Abstract: A cable includes a plurality of elongated sections each composed of a tubular electric conductor, electric insulation surrounding the electric conductor, and an outer cable jacket surrounding the electric insulation. An inner tubular member of titanium or alloyed stainless steel is accommodated in the electric conductor and defines a channel for a cooling medium such as water. The inner tubular members of each two consecutive cable sections have flanges that are welded or soldered to one another, and a bridging element is interposed between the electric conductors of the two consecutive electric conductors and welded or soldered thereto. The electric conductor preferably is a circumferentially complete one-piece tubular element extruded onto the inner tubular member.

Abstract: Three single-conductor cables are laid down such that viewed in cross-section they are located at the vertices of an equilateral triangle, or else they are laid down in a common plane. Each cable is internally water cooled, and provided with a respective return-flow pipe for cooling water. The return-flow pipes are located on phase-angle loci for two phase angles .phi..sub.1.sbsb.1 and .phi..sub.1.sbsb.2, where the phase angle in question is the phase angle of the longitudinal voltage induced in the return-flow pipes by current flowing in the cables. The two phase angles differ by 180.degree.. As a result, no longitudinal voltages are induced in the return-flow pipes and/or the longitudinal voltages induced in successive sections of the pipes cancel each other out so as to result in no net induced longitudinal voltage.