Magnetic Fields Of Industrial Frequency Research Articles

The method for design of combined electromagnetic shield for overhead power lines magnetic field

Aim. Development of the method of designing a combined electromagnetic shield, consisting of active and passive parts, to improve the effectiveness of reduction of industrial frequency magnetic field created by two-circuit overhead power lines in residential buildings. Methodology. The problem of design of combined electromagnetic shield including robust system of active shielding and electromagnetic passive shield of initial magnetic field solved based on of the multi-criteria two-player antagonistic game. The game payoff vector calculated based on the finite element calculations system COMSOL Muliphysics. The game solution calculated based on the particles multiswarm optimization algorithms. During the design of combined electromagnetic shields spatial location coordinates of shielding winding, the currents and phases in the shielding winding of active shielding, geometric dimensions and thickness of the electromagnetic passive shield are calculated. Results. The results of theoretical and experimental studies of combined electromagnetic passive and active shielding of magnetic field in residential building from power transmission line with a «Barrel» type arrangement of wires presented. Originality. For the first time the method of designing a combined electromagnetic shield, consisting of active and passive parts, for more effective reduction of the magnetic field of industrial frequency created by two-circuit overhead power lines in residential buildings is developed. Practical value. Based on results of calculated and experimental study the shielding efficiency of the initial magnetic field determined that shielding factors whith only electromagnetic passive shield is more 2 units, whith only active shield is more 4 units and with combined electromagnetic passive and active shield is more 10 units. It is shown the possibility to reduce the level of magnetic field induction in residential building from power transmission line with a «Barrel» type arrangement of wires by means of a combined electromagnetic passive and active shielding with single compensating winding to 0.5 μT level safe for the population. References 53, figures 15.

Hybrid Active and Passive Cable Contour Shielding of Magnetic Fields of Double-Circuit Overhead Power Lines

The purpose of the work is to design a hybrid screen designed to reduce the level of the magnetic field generated by double-circuit overhead power lines, to increase the efficiency of shielding the original magnetic field in residential buildings, to the level of sanitary standards and to reduce the sensitivity of the system to changes in system parameters. To achieve this goal, the structure of a hybrid screen was determined, consisting of a double contour active and a cable contour passive part. The developed hybrid screen is characterized by increased efficiency in reducing the magnetic field of industrial frequency. Designing a hybrid screen comes down to solving a minimax vector optimization problem, in which the vector objective function is calculated based on solution to Maxwell's equations in a quasi-stationary approximation using the COMSOL Multiphysics software package. The solution to the minimax vector optimization problem is calculated based on multi-particle swarm optimization algorithms from Pareto-optimal solutions taking into account binary preference relations. During the design of the hybrid screen, the coordinates of the spatial location of the two compensation windings, as well as the magnitude of the currents and its phases in the windings of the active screen, were calculated. The important results are theoretical and experimental studies on the effectiveness of the designed hybrid magnetic field shield generated by double-circuit overhead power lines. The significance of the results obtained lies in the fact that practical recommendations are given for a reasonable choice of the spatial arrangement of two shielding windings of a robust system of hybrid shielding of the magnetic field generated by double-circuit overhead power lines.

Assessing the parameters of electromagnetic fields and microclimate in the radionuclide department of the positron emission tomography centre

Currently, in the Russian Federation there is an increase in the number of positron emission tomography scans. As a result, the collective dose from radionuclide diagnostics in 2021 compared to 2020 increased by 62.0%, the average effective dose per one study in positron emission tomography (PET) centres of Moscow from 2015 to 2019. increased from 1.71 to 4.41 mSv. This leads to an increase in radiation doses not only for patients, but also for medical workers, and makes it urgent to develop modern effective measures to prevent the adverse effects of ionizing radiation.
 The aim of the study is to evaluate the parameters of electromagnetic fields and microclimate in the premises of the radionuclide department of the PET centre.
 During the study, in the main working areas of the radionuclide department, the following levels were assessed: the strength levels of electric and magnetic fields of industrial frequency, relative humidity, temperature and air speed using generally accepted measures in occupational hygiene.
 zThe main parameters of electromagnetic fields and microclimate (temperature, humidity, air speed) comply with hygienic standards in industrial workplaces. At the same time, in certain working areas of the radionuclide department, higher levels of electromagnetic fields were recorded, as well as a decrease in relative humidity and air velocity.
 Monitoring the parameters of electromagnetic fields and microclimate is important for improving the working conditions of medical workers in the radionuclide department of the PET centre, which helps maintain the functional state of workers at a high level, increases concentration and accuracy of movements, increases the speed of work manipulations, and reduces the time of contact with radionuclides when administered to patients and thereby reduce the dose load on health workers.
 Ethics. The study does not require the opinion of this committee.

Electromagnetic Shielding of Two-Circuit Overhead Power Lines Magnetic Field

The purpose of the work is to design an electromagnetic shield to reduce the level of the magnetic field generated by double-circuit overhead power lines to increase the shielding efficiency of the initial magnetic field in residential buildings to the level of sanitary standards and reduce the sys-tem's sensitivity to changes in system parameters. To achieve this goal, the structure of the electro-magnetic shield is determined, which consists of a single-circuit active and multi-circuit passive parts and is characterized by an increased efficiency of reducing the magnetic field of industrial frequency. The design of an electromagnetic shield is reduced to solving a minimax vector optimization problem, in which the vector objective function is calculated based on solutions of Maxwell's equations in a quasi-stationary approximation using the COMSOL Multiphysics software package. The solution of the minimax vector optimization problem is calculated on the basis of optimization algorithms by a multiswarm of particles from Pareto-optimal solutions. The most important results are theoretical and experimental studies of the effectiveness of the designed electromagnetic shield of the magnetic field generated by double-circuit overhead power lines. The significance of the results obtained lies in the fact that practical recommendations are given on the reasonable choice of the spatial arrangement of the contours of the multi-circuit passive screen and the shielding winding of the robust system of elec-tromagnetic shielding of the magnetic field generated by double-circuit overhead power lines. The possibility of reducing the induction of the initial magnetic field to the level of sanitary standards has been shown as well.

Markers of adipokine metabolism and hormonal-metabolic disorders in workers exposed to electric and magnetic fields of industrial frequency

Introduction. With the growth of urbanization processes, the problem of professional exposure to electric and magnetic fields of industrial frequency is an increasingly relevant topic. Recently, the scientists paid a special attention to the long-term health consequences associated with prolonged exposure to harmful physical factors. The previously obtained data on the increase in the levels of lipid metabolism and hormonal and metabolic disorders in workers exposed to electric and magnetic fields of industrial frequency determine the relevance of studying adipokine metabolism and assessing genetic risk factors for predisposition to cardiovascular pathology in employees of the electric power industry.
 The study aims to research the relationship of biochemical and molecular genetic markers of adipokine metabolism with indicators of hormonal and metabolic disorders for a comprehensive assessment of cardiovascular risk in workers exposed to electric and magnetic fields of industrial frequency.
 Materials and methods. The researchers examined 144 employees of the main group engaged in the repair and operation of power grid facilities and 40 employees of the control group who are not exposed to electromagnetic fields of industrial frequency.The concentration of leptin and adiponectin was determined in blood serum samples. The authors have calculated the ratio of adiponectin to leptin. We have performed a molecular genetic study of single nucleotide polymorphisms of leptin (LEP) G2548A (rs7799039), leptin receptor (LEPR) A668G (rs1137101) and adiponectin type two receptor (ADIPOR2) G795A (rs16928751) genes.
 Results. The staff of the main group revealed a higher level of leptin (8.1 (3.7; 14.4) ng/ml) relative to the same indicator in the control group (6.0 (4.1; 11.1) ng/ml), p<0.028. Levels of leptin and adiponectin moderately and weakly correlate with hormonal and metabolic parameters. In the group of employees with less than 10 years of experience, a higher level of adiponectin was established compared to the group with 11–20 years of experience (6.1 (4.6; 9.1) mcg/ml and 4.5 (3.6; 6.4) mcg/ml, respectively); with an increase in work experience of more than 20 years, a significant increase in the concentration of leptin was found (p<0.05). Scientists have identified the significance of single-nucleotide polymorphisms of the LEPR, LEP, ADIPOR2 genes in the development of abdominal obesity, an increase in cholesterol levels and a decrease in the level of total testosterone in workers exposed to electric and magnetic fields of industrial frequency.
 Limitations. The study is limited to the number of surveyed (144 employees).
 Conclusion. The results of the study indicate the relationship of biochemical and molecular genetic markers of adipokine metabolism with indicators of hormonal and metabolic disorders in employees exposed to electric and magnetic fields of industrial frequency. When examining workers exposed to electric and magnetic fields of industrial frequency, the use of clinical and laboratory markers of adipokine metabolism (biochemical, molecular genetic) is informative in a comprehensive assessment of cardiovascular risk.
 Ethics. The work complies with ethical standards developed in accordance with the Helsinki Declaration of the World Medical Association "Ethical Principles of conducting Scientific medical research with human participation" as amended in 2000 and the "Rules of Clinical Practice in the Russian Federation" approved by Order of the Ministry of Health of the Russian Federation No. 200n dated 01.04.2016. Informed consent to participate in the study was received from each of the surveyed, approved in accordance with the established procedure by the local ethics committee of Izmerov Research Institute of Occupational Health (minutes of the meeting of the Ethics committee of Izmerov Research Institute of Occupational Health No. 4 dated 12/25/2013).

The influence of the thermal load of the environment on electrical personnel using shielding personal protective equipment in open areas during the warm season

Introduction. The paper presents the results of a hygienic assessment of the intensity levels of electric and magnetic fields of industrial frequency and the functional state of the human body when using shielding personal protective equipment against electric fields of industrial frequency on open switchgears with a voltage of 220-750 kV in the warm season. The study aims to explore the functional state of the human body using personal protective equipment against industrial frequency electric fields during work on open switchgears with a voltage of 220-750 kV, and the possibility of their regulation depending on the thermal load of the environment. Materials and methods. The specialists measured the levels of electric and magnetic fields of industrial frequency in accordance with MUK 4.3.2491-09. Eight volunteers took part in the study to assess the functional state of the human body when using personal protective equipment against industrial frequency electric fields. Volunteers performed the work of electrical personnel for 60 minutes followed by a 30-minute recovery. We monitored environmental parameters based on measurements of the environmental heat load index and recorded indicators such as skin temperature and humidity, temperature and humidity under clothing, moisture loss. Results. At the considered electric grid facilities, the researchers recorded the excess of remote adjustment of the electric field of industrial frequency up to 30 kV/m, in this regard, the use of personal protective equipment is mandatory. The obtained results of studies of the functional state of the human body revealed a tendency to increase the voltage of the mechanisms of thermoregulation of the human body using personal protective equipment against electric fields of industrial frequency when working on open switchgear. Limitations. The number of volunteers was due to limited access to production facilities. Conclusion. The regulation of work and rest modes of personnel when working in an open area during the warm season according to the index of the thermal load of the environment requires adjustment, since the studies have shown the need for stricter time regulation when operating personal protective equipment against an electric field of industrial frequency in a heating environment, taking into account their influence on the thermal and functional state of the human body. Ethics. The study was approved by the Local Ethics Committee of the Izmerov Research Institute of Occupational Health (extract from the minutes of the meeting No. 3 dated 03/23/2022).

Development of models of the electromagnetic environment in buildings and urbanized areas

A set of measures and means to control the electromagnetic situation of the environment in the territories of urban development, in buildings and individual premises has been substantiated and developed. The simulation tools show the ability to rationalize the parameters of overhead lines with voltages of 220 kV and below, which will reduce the electromagnetic load in the territories. Modeling the propagation of fields from underground high-voltage lines has established that the values of magnetic fields compared to overhead lines are lower up to 30 times. Models of propagation of electromagnetic fields of very high and ultrahigh frequency were built. Sources of electromagnetic fields of non-production origin in industrial buildings have been investigated. Uncompensated currents in power networks with nonlinear electric consumers generate magnetic fields by induction of 0.35−1.20 μT, which exceeds the maximum permissible levels of operation of computer equipment. Leakage currents on grounded metal structures generate magnetic fields with 1.52−6.75 μT. Simulation of the propagation of electric and magnetic fields of components of personal computers of controlled ranges according to the MPRII standard was carried out. Models of propagation of the magnetic field of industrial frequency around electric motors and generators with their cross sections were built. On the basis of such models, design schemes for placing equipment in production areas are selected or places of safe stay and movement of personnel are selected. The expediency of using shielding to reduce field levels to safe values due to coating surfaces with liquid protective mixtures was shown. Metal-containing composition based on water-dispersion paint makes it possible to reduce the level of magnetic field of industrial frequency by 2.5−2.6 times, electric field by 1.6−1.7 times, electromagnetic field of industrial frequency – by 1.2−1.3 times.

Magnetic fields in the workplace during the operation of contact spot welding installations

Contact welding is one of the most common types of welding. According to the technological method of obtaining joints, contact welding can be spot, relief, butt, suture. Spot contact welding a high productivity. Specialists use spot welding more often than other types of welding. The formation of permanent joints of materials occurs as a result of electric heating and deformation during compression. Workers warm up the products with pulses of alternating, direct or unipolar current of industrial frequency 50 Hz. Researchers have registered adverse factors at the welder's workplace that have an impact on health. These are high temperature, splashes and metal vapors, pulsed magnetic fields (PMF) of industrial frequency 50 Hz. The study aims to explore the levels of pulsed magnetic fields of industrial frequency of 50 Hz at workplaces during the operation of contact spot welding installations. The study included the study of the technology of contact spot welding, instrumental measurements and hygienic assessment of the levels of PMF of the industrial frequency of 50 Hz at the welders' workplaces during the operation of equipment in normal mode. Specialists have performed instrumental measurements of PMF levels with a TP2-2U milliteslameter during operation of three models of semi-automatic welding machines based on spot welding installations. The researchers recalculated the measured levels of magnetic field induction to the maximum operating current (Imax) possible during the technological process. Instrumental measurements showed that the magnetic field strength at the welders' workplaces depended on the type of installation, the distance from the radiation source, the localization of exposure, and welding of specific products. Experts registered the highest levels of magnetic fields in the arm area from 1096.0 to 5512.0 A/m. At the maximum operating current, the magnetic field strength can reach 13 678.0-11 024.0 A/m. The study showed that the intensity of pulsed magnetic fields of industrial frequency 50 Hz in the workplace can exceed the maximum permissible levels. To protect workers, it is necessary to limit the time of exposure to magnetic fields. Limitations. The studies are preliminary in nature and have limitations on the scope of the study.

MICROPLASTICITY OF 15Kh2NMFA VESSEL STEEL IN A STRESS-STRAIN STATE DURING MAGNETIC TREATMENT

Earlier it was found that the treatment of pre-strained ferrite-pearlite vessel steel 15Kh2NMFA, welded joints of this steel by alternating magnetic field of industrial frequency leads to a decrease in the level and alignment of the stress field’s relief and significantly improves the complex of physical and mechanical properties. When non-stationary magnetic fields are applied to a structurally inhomogeneous ferromagnetic material, several different mechanisms of rearrangement of the domain and defect structure can act. In this work, we propose a model of dislocation system response of ferromagnetic in a stress-strain state to a magnetic effect, based on the microscopic properties of dislocations in a mechanically unstable state.

ЗАСАДИ РОЗРОБЛЕННЯ РІДКИХ СУМІШЕЙ ДЛЯ ЕКРАНУВАННЯ ЕЛЕКТРОМАГНІТНИХ ПОЛІВ ШИРОКОГО ЧАСТОТНОГО ДІАПАЗОНУ

Purpose: A liquid material based on commercially available paints and fine iron ore concentrate has been created. With a filler content of 60-70 %, the coefficients of shielding of the electric field of industrial frequency is 2,6-9,1; magnetic field of industrial frequency is 4,5-6,2; electromagnetic field of ultrahigh frequency is 4,4-8,5. At the same time, the reflection coefficients of electromagnetic waves are at least twice lower than those of metal screens. Method: A calculation tool is provided for converting the weight content into the volume content of the shielding filler. This makes it possible to apply the Lorentz and Maxwell-Garnett ratios to predict the electrical and magnetic properties of metal dielectrics. To determine the reliability of adhesion of the obtained mixtures with the application surfaces, the study of the chemical and colloidal properties of the mixtures for application on gypsum board has been performed. Scientific novelty: It is established that the reduction of surface tension, surface wetting angle, work of adhesion, cohesion and wetting forces, spreading coefficient are within the limits that ensure the reliability and durability of adhesion of the material to surfaces. Results: It is shown that the reduction of the protective properties on the water-dispersion carrier is due to the oxidation of the filler. Liquid compositions are made on the basis of a number of paints and varnishes and iron ore concentrates, which can cover large surfaces in various shapes and configurations. Practical significance: In order to use the obtained mixtures in the fields of ensuring the electromagnetic compatibility of electrical and electronic equipment, it is necessary to increase the protective properties. This is possible by increasing the concentration of the shielding filler or increasing the specific conductivity of materials in the solid state by adding to the liquid mixture of fine material with high conductivity.

Power Frequency Еlectromagnetic Fields of Electrical Installations in Buildings

Introduction: All components of the power supply system are sources of electric and magnetic fields of industrial frequency of 50 Hz, both posing risks to human health. Estimation of predicted magnetic field levels from switchboards and transformers inside buildings is challenging and implies the importance of full-scale measurements of electromagnetic fields from built-in electrical equipment. Objectives: To establish the levels of 50 Hz electromagnetic fields during operation of built-in electrical installations in industrial, public, and residential premises. Materials and methods: We studied 50 Hz electromagnetic fields generated by electrical installations located in buildings. EMF levels were measured near transformers, switchboards, and switchgear. The electromagnetic situation in the rooms above the electrical equipment was investigated. The assessment of EMF levels was carried out in accordance with the current hygienic standards. Results: The intensity of electric fields near the equipment and in the surveyed premises was significantly lower than that of magnetic fields. The excess of maximum permissible levels at workplaces of operators servicing EMF sources in residential buildings was not detected. In the rooms of public buildings located above electrical installations, measured values of magnetic field induction ranged from 0.18 to 31 µT. The intensity of magnetic fields depended on the current load and the distance from EMF sources. Discussion: Electromagnetic field intensity depends on specifications of equipment, current loads, and distances from the sources of electromagnetic fields. Induction of 50 Hz magnetic fields in adjacent rooms may exceed hygienic standards set for residential and public buildings. Additional adverse factors include instability of magnetic fields caused by current load changes and significant magnetic field gradients in premises.

SUBSTANTIATION OF APPLICATION FEATURES OF LIQUID MIXTURES FOR SCREENING OF ELECTROMAGNETIC FIELDS

The protective and rheological properties of composite materials based on water-dispersed paint and iron ore concentrate were studied. Features of liquid mixtures application for shielding of magnetic field of industrial frequency and electromagnetic field of ultrahigh frequency were substantiated. The study of the protective characteristics and rheological properties of composite materials based on water-dispersed paint and iron ore concentrate indicates the possibility of their use for shielding electromagnetic fields of a wide frequency range. It was found that the efficiency of the composite material (total shielding coefficient and reflection coefficient of electromagnetic waves) depends on the dispersion of the shielding filler, so the particle size analysis of iron ore concentrate was performed. The analysis shows that the predominant size of iron-containing particles is 23‒24 μm, which is quite acceptable for their uniform distribution in the body of the matrix. Shielding protective material was made of water-dispersion paint with the addition of iron ore concentrate in weight quantities of 15, 30, 45, 60%. The shielding coefficients of the electromagnetic field of industrial frequency and ultrahigh frequency with different filler content were measured. It was found that if the concentration of filler exceeds 30%, both the rheological characteristics of the mixture and the shielding coefficients of electromagnetic fields are unsatisfactory. A dramatic increase in shielding coefficients occurs at a filler concentration of 40%. This mixture has acceptable adhesive properties. It was established that the shielding coefficients could be enhanced if the dispersion of the filler is increased, which will contribute to the stability of the colloidal mixture and improve the rheological properties.

THE INVESTIGATION OF DISTRIBUTION OF THE MAGNETIC FLUX DENSITY OF OPERATING TWO-CIRCUIT POWER LINE 110 KV «CHTPP-CHERNIHIV-330» IN THE RESIDENTIAL AREA AND METHODS OF ITS DECREASING TO A SAFE LEVEL

Purpose. The problem of evaluation and analysis of magnetic flux density of overhead power lines is very relevant now, since the magnetic field of industrial frequency can have a negative effect on human health. The analysis of the magnetic field of the operating double-circuit overhead transmission line was made in this work. This overhead line is in the residential area of Chernihiv, Ukraine. The purpose of this work is to determine safe habitation conditions as a function of the magnetic flux density along the route of two-circuit power line with the voltage 110 kV «ChTPP-Chernihiv-330». Real modes of operation are taken into account. Recommendations are given for reducing the magnetic flux density level in the residential area to a value that will not exceed the standard value. Methodology. Methods of electromagnetic field theory were used to calculate the magnetic field of power lines. The location of the phase wires on different types of supports of the existing power transmission line and the minimum distance between the conductors and the ground were taken into account. The current value of the current in the phases of the transmission line was taken from the Company «Chernihivoblenergo». Also, the calculation of the magnetic flux density was made for the perspective loads of the transmission line. Estimation of the value of the magnetic flux density was made for the zone of one-story and multi-story buildings near power lines. The option of uniform loading of two power transmission lines was considered and the case where the entire load is transferred along one circuit was also considered. Results. In this work, the distribution of magnetic flux density at a height of 1.8 m in the direction perpendicular to the power transmission line for the sections built on supports of the U110-2 and PB110-2 types was obtained. The graphs show that the magnitude of the magnetic flux density at the boundary of the protection zone of the transmission line will be exceed twice the standard value 0.5 μT for the existing and perspective loads. This problem is relevant in the case of transmission lines in single-circuit mode. The graphs of distribution of magnetic flux density on the facade of an apartment building, located at a distance of 20 m from the axis of symmetry of the transmission line, were constructed. As a result, it is shown that at a height of 11 m from the earth's surface, magnetic flux density will be 1.5-2 μT. Practical value. It is determined that safe habitation along the route of two-circuit power line with the voltage 110 kV «ChTPP-Chernihiv-330» can be achieved when facades of an apartment building are removed from the axis of symmetry of the transmission line at a distance of 33 m for high-rise buildings and at a distance of 27 m for one-storey buildings. Recommendations for reducing the magnetic flux density of this power transmission line have been developed.

Assessment of exposure of electric and magnetic fields of industrial frequency on overhead power lines with voltage of 500 and 750 kV

Introduction. Certain types of work in the vicinity of overhead power lines may be accompanied by prolonged presence of personnel during the work shift in areas where the maximum permissible levels of electric and magnetic fields of industrial frequency are exceeded. The aim of study is a comprehensive theoretical and instrumental assessment of the exposure of electric and magnetic fields of industrial frequency in places where personnel may stay when working near overhead power lines with a voltage of 500 and 750 kV. Materials and methods. The measurement points were determined using a matrix estimation method, taking into account the location of phases and sanitary protection zones of overhead power lines. The development and calculation of numerical models were carried out in the three-dimensional modeling environment SEMCAD X 14.8.6. Results. As a result of instrumental assessment of electric and magnetic fields of industrial frequency, places with exceeding the maximum permissible levels of the electric field of industrial frequency for a work shift were identified, which indicates the need to limit the time spent by personnel without the use of personal protective equipment. At the same time, no excess of the maximum permissible levels of the industrial frequency magnetic field was detected. Conclusions. The obtained numerical models of 500 and 750 kV overhead transmission lines when evaluating the levels of electric and magnetic fields of industrial frequency showed compliance with the data obtained during field measurements. This allows further research to assess the exposure of personnel performing work without removing voltage on overhead power lines of 500 and 750 kV.

The composite facing material for electromagnetic felds shielding

The facing material was developed for the purpose of shielding man-made electromagnetic fields in production working and domestic conditions. The facing material was designed on the base of latex and fine iron ore concentrate as filler. The experimental data on shielding of electromagnetic fields of ultrahigh frequencies and magnetic field of industrial frequency were obtained for different material thicknesses and concentration of screening particles. The significant increase of the shielding coefficients was established and explained by the manifestation of the percolation effect - the increase of the material conductivity at the critical concentration of the conductive component. The calculation apparatus for determining the dependence on the shielding properties of the material on the concentration of shielding substance was proposed. The method of the screening substance critical concentration calculation is shown to enable designing materials of lower thickness, weight and self-cost.

Development and study of protective properties of the composite materials for shielding the electromagnetic fields of a wide frequency range

Composites were shown to be the most promising materials for protection against electromagnetic fields. A technology of magnetic treatment of textile material with magnetic fluid and technology of ultrasonic treatment of a mixture of latex and iron ore concentrate has been developed. This has increased saturation of fibers of the textile material with magnetic fluid nanoparticles, dispersity of the iron ore concentrate, and isotropy of the liquid metal-polymer material. As a result of the use of this technology, the consumption of magnetic fluid for the treatment of the textile material decreased from 45‒50 g/m2 to 35 g/m2 with an improvement of shielding properties. It has been experimentally established that one layer of metal-textile material reduces the magnetic field of industrial frequency by 6 times and the electric field of industrial frequency by 1.5 times. Corresponding figures for the metal-polymer material were 3 and 2. It was found that an electromagnetic field with a frequency of 2.45 GHz is reduced 3.6 times by the single-layer metal-textile material and 5.7 times by the metal-polymer material. It was shown that the metal-textile material with such properties is suitable for the manufacture of personal protective means for personnel operating electrical and radio transmission equipment. Metal-polymeric material is suitable for the manufacture of collective protective means. A calculated evaluation of the effectiveness of protective materials was proposed. It is based on determining the shielding factors of structures of standard shapes. This enables the determination of electrophysical and magnetic properties of the material and their use in the development of protective materials with required shielding factors. The necessity of optimization of shielding factors under conditions of simultaneous influence of electromagnetic fields of heterogeneous sources was substantiated

ДОСЛІДЖЕННЯ ЗАХИСНИХ ВЛАСТИВОСТЕЙ МЕТАЛЕВИХ ЕЛЕКТРОМАГНІТНИХ ЕКРАНІВ ТА ВИЗНАЧЕННЯ УМОВ ЇХ МАКСИМАЛЬНОЇ ЕФЕКТИВНОСТІ

Захисні властивості сплавів у різних частотних діапазонах екрануючих матеріалів мають складний характер. Предмет дослідження даної роботи – визначення амплітудно-частотних залежностей коефіцієнта екранування електромагнітних полів сучасними металевими сплавами. Досліджено: традиційні матеріали; електротехнічні сталі різного класу та алюмінієвого сплаву, які мають різну ширину захисного екрану; металовмісні шнури різного (двошарового та тришарового) сплетіння. Досліджено залежності захисних екранувальних властивостей магнітного поля за рахунок відбиття для електротехнічної сталі класу 121 та сплаву з дюралюмінію та електротехнічної сталі. Мета роботи – визначення коефіцієнтів екранування у низькочастотній та середньо-частотній областях електромагнітного спектра на основі вимірювання коефіцієнтів екранування найбільш поширених металевих захисних матеріалів та надати обґрунтовані рекомендації щодо їх найбільш ефективного використання у робітничих умовах для захисту від електромагнітних полів та випромінювань працюючих та сумісності електричного та електронного технічного обладнання. Розроблено амплітудно-частотні залежності коефіцієнта екранування електромагнітних полів сучасними стандартними металевими сплавами для захисту людей і для забезпечення електромагнітної сумісності електричного та електронного технологічного обладнання. Запропоновано захисні заходи захисту від впливу від електромагнітних полів та випромінювань, що засновані на принципах розумної достатності, з урахуванням мінімальних витрат. Доведено експериментально та економічно обґрунтовано, що найбільш ефективним засобом захисту від електромагнітної безпеки на підприємствах в умовах складної дії різноманітних електромагнітних полів, є електротехнічні сталі. В результаті отриманих співвідношень захисних властивостей (за рахунок електромагнітної енергії та відбиття електромагнітних хвиль) раціоналізовано захисні модифікаційні конструкції з мінімальним коефіцієнтом відбиття електромагнітних хвиль у небажаному напрямку в різному частотному діапазоні. Такі висновки надали змогу запропонувати методологію розрахунку щодо необхідної оптимальної товщини захисного магнітного екрана найбільш сприятливої ефективності у даних умовах. Це дозволяє мінімізувати обсяг довідникових та експериментальних даних та однозначно визначити товщину екрана необхідної ефективності, а також зменшує загальну вартість захисної конструкції.

Development and investigation of protective properties of the electromagnetic and soundproofing screen

We have developed a technology for manufacturing an universal electromagnetic and soundproofing screen based on foam-latex and foam-polystyrene. The dispersity and physical characteristics of components in a material for shielding electromagnetic field and noise have been investigated. The designed material consists of latex and iron ore dust with dominating dispersion of 12 µm. In order to improve the soundproofing properties, latex was supplemented during fabrication with a foam-forming agent − synthetic oleic acid. To reduce the weight, we added granulated foam-polystyrene with the size of granules 1−3 mm to the material. We examined screens with a thickness of 5 mm and 10 mm with a different content of the metallic substance. It was determined that the shielding coefficients of the material 5 mm think containing 5‒20 % of iron ore content are as follows: for electromagnetic field of frequency 2.4‒2.6 GHz ‒ 1.8−44; for the magnetic field of industrial frequency ‒ 1.2−15.0. For the material with a thickness of 10 mm they are 2.9−52.0 and 2.3‒38.4, respectively. The noise reduction index of 41−44 dB is achieved at noise frequencies of 6−8 kHz, which is the most critical for humans. The structural study of the materials' surface was performed. It has been established that at the content of the metallic substance above 15 %, its distribution in the bulk of the material becomes non-homogenous. In order to improve the efficiency of electromagnetic protection, it is expedient to produce a magnetic or rheological fluid from iron dust in advance, to apply it in the technological process for foam-latex fabrication. It has been proven that the combined electromagnetic and soundproofing (acoustic) screens, that are small in thickness and low in weight, could provide reduction of the levels of electromagnetic fields and noise to match the norms, which is especially important when they are applied in the transportat industry

Імунологічні ефекти як критерій канцерогенної небезпеки поєднаного впливу ендогенних нітрозамінів та магнітного поля промислової частоти

Імунологічні ефекти як критерій канцерогенної небезпеки поєднаного впливу ендогенних нітрозамінів та магнітного поля промислової частоти

Computation of electric field inside substations with boundary element methods and adaptive cross approximation

Power system substations and HV power lines are sources of electric and magnetic fields of industrial frequency. Guidelines for permissible electric and magnetic field strengths regarding human exposure and electromagnetic compatibility (EMC) are provided by standards. In this paper a novel method for calculating 3D electric field near power system facilities is presented. Computation procedure is based on integral equations and boundary element methods. The influence of polynomial order of functions used to approximate the unknown linear charge densities over the elements is tested for constant, linear and cubic spline functions. Due to a complex geometry of substations, a large system of equations needs to be solved to find the unknown charge densities over the elements of the model. In order to reduce computational efforts adaptive cross approximation (ACA) is employed. The results of computation are in a good agreement with measurements.