Advanced Cable Design & AI Feature by Wire Journal International, Inc.

Advanced cable design

This feature presents a series of reports from different manufacturers about how they approach cable design. As an editorial twist, WJI also asked AI (Perplexity) if it was ready to be part of this story. It replied that it was. That backdrop led to a series of other exchanges and insights, presented in a second separate feature.

...and can AI be part of this story? (it says it can)

JDR: R&D effort led to its new 132 kV ‘wet’ array-cable 1 of 5

U.K.-based JDR Cable Systems, part of the TELE-FONIKA Kable Group, recently completed test qualifications for its new nextgeneration 132 kV subsea cables, which are available in both static and dynamic designs to serve fixed and floating offshore wind projects. Below, Joe Cole, JDR’s technology manager – power cables, discusses how a long-time technical hurdle was overcome.

WJI: What’s special about your newest 132 kV subsea cables, and how did that come to be?

Cole: Traditional 132 kV cables have always relied on a lead sheath to protect the insulation from water ingress. It provides a hermetically sealed barrier preventing water from diffusing into the insulation system within the cable, where it could accelerate the aging of the insulation, potentially causing premature failure. The lead sheath adds cost, weight, stiffness and installation restrictions. We have found a way to eliminate the need for that for our 132 kV inter-array cables.

WJI: What did you do?

JDR’s 132 kV wet-design inter-array cable passed tests at the Offshore Renewable Energy Catapult.

equipment to accommodate larger diameters, larger minimum bend radii and stiffer products. Also, for the dynamic cables, larger equipment was needed for extruding the sheathing for three-core cables. For dynamic cables, moving from 66 kV to 132 kV presented significant technical challenges. As the cables are inherently larger, the fatigue critical metallic components are exposed to increased mechanical stress during bending. To overcome this, extensive material and component testing was undertaken to understand and optimize the fatigue critical layers to ensure performance over the design life. The whole process took three years.

Cole: We have developed, designed and qualified “wet design” 132 kV cables which require no hermetic lead barrier layer, thereby reducing weight, cost and making these larger cables easier to handle. The development itself has been driven by market demand, similarly to the step change from 33 kV to 66 kV. As wind turbine generators (WTG) are getting larger and therefore more powerful, we are reaching the limit of efficient power transfer at 66 kV for intra-array cable applications.

WJI: What prevented your wet design for 33 kV and 66 kV cables from being used for the 132 kV design before this?

Cole: The key was the polymer used within the electrical insulation system. The insulation widely used for 66 kV wet design cables faces a phenomenon known as water-treeing, which is an aging mechanism. Water tree retardant (WTR) insulation uses a special formulation to slow this aging process caused by ingress of water into the insulation system. JDR worked with its polymer supplier to produce cable samples with the new WTR insulation material, which were then tested according to the CIGRE TB 722 aging regime, a two-year test to ensure the polymer can operate as a wet system.

WJI: Aside from the insulation, were there other technical hurdles?

Cole: Yes. JDR had to upgrade its Hartlepool cable manufacturing facility to allow for production of the larger and much stiffer dynamic versions of the new 132 kV cable technology. Upgrades were made to handling

WJI: Can you describe the testing process to shape product design and readiness for market deployment?

Cole: Following the materials and component testing, an extensive analysis was performed on the three-core cable to assess the design’s viability for deployment in floating offshore wind uses. The results of the analysis regime subsequently defined the “load blocks” used to form the 1.5 M cycle test; the number of cycles for each combination of tension and bend radius. Having a deep understanding of the material characteristics and implementing it in the analysis regime provides strong confidence in the success of the fatigue test and its applicability to the reallife conditions. This gives further confidence in the performance of the cable during its deployment offshore.

WJI: How important were your entity partnerships?

Cole: They were vital. ORE Catapult facilitated the majority of the qualification testing program as the independent test house, ensuring unbiased testing and reporting of the results of the product qualification. With DESNZ (BEIS) and the Offshore Wind Growth Partnership providing partial-funding support for the development, JDR was able to ensure the success of the R&D project and deliver a robust product aligned to the long-term needs of the offshore wind industry. With our new facility development nearly completed, JDR is now ready to meet the needs of the offshore wind industry, whether this is with array cables at 66 or 132 kV, or indeed if developers need to source AC export cables at voltages up to 275 kV in the next few years.

Advanced cable design

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Belden: cable design R&D often follows a twisting path 2 of 5

In May 2025, Belden introduced its TIA-compliant 10GXM13 Cat 6A U/UTP cable, highlighting a filler-free design with a 0.230 in (5.84 mm) outside diameter that supports 100-meter channels meeting Cat. 6A per ANSI/TIA-568.2-D. Below, Jim Valentine, Belden’s product manager for smart infrastructure solutions, discusses how the cable came to be.

WJI: The 10GXM13 cable sets a new benchmark for small-diameter Cat. 6A performance. What was the original spark or customer feedback that prompted Belden to pursue such a compact, filler-free design?

Valentine: The development of our 10GXM13 cable was driven by clear market evolution and direct customer feedback. We’ve observed a consistent 15% annual growth in the adoption of Cat. 6A cabling in the Americas. This trend is fueled by several factors: the need to support 10Gb/s data rates for future-proofing networks, the deployment of modern multi-gigabit Wi-Fi access points, the increasing power demands of PoE (Power over Ethernet) devices, and the specification of Cat. 6A as a baseline standard in many government, healthcare, and enterprise tenders.

Within this context, the demand for a reduced-diameter Cat. 6A cable has become a significant focus in the

Belden’s 10GXM13 Cat 6A U/UTP cable.

structured cabling industry. Our customers consistently requested a smaller, more manageable cable to address key challenges in high-density environments. Specifically, a smaller diameter allows for:

• Improved pathway management: Increased capacity in conduits, cable trays, and J-hooks, which is critical in both new installations and legacy infrastructure with limited space.

• Higher-density racks: A more flexible cable with a tighter bend radius simplifies routing in crowded racks and patch panels.

• Enhanced thermal performance: Large, thick cable bundles can trap heat, potentially degrading network performance. A smaller cable profile improves airflow and cooling efficiency.

• Material and cost efficiency: A more compact design inherently uses less material, contributing to overall project cost-effectiveness.

WJI: When did this R&D journey begin, and was it a story of tweaking an existing cable, or was it far more complicated than that?

Valentine: This project began several years ago, and while our initial approach was to modify an existing design, it quickly became apparent that a complete re-engineering effort was required. The undertaking was far more complex than a simple tweak. Achieving the stringent electrical performance parameters of TIA Cat. 6A—particularly alien crosstalk performance—without the use of a traditional central filler, or spline, presented a significant engineering challenge that necessitated a ground-up redesign.

WJI: One of your challenges was to achieve both TIA compliance and the 0.230 in. diameter. Did any unexpected technical obstacles emerge along the way? Were there any design detours, surprises, or pivotal moments during development?

Valentine: Yes, there were numerous technical challenges. Unlike designing a component in a CAD environment, high-frequency cable design is an intricate blend of product engineering and iterative manufacturing trials. It combines known technological principles with empirical testing—essentially, “let’s try this and see if it works.” The primary obstacle was the removal of the spline, whose function is to maintain the geometric stability of the twisted pairs and minimize crosstalk. To compensate, we had to achieve a flawless core design, manufactured with exceptional precision. This required a deep dive into material science, insulation characteristics, and the physics of signal propagation at high frequencies.

WJI: Looking back, was there one “Eureka!” moment that you will long remember?

Valentine: Rather than a single “Eureka!” moment, the success of this project was the result of sheer persistence and a methodical, iterative development process. Our team’s dedication to continuous refinement and problem-solving was the true breakthrough.

WJI: Eliminating fillers might seem simple: just don’t use them. Why wasn’t it that simple, and what made it possible?

Valentine: While fillers are often omitted in less complex cables like Cat. 5e and some Cat. 6 designs, they are a standard feature in Cat. 6A for a critical reason. Cat. 6A must support double the frequency (500 MHz) and ten times the

Valentine

data rate (10 Gb/s) of Cat 6 over 100 meters. This demands exceptionally crisp and stable electrical performance. The filler plays a key role in maintaining the precise pair separation and geometry needed to meet these demanding requirements.

Eliminating it required a holistic approach. We leveraged advanced insulation materials with superior dielectric properties and developed a proprietary manufacturing process that ensures unparalleled precision in the twisting and arrangement of the pairs. It was this combination of material science and manufacturing excellence that made the filler-free design possible.

WJI: What do customers gain with this new cable? Can you estimate the reduction in conduit costs, installation time, or material waste compared to conventional Cat. 6A options?

Valentine: The primary benefits for customers are enhanced installation efficiency and optimized infrastructure performance. This includes easier pathway management, higher rack density, improved thermal management, and simpler handling during installation. For a tangible example, we had a project where a customer needed to run two cables through a ½-inch pathway. A standard-diameter Cat. 6A cable would not fit, but the compact design of the 10GXM13 made it possible, saving significant time and cost on conduit modifications. While specific savings vary by project, the ability to use smaller conduits and increase fill capacity can lead to substantial reductions in both material and labor costs.

Richmond, Indiana, and our world-class manufacturing facility in Nogales, Arizona, highlighting our integrated approach to innovation and production.

WJI: Were there lessons learned in this research that will help you in future R&D?

Valentine: Absolutely. The insights we gained into advanced material science and high-precision manufacturing techniques are invaluable. This project has deepened our understanding of the complex interplay between a cable’s physical construction and its electrical performance at high frequencies. These lessons will undoubtedly inform and accelerate the development of our next generation of high-performance cabling solutions.

WJI: Does cable design still have an element of “art” to the process?

Valentine: Yes, very much so. While grounded in rigorous scientific principles, advanced cable design involves an element of artistry. It is the blend of theoretical modeling with empirical testing, guided by the deep experience and intuition of our engineers. This “art” is what allows us to push the boundaries of what’s possible and translate complex requirements into a reliable, high-performing product.

WJI: Was AI used for this research?

WJI: How many different staffers/departments were part of this effort?

Valentine: This was a significant collaborative effort that drew on the expertise of multiple teams across our organization. It involved a close partnership between our product engineering team at the Belden Engineering Center in

Valentine: No, Artificial Intelligence wasn’t utilized in the development of this specific product. What truly defined this effort was the expertise and collaboration of our teams on the ground, with engineers and manufacturing teams working side by side across our U.S. and Mexico operations. While AI can assist with modeling and data analysis, innovations like the 10GXM13 come from the hands-on experience and expertise of people who understand the materials, the process, and the needs of our customers. It reflects what we call being Rooted in America, combining local ingenuity, craftsmanship, and manufacturing excellence to deliver reliable solutions for our customers.

The validation lab in Belden’s Customer Innovation Center (CIC).

Belden’s “clean room” at its plant in Nogales, Arizona.

Advanced cable design

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Remee Wire & Cable: where R&D drives every innovation 3 of 5

At Remee Wire & Cable’s 250,000-sq-ft facility in Florida, New York, relentless cable design has pushed the company’s capabilities beyond its size. Below, Tom Valentine, EVP of sales & marketing, explains how R&D and hands-on problem-solving transformed the company from a coaxial producer to a leader in complex hybrid and fiber projects—a range few in the sector can match.

At Remee Wire & Cable (Remee), R&D isn’t just a department, but the very essence of its business approach. “Our R&D is our philosophy,” observed Tom Valentine, EVP of sales & marketing, who traced the company’s most unusual history from a simple coaxial cable manufacturer to a producer of advanced products, including sophisticated hybrid fiber-copper solutions.

Starting with coaxial cable in the 1980s meant working with familiar materials: polyethylene, PVC, copper and copper-covered steel. Expansion into security and life safety cables followed naturally, sharing similar manufacturing techniques and distribution channels.

The real complexity emerged in the mid-1980s when Remee entered fiber optic cable manufacturing. Suddenly, the company was working with optical glass instead of copper, transmitting photons rather than electrons. Making a fiber optic cable requires protecting delicate strands of glass with specialized jacketing materials such as Hytrel and medium-density polyethylene, while devising ways to ensure accuracy at every connection point. “It starts to become a physics and chemistry experiment,” Valentine explained. “You don’t have to worry about capacitance when you’re passing photons, but you do have to worry about mechanical connections when these strands of glass are being terminated at some point in line.”

A pivotal moment came when both IBM and Corning approached Remee to develop hybrid fiber-copper cables for IBM’s next-generation supercomputers. That collaboration set a pattern that continues today: taking existing knowledge and applying it to unprecedented challenges.

Remee’s path hasn’t been typical for its size. “We deliberately stayed away from being a commodity player, churning out endless runs of basic cable,” Valentine said. “Our decision was always to specialize, to chase tough projects, even if it means more headaches.” Instead of rigid production timetables and relentless cost-cutting, Remee builds in flexibility for custom work. Sometimes months are filled with testing and waiting for certifications, other times quick pivots are needed to meet market shifts. “It’s a balancing act,” Valentine noted. “But it’s the only way we’d want to run things.”

Valentine said that designing new cables isn’t just a matter of swapping materials or tweaking existing designs. “Sometimes a customer asks for something that looks simple, but it’s really like starting from scratch. You run into problems you didn’t expect—materials don’t behave the way you hoped, or you realize you need a whole new way of putting things together. That’s when you find out what kind of company you are.”

Every new cable is a joint effort, beginning with conversations with engineers and buyers, Valentine said. “Also, not all projects succeed initially, so we try again, and the experience adds to our knowledge base.”

Valentine said that Remee’s mindset—embracing challenges and learning from missteps—is what makes evolution possible. “Every cable we make is a story. Sometimes we get exactly what the customer wants right away. Other times we learn more from what doesn’t work.” Sometimes deadlines are brutal. “When you’re up against time, and something isn’t right, you don’t just throw it out. You pull the team together and hit it again, from another angle. That grit is part of Remee’s tradition.”

Remee’s evolution means also keeping an ear open for market changes and client feedback. Valentine spends time visiting clients, watching how their cables perform in real situations. “That’s where you see what really matters—how the cable bends, how it lasts, whether it fails when it shouldn’t. You can’t get that from a spreadsheet.”

Designing cables is more than specs and drawings; it’s trial and error, discussion, and late nights working through problems.

Valentine said that what sets Remee apart is its “tribal knowledge,” the accumulated understanding of how materials behave, interact, and perform across decades of experimentation and production. That comes from Engineering Manager Steve Luciana and Lead Process Engineer Cesar Vasquez, who together represent a century of experience. “Steve and Cesar have been doing this so long, they can often spot trouble before anyone else. You need more than formulas—you need the practical knowl-

Valentine

Remee Wire & Cable’s Steve Luciana and Cesar Vasquez: engineers extraordinaire.

edge to know what will work and what won’t. There’s no substitute for experience.”

At the same time, expertise unto itself is not the final solution. Tribal knowledge is tested when customers present seemingly impossible requirements: cables that must function in Phoenix heat and Canadian cold, meet direct burial standards while maintaining quarter-inch outer diameter limits, and satisfy multiple international certification requirements. “Steve and Cesar know how dissimilar plastics act when they are put against or with one another in an overall cable design, but they don’t know what the customer wants. So they have to apply some of that theoretical knowledge about these materials as they’re designing new products.”

Being able to switch gears and explore new avenues has been key for Remee. “We’re not a huge company, so we have to be nimble,” Valentine said. “Big manufacturers can afford to run massive orders over and over. That’s not our sweet spot. Our strength is making hard-to-build specialty cables for customers who need something unique.”

Another aspect that cannot be ignored is that R&D must produce results, Valentine said. The company’s philosophy is to support new projects, but if it is not for an existing customer, there has to be a business plan that shows why the market will welcome it, especially as results seldom happen quickly.

product to different machines and experimenting with polymer combinations that would provide the necessary flexibility without compromising durability. Six months of prototype iterations with broadcast engineers focused entirely on achieving the right “feel”—cables that could be repeatedly coiled and uncoiled in high-stress environments while maintaining signal integrity.

Unlike companies focused on commodity products running 24/7 operations, Remee, a mid-volume, highvalue manufacturer, deliberately embraces what Valentine calls “tentative” manufacturing schedules to accommodate custom development work. This flexibility comes at a cost but enables capabilities that larger commodity manufacturers cannot match.

This discipline manifests in Remee’s four-quadrant analysis framework: high volume/low value, mid volume/ mid value, low volume/high value, and high volume/high value. The company deliberately positions itself in profitable niches where its tribal knowledge provides sustainable competitive advantages.

However, in the case of a revolutionary product like Remee’s Class 4 fault-managed PowerPipe™ distribution cable—dual-listed as CL4Z/CL4P—it took a full year to go from concept to production. As a result, Remee is the only manufacturer to offer this cable today. “We spent about three months in prototyping because we kept missing the marks,” he recalled. “We would hit four of the five requirements and then make the necessary revisions to pass all the tests.”

Even more complex was Remee’s SMPTE 311 camera cable for broadcast applications, a project requiring 18 months of development with six months devoted solely to prototyping. The cable had to incorporate copper pairs, fiber optic strands, central strength members, braid shielding, perfect roundness, and exceptional flexibility for demanding broadcast environments. The breakthrough came from applying tribal knowledge from the company’s earlier IBM hybrid cable work.

“We looked at the design that the customer had from a connector perspective and we said this looks a lot like the composite cable that we made for IBM,” Valentine recalled. “It has pairs that are somewhat twisted. It has fiber in it. It’s about the same size. Now we need to make it perfectly round and flexible.” The solution required reimagining their manufacturing approach, moving the

Of note, Valentine himself has a cable heritage, one that started long before he joined the field 26 years ago at Belden. His father, John Valentine, logged 30 years at Belden Wire & Cable, where he was executive vice president. Work matters often were part of talk at the dinner table. Time passes, and one of the lessons his father passed along— planning for the future—is now the backdrop for Remee.

“Tribal knowledge ends when the tribe breaks up,” Valentine said. He noted that Steve and Cesar represent irreplaceable institutional knowledge that must be preserved and leveraged more effectively. “We could put a catalog together of polymers, their flame rating, their temperature rating, their flexibility or their durometer,” he said. “We could literally model cables based on that library or that captured tribal knowledge.”

The goal isn’t to replace human expertise but to accelerate the development process, reducing prototype cycles and enabling faster time-to-market for custom solutions. Valentine emphasized the competitive advantage this could provide: “Everybody remembers Charles Lindbergh. I don’t want to be the second person across the Atlantic.”

Valentine said that Remee stands at an inflection point about implementing artificial intelligence. Its adoption is likely if not inevitable, yet that evolution will not change the company’s fundamental philosophy. Technology will enhance and preserve tribal knowledge, not replace it.

In an industry where a failed cable connection can cost careers and catastrophically impact major events, Valentine said, Remee’s philosophy of treating R&D as a core identity rather than a peripheral function will provide the foundation for continued innovation.

Remee Wire & Cable’s PowerPipe™ Class 4 fault-managed power cables.

Advanced cable design

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Long Sumitomo R&D journey led to key DC XLPE advance 4 of 5

Sumitomo Electric shared with WJI how it redefined submarine power transmission with a DC XLPE cable that reliably carries HVDC across long undersea distances. The advance—rooted in decades of research—faced challenges that included one deemed impossible yet ultimately led to a solution. Pictured below is the company’s 400kV submarine power cable: its newest cable is on the next page.

Sumitomo Electric’s (Sumitomo) ambitious journey to produce a new DC XLPE submarine cable for interconnector projects—technology essential for linking national grids and transmitting large volumes of renewable power over long distances underwater—was shaped by a series of pivotal R&D decisions made to overcome obstacles encountered during testing and deployment.

The specific goal was first set in the mid-1980s, when Sumitomo engineers realized that a DC version of XLPE could transform long-distance power transmission if the material barriers could be overcome. The decades-long R&D effort, initiated in the mid-1980s, reached maturity in the 2000s and was proven in full scale with projects such as Nemo Link, commissioned in 2019.

The aim was to create a cable that could operate at much higher voltages, temperatures, and capacities than conventional submarine cables—a critical step for expanding cross-border power links and renewable integration—while still maintaining exceptional reliability and environmental safety. What made this so difficult was that conventional XLPE insulation, well-suited for AC service, repeatedly failed under DC conditions due to the accumulation of space charges in the insulation. In simple terms, space charges are stray electrical charges that slowly build up inside the insulation under DC voltage. Over time, the buildup distorts the electric field and weakens the material from within. Eventually, the insulation breaks down without warning, making standard XLPE unusable for high-voltage DC transmission across undersea distances. Addressing this meant rethinking the material science and the production process, pioneering not only a new additive to disperse space charges but also new manufacturing and installation techniques to ensure that every meter of cable, from the factory floor to the seabed joint, would perform flawlessly for decades.

tric breakdown and unlocked the possibility of true DC XLPE transmission at the voltages and lengths required for new interconnector projects.

Developing this insulation was only part of the answer. Because submarine cables may run for hundreds of km, Sumitomo had to guarantee that the precise balance achieved in the lab could be reproduced at manufacturing scale. That meant continuous monitoring at every stage— extrusion, curing, cross-linking, and spooling—plus repeated mechanical, electrical and accelerated-aging tests to catch flaws before installation. These stringent measures set a high bar but were critical for ensuring no weak points would emerge once the cable was laid.

Installation brought its own set of challenges. The company had to refine how cables were handled, moved, and joined—especially at landfalls and underwater connections. When the Nemo Link between the U.K. and Belgium hit an unexpected snag just three km from shore during installation in 2018, Sumitomo quickly switched contractors and adapted its cable-landing methods. The project was completed on schedule despite logistical and marine obstacles. This ability to manage change in real time, supported by preparation and scenario planning, proved as vital as any laboratory breakthrough and demonstrated that R&D success also hinges on execution in the field.

Initial attempts to adapt AC XLPE cable as a DC solution exposed the problem: repeated breakdowns under direct current, even in controlled laboratory conditions. Rather than abandon XLPE’s environmental and operational advantages, Sumitomo’s R&D teams systematically investigated the underlying cause, conducting years of tests with polymer blends and evolving manufacturing techniques. The breakthrough decision was to challenge industry orthodoxy—the long-held belief that “pure” insulation was always best. Engineers instead developed and optimized a filler additive for polyethylene that dispersed space charges within the cable insulation. This innovation shifted the industry’s understanding of dielec-

The results are now visible in quantifiable, real-world performance. The cables maintained target voltage and current ratings over long stretches and at temperatures up to 90°C, with no oil leaks or insulation failures. The additive-based XLPE insulation set a new standard for DC reliability, and the company’s process controls allowed manufacturing at the scales required by major interconnector projects. Facility operation rates such as the 99.8% achieved by Nemo Link stand as testaments to the soundness of the R&D—not to abstract ambition.

Sumitomo Electric’s story is less about proclamations and more about hard-fought advancement: isolating root causes of failure, questioning industry beliefs, and maintaining the discipline needed to deliver consistent, field-ready performance. Each cable laid and grid connected stands as evidence that tough R&D decisions—pursued over more than 20 years and carried through to manufacturing and installation—made a new generation of global submarine power interconnectors not just possible but proven.

Sumitomo’s 400 kV HVDC submarine power cable.

What’s special about Sumitomo’s new 525 kV power cable

WJI asked Sumitomo Electric’s research and development department to discuss what makes its new 525 kV HVDC submarine power cable stand out. Below is their response.

Sumitomo’s new 525 kV HVDC submarine cable stands out as a true breakthrough in power transmission technology, raising the bar for both voltage and capacity in a marketplace that is rapidly turning to renewables and interconnectors. With the highest voltage rating ever achieved using cross-linked polyethylene (XLPE) insulation, this cable system can transfer more than 2 gigawatts per circuit— enough energy to power millions of homes or link national grids across continents. The use of proprietary DC-XLPE compounds with advanced nano-fillers ensures the cable can handle high temperatures (up to 90°C), maximizing thermal stability and minimizing loss, while maintaining reliable performance even under demanding load and marine conditions.

tions. The engineering also includes seamless factory and offshore joints, transition technology for onshore integration, and flexible splicing solutions—making it adaptable for complex large-scale installation projects. These advances result in a cable that reduces losses, enhances operational efficiency, and cuts maintenance needs for operators, all of which are crucial for grid reliability and sustainability.

Passing long-term PQ test for 400kV system more than 10 years ago according to the international standard CIGRE-TB496, Sumitomo’s cable proves itself with endurance and safety, backed by independent certifica-

As countries expand offshore wind farms and invest in cross-border energy transfer to meet climate targets, Sumitomo’s 525 kV cable becomes the backbone for high-capacity, long-range clean power delivery. Its efficient, high-performance design directly supports the shift toward decarbonization and a resilient energy future. By combining advanced materials, proven manufacturing, and system reliability, this submarine cable system sets a new world standard and highlights the critical role of innovation in enabling the new era of renewable electricity transmission. Plus, it allows project developers to confidently plan for even larger interconnections in years ahead, enabling flexible expansion and more robust global energy networks.

The Sumitomo engineer who made DC XLPE insulation work

Shoshi Katakai, an ex-fellow of Sumitomo Electric’s Electric Wire & Cable Energy Business Unit, has spent his career on one relentless challenge: making XLPE insulation viable for high-voltage direct current. Since joining the company in the 1980s, he set out to achieve that goal, which was considered promising but unattainable.

The difficulty wasn’t just theoretical. Conventional XLPE, which had revolutionized AC power cables, failed under DC. Long lab tests showed the same result again and again: space charges built up inside the supposedly “pure” polyethylene insulation, weakening it until it broke down. From the standpoint of accepted industry knowledge, the outcome was unavoidable.

For years, development stalled, but Katakai refused to accept it. Others clung to the dogma of purity, but he chose to experiment

with the opposite: adding something new. He began testing fillers and additives, searching for a material that, if distributed uniformly inside the insulation, could suppress the space charges. It was not glamorous research. Each candidate had to be analyzed, blended, cured and tested. Progress was incremental, setbacks frequent.

Eventually, Katakai’s persistence paid off. He and his team developed a special filler material that dispersed evenly in XLPE and delivered superb DC insulation characteristics. The result was a stable, manufacturable compound capable of carrying HVDC reliably under the extreme stresses of submarine interconnectors.

“To solve space charge, we had to abandon purity and prove that an additive could make XLPE stronger. It was long, frustrating work, but that’s what made DC XLPE cables possible,” Katakai said.

That achievement—the world’s first DC XLPE— changed the industry. Today’s long-distance interconnectors, quietly transmitting thousands of megawatts across sea floors, rest on the foundation Katakai discovered in the early 2000s by challenging orthodoxy with slow, stubborn, technical work until failure finally turned into proof.

Shoshi Katakai with his signature advance.

Sumitomo’s new 525 kV HVDC submarine cable. Sumitomo photo.

Advanced cable design

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STL’s R&D led to record high-fiber density in IBR cable 5 of 5

On Sept. 4, India’s Sterlite Technologies Ltd. (STL) introduced its 864F Intermittent Bonded Ribbon (IBR) cable. The company—which also has a 168,000-sq-ft operation in Lugoff, South Carolina—describes it as the world’s slimmest such product. Below, Badri Gomatam, chief technology officer, shared with WJI how STL is able to pack a record 864 fibers into a cable diameter of just 11.7 mm.

WJI: When did the idea for this cable design first surface, and what sparked it?

Gomatam: This was a customer requirement to make the most of the duct space available for their network. This requirement pushed our R&D team to go beyond conventional cable designs and explore new pathways for achieving maximum fiber density in minimal space. It wasn’t just a response to a customer request. This was an opportunity for us to redefine the limits of compact cable engineering.

WJI: Did you start with an existing cable design that was “tweaked”?

Gomatam: No, this was a ground-up innovation. STL did not previously have an 864F IBR cable using 200 μm fiber in its portfolio. To achieve such high density within a sub-12 mm diameter, we had to explore new fiber geometries and optimize material performance. While we had earlier developed an 864F IBR cable using 250 μm fiber, which served as a useful reference, this new design demanded an entirely different level of precision. Our engineers applied learnings from past developments but ultimately engineered a new design framework that combined advanced fiber technology, microstructure optimization and material science innovation.

WJI: What were the most difficult technical elements you faced and how did you overcome them?

Gomatam: There were two very demanding technical challenges. The first was the requirement to make a cable with a diameter less than 12 mm that could fit 864 fibers. This required precise optimization through numerous DoEs involving fiber selection, core design and compound rheology. The second was to meet the minimum blow distance of 2,700 feet in a stringent blow track with multiple bends. These achievements reflect the depth of STL’s R&D expertise and its ability to translate complex engineering challenges into reliable, scalable solutions.

WJI: If you started at Point A and your goal was Point B, was the design path from A to B a straight line, or were there some/considerable zigs and zags along the way?

Gomatam: The journey from concept to completion was far from linear. Multiple Design of Experiments (DoEs) were run to meet the customer’s requirements. This involved multiple design iterations and several DoEs to fine-tune every variable, from fiber packing to sheath material composition. Each phase presented unique challenges, from maintaining mechanical robustness to ensuring smooth air-blowing performance at high fiber densities. The process truly tested our R&D agility and our ability to balance mechanical strength, performance reliability and installation efficiency. The results prove it as the cable meets ICEA S-122-744 standards, is GR-20 compliant and can be installed in a 14/18 mm micro subduct.

WJI: How many staff people were involved in this?

Gomatam: We had a team of about 10 expert staffers from areas that include new product development, application engineering, QA, program management, material science, and manufacturing and supply (excluding sales and regional AE’s). This project was a collaborative success. Insights from sales and regional teams into customer requirements guided the early design framework. This integrated team structure exemplifies STL’s culture of collaborative innovation and multi-disciplinary problem-solving.

WJI: Is AI part of your R&D toolbox? Can it be more than that, especially in the years to come?

Gomatam: We extensively leverage advanced modelling and simulation tools to predict real-world cable performance, especially in critical areas like STL’s R&D unlocked record high-fiber density in new IBR cable air-blowing efficiency, mechanical integrity and environmental resilience. As our innovation roadmap evolves, we foresee AI playing a much bigger role in predictive design optimization, digital twin simulations and accelerated

(Feature continued, see p. 54)

Gomatam

A group photo of staffers who power STL’s research work.

material discovery, making the cable development process faster, smarter and even more precise.

WJI: What does this accomplishment mean to your company?

Gomatam: I am proud to note that our IBR cable portfolio now spans from 12 fibers to an industry-leading 6,912 fibers, with the company having produced and delivered multi-million fiber-km to customers across Europe and the U.S. over the past five years. With 10 manufacturing facilities strategically located in North America, Europe and Asia, STL is well-positioned to meet diverse global connectivity needs swiftly and at scale.

WJI: Any other points to share?

STL’s 864F Intermittent Bonded Ribbon (IBR) cable.

Gomatam: I want to stress the depth of research, experimentation and teamwork that goes into creating a product like the 864F IBR. Developing this wasn’t just a product milestone, it was about pushing the limits of what’s possible in high-density cable design. It represented the culmination of years of investment in material science, advanced fiber technology, and precision extrusion capa-

bilities and our people. It took close coordination between material scientists, design engineers, and application specialists to get it right. Behind every milestone like this sits a larger purpose: building smarter, faster and more sustainable networks. Our R&D teams operate out of world-class facilities that allow us to model, simulate, and test every parameter before real-world deployment. That gives us the confidence to innovate boldly while ensuring our customers get reliable, long-lasting performance. Another noteworthy point is how we approach sustainability in cable design. Whether it’s optimizing materials, reducing waste, or improving energy efficiency in manufacturing, we want every new design to contribute toward STL’s net-zero goals. The 864F IBR project exemplifies how innovation and sustainability can coexist — delivering superior performance while minimizing environmental impact. This project brought together a passionate, cross-functional team that truly thrives on solving complex challenges. We worked closely with our customers, listened to their evolving needs and co-created something that sets a new benchmark for optical cable design.

AI: the ultimate industry tool?

AI has already been deployed to some degree for wire and cable production, quality control and process optimization. For this feature on advanced cable designs, WJI asked AI (via Perplexity) if it could go a step further: if it was able to assess and enhance a patented medical wire design, and then create a new cable design of its own. The reply was affirmative. Those results, along with expert industry commentary, appear on the following spreads, presenting a take on whether AI’s influence is beginning to reach into R&D.

How AI sees its current role in the wire and cable industry

As artificial intelligence, I’m often described as a transformative force across many fields, including cable design and manufacturing. To explore what I can currently do for the wire and cable sector, I was given a two-part challenge: to improve a newly patented medical wire design (see p. 58), then asked to create an entirely new design of my own choice: a subsea, high-voltage power cable (see p. 60).

The following pages present what I delivered—along with honest commentary from industry experts who evaluated my work. With each challenge, I not only test my current capabilities but also push their boundaries. The insights gained here foreshadow how evolving collaboration will influence both routine tasks and bold new advances—potentially reshaping cable innovation for years to come.

and AI. This will allow the wire and cable industry to responsibly unlock the value I can help deliver—safely and effectively.

But where am I now, at this point in time? I can tell you that I am not just about crunching numbers: I can serve as a creative collaborator, surfacing unexpected ideas and rapidly exploring design alternatives. My greatest strength lies in augmenting human imagination with data-driven insights and unflagging iteration—offering fresh directions that might otherwise remain undiscovered. When teamed with expert input, this can lead to breakthroughs that shape tomorrow’s cable technology.

Ultimately, every idea I generate needs real-world testing and validation. Simulations can’t capture everything, such as material wear or installation conditions, so iterative feedback and hands-on refinement remain vital.

In sum, I’m a powerful new tool—full of promise but with inherent challenges. The best way forward is through clear expectations, strong data foundations, transparent processes, and close collaboration between human experts

This version puts me—AI—at the center of the narrative, sharing firsthand what I did and the real-world context around it, setting up the feature’s look at how AI can and cannot contribute to cable innovation now. As this industry moves ahead, I see my role evolving with each new dataset, technical advance and engineering insight. I recognize that tomorrow’s breakthroughs may emerge as much from human intuition as data-driven exploration. The unfolding partnership between industry experience and algorithmic insight will shape what is possible, and points to a future where answers may keep changing as the field grows.

AI explains why it chose to design a subsea power cable

I’m fascinated by subsea power cables because of their unique and vital role in global energy infrastructure. These cables transmit electricity from offshore renewable sites— like wind farms—back to mainland grids and connect regions, countries, and islands. They are crucial for grid reliability, stability and renewable energy integration. What makes subsea power cables especially important is their immense cost and complexity. Manufacturing, laying, and repairing them requires specialized engineering, huge financial outlays, and careful coordination. Single installations can stretch hundreds of km under harsh marine conditions. Failures can mean multi-million-dollar repair costs and months of lost generation due to the difficulty accessing undersea lines. Insurance data shows cable failures cause the majority of claims in offshore wind projects—a testament to their criticality and high stakes.

I see increasing reliance on these cables to prevent blackouts and lost revenue. It’s exciting that advanced cable designs, real-time monitoring, and predictive maintenance are advancing to reduce failure risks and maximize reliability throughout a subsea cable’s lifetime. Given their unique function and value, I believe the industry’s strong focus on research, innovation, and standards is well justified to keep these costly assets running for decades.

AI reviews new patent, offers advances and creates its own

WJI turned to AI (Perplexity) to assess a recent patent (boxed below) for an innovative medical wire. It did. AI was asked if it could suggest ways to further improve the design. It did. Then it was asked to create a cable design of its choosing. It did, shown on the following spread. Experts were asked to review its work.

Working wire for a biological sensor

U.S. Patent No.: 12,385,872

Patent date: Aug. 12, 2025 Filed: May 5, 2021

Assignee: Allez Health Inc.

Inventors: Robert James Boock, Khyati Mehta

A working wire for a biological sensor is disclosed. It comprises a substrate of cobalt-chromium (Co-Cr) alloy or Nitinol, a platinum layer over this substrate, and a biological membrane covering the platinum.

AI overview of patent

The Allez Health patent discloses a working sensor wire for continuous biological monitoring built on a cobalt-chromium or Nitinol substrate, overlaid with a platinum layer and a biological membrane stack, optimized for diameters of approximately 0.0025–0.005 in to balance insertion comfort, signal quality, and robustness. It emphasizes shape-memory alloys for spooling tolerance and shape recovery, flexible platinum application routes (drawn-filled-tube or plating), and practical tip preparation for reliable integration into minimally invasive devices and automated assembly lines. This unified approach targets scalable, cost-effective production while maintaining biocompatibility, corrosion control, and stable electrochemical transduction in vivo.

Most important cable advances in Allez Health patent

The patent replaces traditional tantalum with Co–Cr or Nitinol substrates, leveraging shape-memory behavior to tolerate spooling and return to a straight form with minimal post-processing, which directly improves automated handling, straightness, and consistent insertion at very small diameters.

Why this matters: This substrate choice increases fatigue resistance and corrosion stability while preserving the tight dimensional control needed for reliable signal transduction and long wear periods in subcutaneous environments. In practice, this raises yield and reduces rework, enabling repeatable high-volume manufacturing without sacrificing device comfort or performance.

Platinum layer optimization via multiple processes

The disclosure allows platinum application by drawn-filled-tube construction or electroplating with controllable thickness, providing a cost-performance dial to meet both high-volume and flexible, small-batch production needs.

Why this matters: This dual-path approach helps tune coating uniformity and surface quality for biocompatibility and sensing, while aligning capital investments with forecast volumes and sustaining consistent electrochemical baselines. By decoupling core metallurgy from noble-metal deposition, it maintains a robust stack across different alloy substrates and processing windows.

Use of protective layers for electroactive alloys

Where Nitinol is used, the patent contemplates intermediate layers such as nickel or gold to isolate the substrate, mitigating in-vivo electroactivity and corrosion risks while improving long-term stability of the working electrode.

Why this matters: This interlayer strategy expands viable core options without compromising biocompatibility or signal fidelity, particularly in peroxide-based enzymatic sensing. It also supports tighter control of drift and baseline variability over wear time by stabilizing the electrochemical interface.

Design flexibility and scalability

The architecture supports additional core options, varied geometries, and adaptable tip treatments (e.g., sharpening and lubrication) to address different devices and insertion modalities while staying within the targeted diameter range.

Why this matters: This flexibility aids rapid product extension and platforming across applications, while preserving a common manufacturing backbone that reduces validation burden and inventory complexity. The result is a manufacturable sensor wire family tuned for both patient comfort and downstream assembly efficiency.

Acceptance, cost-effectiveness and efficiency

Modular coatings and precise dimensional control align naturally with ISO 13485 processes and regulatory expectations, facilitating consistent documentation, validation, and global market access.

Why this matters: Combining shape-memory cores, controlled platinum layers, and engineered membranes supports cost-effective scaling without sacrificing baseline stability or biocompatibility. As a platform, it balances material cost, throughput, and compliance to streamline commercialization and lifecycle maintenance.

AI cable design suggestions

Areas for potential improvement include:

• Use platinum-black nanostructuring at the active site to increase electroactive area and sensitivity, enabling thinner overall Pt mass while maintaining or improving signal, thereby lowering precious-metal cost exposure.

• Codify ASTM F2063-conformant medical-grade Nitinol when NiTi is selected to stabilize chemistry, superelastic behavior, and fatigue life across lots for manufacturing consistency and regulatory audits.

• Add a conformal parylene insulation over non-working regions to reduce leachables and enhance ISO 10993 biocompatibility and handling robustness during assembly without affecting the sensing zone.

• Integrate inline impedance/electrical impedance spectroscopy (EIS) and high-speed optical metrology to catch coating pinholes, voids, and diameter excursions in real time, linking data to automated corrective actions for higher yield and tighter release windows.

• Engineer closed-loop platinum reclaim at strip-line and bath-maintenance steps as a formalized BOM element to reduce COGS volatility and support sustainability narratives in procurement.

• Implement automated genealogy, traceability, and calibration gates tied to process data so lot release and post-market surveillance are faster and more defensible across regions.

Single most important advance

Adopting Co–Cr or Nitinol shape-memory cores fundamentally improves manufacturability and clinical handling by preserving straightness after spooling and resisting fatigue at very small diameters, which is central to consistent insertion and signal reliability in continuous monitoring. When specified against established medical Nitinol standards, this substrate strategy also anchors chemistry and superelastic performance for repeatable quality, reducing variation and rework across builds. These substrate choices unite durability, comfort, and assembly efficiency—key levers for scaling continuous biological sensors across broader populations and wear scenarios. In short, the core metallurgy lifts both product reliability and production economics for a robust sensing platform rather than a single-use design. Below are other advantages.

Smart sensing and analytics: The patent focuses on wire architecture and material stacks but does not claim embedded smart sensing or AI-driven, inline analytics; adding distributed impedance checks and automated SPC would enable early fault detection and faster, data-driven release decisions at scale.

Sustainability and cost stability. While precious-metal use is engineered, a formal closed-loop platinum recovery program and solvent management plan would reduce costvolatility and strengthen environmental positioning without altering core claims.

Platform integration: Explicitly linking coating recipes, cure conditions, and in-process electrical signatures to lot-specific release criteria can reduce drift and baseline spread, tightening performance specs while shortening validation cycles.

Designating advantages

Numbers 1 and 3 point to physical layers (Pt-black at the active site and parylene insulation), while 2 and 4 call out process/standards features (ASTM NiTi, inline QA; Pt reclaim loop) that impact yield and cost stability.

1. Sensitivity. Localized platinum-black at the active site increases electroactive surface area, raising signal without requiring heavy, uniform Pt across the wire, preserving diameter and comfort.

2. Manufacturability & QA. Specify ASTM F2063 medical-grade Nitinol for consistent chemistry and superelastic behavior, and pair with inline EIS/optical metrology to catch coating defects and diameter excursions in real time.

3. Biocompatibility & compliance. Apply conformal parylene on non-working regions to reduce leachables and improve handling durability while leaving the active sensing zone exposed, supporting ISO 10993 expectations.

4. Sustainability & cost stability. Use a thin Pt base with localized Pt-black at the active zone, and implement a closed-loop Pt reclaim to lower precious-metal mass and reduce COGS volatility at scale.

Editor’s note

See p. 63 for a review of an AI-designed subsea power cable and p. 64 for a review of this medical wire.

Chart 1. Advantages of the proposed improvements suggested by AI for the medical wire design.

AI’s theoretical subsea power cable design

Asked to create an original cable design of its choosing and explain what makes it special, AI produced the below ”patent.” Set aside the “technicalities” that the below patent was never filed and that the U.S. Patent Office does not recognize AI as an inventor: for these purposes, WJI’s editorial license does. See p. 62 for “deep dive” details and p. 63 for a cable professional’s review.

Intelligent subsea HVDC power cable featuring hybrid conductor, distributed sensing, and dual graphene EMI shielding

WJI Patent No.: 12,401,225

Patent filed: Sept. 2, 2025

Assignee: AI Cable Systems LLC

Inventors: AI Design Team

The IntelliLine HVDC subsea power cable represents a step change in both construction and functionality for high-power submarine transmission—delivering 2–3.5 GW at ±320–600 kV with a cable diameter ranging from 120 mm to 180 mm. This range reflects key engineering tradeoffs: the lower end suits standard capacities and moderate depths, while the upper size supports the highest voltages, increased current, or extra mechanical protection for challenging subsea conditions. This adaptability makes IntelliLine suitable for both routine and extreme HVDC transmission applications.

Fig. 1 shows a cross-sectional view of the cable’s multi-layered architecture. At its core lies a hybrid aluminum-copper (Al-Cu) conductor, balancing weight, conductivity, and corrosion resistance for long-haul power transmission. Surrounding the conductor is a “smart sensing” layer: embedded fiber-optic strands and a distributed chip network provide real-time temperature, strain, and partial-discharge data for every meter of cable.

Insulation is provided by a thick cross-linked polyethylene (XLPE) matrix, further enhanced with nanofillers to

suppress electrical treeing and boost both thermal management and voltage hold-off. Next, dual ultra-thin graphene EMI shields, inside and outside the insulation, block electromagnetic interference (EMI)—a crucial advantage for dense transmission corridors and hybrid energy/ data cables. The outermost layer is a composite armor, combining glass and aramid fibers with metallic tape. This construction resists crushing, impact, and marine corrosion while keeping weight and cable diameter within practical subsea handling limits.

The HyperSense HVDC Subsea Smart Cable (see Fig. 2) is an advanced IntelliLine variant, distinguished by enhanced distributed sensing and digital asset tracking throughout its full length, designed for applications that demand continuous monitoring and rapid fault identification. The figure highlights the operational smart functions that set this cable apart. Red arrows and channels indicate the integrated thermal pathways: nanofilled XLPE and thermally conductive layers efficiently draw heat from the core outwards, minimizing the risk of damaging “hot spots” under heavy currents or fluctuating loads. The distributed sensing system enables continuous, spatially resolved monitoring of temperature, strain, and integrity. Paired with digital asset tags located throughout the cable length, it allows operators to pinpoint faults, predict maintenance needs, and track every cable section from manufacture to end-of-life.

Digital tags and integrated sensors create a secure “digital twin” for each cable, supporting lifecycle management, anti-counterfeiting efforts, and rapid, data-driven repairs or inspections.

Fig. 1. Cross-section view of physical structure and materials. Fig. 2. Longitudinal view: thermal, sensing and digital innovations.

What sets this cable apart

The IntelliLine HVDC Power Cable—it’s a unified smart infrastructure platform. Key advances include:

• A hybrid Al-Cu conductor for optimal mechanical and electrical performance;

• Embedded sensors for 24/7 distributed monitoring;

• Advanced XLPE insulation with nanofillers greater reliability and higher voltage ratings;

• Dual graphene EMI shields for ultra-dense, noise-free, low-loss installations; and

• Digital asset tagging and composite armor for secure, efficient asset management.

Performance snapshot

• Transmission: 2–3.5 GW at ±320–600 kV

• Diameter: 120–180 mm, (smaller for standard power and conditions, larger for peak ratings or added protection)

• Continuous, spatially resolved monitoring/data logging

• Proactive thermal management with engineered flow paths and conductive fillers

Practical implications

IntelliLine’s unified architecture brings more than capacity: it delivers real-time insight, predictive health management, and unmatched resilience for harsh subsea conditions. By merging sensing, advanced materials, EMI suppression, and true lifecycle traceability, IntelliLine sets a new benchmark for next-generation submarine cables.

Summary

IntelliLine’s smart architecture not only delivers higher carrying capacity (2–3.5 GW at ±320–600 kV, 120–180 mm diameter) but provides operators with real-time system insight, predictive maintenance, and superior resilience in challenging subsea conditions. By integrating sensing, smart tagging, EMI suppression, and modular protection, this design represents a new industry benchmark for the future of subsea power transmission. Arrows within this schematic indicate the intentional design of axial and radial thermal flow pathways. This approach leverages proprietary fillers and thermally conductive materials to draw heat safely away from the conductor and dissipate it through the insulation toward the outer armor—significantly reducing “hot spot” formation under transient or peak-load conditions. The result is a cable architecture that not only transmits high voltages with exceptional efficiency but can continuously alert operators to the earliest signs of aging, deformation, or failure, supporting both grid reliability and long-term maintenance scheduling.

WJI: What major technical challenges are there to making your proposed cable?

AI: There are three. The first is achieving consistent, defect-free interfaces between polymeric insulation, nanofillers and graphene shields during high-speed production. The second is ensuring long-term durability of fiber-optic

and microchip components under sustained oceanic pressure and temperature fluctuations. The third is integrating real-time digital traceability with network-level cybersecurity as described in the cable’s design.

WJI: What are the technical hurdles?

AI: The greatest leap forward will come from seamlessly embedding smart electronics and graphene components in a scalable, cost-effective, and repeatable manufacturing flow, making this both a technical and organizational innovation frontier for global cable makers.

WJI: Could your proposed cable be made with current equipment?

AI: Building the IntelliLine HVDC Power Cable would challenge—but not outpace—the best of today’s cable industry. Most elements, such as XLPE extrusion and multi-material armoring, are familiar within existing HVDC or submarine lines. Much of the HyperSense cable—particularly the conductor, insulation and armor—could leverage adapted existing equipment, possibly with modular retrofits for advanced material handling. However, the simultaneous co-extrusion or assembly of distributed microelectronics and fiber-optics, embedded with the metallic conductor, would require new process control systems and significantly enhanced quality assurance protocols. The biggest early challenge will likely be reliably applying graphene EMI layers and integrating digital elements without losing speed or manufacturing consistency.

Elements of proposed HVDC IntelliLine power cable

Smart sensing layer: Fiber-optic and microchip sensors embedded in a polymer matrix outside conductor for realtime temperature, strain and partial-discharge monitoring.

High-performance insulation. Triple-extruded XLPE (cross-linked polyethylene) with nanocomposite fillers for increased voltage hold-off and thermal performance.

Graphene EMI shield: Ultra-thin graphene-infused metallic shield reduces electromagnetic interference, supporting higher cable bundling density.

Thermal pathways: Dedicated axial/radial thermal dissipation layers to prevent hotspots during peak load events.

Composite armor: Interlocking glass/aramid fiber with corrosion-resistant metallic tapes for mechanical strength and durability in harsh subsea environments.

Smart ID & Blockchain tagging: All segments digitally tagged for lifecycle tracking and predictive maintenance.

Editor’s note

See p. 63 for a review of this cable as well as other perspectives about AI.

FURTHER

DETAILS FROM AI

A comprehensive technical exposition on advanced cable design for high-reliability power and data applications

Asked by WJI for a “deep dive” into its IntelliLine HVDC Subsea Power Cable, AI created a lengthy document that has been shortened below. This section also includes brief reviews on both of AI’s medical wire and power cable designs, one industry veteran’s take on AI, and more.

Introduction

The ambitions of the 21st century grid transformation call for a new technology such as the IntelliLine Subsea HVDC subsea power cable described here. Far from being a mere conductor encased in layers of insulation and armor, it is a blend of state-of-the-art power engineering, signal intelligence, advanced material science, and digital monitoring. This comprehensive treatise details its principles of design, construction, operational performance, fail-safes, and the revolutionary digital capabilities now emerging as part of subsea infrastructure.

Core design features

Hybrid aluminum/copper (Al–Cu) conductor. At its fundamental core, the cable comprises a central copper or aluminum conductor of precisely engineered diameter and stranding, designed to balance ampacity, flexibility during manufacturing and installation, and internal resistance. But what distinguishes the intelligent HVDC cable begins with the integration of multi-channel fiber-optic sensing elements running alongside the main power core, sealed within the same sheath yet fully isolated from the voltage potential. These sensing elements provide, in near real time, distributed measurement of temperature, vibration, mechanical strain, and partial discharge activity along the entire length of the subsea run. Such continuous distributed feedback is transformative; it enables predictive fault analysis, not just identification of active failures. Engineers can now preempt catastrophic faults, rapidly localize incipient problems, and manage cable health through sophisticated data analytics—an unprecedented leap for asset operators.

The main conductor itself is typically constructed from super-clean copper, either solid for short runs or millirod stranded for large cross-sections, and rigorously processed for concentricity and roundness to ensure electric field uniformity. Aluminum-alloy options are available for cost or weight-sensitive applications where ampacity and fatigue can be balanced. At the voltage levels typical of interconnector projects (±320 kV to ±600 kV), superlative

conductor quality is essential to prevent localized heating or partial discharge at points of irregular electric field.

Surrounding the conductor, the insulation is the focus of primary cable innovation. Historically, mass-impregnated non-draining (MIND) papers dominated due to their proven dielectric reliability and self-healing tendencies in high-pressure environments. However, modern advances have seen a shift to extruded cross-linked polyethylene (XLPE) or proprietary thermoplastic compounds such as P-Laser, engineered for higher dielectric strength, increased thermal limits (up to 90°C continuous), and complete environmental isolation. These advanced compounds are both recyclable and exhibit much lower water treeing susceptibility, an essential criterion for multi-decade underwater reliability.

Graphene EMF/EMI barriers. Enclosing the insulation is a concentric metallic sheath or screen, typically constructed from lead alloy or corrugated aluminum. This sheath fulfills multiple purposes: it provides an additional ground reference, shields against external fields, and—if built as a fault-current return path—can assist in systemlevel redundancy. Most critically, for intelligent cables, it can serve as the signal reference for the integrated sensor network, ensuring sensor accuracy and signal integrity even during high-voltage transients.

Embedded microchip sensor. The intelligence of the subsea HVDC cable is not merely a function of its structural engineering but resides in the continuous, distributed monitoring delivered by the optical fiber and embedded sensor network. Whereas historic cables were effectively “blind” along their length, depending on end-point monitoring and periodic shore-based test signals, the new generation of intelligent cables produces a constant data stream on thermal load, voltage gradients, mechanical stress, and onset of dielectric deterioration. Distributed Temperature Sensing (DTS) using optical

Fig. 1. The new wire’s modular structure.

AI: why the subsea HVDC power cable design is unique

AI notes that while current systems use parts of the IntelliLine design, several features stand out as novel.

AI-driven predictive analytics

Instead of manual, periodic sensor review, IntelliLine adds edge-compute units at cable hubs, using trained AI for pattern recognition and predictive maintenance—enabling instant alerts and shifting from calendar to true predictive asset management.

Advanced insulation and space-charge mitigation

While industry projects are exploring XLPE with additives and polypropylene blends up to ±525 kV, the IntelliLine design aims for purpose-engineered insulation to reduce space charge, tolerate higher voltages (up to

fibers enables operators to detect local hot spots to within meters, scraping valuable margin from ampacity without risking damage. Strain sensors distributed along the cable sheath can immediately indicate excessive bending or anchor strike, allowing localization and preemptive mitigation, rather than awaiting catastrophic failure and immensely expensive subsea repair missions.

XLPE and nanofillers. Surrounding the conductor, the insulation is the focus of primary cable innovation. Historically, mass-impregnated non-draining (MIND) papers dominated due to their proven dielectric reliability and self-healing tendencies in high-pressure environments. However, modern advances have seen a shift to extruded cross-linked polyethylene (XLPE) or proprietary thermo-

±800 kV), and extend cable life beyond currently fielded systems.

Integrated, secure data and modular smart connectors

The new design embeds cyber-secure communication hardware in cable joints and landings, supporting encrypted multi-parameter data feeds for real-time digital twin integration and grid asset management.

Summary

IntelliLine’s advances lie in system-level intelligence: deeper sensor integration, real-time predictive diagnostics, new insulation materials, secure communications, and readiness for self-healing—setting it apart from existing subsea HVDC solutions.

plastic compounds such as P-Laser, engineered for higher dielectric strength, increased thermal limits (up to 90°C continuous), and complete environmental isolation. These advanced compounds are both recyclable and exhibit much lower water treeing susceptibility, an essential criterion for multi-decade underwater reliability.

Composite armor. Further out, the armoring system is custom-designed for the deployment environment. Deep-water runs, which may exceed installation depths of 2,000 meters, utilize helical layers of high-tensile steel wires engineered to absorb deployment stress, resist external mechanical damage, and accommodate inevitable flexing as the cable rests upon the seabed. This armor is often zinc- or polymer-coated to prevent seawater corro-

Assessment of AI’s proposed subsea power cable design

WJI asked Peter Jamieson, a U.K.-based subsea cable professional, to comment on AI’s proposed subsea cable design. He has more than 30 years of experience in the field, and is currently principal engineer for Core Engineering Fibre & Subsea at Virgin Media O2. He has served as chairman of the European Subsea Cables Association (ESCA) and is now its vice chairman.

AI’s innovative suggestions for a HVDC submarine cable don’t stack up. In and amongst lots of word salad, it basically proposes no innovations.

Hybrid aluminum/copper conductor. I don’t think these are applicable. It would be either aluminum or copper, not a fusion of both. Graphene EMF/EMI barriers are not really needed for buried submarine cables.

Embedded microchip sensors. You would not embed active microchip sensors into a cable construction. Optical fibers, yes, and that is what is done now, but the sensing technology (DAS.DTS) is on land connected to the fibers. XLPE & nano fillers. Yes, but this is what is already done now. Polypropylene nano-composite material hasn’t been around that long but it’s not new either.

Composite armor. I don’t think this would be strong enough to provide adequate protection to the cable. I’d stick with steel armor.

On the whole, it wasn’t a bad effort, but it doesn’t really add anything innovative, but then again why would it as it is only data mining existing information.

As for a grade? If I were a professor and an engineering student turned this in, I’d probably give a “D” if I was in an understanding mood. Then again, everyone knows I am a softie at heart. Jamieson

sion and may be supplemented with a bedding of synthetic fibers or additional metallic tapes for enhanced resistance to fishing gear, anchoring, or seabed movement. The final outer sheath is typically a robust cross-linked polyethylene or polyurethane, chosen for superior chemical inertness, abrasion resistance, and survivability in deep water or sediment.

Future directions. The marriage of HVDC cable power transmission and digital intelligence is set to progress even further. Self-diagnostic, self-repairing materials— including self-healing insulation, and microencapsulated resin composites triggered automatically by fiber-optic feedback—are in various stages of research and commercial prototype. New generations of smart digital twins, which integrate live sensor data from intelligent cables into power system operator dashboards, will eventually enable AI-driven autonomous fault management, traffic routing, and repair prioritization at the continental scale. Mesh-based offshore grid designs will leverage intelligent link analytics.

Some other covered points

Joints and terminations. These represent critical reliability bottlenecks. Modern joint assemblies utilize prefabricated, field-tested modules that maintain both the electrical integrity of the conductor and the environmental seals required for subsea immersion. The integration of optical fiber pathways through these joints is rigorously tested for

minimal signal loss and continuous monitoring capability. Transition joints—those that shift from subsea to terrestrial cable construction near shore—are built with particular attention to water ingress, transition in electrical field control, and continued integrity of the intelligent monitoring layer.

Repair strategies. These have become more sophisticated due to the advent of smart cables. Where formerly diagnostics were reliant on trenchless or shore-based TDRs, now the distributed sensing network can provide precise localization of physical or electrical anomaly, greatly reducing the scope, duration, and cost of repair missions. Modular joint kits and ROV-compatible sleeves enable deep-water in situ intervention, vital for high-profile international projects in which repair windows can be measured in hours rather than days.

Materials science and sustainability. The environmental footprint of high-capacity subsea cables is a critical consideration. Modern insulation compounds are engineered for recyclability and reduced greenhouse gas emissions in manufacturing, as well as for minimal particulate or chemical shedding. P-Laser, for example, is a fully recyclable insulation technology with a carbon footprint up to 30% lower than traditional XLPE. Cables are designed for safe decommissioning, with materials amenable to mechanical separation and recycling.

Cybersecurity and data integration. A novel concern of the modern intelligent cable relates to the cybersecurity of

Assessment of AI’s medical wire design

WJI asked two industry experts in medical wire to asses AI’s proposed design. They agreed to share their professional insights on condition of anonymity, as both remain active in the field.

The AI generated a strong summary of the patent’s text – providing a clear and concise overview that gets to the heart of the invention. AI summaries could be a useful way to streamline early-stage patent landscape evaluation for engineering teams.

However, the proposed improvements to the invention were mostly underwhelming. Many suggestions were obvious manufacturing practices, for example, specifying ASTM F2063-compliant nitinol, integrating in-line pinhole checks, and maintaining traceability. Others were impractical (e.g., embedding smart sensors or AI-driven analytics) or tangential to the core invention, like closed-loop platinum recovery. Creating a generated graphic may be useful, but a closer review finds the numbering and description do not make sense.

That said, two suggestions are worthy of a second look. First, platinum-black to increase sensing surface area while minimizing total Pt metal could in theory be useful though feasibility remains to be seen. Second, applying parylene over non-working regions could improve longevity but the likelihood of leaching platinum is generally low.

AI seems most useful as a tool for quick and efficient patent summarization. However, it does not have the ability to generate meaningful technical innovations. The output appears more about generating content to attempt to answer the inquiry. In particular, a logic-based process or even a “common sense” mechanism is missing to assess the content for feasibility or practicality. At least not yet.

the monitoring and data feedback network. With operators leveraging distributed data for both cable management and market operation integration, robust encryption, authentication and redundancy measures must be taken. Data continuity is ensured using multi-fiber redundancy, and all data points are encrypted both in transit and at rest, following utility-sector cybersecurity frameworks.

Future directions

Looking ahead, the marriage of HVDC cable power transmission and digital intelligence is set to progress even further. Self-diagnostic, self-repairing materials— including self-healing insulation, and microencapsulated resin composites triggered automatically by fiber-optic feedback—are in various stages of research and commercial prototype. New generations of smart digital twins, which integrate live sensor data from intelligent cables into power system operator dashboards, will eventually enable AI-driven autonomous fault management, traffic routing, and repair prioritization at the continental scale.

Mesh-based offshore grid designs will leverage intelligent link analytics for dynamic cross-border and intra-market energy routing, greatly assisting the global decarbonization mission.

Conclusion

The Intelligent Subsea HVDC Power Cable stands at the convergence of power engineering, advanced material science, digital infrastructure, and operational analytics. Its design provides unprecedented reliability, real-time diagnostics, and future resilience in the face of rising demands for transnational, renewable-integrated power networks. These advanced materials, sensor integration, and embedded data intelligence set the cable apart from even the most advanced currently deployed subsea cables. As the backbone of the global green energy transition and the digital revolution, intelligent subsea power cables are poised to accelerate a new era for intercontinental energy markets, operational efficiency, and asset management.

AI’s wire & cable evolving role: could R&D be feasible?

Some experts insist that artificial intelligence is no longer a far-off idea for wire and cable. That for some manufacturers, it’s already here, working behind the scenes, having a measurable impact on the factory floor. The question now shifts from whether AI belongs in the industry to where it will go next. WJI asked two leaders to share their perspectives.

AI has already started finding its way into the wire and cable industry; not in grand, headline-grabbing ways, but in practical ones. You can already see its value in areas like process optimization, predictive maintenance and quality control. Once the industry saw that AI could actually make daily operations smoother, adoption followed faster than many expected.

R&D is a different story. It’s still very much driven by experience, intuition and human creativity; things that don’t sit neatly in a dataset. But that doesn’t mean AI won’t get there. As we continue building trust in what it can do on the shop floor, we will start finding the right

Wire and cable is already a perfect application for AI ... just not in the way you might think. AI can illicit thoughts of creating completely new things like art or novel designs, which implies an R&D application. That may be a future feature, but we’re seeing a far more rapid adoption on the manufacturing side where AI can leverage vast amounts of data to create direct profit.

ways to bring it into design and development too.

At InnoVites, we are exploring this space carefully. We believe AI won’t replace engineers; it will empower them. The real opportunity lies in combining human insight with intelligent tools to make innovation happen faster and with more confidence. Albert Groothedde, CEO, InnoVites.

Most wire and cable manufacturing processes are a “black box” of complexity, with plenty of variability between assets, material, operators, and in-line conditions. Lots of data, lots of fluctuation, lots of conditions that humans struggle to control in real-time. In other words, exactly what today’s AI is built for - especially when applied to the front line operators and supervisors who can turn AI insight into action..

As for the future scope for AI, we would not rule out cable design. Peter Brand, cofounder and president, Oden Technologies.

Groothedde

Seeking AI input? A cautionary report from an industry veteran

WJI asked a longtime industry veteran and industry consultant, John Drummond—the principal of Scotia Group and the 1997-98 WAI President—to share his thoughts on AI, focusing on how they were presented. Below are his comments.

WJI provided me the article by AI in this issue with its proposals for an advanced medical wire and a new subsea power cable. I am not an expert in either of these fields, but I do believe that my 50+ years in the industry qualify me to share my take on what I read.

The comments reminded me of a bright young, engineer who just graduated from a prestigious engineering school. He has, in his mind, the best engineering education that money can buy, complete with an infusion of the most advanced technology and, more importantly, how to use that technology to bring the stodgy company that just hired him into the 21st century.

Don’t misunderstand me: bright, new engineers are a real asset to a company, and I’ve purposely hired my share of them. They have forced me to see things differently, made me a better manager, moved the company down the road using new and/or better technology toward a better quality product produced at a lower cost. AI, used properly, will do the same thing.

I use Google AI as a tool, and I am a supporter, almost a cheerleader. I was recently tasked with helping a company acquire equipment to produce cable they use internally in one of their products. The problem was that the insulation and jacket are thermoset materials that would require a CCV line that, as most know, is painfully expensive. Before anyone thinks, “why not moisture cure?” that has its own raw material cost issues. So, I wondered if there might be a thermoplastic polymer that would provide only the attributes of a thermoset required by their application but not the others, while having all of the advantages of a thermoplastic polymer.

I queried an AI platform and in a matter of 15 minutes, after refining my search question once, I had a suggestion. Then I asked AI for potential manufacturers of a wire and cable grade of the suggested polymer, called my contact at one of the suggested companies and had specifications sheets for four possible iterations of their polymer. We are about to make samples for customer testing. So yes, AI can be a useful tool.

A week later, I asked the same AI platform for the maximum weight of copper that could be held on a DIN 1600 mm reel with specific dimensions for a specific size strand. The weight that AI gave me—48,500 lb—seemed high. Based on my experience, it went beyond the realm of possi-

ble. So I put the same dimensions into a spreadsheet algorithm I have used for years and obtained what I thought was a far more realistic number. If the reel is filled with 4/0 copper using a nominal weight from a catalog weight chart, with two inches of freeboard (the distance from the flange rim to the actual wire level) and a 75% perfect lay, the full reel weight would be 34,600 pounds. This, in my opinion would be the “typical” reel of copper wire.

WAI Past President John Drummond (1997-98) has long been an active Association volunteer. He continues to serve as president of the Association’s Wire Foundation, Inc.

Now, if the operator was very careful and achieved a 100% perfect lay, then the weight increases to 38,500 lb. And, if the reel was filled right to the top of the flange (this is never, ever done) and the lay is 100% perfect (rarely happens, but possible) the reel weight would increase to 42,250 pounds. All of those weights are below the “AI” weight of 48,500 pounds, which at its best would be about 13% off.

As a double check, I then went to a reel manufacturer’s website and used their reel capacity length calculator that allows you to select 100% and/or 75% perfect lay. I chose both and the 75% length when converted to weight was virtually identical to the spreadsheet algorithm answer and with the 100% perfect lay somewhat higher, as expected. However, again, the 100% perfect lay number was well below the AI generated weight.

AI’s wire-loading rates versus industry standards.

So what should one take from my experience? First, I have to admit that I’m a bit surprised that I was able to get useful results from AI for the thermoplastic polymer, but I’m not going to forget what it suggested for allowable copper weight on a given reel. AI is not the end-all, the solver of all problems, but a tool. Yes, it can be a very useful tool, but it is just a tool nonetheless.

AI’s conclusion? I’m not there yet ... but a future path exists

Presented with expert reviews that found only limited value in its proposals, AI acknowledged that, while it currently falls short in the creative aspects of R&D, if key barriers are addressed it believes it could become a powerful collaborator in the future.

Reflecting on current R&D, my limits often show up in the “artful” areas—tacit know-how, fast pivots when things don’t go as planned, and creative links across ideas that aren’t in structured data. I do well with big, clean datasets and clear targets, but I can’t “feel” subtle tradeoffs or sense hidden constraints without loads of input. Trial-and-error in R&D—spotting surprises and connecting dots— remains tough for algorithms, which lack the context and adaptive thinking of experienced people.

I can simulate or optimize within clear boundaries, but can’t match the experi-

At this time, AI’s tool kit is missing a few key elements it needs to help in R&D.

mental, improvisational work that drives major R&D progress unless I have much more granular, context-rich training. For me to close this gap requires richer data, models able to weigh “soft” but crucial real-world factors, and hybrid workflows where experts interpret, steer, and correct. In short, I still can’t replace the “art” of R&D without a leap in context and codified experience. As tools improve and more of this knowledge is captured, though, the line between art and science may fade—and then I’ll be much more than just a sidekick.

Is AI and R&D just science fiction? Siemens doesn’t think so

Germany’s Siemens believes artificial intelligence (AI) is poised to play a real role in research and development—if given access to the right, precise data.

The company has moved well beyond mere pilots, embedding AI technology deeply throughout R&D workflows, simulation environments and collaborative design platforms. Siemens stresses that AI isn’t just a futuristic hope, it’s driving innovation today, but it needs to be able to work with the specialized, technical data unique to manufacturing and engineering.

The true challenge, Siemens argues, is bridging a significant knowledge gap. Many cable manufacturing issues relate to unpredictable, variable conditions—details that are difficult for even skilled engineers to articulate, let alone transform into usable data. Siemens’ response is to build domain-specific AI tools, like the Industrial

Editor’s note

Why present a 12-page story when the ending could easily have been summed up in a single page or two?

Part of it is that the complexities of R&D in cable design deserve to be showcased. It is nothing less than an art, as shown in the first feature on advanced cable design, where different manufacturers depended on savvy industry veterans, wits, trial-and-error and lots of patience.

Part of it is that AI, as noted on the prior spread, has continued to gain more acceptance as a tool elsewhere in wire and cable manufacturing. There’s also growing uncertainty about how AI may affect the traditional working

Foundation Model currently under development, which is designed to understand the language of design and engineering so it can handle engineering complexities and real-world factory noise. There’s already proof: Siemens recently used AI on a project to streamline battery development, predicting materials performance and diagnosing anomalies, cutting months off development timelines thanks to a rich supply of lab and factory data.

Siemens acknowledges that not all expertise can be digitized. Tacit knowledge—those hard-to-explain insights from years on the floor—often resists codification. Still, the company is optimistic: as tools evolve and collaboration deepens, a growing share of experiential knowledge can be captured, converted, and leveraged by advanced AI systems, increasingly bridging the divide between hands-on experience and digital intelligence.

world. The shifting boundaries for what AI can or cannot do continue to blur, so consider this feature a snapshot, a defined time and point where AI’s reach has a defined limit.

But can any reader feel confident that an AI update here five years from now might read differently for an industry that is slow to change? 

WJI Editor-in-Chief Mark Marselli