Shielding of magnetic fields caused by cable conduits
Generation of magnetic fields requires attention and special materials to be able to provide valid, economical solutions in relation to the alternative, Mu-metal, which is very costly for certain applications. MT/BT transformation electrical lockers that power entire plants generate magnetic fields higher than 10 micro Tesla. One concept is to utilise metallic plate stratification so as to saturate and attenuate their propagation into surrounding areas. Generally aluminium panels are used with overlapping of layers of other highly permeable material. It is just this stratification and combination of thin sheets with high magnetic permeability sustained by others in steel or other alloys that can attenuate these propagations. The attached photographs give an overview of various realisations that have brought the values below levels set by the EN 500082-1 regulations in force, which establish that the magnetic field must be below 3 ampere metres, that is, 3.75 micro – Tesla and the law that disciplines exposition is the DPCM, which fixes the exposition limit at 50 Hz. Cables, Busbars, MT/BT transformers, high tension lines are all generators that today are always encountered more often in an environment where small electronics detect the presence of the magnetic field’s strength.
With the utilisation of overlapped panels set side by side along a cable line or set around a transformer, these panels adequately provide the shielding necessary to bring the emission parameters in line with the limits set by law.