A device for electric connection to an energy supply conductor for medium and/or high voltage having a voltage-carrying element with an outer periphery, and a tubular outer shell with an inner periphery, the outer shell being formed by a polymer, and along at least a part of the axial extension of the element the outer shell extends axially with a space between its inner periphery and the outer periphery of the element, at least along a section of said part of the axial extension of the element the space is filled with a filler of an electrically insulating material other than that of the outer shell. An electric installation including the device, and a method for producing the device.