Study on Development of Extruded Ethylene Propylene Rubber Insulated Superconducting Cable

Abstract

A superconducting power cable is one of the promising ways of underground transmission of huge electric power in the future. We have long proposed the idea of the extruded polymer insulation for superconducting cables. The prominent features of the design are to exploit the excellent electrical properties of polymer in the cryogenic temperatures and to separate the helium coolant from the electrical insulation. Although the extruded cross-linked polyethylene cable has proved an ability at the liquid nitrogen temperature, the cable insulation cracked due to mechanical stress during cooling to the liquid helium temperature.
To overcome this problem, ethylene propylene rubber (EPR) was selected as a new insulating material considering the good results of mechanical and electrical tests of EPR pieces at cryogenic temperatures. An extruded EPR insulated superconducting cable in 15m length was fabricated and cooling test down to the liquid helium temperature and voltage test at the liquid helium temperature were carried out with fair success. This is a breakthrough in terms of the electrical insulation design of cryogenic cables.