Abstract: A current transformer includes transformer units combined into a bundle, each of the transformer units including an annular iron core surrounding a bus conductor and a secondary winding wound around the iron core for measuring an electric current flowing through the bus conductor, and a shield winding wound around the bundle of the transformer units. The secondary winding may be provided with an air gap in which no secondary winding is present, located at a portion of the current transformer in a direction of a resultant vector, perpendicular to a line connecting bus conductors neighboring the bus conductor to be measured and passing through the bus conductor to be measured. A second air gap may be provided at the position opposite the air gap of the transformer, relative to the bus conductor to be measured, and the shield winding may be divided into two parts at the air gap and opposite the air gap relative to the bus conductor to be measured.