High-current dc power transmission in flexible RE–Ba2Cu3O7 − δ coated conductor cables**Contribution of NIST, not subject to US copyright.

Abstract

Transmission cables made from high-temperature superconductors have been successfullydemonstrated within the electric power grid. These cables carry an ac current of up to3000 A in a much smaller cross-sectional area than conventional transmission lines,but they are not flexible enough for certain applications that involve very tightcable bends. Certain on-board Air Force applications require 5 MW of dc powertransmission at 270 V and current of 18 500 A and would benefit from superconductingtransmission in lightweight, flexible cables that would be cooled with helium gas down toabout 55 K. To address these needs, we have constructed a 10 mm diameter RE–Ba2Cu3O7 − δ (RE = rare earth) coated conductor cable that is lighter and more flexible than the current generationof superconducting cables, and that has a critical current of 7561 A at 76 K. The cable isexpected to have a critical current of more than 20 000 A at 55 K and therefore willlikely exceed the requirements for 5 MW on-board power transmission. The cableconsists of two electrically insulated phases that can be operated in differentmodes, which allows us to study the effect of self-field on the cable performance.