A method for enhancing the dielectric properties of at least one in-service electrical cable section having a central stranded conductor encased in a polymeric insulation jacket and having an interstitial void volume in the region of the conductor. The method includes filling the interstitial void volume with at least one dielectric property-enhancing fluid and then 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 cable section and being below the elastic limit of the insulation jacket. The cable section is heated by imposing a potential of no more than about 500 volts across the conductor during at least a portion of the time required to complete the other described steps.