Thermal-buble initiated breakdown characteristics of liquid helium and nitrogen at atmospheric pressure
Experiments show that electric field promotes to form a vapor locking in a gap with a hot spot and in turn the formation of locked vapor produces the serious reduction of breakdown voltage. Especially it is argued that the dielectric strength of liquid helium under serious hot spot conditions decreases below that for saturated gas.
Surface Discharge Characteristics of GFRP in GN2 and LN2 for Designing a Superconducting Coil System
Solid insulation materials used in the application of a superconducting apparatus need to be robust in terms of both mechanical and dielectric performance. The surface discharge characteristics of solid insulation materials are inferior to their penetration breakdown characteristics. Therefore, dielectric accidents in a superconducting appliance can occur as a form of surface discharge rather than as a form of penetration breakdown. In this paper, dielectric experiments on the surface discharge characteristics of glass-fiber-reinforced plastic in gaseous nitrogen (GN2) at room temperature and liquid nitrogen (LN2) at 77 K are conducted to design a high-voltage superconducting coil system with high reliability. As a result, the electric field intensity at surface discharge voltage VSD under ac and dc voltages is deduced as an empirical formula.
Die Einleitung des elektrischen Durchschlags in verflüssigten tiefsiedenden Gasen
ÜbersichtDie vorliegende Arbeit beschreibt eine Modellvorstellung für den elektrischen Durchschlag von verflüssigten Gasen am Beispiel des Flüssigstickstoffes, die ohne die Annahme von Verunreinigungen auskommt. Das Modell wird anhand experimenteller und theoretischer Ergebnisse aus Durchschlagsuntersuchungen begründet.ContentsThis paper describes a breakdown model for liquified gases, especially for liquid nitrogen, without assuming any impurities. The model is explained, by experimental and theoretical results.