The present invention relates to a crosslinked polymer composition comprising a crosslinked polyolefin, wherein the polymer composition comprises, prior to crosslinking, a polyolefin and peroxide which is in an amount of less than 35 mmol —O—O-/kg polymer composition, characterized in that the crosslinked polymer composition has been in a direct contact with a semiconductive composition for 24 h at 70° C., and that the crosslinked polymer composition thereafter has an electrical DC-conductivity of 150 fS/m or less, wherein the electrical DC-conductivity is measured in accordance with “DC conductivity method”, as described under “Determination methods”, on a plaque of the crosslinked polymer composition at 70° C. and 30 kV/mm mean electric field from a non-degassed and 1 mm thick plaque sample of the crosslinked polymer composition; a layered structure, cable, e.g. a power cable, use of the crosslinked polymer composition and the structured layer, both, for producing a crosslinked power cable, e.g., a cross linked direct current (DC) power cable; and a process for producing a cable.