A 600m long 138kV liquid nitrogen-cooled superconducting cable was installed in Albany near New York in 2008 capable of carrying 574 MVA. Proposals have been made to use buried 2000kV direct current superconducting cables to carry 5GW of power for distances of over 1000 miles. Superconductors can also be used for compact electricity generators, motors, transformers and for energy storage.

Cross sections of two superconducting
power cables - source Nexans (courtesy
Applied Superconductors) and Wikipedia

Superconducting power cable used at
Albany - source Sumitomo Electric

When a fault such as a short circuit occurs on the electricity grid system, massive fault currents can flow that can damage expensive pieces of equipment such as transformers. Superconductors can be used to limit these fault currents based on their characteristic of changing from superconducting to resistive at critical current densities, thus limiting current flows over a predetermined value. This is increasingly important in ever more complex and “smart” distribution systems.

SQUID magnetometer - source Wikipedia via Zureks

Superconducting fault current limiter – internals, elements and
complete unit under test - courtesy Applied Superconductors

Lower power uses of superconductors could be in high-frequency filters, high-speed computing, very sensitive magnetic detection using “superconducting quantum interference device” or “squids” that can detect minute currents, especially used for brain scans, submarine detection and oil prospecting. Research is also taking place into superconducting transistors.

Although Frohlick and Bardeen developed a theory of superconductivity in the 1950’s, a completely satisfactory theory to explain the reason for high temperature superconductivity has still to be developed.