Abstract: A high-voltage column current transformer comprising a column insulating body and a head arranged thereon is disclosed, whereby the head defines a volume and comprises arranged therein a primary winding conductor, a secondary winding core assembly having secondary winding leads and a conical insulator spacer tapered from a base to an apex with a lateral face therebetween, the conical insulator spacer is arranged with its base on a bottom of the head facing the column insulating body and its apex holds the secondary winding core assembly distant from a wall of the head, the conical insulator spacer comprises at least one ring-shaped electrode embedded in and surrounding the base and another flat, circular shaped electrode embedded in and surrounded by the apex, and the conical insulator spacer comprises at least one opening in the lateral face.