Prediction of Impulse Breakdown Voltage in Dry Air at High Pressure Using Volume-Time Theory

Dry air is promising as an alternative insulation medium for SF₆ gas in high-voltage equipment. Since its dielectric strength is about one-third of that of SF₆ gas, one of the most effective ways to apply dry air to high-voltage gas-insulated switchgears (GISs) is to further increase gas pressure. In this article, impulse breakdown strength of dry air at high pressure under quasi-uniform electric field is measured. Furthermore, the probability distribution of breakdown voltage is predicted using the volume-time theory in consideration of initial electron generation probability in gas gap and field electron emission from an electrode. The predicted distribution of breakdown voltage by the volume-time theory is in line with the experimental results.