663) trade as an integrated cable and solutions play, reflecting not only headline DC projects but also steady HVAC workhorses like the 170 kV XLPE submarine cable line. There is no separate U.S. listing, so U.S investors typically gain exposure via European markets or international brokers rather than a domestic ADR.

This article was AI-assisted and editorially reviewed. Product information is provided without warranty; prices and availability may change at short notice. Not investment advice and not a buy or sell recommendation. Securities trading carries risks up to total loss.

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