Polyethylene-insulated coaxial cable

A 138-kv underground oil-filled cable power circuit, recently installed between the Sherman Greek generating station of the Consolidated Edison Company of New York, Inc., and the Dunwoodie substation of the Yonkers Electric Light and Power Company 8.1 miles away, needed an underground carrier current circuit to tie-in with the carrier current circuit superimposed on a 138-kv overhead line from Dunwoodie to Millwood, a distance of 21 miles. The two power circuits are connected at Dunwoodie and the 60-kc carrier circuit controls high-speed directional relays which protect the power circuits. The cable for this circuit is installed in the same underground system with the power cable and terminates at the same stations. The carrier transmitting and receiving equipment required a cable with approximately 70-ohm characteristic impedance and with an attenuation within specified maximum limits at frequencies from 50 kc to 150 kc. A coaxial cable consisting of a number 13 stranded copper conductor, 185 mils of polyethylene insulation, a woven copper braid shield, and a 78 mils thickness neoprene outer jacket was selected.