Abstract
The breakdown properties of air are well studied at ambient pressure. For higher pressures, less information can be found in the literature. In this paper, switching impulse breakdown properties in technical air as a function of pressure are investigated. The study focus on a spherical electrodes with 30 mm and 10 mm diameter with a distance to a ground plane of 100 mm. From prebreakdown photomultiplier signals and photographs taken with an ultrahigh-speed camera also the initiation voltages are measured. From the analysis of the results, streamer initiation fields as well as propagation fields are extracted. As expected, the breakdown voltages as well as the initiation voltages increases with pressure, for both positive and negative polarity. Streamer integrals are used to evaluate the initiation fields. The observed streamer initiation voltage agrees well with streamer integral theory in the studied pressure range 1 Bar to 6 Bar. The pressure dependence of streamer propagation is also analyzed and is found to approximately scale linear with the pressure for both polarities.
Highlights
Air is frequently used as an insulation media for high voltage equipment at ambient pressure
No information regarding the propagation field is found in the literature for negative polarity at pressures > 1 Bar
The initiation voltages predicted by the streamer integrals are shown
Summary
Air is frequently used as an insulation media for high voltage equipment at ambient pressure. At ambient pressure the initiation as well as breakdown properties are well studied [1,2,3,4,5,6,7]. Pressurized gases are known to have improved electrical withstand properties compared to gases at 1 Bar, and are frequently used in high voltage equipment such as GIS, bushings, cable terminations etc. One of the most frequently used pressurized insulation gas is SF6 that is carefully studied [8]. For pressurized Air, much less information can be found in the literature. The aim of the work presented in this article is to gain additional understanding of the breakdown properties of pressurized air
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