Transmission at 220 Kv. on the Southern California Edison System

The object of this composite paper is the presentation of a fairly complete description of this 220-kv. system and its operation, together with an account of some work which is being done in preparation for a third line to Big Creek. The first section is descriptive of the system and the flashover troubles, giving a detailed account of the bird theory for the cause of fiashovers and of the evidence substantiating that theory, also of the measures being taken to prevent the birds from causing flashovers. The balanced relay protection for the lines and the relay installations to control a flashover or other accidental ground in case the balanced relays are not allowed to function, together with some information obtained from a study of flashovers are contained in the second section. Section three is devoted to a study which is being made to determine the mechanical and electrical characteristics which will give a most economical third line from Big Creek to Los Angeles. Both aluminum and copper conductors of various large sizes and working at various tensions are considered, and tower locations on ten miles of profile were made. Section four reports that vibration, particularly in the longer spans, has apparently caused some failures of ground wires and possibly of conductors. Frequencies of 13 to 30 cycles per second and amplitudes up to one inch have been recorded. The vibrations are believed to be due to air currents, but no means of preventing them has been discovered.