Publications

Abstract not provided.

High-pressure, ultra-zero air is being evaluated as a potential replacement to SF6 in a strategic focus to move away from environmentally damaging insulating gasses. There are a lot of unknowns about the dominant breakdown mechanisms of ultra-zero air in the high-pressure regime. The classical equations for Paschen curves appear to not be valid above 500 psig. In order to better understand the phenomena of gas breakdown in the high-pressure regime, Sandia National Laboratories is evaluating the basic gas physics breakdown using nonuniform-field electrode designs. Recent data has been collected at SNL to study the breakdown of this high-pressure regime in the range of 300 - 1500 psi with gaps on the order of 0.6 - 1 cm with different electrode designs. The self-breakdown voltages range from 200-900 kV with a pulse-charge rise times of 200-300 ns and discharge currents from 25-60 kA. This research investigates the phenomenon of high-pressure breakdown, highlights the data collected, and presents a few of the mechanisms that dominate in the high-pressure regime for electronegative gasses.

In the high-pressure regime above 300-500 psig, voltage-breakdown models such as the Paschen's law fail [1]. Below 300 psig the E/p values suggest that the breakdown mechanism, specifically at high E/p values is dominated by the ionization mechanism. As the air pressure is increased, the breakdown mechanism shifts from an ionization dominated regime to an attachment dominated regime at E/p values below 30. Thus, current Paschen equations will over predict the breakdown voltage and the electric field at which high-pressure spark gaps can be operated. Notably, as the attachment mechanism starts to dominate the breakdown physics the breakdown field in a high-pressure spark gap asymptotes at 1-1.2 MV/cm. Using recent data collected at Sandia National Laboratories, we have implemented corrections to breakdown prediction modeling using COMSOL to predict the breakdown voltage that can be achieved in the high-pressure regime, from 500-1500 psig. This research highlights how these corrections to the breakdown prediction models are implemented and the results of the simulations are compared to our data as well as other small gap data. We also compare the model to published literature values and to large gap breakdown in the 0.6-cm to 1.0-cm regime.