Where superconducting power cables run today

Which superconducting power cables are in service?

KEPCO and Nexans report utility installations at Korea's Shingal link and Chicago's ComEd Resilient Electric Grid, respectively [3][10]. A paper in Superconductor Science and Technology, published by IOP, describes KEPCO's 23-kilovolt, 1-kilometer cable [2]. KEPCO's company magazine identifies the linked substations as Shingal and Heungdeok and reports commercial operation beginning in November 2019 [3]. These first-party records establish reported service, not independently monitored uptime through the present day.

Nexans announced that it had installed and commissioned the ComEd REG cable in a permanent Chicago installation in 2021 [4]. Nexans's release reports a 12-kilovolt AC system carrying 3,000 amperes and up to 62 megavolt-amperes; its current project page describes REG as operational since 2021 [4][10]. Those are company reports, not an independent availability record.

Essen's AmpaCity is a completed demonstration, not evidence of current grid service. The Karlsruhe Institute of Technology's commissioning release describes a 1-kilometer, 10-kilovolt link with a 40-megawatt design capacity, inaugurated in 2014 [11]. Nexans later reports that it operated continuously for seven years; a sample from the project is now exhibited at London's Science Museum [1]. Munich's SuperLink is different again: SWM reports a prototype under test and a proposed commercial route, not an operating city-scale cable [5]. Project pages establish status only as of their reporting dates, so a utility should confirm current asset operation directly.

What is inside an HTS power cable?

A superconducting cable is a layered assembly. The current-carrying core uses superconducting tape, electrical insulation separates the phases, and metallic screens and protective layers manage fields, shielding, and handling. An insulated cryostat contains the core, and circulating liquid nitrogen keeps it cold. The system also includes coolant passages, circulation equipment, sensors, terminations, and control and protection equipment. A utility-scale cable is therefore a coupled electrical, thermal, and fluid system, not simply a special conductor. [6]

Common AC designs include a single-core cable, three separate cores in one arrangement, or three phases nested concentrically. In a concentric cable, phase conductors are arranged around a common former. With balanced phase currents, their magnetic fields largely cancel, reducing the need for a separate superconducting shield. A design reported by Shenzhen Power Supply uses this arrangement and explains why its compact geometry can reduce tape use and the cooling burden compared with some other layouts. The best configuration still depends on voltage, current, fault duty, route, and installation constraints. [6]

How do BSCCO and REBCO tapes carry current?

BSCCO and REBCO are families of copper-oxide superconductors made into tape conductors. Early cable systems used BSCCO tape, while later projects have used REBCO, including YBCO tape. The Shenzhen cable paper documents a YBCO concentric system, and the REBCO coated-conductor literature describes a conductor format developed for high-power electrical applications. These materials are ceramic superconductors supported in manufactured conductor structures, rather than bare strands of superconducting ceramic. [6][7]

The material name alone does not set the cable's useful current. Current capacity depends on temperature, magnetic field, conductor quality, tape orientation, and operating margin. Engineers wind multiple tapes into phases and combine those phases with insulation and stabilizing metal. The cable's tested rating must account for the full assembly, joints, terminations, and cooling conditions. A tape specification measured by itself is not a substitute for a system-level rating at the intended operating conditions. [6][7]

What advantages can a superconducting cable offer?

The strongest advantage is power density: an HTS cable can move large current through a narrow route where trench space, ducts, or substation land are constrained. In a dense city, one compact medium-voltage link may avoid some of the footprint required by several conventional circuits or by a higher-voltage substation arrangement. Nexans describes that urban-grid motivation for AmpaCity, and KEPCO presents the same compact-corridor argument for its commercial cable project. Those benefits are site-specific; they do not mean every superconducting cable is cheaper or more efficient than a conventional line. [1][3]

The superconducting material has very low electrical resistance while operating within its superconducting state. But AC cables still have conductor and shielding losses, and the system needs power for refrigeration, coolant circulation, and controls. The correct efficiency comparison includes this auxiliary demand along with the conductors and the electrical equipment that a proposed cable might replace. A compact route can be valuable even where energy savings alone do not justify the installation. [6]

What can fail in a superconducting cable?

Cooling failure is a direct operational risk. A pump fault, loss of coolant circulation, degraded insulation, or cryostat leak can raise conductor temperature and reduce current margin. A local defect, overload, or electrical fault can trigger a quench, a resistive zone that heats the conductor and may threaten insulation and nearby components without rapid protection. Shenzhen Power Supply reports that a resin-impregnated fiberglass high-voltage bushing could crack under liquid-nitrogen thermal shock, illustrating why cryogenic components need qualification. The authors identify cost, long-term reliability, and operational simplicity as barriers to wider deployment. [6][8]

Protection therefore has to do more than detect an ordinary short circuit. IEEE research on HTS cable protection treats quench detection and fault protection as central safety functions, with coordinated responses for electrical and thermal events. IEC 63075 specifies tests for HTS AC cable systems and accessories, but explicitly excludes cooling-system tests. Owners should require a separate qualification plan for refrigeration, coolant circulation, vacuum integrity, terminations, joints, fault response, and controlled restart after an outage. [8][9]

Is Munich's SuperLink cable already operating?

No, not as a commercial route. Stadtwerke München reports that a prototype entered testing at its Menzing substation in October 2024 [5]. Stadtwerke München plans a 15-kilometer high-voltage superconducting cable from Menzing to Sendling, with commercial operation targeted for 2030 if the prototype meets requirements [5]. That is a utility-backed development and test program, but the proposed route should not be counted among cables already serving the grid.

For a buyer comparing projects, ask whether the cited evidence is a laboratory test, a commissioning result, a temporary demonstration, or continuing utility service. Then request the cable's design conditions, measured heat load, cooling redundancy, protection records, repair strategy, and whole-life cost. Successful operation at one voltage, route, or current does not establish performance at another. The useful reference is a documented installation whose configuration and operating conditions are close to the proposed duty. [6][8][9]