HTS Triax Superconducting Cables

Superconductivity

Superconductivity is the phenomenon that occurs when materials exhibit zero electrical resistance to direct currents (DC). There is a wide range of materials that have this characteristic and the first discoveries were made in 1911 – so this is not a new technology by any means.

What is Superconductivity? Press "Play" on the video player below to learn more about superconducting cable technology.

Three boundary conditions exist that must be met to achieve the superconducting state of a material. Each of the 3 criteria have critical values beyond which superconductivity ceases. These 3 criteria are temperature, magnetic field and current density.

Three phase boundary diagram - Superconductivity

The first materials to show superconducting properties were pure metals such as mercury at temperatures approaching absolute zero (-273° C, -420° F, 0 K). This group of materials later included metal alloys such as niobium tin which had critical temperature values near absolute zero and required liquid helium as a coolant.

In 1986 researchers at IBM discovered superconductors made from copper oxide ceramics (cuprates). These materials have much higher critical temperature values and are now commonly referred to as high temperature superconductors (HTS), where previous materials are now referred to as low temperature superconductors (LTS). HTS materials must still be cooled to approximately -200° C – so “high temperature” is a relative term.

Since 1986 many advances and developments have taken place to enable manufacturing of HTS wires in long continuous lengths. Wires available today may be commercially purchased in lengths in excess of 600 meters (2,000 feet) with ability to carry more than 150 Amps in a wire with dimensions of 4 mm width by 0.2 mm thickness.

Additional detail about chemistry and the physics of superconductivity and material behavior is available at Superconductors.org and the Oak Ridge National Laboratory Web sites.