Dielectric surface flashover in vacuum at 100 K

A. Neuber, M. Butcher, L. L. Hatfield, M. Kristiansen, H. Krompholz

Research output: Contribution to conferencePaperpeer-review

1 Scopus citations

Abstract

Cryogenic components in high power electrical systems and in power electronics gain more and more importance. The behavior of insulators for cryogenic conditions, however, is virtually unknown. In a fast coaxial setup, dielectric test sample and electrodes in vacuum are cooled to less than 100 K and the flashover development process is characterized using fast electrical and optical diagnostics. Three consecutive development stages for flashover in self-breakdown mode with a gap distance of 0.5 cm can be distinguished: (1) A fast current rise to mA-amplitudes within several nanoseconds which is probably associated with field emission, followed by (2) a slow current rise to ampere-amplitudes with a duration of several 10's to 100's of nanoseconds associated with secondary emission avalanche saturation, and (3) a transition to a rapid gaseous ionization above the sample caused by electron induced outgassing, leading to impedance-limited current amplitudes of several 100 A. The temperature dependence of these three stages is investigated for different materials. Phase (1) shows a higher final current at lower temperature, which is probably due to a higher initial velocity of the secondary electrons, the duration of phase (2) is a decreasing function of breakdown voltage and only slightly different for low and room temperature, which points to a weak temperature dependence of the outgassing process. Flashover potentials show a slight increase at lower temperature, in general.

Original languageEnglish
Pages815-818
Number of pages4
StatePublished - 1998
EventProceedings of the 1998 18th Interantional Symposium on Discharges and Electrical Insulation in Vacuum. Part 1 (of 2) - Eindhoven, Neth
Duration: Aug 17 1998Aug 21 1998

Conference

ConferenceProceedings of the 1998 18th Interantional Symposium on Discharges and Electrical Insulation in Vacuum. Part 1 (of 2)
CityEindhoven, Neth
Period08/17/9808/21/98

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