Economics of Underground Transmission With Cryogenic Cables

A detailed study is presented of the economics of conventional underground transmission lines utilizing oil-paper insulated pipe-type cables. Three cryogenic ac transmission lines, cooled, respectively, by nitrogen, hydrogen, and helium, are compared with conventional cables and overhead lines. The nitrogen-cooled system, so far the most simple form of cryogenic cable proposed, is found to be the most attractive from the point of view of low-cost underground transmission.