Method for shielding the magnetic field generated by an electrical power transmission line, and magnetically shielded electrical power transmission line

A method for shielding the magnetic field generated by an electrical power transmission line comprising at least one electrical cable, said method comprising:

• providing a magnetic shield having multiple ferromagnetic layers in a position radially external to said at least one electrical cable, the maximum relative magnetic permeability of said magnetic shield increasing in a radial direction from the inside toward the outside of said magnetic shield, wherein said magnetic shield comprises:
• a first radially inner layer comprising at least a first ferromagnetic material;
• and
• at least a second layer radially external to the first layer, said at least a second layer comprising at least a second ferromagnetic material, the maximum relative magnetic permeability of said at least a first ferromagnetic material being lower than the maximum relative magnetic permeability of said at least a second ferromagnetic material.