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 DEG 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 3x10-5 to 3x10-6 cm2/sec at temperatures below the dropping point temperature of the composition.