Discussions on Insulating Properties of Sulfur Hexafluoride Gas.

This paper reviews, first of all, fundamental aspects of the discharge mechanism, in the light of current knowledge. Then it proposes semiempirical criteria to predetermine the dielectric strength of SF//6 sulfur hexafluoride insulations. The validity of these criteria is confined, for the time being, to cases in which the discharge voltage coincides with the corona threshold. However, they allow both for main parameters, such as the electrode geometry and gas pressure, and some secondary factors, such as surface conditions of electrodes and the presence of separator baffles of plastic material, and therefore they can be suitably used at the planning stage. To illustrate the general properties listed and show the validity of the methods set forth, the results of some tests carried out at CESI are reported. Lastly, mention is made of the special physical measurements used during experimental investigations to better study the development of discharge process.