Lossless Cables:
How Superconductivity and Graphene Are Changing Power Transmission

Conventional copper cables lose some of the transmitted energy as heat — a fact energy engineers have accepted for decades. Superconducting and graphene cables offer a fundamentally different picture: transmission losses approach zero.

Why copper is no longer satisfying

Copper and aluminum continue to form the backbone of the global cable infrastructure — they are readily available, well-studied, and easy to install. However, any metallic conductor has electrical resistance, and the longer the line, the more energy it dissipates. On long transmission lines, losses can reach several percent of the transmitted power, which, on the scale of a large city, can be quite significant.

Furthermore, copper cables heat up under heavy loads, limiting their throughput and forcing designers to include a substantial oversize. A solution was sought for a long time and was found in two directions.

The Physics of Superconductivity in a Nutshell

Superconductivity is a phenomenon in which a material’s electrical resistance vanishes when cooled below a certain temperature. It was first discovered in mercury at about -269°C, but over time, scientists synthesized compounds that retain these properties at -135°C to -196°C. High-temperature superconductors based on compounds of bismuth, yttrium, and other rare earth elements with copper oxides have gained practical importance for the cable industry: when properly cooled, current flows in them without any resistance.

Design: thermos inside the power line

If you cut a superconducting cable crosswise, it resembles a thermos. At the center is a cryogenic tube through which liquid nitrogen circulates at -196°C. Surrounding it are conductive strands of superconducting material deposited on a metal substrate, and on the outside is a multilayer thermal insulation. The liquid nitrogen serves a dual purpose: it cools the conductor to its operating temperature and simultaneously acts as a dielectric, as it does not conduct current. This allows multiple phases to be compactly packaged within a single sheath.

A cable with a diameter of approximately 15 cm can replace several traditional high-voltage lines, while taking up significantly less space in the cable manifold.

It is this property that makes superconducting lines particularly attractive for dense urban developments, where there is simply no room to expand underground channels. When designers consider replacing an obsolete cable route — say, where flexible, frost-resistant KGTP-HL 4 25 cable has been laid for decades in damp, cold sewers — they face a strict limitation: the channel diameter is set once and for all. A superconducting line of the same diameter carries several times more current, making it a viable alternative to costly new tunnel construction.

Behavior in case of accidents

One of the unique advantages of such lines is their response to short circuits. A conventional cable would overheat in such a situation, the insulation would deteriorate, and the protective circuitry would immediately de-energize the line. A superconducting cable, when the permissible current is exceeded, switches to a resistive state — it begins to resist — and thus limits the short-circuit current. This property is called the current-limiting effect, and it reduces the load on the entire network’s protective infrastructure without requiring additional equipment.

Graphene conductors: another way

Graphene — a monolayer of carbon atoms in a hexagonal lattice — has electrical conductivity superior to that of copper while weighing incomparably less. Its electrical resistivity is approximately one and a half times lower than that of copper, and its theoretical tensile strength is orders of magnitude higher. Furthermore, no cooling is required — graphene operates at room temperature, which fundamentally distinguishes it from cryogenic solutions.

Graphene is used in cable production in two ways. The first is by adding graphene nanoplatelets to a copper or aluminum matrix, which increases conductivity and mechanical strength. The second is by creating pure carbon conductors without any copper at all. It is the latter approach that interests developers of aviation and space systems, where the weight of the cable network is paramount. Furthermore, copper wire breaks over time when repeatedly bent, whereas graphene fiber withstands such loads significantly better, hence the interest from wearable electronics manufacturers.

Where does it already work and how much does it cost?

Several superconducting cable projects have been implemented in densely populated urban areas of Europe, Asia, and North America. Lines ranging in length from several hundred meters to several kilometers are successfully used in locations where expanding cable ducts is physically impossible. In electrolysis shops with currents of tens of thousands of amperes, superconducting busbars reduce the cost of compensating for heat loss — under constant loads of this magnitude, even minimal resistance results in enormous heat generation.

When designing such networks, engineers compare the characteristics of traditional solutions: for example, the frost-resistant KGTP-HL 4 25 cable, designed for open installation in low-temperature conditions, is compared with the performance of cryogenic lines. It is from this comparison that the optimal solution for a specific site is selected.

The economics of these technologies are structured differently.

For superconducting lines, the payback calculation is based on savings from reduced losses and the avoidance of building new collectors. In cities where laying one kilometer of underground cable costs hundreds of millions of rubles, this argument often outweighs the high cost of the cable itself. For graphene solutions, the logic is different: the gains are achieved through reduced weight and increased service life in aggressive environments where copper corrodes or requires frequent replacement.

Limitations that are not usually discussed

Cryogenic infrastructure — pumps, heat exchangers, and a nitrogen leak monitoring system — adds a significant cost to the project and is usually the last item mentioned in presentations.

Failure of the cooling system means immediate loss of superconducting properties and forced line shutdown — without redundancy, this is unacceptable for critical facilities.

Graphene cables face a different kind of production barrier: synthesizing high-quality graphene on an industrial scale remains expensive, and methods that work well in the laboratory are difficult to transfer to the factory floor without compromising the material’s quality. Another open question is durability. Traditional copper cables last for decades, and their failure rates are well-studied. Cryogenic and graphene cables simply don’t have such statistics — they haven’t been in service long enough to draw reliable conclusions about their actual lifespan.