The present invention relates to a thermoplastic insulation system for jointing of high voltage conductors, comprising at least one joint element, wherein each joint element comprises an insulating layer made of a thermoplastic insulating material, and wherein the at least one joint element is adapted for surrounding the electric conductor joint and wherein the pre-moulded thermoplastic insulation constitutes a cylindrical layer around the electric conductor joint. The invention also relates to a method to produce such an insulation system.