Practical AC loss and thermal considerations for HTS power transmission cable systems

The use of high-temperature superconducting materials for power-transmission cable applications is being realized in prototype situations. It is well known that AC loss decreases as the temperature of the conductor decreases. Also, thermal losses are higher at lower temperatures, owing to the increased temperature difference between ambient and cryogenic operating conditions. Both counterflow and parallel-flow cooling arrangements have been proposed in the literature and significantly affect temperature distribution along the cable. In this investigation, the counteracting AC loss and thermal losses are analyzed for both cooling configurations to determine the benefits and limits of each. The thermal-insulation performance levels of materials versus those of typical systems in operation are presented. Widespread application of long-length flexible cable systems, from the refrigeration point of view, will depend on an energy-efficient cryogenic system that is economical to manufacture and operate. While the counterflow arrangement will typically have a lower heat load, it has a length limit arising from the large pressure drop associated with the configuration.