Magnetic field in residential premises adjacent to the walls of built-in transformer substations and methods for its mitigation

Problem. Transformer substations (TSs) built into residential buildings are one of the most powerful sources of power-frequency biotropic magnetic fields (MF), which negatively affect public health. However, the problem of determining the distribution and normalization of the MF of built-in TSs remains insufficiently studied, particularly for residential premises adjacent to the walls of built-in TSs under non-uniform loading of their outgoing feeders. Goal. Determination of magnetic flux density distribution in residential premises adjacent to the walls of built-in transformer substations under uneven loading of output feeders, and methods for its normalization. Methodology. Mathematical modeling of the TS MF distribution based on the Biot-Savart-Laplace law with experimental validation of the results, and the development of shielding systems to reduce MF flux density to the maximum permissible level (MPL) of 0.5 μT. Results. A minor effect of non-uniform loading of TS outgoing feeders (with a spread of ±30 %) on the MF flux density level in premises adjacent to the TS was identified, and active and passive MF shielding methods were proposed for its normalization. Scientific novelty. It was theoretically proven and experimentally confirmed that the most significant MF flux density effect (up to 12 μT) is exerted on residential premises adjacent to the wall of the TS room located closest to its main low-voltage horizontal conductor. For the first time, active shielding systems (ASSs) with two orthogonal compensation coils were synthesized to ensure MF shielding in adjacent premises lateral to the TS. Practical value. The proposed methods and means for shielding the MF of 100–630 kVA TSs ensure the normalization of MF flux density in residential premises adjacent to the walls of built-in TSs at short distances (1.0 m to 1.4 m) from the low-voltage conductor. References 55, tables 1, figures 16.