Polarity effects on breakdown of short gaps in a point-plane topology in air

Hogg, Michael and Timoshkin, Igor and MacGregor, Scott and Wilson, Mark and Given, Martin (2015) Polarity effects on breakdown of short gaps in a point-plane topology in air. IEEE Transactions on Dielectrics and Electrical Insulation, 22 (4). pp. 1815-1822. ISSN 1070-9878

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    Abstract

    Electrical breakdown in air in a point-plane topology involves complex processes that are still not fully understood. Unlike uniform-field topologies, the highly-divergent fields produced by point-plane topologies create pre-breakdown corona with volumetric space charge. It is known that space charges developed by corona discharge have significant impacts on the breakdown voltage in non-uniform electrode topologies. With large inter-electrode gaps (>cm) the breakdown voltage for a HV point cathode in air at atmospheric pressure is noticeably larger than a HV point anode. However, this paper shows that in shorter point-plane gaps in air (less than ~10 mm), in the air pressure range 0.1-0.35 MPa, an HV point anode has a similar breakdown voltage which eventually is surpassed by the HV point cathode as the inter-electrode gap is increased. The inter-electrode gap at which the HV cathode has a higher hold-off voltage is found to be dependent on the gas pressure and radius of the point electrode.