9 systems and installations for the transmission, distribution and switching of high and medium voltages, in particular distribution and switching installations, substations, transformer stations and connecting lines and busbars between distribution and switching installations, as well as components of these systems and installations, in particular switches, measuring transformers, arrestors, connecting elements, bushings, transformers, control and monitoring devices and high-voltage lines, above all encapsulated, in particular plastic-encapsulated, gas-insulated gas-filled pipeline cables and busbars, which can in particular be laid underground and are suitable for the transmission of electric power in the megawatt and gigawatt range, and spare parts necessary therefor