Direct current cable insulation with insulating composition including electronegative gas

摘要

A direct current electric cable with a conductor, a semi- conductive screen around and contacting the conductor, a plurality of layers of insulation formed by tapes of insulating material around the semi- conductive screen, a further semi-conductive screen around the layers of insulation and a metal sheath around the further semi- conductive screen, the layers of insulation being impregnated with a non- migrating, insulation composition having a dropping point temperature at least 5. degree. C. above the maximum operating temperature of the cable and having an electronegative gas dissolved therein, the gas having a coefficient of diffusion in the composition in the range from 310. sup.-5 to 310.sup.-6 cm.sup.2 /sec at temperatures below the dropping point temperature of the composition.