Superconducting power cables

In plain language

A superconducting power cable carries electricity through wires made from materials that have almost no electrical resistance when kept very cold. Ordinary copper and aluminium cables lose some energy as heat along their length. Superconductors do not, but only while they stay below a critical temperature, so the cable needs a cooling system that circulates a coolant along its route.

Because the conductor can carry a large current in a small space, these cables may suit crowded city streets, industrial sites or data-centre campuses, where digging new trenches or building new substations is expensive. The cable is only one part of the installation. Pumps, refrigerators, electrical joints and protection equipment all use energy and can fail, so whether the approach makes sense depends on the particular site.

Technical explanation

The conductors in grid cables are usually second-generation high-temperature superconducting (HTS) tapes, commonly made from rare-earth barium copper oxide (REBCO). Below a material- and geometry-specific critical temperature and current, the tapes carry direct current with near-zero DC resistance. Alternating current still causes hysteresis and coupling losses in the conductor, so the loss depends on the current waveform, the magnetic field and the cable design. A practical cable combines many tape layers, stabilising metals, electrical insulation, a thermal envelope and terminations. Designs differ in whether the insulation is warm, at ambient temperature outside the cold conductor, or cold. AC and DC links need different equipment, losses and protection.

An operating link needs far more than the cable. Heat leaks into the cold region through the thermal envelope and must be removed continuously. Refrigerators reject this heat and consume electricity, and the electricity per unit of cooling depends strongly on operating temperature. Coolant pumping causes pressure drop, which limits the distance between cooling stations. Electrical terminations cross between warm and cold parts and add losses and failure points. DC links also need converter stations. An honest efficiency comparison therefore covers the full system at a stated load and route length, not only the conductor. A 2026 technology review lists the cost and reliability of active cooling systems, limits on cable length without intermediate cooling stations, and limited black-start capability as open challenges.

Fault-current limiters are a related but separate application. A superconducting fault-current limiter (SFCL) normally presents low impedance, then rises sharply in resistance during a short circuit to restrict the current before a breaker interrupts it. In a 2025 laboratory test at SuperGrid Institute, a resistive SFCL combined with a mechanical DC breaker reduced a prospective 43 kA peak current to 5.5 kA at 50 kV DC. That test used a high-power laboratory source rather than a live network, so field reliability and recovery after faults remain untested in that configuration.

What the evidence says

Each statement is typed by the strength of its evidence and linked to the source that supports it.

Limitations and open problems

• The installations described in the sources are few and in specialised settings. No fully superconducting grid exists.
• Most operating figures come from project partners or suppliers. The sources reviewed here did not provide an independent multi-year dataset on availability, cooling energy, maintenance or lifecycle cost.
• Cooling, pumping, AC losses and terminations mean that the conductor's zero DC resistance does not make the whole installation lossless.
• The 50 kV DC fault-current limiter result comes from a laboratory test under simulated fault conditions, not from a commercial grid.
• The 2026 review says the maximum cable length is limited without intermediate cooling stations, and that superconducting cables remain more expensive than conventional cables with a similar power rating. No cost model for a built link is cited in this record.

Possible future uses

Timeline

1. 30 Apr 2014Karlsruhe Institute of Technology announces the commissioning of the AmpaCity project in Essen, Germany: a one-kilometre, three-phase superconducting cable at 10 kV connecting two transformer stations. Sources: [1]
2. 28 Sept 2021A 10 kV coaxial HTS cable in Shenzhen begins supplying the Ping An Finance Center, according to the supplier. Sources: [2]
3. 22 Dec 2021The 1.2 km, 35 kV HTS cable between the Changchun and Caoxi substations in Shanghai is put into operation, according to the supplier. Sources: [2]
4. 20 Jan 2025SuperGrid Institute reports a 50 kV DC laboratory test in which a superconducting fault-current limiter and a mechanical breaker reduce a prospective 43 kA peak current to 5.5 kA. Sources: [3]
5. 2 Feb 2026Superconductor Science and Technology publishes a review of HTS high-power cable development status and technology roadmap. Sources: [4]

Futures this could help bring about

How far away?

Power cables with zero resistance

Pilots · 4 of 7 steps done

Glossary

High-temperature superconductor (HTS)

A superconducting material that works at temperatures warmer than older superconductors, though still far below room temperature and usually requiring liquid nitrogen or similar cooling.

REBCO

Rare-earth barium copper oxide, a ceramic HTS material often deposited as a thin layer on a flexible tape.

Fault-current limiter

A device that restricts the size of a short-circuit current in an electrical network, so that equipment is not overloaded before a breaker acts.

Cryostat

A thermally insulated container that keeps a superconducting conductor at its operating temperature.

Sources

1. university press release
   Operation of Longest Superconducting Cable Worldwide Started
   Karlsruhe Institute of Technology, 30 Apr 2014. Accessed 21 Oct 2026.
2. company announcement
   Superconducting Electric Power: project descriptions
   Shanghai Superconductor, 2021. Accessed 21 Oct 2026.
3. other
   SuperGrid Institute achieves first 50kV DC breaking by combining a superconducting fault current limiter with a circuit breaker
   SuperGrid Institute, 20 Jan 2025. Accessed 21 Oct 2026.
4. review article
   Superconducting high-power cables and lines: development status and technology roadmap
   M. Noe, T. Puig, X. Obradors et al.. Superconductor Science and Technology, 2 Feb 2026. DOI: 10.1088/1361-6668/ae15c2. Accessed 21 Oct 2026.

Revision history

3 changes since this profile was created.