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

The power-frequency magnetic field originating from an existing substa tion 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 us ing 5 mm thick shields on the ceiling and walls. The shield materials used were iron, aluminum and copper. The aluminum and copper shields g ave the best average attenuation, 25 dB, while iron gave 10 dB attenua tion of the magnetic flux density in the room above the substation. St udies of varying shield geometry in the substation showed that shieldi ng of the switch-gears, containing the high current busbars, in combin ation with a shield on the ceiling give a calculated attenuation of th e field comparable to that of a shield on the ceiling and walls. The c alculations have been compared with measurements for one shielding cas e.