Abstract: A three-phase electrical power line comprising a sealed tubular envelope of steel filled with insulating gas under pressure, e.g. nitrogen or carbon dioxide CO.sub.2, and having three conductive bars placed therein together with a thin tubular envelope of aluminum which is located between the steel envelope and the bars, wherein the conductive bars are held by collars made of non-magnetic material, having an outside diameter equal to the inside diameter of the aluminum tubular envelope, and possessing three radial arms which are screwed to tabs of insulating supports that enclose the conductive bars.

Abstract: The invention relates to an installation for transmitting electrical power which includes a safety device for providing protection against the effects of electric arcs, said installation including a metal casing (5) filled with a dielectric gas under pressure and having a coaxial central conductor (1,2). In such an installation, where a conductor (1,2) and a casing (5) are held in position relative to each other by a transverse insulator (8), said safety device comprises a tubular electrode (9) situated close to the casing (5) and to the insulator (8) and upstream therefrom relative to the direction of power transmission. The tubular electrode is electrically connected to the casing (5) by conductors (12) which are disposed at a small number of points around its periphery. The invention applies to protecting high-tension electric installations contained in metal casings.