Exemplary embodiments are directed to a current transformer having a toroidal magnetic core around which an even number of shielding coils is wound. The shielding coils are operatively associated two by two to form corresponding couples. The shielding coils of each couple are wound on parts of the toroidal magnetic core opposite to each other and are connected in parallel to each other for obtaining a magnetic flux in them. The magnetic flux in a first shielding coil of a couple of shielding coils has an opposite direction with respect to a magnetic flux in a second shielding coil of the couple. The couples of shielding coils are connected in series.