The present invention relates to a process for manufacturing a power cable, which power cable comprises at least one core comprising a conductor and an expanded and crosslinked insulation layer surrounding said conductor, wherein said process comprises the steps a) to d): a) providing a blend of: a polymer composition comprising a polyolefin material, which polyolefin material bears silane moieties; a catalyst and a foaming system, wherein the provided blend will comprise at least 0.1% by weight of a foaming agent, with respect to the total weight of the polyolefin material; b) extruding a blend, as described in step a), on the conductor to form an insulation layer; c) foaming the insulation layer; and d) crosslinking the insulation layer; a power cable which is obtainable by the process, and use of the power cable.