Dielectric-directed surface flashover under atmospheric conditions

Summary form only given. High-voltage arc formation near a dielectric material is a complex process by which surface charging, secondary electron emission, and photoelectron emission modify the local electric field to determine the arc path and breakdown threshold. Strong electric field enhancement at the triple-point junction of dielectric, metal, and atmosphere may act to generate initiating electrons to seed prompt formation of streamers. This study investigates the fundamental role of dielectrics in influencing voltage breakdown threshold, statistical time lag, and reproducibility under high voltage conditions with and without external ultraviolet stimulation. We are investigating whether field emission at triple points can sufficiently minimize variance in atmospheric breakdown. The experimental data presented here are from the Advanced Component Development laboratory at Sandia National Laboratories. The experiments were performed in dry air at 600-Torr using a low-inductance test-stand. Dielectric granules were placed on a planar brass electrode, offset from a rounded brass rod electrode which defined the 1-mm gap. 200 μm dielectric granules minimally affect electric field in the majority of the gap, but set up high field cathode triple points on the ground plane. We will discuss how dielectric material properties impact surface charging, electron emission, and material conversion, thereby directing the flashover path. Concurrent continuum modelling of surface flashover examines the mechanisms of electron absorption and emission at the surface (c.f. H. Hjalmarson et al.) Furthermore, these flashover experiments are to be used in validation efforts of our PIC-DSMC code (c.f. “Development and Validation of PIC-DSMC Air Breakdown Model in the Presence of Dielectric Particles”).