ACTIVE SHIELDING OF EXTERNAL MAGNETIC FIELD OF BUILT-IN TRANSFORMER SUBSTATIONS

This paper deals with the mitigation of low-frequency magnetic field of build-in transformer substations down to the reference level 0.5 [micro]T in nearby living spaces. To meet the reference level, we substantiate the actuality of the usage of active shielding methods having higher efficiency, comparably to metal consuming passive shielding. We show that the optimization of parameters and localization of compensation coils is the main goal of the synthesis of the active shielding system. The solution of synthesis problem is based on the developed 3D numerical model by using particles multiswarm optimization algorithms from Pareto-optimal solutions set taking into account binary preference relations. This allows justifying the usage of simple active shielding system for magnetic field mitigation down to the reference level in living spaces, located near build-in transformer substations (2 * 400 kVA, 6/0.4 kV). The synthesized active shielding system has two plane compensation coils installed near the ceiling (wall) of the substation room. The area of each coil is less than 10 [m.sup.2] and the number of ampere-turns is less than 30. We show that the efficiency of the active shielding system is 6 when it electric power consumption is less than 100 W. This allows mitigating the magnetic field down to 0.5 [micro]T in 40 [m.sup.2] living space located on top or side from the substation. The application of synthesized active shielding system (subject to the positive results of experimental studies of their full-scale physical models) allows solving the actual and socially significant problem of the health protection of tenants of residential buildings with build-in transformer substations from the negative effects of power frequency magnetic field. References 16, tables 2, figures 8.