Development of superconducting power transmission technology

Superconducting power transmission cables are the latest innovation in a technology which is as old as electric power engineering. Distribution of power by means of wires suspended from poles was tried briefly but the densely populated areas chosen as sites for the early generators soon forced the distribution system underground. Edison's low voltage dc system was a technological dead-end but by 1890 Ferranti had built a 7 mile-long underground cable system which operated at the then unprecedented level of 10,000 V, alternating current. Ferranti was remarkably prescient in his choice of wrapped brown paper for the cable insulation, a material which has continued to be used in this application until the present day. Paper was chosen for the insulation because it gave good operating performance at low cost compared to other insulating materials then available, such as rubber and gutta percha. Economic considerations must be weighed carefully in the design of underground power transmission systems and they have been a compelling factor in the pattern of development from the turn of the century to the advanced superconducting systems under test in the 1980's.