Enclosed spark gaps

Abstract

Ionizing radiation has been discovered to be present in spark gaps of the type commonly used in commercial lightning arresters for the last 15 years. This radiation is emitted from discharges near the insulator-electrode contacts, when impulse voltage is applied to the gap. Ionization is produced by the absorption of this radiation in the spark gap. This effectively reduces the time lag of breakdown. The presence of this radiation explains why higher impulse breakdown voltages are obtained with a sphere gap in the dark than with a lightning-arrester spark gap with porcelain spacer. The radiation effect observed here is similar to that investigated by Wynn-Williams in the three-point gap. This paper tells of experiments performed to determine the reason for the low impulse ratios observed with rutile-spacer spark gaps. The results of this study explain the reason for the low impulse ratio of the “quench gap” and the “ionization gap” utilized in lightning arresters. This new information aids in understanding why low impulse ratios are obtained in high-voltage lightning-arrester spark gaps.