H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
H01H33/70—Switches with separate means for directing, obtaining, or increasing flow of arc-extinguishing fluid
H01H33/76—Switches with separate means for directing, obtaining, or increasing flow of arc-extinguishing fluid wherein arc-extinguishing gas is evolved from stationary parts; Selection of material therefor
H01H33/78—Switches with separate means for directing, obtaining, or increasing flow of arc-extinguishing fluid wherein arc-extinguishing gas is evolved from stationary parts; Selection of material therefor wherein the break is in gas