Title :
Dielectric surface flashover in vacuum at cryogenic temperature (100 K)
Author :
Neuber, A. ; Krompholz, H. ; Hatfield, L.L.
Author_Institution :
Dept. of Electr. Eng. & Phys., Texas Tech. Univ., Lubbock, TX, USA
Abstract :
Recent developments in high power systems use cryogenic components, where the performance of insulators at such low temperatures is unknown. In a fast coaxial setup, electrodes and dielectric sample are cooled to less than 100 K in vacuum, and the flashover initiation processes for gap distances on the order of 1 cm are characterized using fast electrical and optical diagnostics. As reported before, two development stages can be distinguished: a first phase with slowly rising current and the presence of free electrons, with a duration of 10-50 ns, and a second stage with a fast current rise due to gaseous ionization and collision dominated electrons. First experiments comparing cooled samples and samples at room temperature do not show discernible differences for Lexan. For Alumina, however, an increase of the duration of phase 1 is observed, with a higher current amplitude at the transition from phase one to phase two. Also, the current rise in phase two is reduced. These results indicate a temperature dependence of the electron induced outgassing process which is expected to cause the transition from phase one to phase two
Keywords :
cryogenics; flashover; insulation testing; 100 K; Al2O3; Alumina; Lexan; coaxial electrode; cryogenic temperature; current rise; dielectric surface flashover; electrical diagnostics; electron collisions; gaseous ionization; high power system; insulator; optical diagnostics; outgassing; vacuum; Breakdown voltage; Cryogenics; Dielectrics and electrical insulation; Electric breakdown; Electrodes; Electron emission; Flashover; Surface discharges; Temperature; Transmission lines;
Conference_Titel :
Electrical Insulation and Dielectric Phenomena, 1997. IEEE 1997 Annual Report., Conference on
Conference_Location :
Minneapolis, MN
Print_ISBN :
0-7803-3851-0
DOI :
10.1109/CEIDP.1997.641139