Some Electrical Characteristics of a DC Superconducting Cable

When fully developed, dc superconducting power transmission lines (SPTL´s) will be able to transmit 5GW or more of power at very high power densities and efficiencies. Although the SPTL has zero resistance to pure dc, it experiences hysteresis and resistive losses under ac and ripple. During faults, the current may be driven out of the superconductor into the cryostabilizer which causes additional resistive losses. A well-designed SPTL should have minimum steady-state ac losses, and it should be able to recover from a transient fault quickly and reliably. The paper discusses the performance of three dc SPTL designs, rated at 2.5 GW, 5 GW, and 7.5 GW, and shows that the operating conditions can be met successfully.