Economics of High-Voltage Cable

The 182-kv. oil-filled cable placed in service in Chicago in 1927 was designed by the manufacturers in 1925 to have the largest carrying capacity commercially feasible for that voltage in the state of the art as it then existed. During the succeeding years the advancement in the art was so rapid that the cable for the same voltage installed in 1930 had a carrying capacity 75 per cent greater and a cost 20 per cent less than the 1927 line. Improved oil, new designs of oil supply tanks and methods of shipping and connecting cable had reduced the cost of installation and the design of the terminals. Successful operating experience with devices and methods for eliminating sheath losses had removed the previous limitation on the economical size of the conductor. Operating data and test results indicated that the insulation on the first line was thicker than necessary and this led to an inquiry regarding the economy of using the oil-filled type of insulation at higher and lower voltages. Other questions concerned with future developments in the Chicago region indicated the necessity of a careful study of all recent advances in the art, and resulted in extending the investigations so as to include an economic study of transmission cable for all voltages, present and prospective.