A method for enhancing the dielectric properties of an electrical cable segment having a central stranded conductor encased in a polymeric insulation jacket and an interstitial void volume in the region of the conductor, including filling the interstitial void volume with a dielectric property-enhancing fluid at a pressure below the elastic limit of the polymeric insulation jacket, and confining the fluid within the interstitial void volume at a residual pressure greater than about 50 psig, with the pressure being imposed along the entire length of the segment but below the elastic limit of the polymeric insulation jacket. Preferably, the residual pressure is sufficient to expand the interstitial void volume along the entire length of the cable segment by at least 5%.