Kundius K. Active shielding system of magnetic field for built-in transformer substation

Dissertation for the degree of Doctor of Philosophy in specialty 141 "Electrical Engineering, Power Engineering and Electromechanics" (14 – Electrical engineering). – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2023. The object of the study is the external magnetic field urban transformer substation. The subject of the study is the active shielding system of external magnetic fields for built-in transformer substations. In the dissertation the scientific and practical task of the synthesis of an active shielding system of external magnetic field for built-in urban transformer substation power 100–1260 kVA in residential buildings is solved, to reduce they magnetic flux density to a level safe for the population in nearby residential premises. The research was performed based on the fundamental principles of the theoretical electrical engineering, on methods of mathematical and physical modeling of magnetic field sources, on analytical and numerical methods of analysis, and modern information technologies. The scientific results obtained in the dissertation: 1. The improved multi-dipole mathematical model of the external magnetic field of the three-phase current conductor is proposed and experimentally proved, which based on a two-phase dipole model of a three-phase electric circuit. The proposed model in comparison with the well-known three-phase multi-dipole model, allowing to double bring closer the calculation zone, without increasing the error, the provides calculation of the magnetic field of the built-in transformer substation for all spaces of the building close to it, which are located at a distance of 1 meter. 2. For the first time the method of synthesis of active magnetic field shielding systems of built-in transformer substations power 100-1260 kVA was developed and experimentally substantiated. It is based on the improved two-phase multi-dipole mathematical model of the magnetic field of the current conductor, on the Biot-Savart law for determining the magnetic field of the shielding system, as well as on the system elements optimization method of the multiswarm of particles from the Pareto set of optimal solutions considering binary preference relations, which allowing made it possible to synthesize systems with a shielding factor of 6–16 units, which reduce the magnetic field in nearby residential premises to the level of sanitary standards. 3. For the first time, it was proposed to carry out the synthesis of systems of active shielding of the potential magnetic field of built-in transformer substations with the determination of the magnetic field not in the entire volume of the residential premise, but on the control plane D, which is as close as possible to the substation, and located in the living room parallel to the floor (wall), allowing you to significantly reduce the amount of the calculations with a guaranteed reduction of the potential magnetic field in the entire volume of the living room along the plane D. 4. The methods of calculating the external magnetic field of active structural elements of a transformer substation was further developed. The methods are implemented on the multi-dipole model of the magnetic field of current conductors, on cylindrical spatial harmonics of the magnetic field of cables, and on the probabilistic-statistical method of predicting the transformer magnetic field, which allowed revealing and experimentally substantiating the low-voltage current conductor as the main source of the substation's magnetic field, whose contribution to the total magnetic field at the distance of 2 m is more than 90%, this allows in engineering calculations to ignore other sources of the magnetic field. The reliability of the theoretical results obtained in the dissertation was confirmed by experimental verification of the improved mathematical model of the magnetic field 100 kVA substations and by constructing the active shielding system on laboratory installation with full-scale physical models of current conductor substations 100 kVA and synthesized active shielding system, the results of which showed the coincidence of the theoretical provisions obtained in the dissertation and the experiment with an error of less than 10%. The research results were used in the following planned topics: 1. «Rozvytok naukovykh zasad normalizatsii heomahnitnoho polia v prymishchenniakh suchasnykh zhytlovykh budynkiv» (№ DR 0116U005462), where the researcher was the responsible executor Researcher; 2. « Rozvytok metodiv ta zasobiv normalizatsii mahnitnoho polia promyslovoi chastoty u prymishchenniakh zhytlovykh budynkiv, shcho stvoriuietsia vbudovanymy transformatornymy pidstantsiiamy ta pobutovym elektroobladnanniam (№ DR 0122U001772), where the researcher is the executor of certain sections. The results of dissertation research are submitted for implementation of TOV «KievPromElectroProject».