Grinchenko V. Increase of efficiency of three-phase busbars magnetic field screening by un-closed electromagnetic shields

The dissertation is devoted to the solving of actual scientific applied problem of increase screening efficiency of underground three-phase busbars magnetic field by un-closed electromagnetic shields and keeping their minimal size. In this work the mathematical model of magnetic field electromagnetic screening has been further developed and extended to model flat and U-shaped elements systems shielding properties. By means of research provided on the basis of introduced mathematical model, it was shown, that screening efficiency of the three-phase busbars magnetic field, in the case of two conducting elements, can be increased by placing one of the elements near the magnetic field source and putting the other in some optimum location between the busbars and the region to be protected. As result of research, the new construction of un-closed electromagnetic shield has been developed. It consists of the two U-shaped elements located above each other with height equal to interphase distance and width of four times of that. Using such screen with walls thickness from 1 mm to 2 mm allows to increase the screening efficiency of the region located above the busbars on 20% approximately, compare to U-shaped screens with the same volume. The possibility of the three-phase busbars magnetic field screening factor increase by using two conducting elements shield, if one of the elements is placed near busbars and the optimum location height of the other one is chosen, have been confirmed experimentally.