Electrical power transmission line comprising: - at least one electrical cable; - a shielding element, made of ferromagnetic material, surrounding said at least one cable for shielding the magnetic field generated by said cable, said shielding element comprising a U-shaped base, with a bottom wall and a pair of side walls (10b, 10c), with said at least one cable laid into it and a separate cover, in the form of a flat plate, leaned onto the pair of side walls (10b, 10c) of base, wherein the base and the cover of the shielding element comprise respective sides reciprocally superimposed for a portion of predetermined length in lateral direction, said sides being lateral portions of the base and the cover, which are opposite with respect to the longitudinal axis of the shielding element; - the electrical power transmission line further comprises supporting elements for supporting and providing mechanical resistance to the walls (10a, 10b, 10c, 11a) of the base and the cover of the shielding element; - the ferromagnetic material has a maximum value of relative magnetic permeability μ max greater than about 20000; characterised in that: - the electrical power transmission line comprises only one shielding element made of one ferromagnetic material, - the walls (10a, 10b, 10c; 11a) of said base and said cover have a thickness comprised between about 0.10 mm and about 0.60 mm, and - the supporting elements are substantially flat plates made of an electrically non-conductive and non-ferromagnetic material, and are coupled to the walls (10a, 10b, 10c, 11a) of the base and the cover to cover and mechanically support, over substantially all their surface, the walls (10a, 10b, 10c, 11a) of the cover and the base of the shielding element. - at least one electrical cable; - a shielding element, made of ferromagnetic material, surrounding said at least one cable for shielding the magnetic field generated by said cable, said shielding element comprising a U-shaped base, with a bottom wall and a pair of side walls (10b, 10c), with said at least one cable laid into it and a separate cover, in the form of a flat plate, leaned onto the pair of side walls (10b, 10c) of base, wherein the base and the cover of the shielding element comprise respective sides reciprocally superimposed for a portion of predetermined length in lateral direction, said sides being lateral portions of the base and the cover, which are opposite with respect to the longitudinal axis of the shielding element; - the electrical power transmission line further comprises supporting elements for supporting and providing mechanical resistance to the walls (10a, 10b, 10c, 11a) of the base and the cover of the shielding element; - the ferromagnetic material has a maximum value of relative magnetic permeability μ max greater than about 20000; - the electrical power transmission line comprises only one shielding element made of one ferromagnetic material, - the walls (10a, 10b, 10c; 11a) of said base and said cover have a thickness comprised between about 0.10 mm and about 0.60 mm, and - the supporting elements are substantially flat plates made of an electrically non-conductive and non-ferromagnetic material, and are coupled to the walls (10a, 10b, 10c, 11a) of the base and the cover to cover and mechanically support, over substantially all their surface, the walls (10a, 10b, 10c, 11a) of the cover and the base of the shielding element.