A Study on the Actual Application of Superconducting Cables to the Network

Superconducting cables can transmit large electricity with compact size. They are expected to be installed in crowded underground at larger city. Actually, some superconducting cables are being operated in the world. In order to apply this superconducting cable to network, it is necessary not only to pass the commissioning tests, but also to ensure long-term reliability and to ensure safety in the event of a possible accident. The authors have conducted actual system operation of superconducting cables in Yokohama and have grasped their long-term characteristics. In addition, we have been conducting research on analysis when a short-circuit current flows through a superconducting cable and phenomena when a ground fault occurs. When a short-circuit current flows, it is important how to suppress the temperature rise. For that purpose, it is effective to connect copper wires in parallel with the superconducting conductors. It has been pointed out that the thermal insulation pipes may be destroyed in a ground fault, and it is necessary to take measures when liquid nitrogen leaks to the outside of the cable. This paper reports the items to be considered when applying superconducting cables to the network and the measures in the event of an accident.