CURRENT-CARRYING AND SHORT-CIRCUIT TESTS ON EHV CABLES INSULATED WITH SF6 GAS

An EHV pipeline cable with compressed SF gas insulation was produced experimentally. Some dielectric tests were made with regard to 50-Hz impulse and switching surge voltages in 1965. Successively the second and third cables of three-phase type, about 45 feet in length, have been manufactured. Due to current flow greater than 5000 A through the second three-phase cable whose outer shell and inner conductor are made of aluminum, the temperature rise could be assured to remain lower than 50°C. For the third cable with stainless-steel outer sheath, the mechanical behavior was measured with a three-phase or single-phase short-circuit current of about 40 kA flowing in the line during six cycles, and sufficient safety as to the mechanical strengths of all portions of the pipes was verified. Furthermore, heavy current arc discharges of about 40 kV were generated inside the pipe lines during six cycles, and the pressure rise, metal erosion, and gas decomposition owing to arc generation have been measured or observed. The outer stainless-steel pipe of 4-mm thickness proved to be able to endure the arc discharge of such an order. The decomposition of SF6 gases due to arc discharges was insignificant. As a result of these tests it will be possible, in the near future, to install such an air-mounted pipe line cable insulated with SF6 gas of a few atmospheres pressure. Copyright © 1969 by The Institute of Electrical and Electronics Engineers, Inc.