A method of building an insulation system around an axial section of a conductor (5) of a power cable (1), the method comprising: a) providing a power cable (1) including a conductor (5) and an insulation system (7a, 7b, 9a, 9b, 11a, 11b) arranged around the conductor (5), the insulation system (7a, 7b, 9a, 9b, 11a, 11b) comprising insulation system layers, including an inner semiconducting layer (7a, 7b) arranged around the conductor (5), an insulation layer (9a, 9b) arranged around the inner semiconducting layer (7a, 7b), and an outer semiconducting layer (11a, 11b) arranged around the insulation layer (9a, 9b), wherein the power cable (1) comprises an axial section between a first insulation system section and a second insulation system section of the insulation system (7a, 7b, 9a, 9b, 11a, 11b) which at least is without an outer semiconducting layer (19), b) winding a tape around the conductor (5) along the axial section in a plurality of layers to form a plurality of layers of tape connecting with the first insulation system section and the second insulation system section, and c) heating the plurality of layers of tape to melt and fuse the plurality of layers of tape to form an insulation system layer (17; 19) between the first insulation system section and the second insulation system section, wherein the tape has a width defined by a distance between lateral edges, wherein the tape has a mid-section between its lateral edges, wherein in the mid-section the tape has a largest thickness, and wherein the thickness of the tape decreases from the mid-section towards both lateral edges.