CALCULATION OF LOW-FREQUENCY MAGNETIC SHIELDING OF A SUBSTATION USING A 2-DIMENSIONAL FINITE-ELEMENT METHOD

The power-frequency magnetic field originating from an existing substation has been calculated using a two-dimensional finite-element model. With this model, the shielding effectiveness for different shielding materials and geometries has been simulated. Calculations were made using 5 mm thick shields on the ceiling and walls. The shield materials used were iron, aluminum and copper. The aluminum and copper shields gave the best average attenuation, 25 dB, while iron gave 10 dB attenuation of the magnetic flux density in the room above the substation. Studies of varying shield geometry in the substation showed that shielding of the switch-gears, containing the high current busbars, in combination with a shield on the ceiling give a calculated attenuation of the field comparable to that of a shield on the ceiling and walls. The calculations have been compared with measurements for one shielding case.