The present invention relates to a power transformer/reactor (100) comprising at least one winding (221, 222). The winding/windings (221, 222) comprises/comprise at least one electric conductor, a first semiconducting layer (14) arranged around the conductor, an insulating layer (16) arranged around the first semiconducting layer (14), and a second semiconducting layer (18) arranged around the insulating layer (16). The winding/windings (221, 222) is/are enclosed in a container (102) filled with a liquid, said liquid accomplishing a cooling.