Abstract: A current transformer including a tubular electrically conducting member of a circular cross section connected to one end of a primary winding in the form of a tubular electrically conducting coil having a single turn, a cruciform conducting member coaxially disposed within the tubular member to be connected to the other end of the coil, and a hollow cylindrical dielectric member coaxially disposed within the tubular member to form an incoming and an outgoing flow path between the tubular and dielectric members and between the dielectric and cruciform members, respectively. The tubular coil and the tubular member are wrapped in an insulating member and a secondary winding is wound around the primary winding through the insulating member. The transformer is immersed in a dielectric fluid a part of which fills the two flow paths and the interior of the primary winding communicating with them.