Electrical and Optical Investigation of an Electric Arc in Hydrogen for short gaps

Abstract

Hydrogen or mixtures containing hydrogen represent attractive gases for low-voltage switching devices because of increased arc quenching behaviour. However, fundamental electrical properties of arcs in hydrogen are still not well known. In this paper, first results of a study of a DC switching arc in pure hydrogen at 1 bar between graphite electrodes are presented for low currents of 8 and 16 A. The arc voltage and current are measured during contact separation. High-speed images of the arc are processed to determine the arc length considering the high arc dynamics with erratic elongations and jumps of the electrode attachment. The arc voltage dependence on the length results in a typical sheath voltage of approximately 23 V and mean electric fields in the arc column of 18.7 V/mm at 8 A and 10.8 V/mm at 16A.