220-Kv. Transmission Southern California Edison Company System, and Some 220-Kv. Researches

The rapid growth in the demand for electric power and the increasing distances to which transmission is desirable, have constantly forced the use of higher transmission voltages. The Southern California Edison Company, having two single-circuit tower lines 241 miles long from its Big Creek hydroelectric plants to near Los Angeles, had the alternative of either duplicating these lines or of raising the voltage upon them. The latter procedure was found to be vastly the more economical. Other things being equal, the amount of power that can be transmitted varying with the square of the voltage, and the existing voltage being 150 kv., a doubling of capacity will result by raising the voltage to 220 kv. To avoid the difficulties inherent in changing over generating and substations built for the lower voltage, and in which adequate clearances would be very difficult to obtain, it was decided to use auto-transformers at each such station, transforming between 150 and 220 kv. Additional sectionalizing switching stations will be built in the line, making six in all, so that the rebuilding of the line may be done without crippling service, and insulator testing can be done at any convenient time. An extension of the line 30 miles in length will be built so that the completed 220-kv. system will be 270 miles long. Preparatory to the final design, a considerable amount of investigation and research was carried on.