Enclosed spark gaps

L. J. Berberich and M. E. Bell (nonmember; both of Westinghouse Electric and Manufacturing Company, East Pittsburgh, Pa.): Mr. Berkey has pointed out a very interesting phenomenon in connection with lightning-arrester spark gaps. This was first observed when a rutile spacer was substituted for the usual porcelain spacer. The wide difference between the dielectric constants of rutile and of air leads to large stress concentrations at the edges of the spacer. Radiations are produced in these highly stressed air spaces which aid in initiating the gap discharge, resulting in a materially lowered impulse ratio. The same effects can be observed, but to a lesser degree, with porcelain spacers, particularly if the physical arrangement is such as to increase the stress concentrations at the metal-porcelain boundary.