A note on the design of insulating bushings

THE break-down of an insulator usually sets in at the spot where the density of the electrostatic flux due to the conductor it is intended to insulate, is a maximum; for, as is well-known, this density is a measure of the volts per centimeter acting at that point upon the insulating medium. Observation of the discharges from an electrostatic machine shows that the atmosphere around a highly charged conductor breaks down most readily at points and sharp corners, while both theory and experiment show the advantage, if corona is to be avoided, of using, for a high-voltage transmission line, conductors of large diameter.