Applications of high temperature superconductors to direct current electric power transmission and distribution

For several reasons, the application of superconductors to both the transmission and distribution of electric power is a desire that is best accomplished by using direct current. The inherent low loss, high current capability of dc superconducting cables allows the replacement of ultra-high voltage apparatus and the associated high cost and inversion-rectification difficulties with a compact potentially lower cost, low profile, high current, cable system. This paper discusses the history of dc transmission and distribution applications and the reasons that high temperature superconductors, modern cryogenic systems, and cryogenic power electronics are the potential enabling technologies. The economic and performance enhancements that follow from the integration of these high current, superconducting dc systems into the electric grid are presented together with the expected potential operational benefits. Possible cable and rectifier-inverter configurations are summarized along with the technical and economic challenges that must be overcome to achieve a significant penetration of dc cable technology on both the transmission and distribution grids. Finally, the steps needed to achieve large-scale applications of high-current dc transmission and dc distribution in the future electric grid are summarized.