DIELECTRIC-BREAKDOWN OF CRYOGENIC GASES AND LIQUIDS

Cryogenic gases and liquids exhibit interesting dielectric properties. Their resistivities are extremely high, their permittivities are low and their dielectric losses are negligible at low field strengths. The dielectric strength of the gases can be described by means of generalized similarity laws up to field levels of 107 V m-1. Breakdown of liquids is initiated within bubbles. All these properties and mechanisms are well understood in principle. The dielectric strength of very dense gases as well as of liquids is very sensitive to field distortions which are never completely avoidable in practice. Boundary effects have a considerable influence. Weak-linked breakdown mechanisms have to be assumed resulting in size and area effects. Some of the most important experimental results are discussed. © 1979.