Abstract: A transformer includes an upper-voltage winding and a lower-voltage winding for potential separation. An insulation arrangement is disposed between the upper-voltage winding and the lower-voltage winding. The insulation arrangement includes a layer structure having an inner insulation, at least one semiconducting layer adjacent to the inner insulation, and an electrically conducting layer adjacent to the at least one semiconducting layer and having a defined potential applied thereto that is at least about equal to a lower voltage of the lower-voltage winding.