Power Frequency Magnetic Fields Research Articles

Power frequency magnetic field interference suppression method for online frequency response analysis of power transformers

AbstractFrequency response analysis is widely used for the offline diagnosis of winding deformations in power transformers. To apply this approach to a working transformer, the magnitude of the response current needs to be measured by using Rogowski coil sensors across a load current. The saturation of the power frequency magnetic field in these current sensors must be prevented to ensure accurate measurement of such small response currents. Here, a method is presented to suppress the power frequency magnetic field using a sensing system including a special connection of three‐phase current sensors based on the sum of the three‐phase power frequency load currents of the transformer being close to zero. Each sensor comprises two secondary coils: a measuring coil and an anti‐saturation coil. The anti‐saturation coils are connected in parallel with one another through small inductors to eliminate the power frequency magnetic field in the cores of the sensors. Theoretical analysis is used to derive a solution for this system. The experimental results verify the proposed method as enabling the sensors to function with a transformer carrying a load current of 2333 A.

Research on the influence of power frequency magnetic field of pantograph on pacemaker wearers' health in high-speed EMU.

When the popular means of transportation-high-speed trains meet the increasing rate of pacemaker implantation year by year, the research on the magnetic field environment on the health of pacemaker wearers in the carriage becomes an urgent problem. In this work, models of an electric multiple unit carriage with a pantograph as well as passengers with pacemakers were built by using COMSOL Multiphysics software. The B, Ein and Jin of human heart and other tissues, and the induced voltage (Vin) at the pacemaker electrode were calculated under the pantograph operating condition, so as to assess the effect of its magnetic field on the health of pacemaker wearers. The results showed that Bmax in the carriage without passengers is 121.246 μT, occurs near the window. In the carriage, the Bmax, Ein max and Jin max of heart and body, Vin at the pacemaker electrode of the passenger next to the window are greater than that in the middle of the carriage. The Bmax, Ein max and Jin max of passengers' heart are 11.301μT, 1.613mV/m and 139.030μA/m2, respectively. The Bmax, Ein max and Jin max of passengers' body are 12.597μT, 0.788mV/m and 75.299μA/m2, respectively. The maximum value of Vin at the tip of the pacemaker electrode of the passengers' is 0.048mV. The Bmax, Ein max in all tissues of passengers are much smaller than the basic limits of electromagnetic exposure to the public set by the International Commission on Non-Ionizing Radiation. Vin at the electrode tip of passengers' pacemakers are less than the perception sensitivity set by the International Organization for Standardization. This work illustrated that the magnetic field generated by the pantograph is within the recognized accepted limits for passengers with pacemakers, but we still recommended that passengers wearing pacemakers should stay as far away from windows as possible.

Method for design of two-level system of active shielding of power frequency magnetic field based on a quasi-static model

Aim. Development of method for design a two-level active shielding system for an industrial frequency magnetic field based on a quasi-static model of a magnetic field generated by power line wires and compensating windings of an active shielding system, including coarse open and precise closed control. Methodology. At the first level rough control of the magnetic field in open-loop form is carried out based on a quasi-static model of a magnetic field generated by power line wires and compensating windings of an active shielding system. This design calculated based on the finite element calculations system COMSOL Multiphysics. At the second level, a stabilizing accurate control of the magnetic field is implemented in the form of a dynamic closed system containing, in addition plant, also power amplifiers and measuring devices of the system. This design calculated based on the calculations system MATLAB. Results. The results of theoretical and experimental studies of optimal two-level active shielding system of magnetic field in residential building from power transmission line with a «Barrel» type arrangement of wires by means of active canceling with single compensating winding are presented. Originality. For the first time, the method for design a two-level active shielding system for an power frequency magnetic field based on a quasi-static model of a magnetic field generated by power line wires and compensating windings of an active shielding system, including coarse open and precise closed control is developed. Practical value. 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 active canceling with single compensating winding with initial induction of 3.5 µT to a safe level for the population adopted in Europe with an induction of 0.5 µT.

Electromagnetic Environment Assessment and Safety Research of Electrified High-Speed Railway Carriages

With the advent of modern, high-speed electrified rail systems, there has been increasing concern about electromagnetic safety in rail carriages. The aim of this study was to assess the electromagnetic safety of passengers on trains by utilizing advanced 3D electromagnetic simulation software. A comprehensive model of the electromagnetic environment experienced by passengers on a CR400AF train, specifically under the influence of catenary radiation, was constructed. We analyzed the magnetic field strength, electric field strength, and current density in the brains of 20 passengers in various positions in the train. The findings revealed that among the 20 passengers analyzed, the maximum and minimum magnetic induction intensity recorded in the brain were 8.41 and 0.01 μT, respectively. The maximum and minimum induced electric field intensities were 1110 and 10 μV/m, respectively. Lastly, the maximum and minimum induced current densities were 1200 and 10 μA/m2, respectively. The results show that when people ride on the CR400AF train, the magnetic induction intensity, induced electric field strength, and induced current density in the brain are below the recommended basic limits of exposure to power frequency electromagnetic fields in the guidelines of the International Committee on Non-Ionizing Radiation Protection. The power frequency magnetic field generated by the catenary can be effectively shielded by the aluminum alloy car body. The final result of this study indicates that the electromagnetic exposure from the contact wire at the level 25 kV does not pose a threat to the health of passengers on the CR400AF train.

Study on UAV Inspection Safety Distance of Substation High-Voltage and Current-Carrying Equipment Based on Power-Frequency Magnetic Field

Study on UAV Inspection Safety Distance of Substation High-Voltage and Current-Carrying Equipment Based on Power-Frequency Magnetic Field

Calculated residential exposure to power frequency magnetic fields for an epidemiological study in France and comparison to measurements

The GEOCAP epidemiological study of paediatric cancers in relation with various environmental factors is currently being carried out in France. Proximity to high voltage overhead lines (63–400 kV) related to exposure to extremely low frequency magnetic field (ELF-MF) is one of studied factors. The study covers the mainland French territory and includes 4174 leukaemia cases and 45 000 controls recruited from 2002 to 2010. Residential exposure was calculated for 1124 subjects whose distance to power lines was small enough for their residential exposure to possibly exceed the background reference level 0.1 μT. Residential exposure was calculated by modelling all the influencing spans close to the subjects’ residences. At final, 371 subjects out of 1124 have a calculated exposure over 0.1 μT, including 123 subjects over 0.4 μT, i.e. 0.25% of the study population. These 371 calculated exposures exceeding 0.1 μT have been matched to an existing database of ELF-MF measurements performed in inhabited areas crossed by power lines, and measurements were found for 206 subjects. Comparison was possible for 156 of them. After extrapolation of the measured values to match to calculation conditions, the difference between calculations and adjusted measurements was lower than 30% for 124 subjects (80%), with no clear tendency for over/under estimation. Differences higher than 30% have been analysed and explained.

Evaluation of the Effects of Power-Frequency Magnetic Field Exposure on B-Cell Differentiation From Human Hematopoietic Stem/Progenitor Cells.

The causal relationship between exposure to power-frequency magnetic fields (MFs) and childhood leukemia has long been controversial. The most common type of childhood leukemia is acute B-lymphoblastic leukemia caused by abnormal proliferation of B cells in the early differentiation process. Here, we focused on B-cell early differentiation and aimed to evaluate the effects of exposing cells to power-frequency MF. First, we optimized an in vitro differentiation protocol of human hematopoietic stem/progenitor cells (HSPCs) to B-cell lineages. Following validation of the responsiveness of the protocol to additional stimulations and the uniformity of the experimental conditions, human HSPCs were continuously exposed to 300 mT of 50 Hz MF for 35 days of the differentiation process. These experiments were performed in a blinded manner. The percentages of myeloid or lymphoid cells and their degree of differentiation from pro-B to immature-B cells in the MF-exposed group showed no significant changes compared with those in the control group. Furthermore, the expression levels of recombination-activating gene (RAG)1 and RAG2 in the B cells were also similar to those in the control group. These results indicate that exposure to 50 Hz MF at 300 mT does not affect the human B-cell early differentiation from HSPCs. © 2023 The Authors. Bioelectromagnetics published by Wiley Periodicals LLC on behalf of Bioelectromagnetics Society.

Calculation and test analysis for power frequency electromagnetic field of transmission line crossing agricultural greenhouse area

To assess the electromagnetic environment (EME) of high-voltage AC transmission lines (TLs) across agricultural greenhouses (AGs), a program that can calculate the power frequency electromagnetic field (PFEMF) under various AC TLs is compiled based on the principle of the simulated charge method and the simulated current method, and the power frequency electric field (PFEF) and magnetic field (MF) strength of AGs are calculated and compared with the field measurement results. The results show that the field measurement values of PFEF intensity and magnetic induction intensity in AGs do not exceed the standard requirements of 10kV/m and 0.1mT. The existence of AGs has a certain influence on the electric field (EF) distribution, but has little influence on the power frequency magnetic field (PFMF). For the PFEF and PFMF in AGs, the numerical calculation results are basically consistent with the field measurement results. The above results provide a reference for the EME assessment of high-voltage AC TLs across AGs.

Evaluation of the power frequency magnetic field generated by three-core armored cables through 3D finite element simulations

The great expansion in offshore power plants is raising the concern regarding the cumulative effect of the electromagnetic field emissions caused by submarine power cables. In this sense, owners are required to predict these emissions during the permitting and consenting process of new power plants. This is a challenging task, especially in the case of HVAC three-core armored cables due to their complex geometry. Customarily, 2D approaches based on the finite element method (FEM) have been employed for evaluating the magnetic field emissions caused by these cables. However, inaccurate results are obtained since the phase conductors and armor twisting is omitted. This work develops, for the first time in the literature, an in-depth analysis of the magnetic field caused by this type of cable through an ultra-shortened 3D-FEM model, which is also faced to experimental measurements taken on an actual 132 kV, 800 mm 2 three-core armored cable. Relevant conclusions are derived regarding the impact of the cable design on the magnetic field emissions, including material properties, as well as single and double-layer armors, presenting the proposed model not only as a valuable tool for predicting purposes, but also for optimizing cable design in terms of magnetic field emissions. • 2D approaches overestimate the magnetic field emitted by three-core armored cables. • Ultra-shortened 3D-FEM models include the effect of conductor and armor twisting. • Good accuracy in predicting the magnetic field emitted by the three-core cable. • In-depth analysis of the impact of cable design on magnetic field emissions. • Application for evaluating the environmental impact of power cables in the seabed.

Design of a Fluxgate Weak Current Sensor with Anti-Low Frequency Interference Ability

According to the requirements of weak current measurement in power grid, a weak current sensor with anti-low frequency interference ability is developed. The sensor adopts the principle of fluxgate detection and adds a magnetic ring on the original basis. The structure of the magnetic ring is simulated using comsol to further improve detection sensitivity. In order to solve the problem that the electromagnetic current sensor is vulnerable to the interference of geomagnetic field and power frequency magnetic field in weak current measurement, a magnetic shielding method with low cost is selected, and the shielding shell structure is designed using a finite element analysis method. The experimental results show that the minimum measurable current is 1 mA, the measurement range is 1 mA–1 A, and the bandwidth is DC-16 kHz. The designed magnetic shielding shell can effectively reduce 97.3% of the DC magnetic field interference and 95.7% of the power frequency magnetic field interference. The sensor can realize accurate measurement of weak current in power grid.

A Shear-Mode Magnetoelectric Heterostructure with Enhanced Magnetoelectric Response for Stray Power-Frequency Magnetic Field Energy Harvesting.

This paper devises a magnetoelectric (ME) heterostructure to harvest ambient stray power-frequency (50 Hz or 60 Hz) magnetic field energy. The device explores the shear piezoelectric effect of the PZT-5A plates and the magnetostrictive activity of the Terfenol-D plates. The utilization of the high-permeability films helps to enhance the magnetoelectric response to the applied alternating magnetic field. A theoretical model is developed based on the piezomagnetic and piezoelectric constitutive equations as well as the boundary conditions. The ME response of the device is characterized theoretically and experimentally. The measured ME voltage coefficient attains 165.2 mV/Oe at the frequency of 50 Hz, which shows a good agreement with the theoretical result. The feasibility for extracting energy from the 50 Hz magnetic field is validated. Under an external alternating magnetic field of 30 Oe, a maximum power of 8.69 μW is generated across an optimal load resistance of 693 kΩ. Improvements of the ME heterostructure are practicable, which allows an enhancement of the ME voltage coefficient and the maximum power by optimizing the structural parameters and utilizing PMN-PT with a higher shear-mode piezoelectric voltage coefficient (g15).

PSO/DE combined with simulation current method for the magnetic field under transmission lines in 3D calculation model

Due to the construction of ultra-high voltage transmission lines, the lines will inevitably pass through residential areas. The power frequency magnetic field created by transmission lines will affect the location and design of transmission lines, as well as people’s health. In this paper, the intelligent optimization algorithm is used to optimize the Simulation Current Method (SCM) and study the magnetic field distribution under the transmission line. Firstly, the actual three-dimensional shape of the transmission line is considered in this optimized simulation current method (OSCM). Secondly, we combined the magnetic position error with the magnetic field error to construct the fitness function, and we used the algorithm to optimize position and number of simulated currents. Finally, the finite element method (FEM) is used to verify the calculation results. We calculate a 500 kV 3-D transmission line model and verify that the optimized SCM can reduce the calculation effort and ensure the accuracy of the calculation. In addition, the OSCM solves the problem that the number and location of the simulated current can only be determined empirically. On the one hand, the actual physical shape of the transmission line is considered, which makes the calculation precision higher; on the other hand, the calculation time is much lower than that of FEM. At the same time, it provides a theoretical basis for the magnetic field distribution of transmission lines and has a theoretical guiding significance for the construction of high-voltage transmission lines.

Analysis for magnetic field disturbance of modular multilevel converter based high voltage direct current (MMC‐HVDC) converter valve

The standardised design and operational reliability enhancement of the flexible DC converter valve are impending with the construction of high shares of renewables and power electronics power system. A power frequency magnetic field calculation model able to obtain the electromagnetic disturbance at the submodule (SM) drive board during normal operation of a flexible DC converter valve is presented. Hundreds of SMs with complex structures in a converter valve tower are simplified by the equivalent to the line current to fulfil calculation accuracy requirements. In addition, a random function is employed to simulate the non-sequential switching process of the SMs. By comparing the calculated results with the measured data obtained from the SM equivalent operation experiment of 2200 V/2150 A, the validity of the calculation model is confirmed. According to the final calculations, the influence of non-sequential switching cannot be ignored when recognising the time-domain distribution features of the power frequency magnetic field of the drive board. However, engineering design can be guided only by the power frequency magnetic field intensity of the drive board calculated based on SM’s full removal in the valve tower.

Evaluation of the Effects of Exposure to Power-Frequency Magnetic Fields on the Differentiation of Hematopoietic Stem/Progenitor Cells Using Human-Induced Pluripotent Stem Cells.

The causal association between exposure to power‐frequency magnetic fields (MFs) and childhood leukemia has been under discussion. Although evidence from experimental studies is required for a conclusion to be reached, only a few studies have focused on the effects of MF exposure on the human hematopoietic system directly related to leukemogenesis. Here, we established an in vitro protocol to simulate the differentiation of human mesodermal cells to hematopoietic stem progenitor cells (HSPCs) using human‐induced pluripotent stem cells. Furthermore, we introduced MF in the protocol to study the effects of exposure. After a continuous exposure to 0–300 mT of 50‐Hz MFs during the differentiation process, the efficiency of differentiation of mesodermal cells into HSPCs was analyzed in a single‐blinded manner. The percentage of emerged HSPCs from mesodermal cells in groups exposed to 50‐Hz MFs indicated a lack of significant changes compared with those in the sham‐exposed group. These results suggest that exposure to 50‐Hz MFs up to 300 mT does not affect the differentiation of human mesodermal cells to HSPCs, which may be involved in the initial process of leukemogenesis. © 2022 The Authors. Bioelectromagnetics published by Wiley Periodicals LLC on behalf of Bioelectromagnetics Society.

Influence of Power Frequency Magnetic Field Interference in Substation on 5G Base Station Deployment

Influence of Power Frequency Magnetic Field Interference in Substation on 5G Base Station Deployment

Calculation of Internal Electric Fields Induced by Power Frequency Magnetic Fields During Live-Line Working Using Human Models With Realistic Postures

Worker exposure to high-intensity magnetic fields encountered during bare-handed live-line working on a conductor of an overhead transmission line is a major safety concern. In this article, internal ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> ) electric fields in a live-line worker induced by power frequency magnetic fields were numerically calculated considering realistic exposure conditions, i.e., different working postures on a conductor bundle of an overhead transmission line. The scalar potential finite difference (SPFD) method was adopted to voxel-based human models with realistic postures to calculate internal electric fields inside the models. The results showed that the internal electric fields were far below the basic restriction for occupational exposure stipulated in the International Commission on Nonionizing Radiation Protection guidelines even when the maximum magnetic field exceeded the reference level in the guidelines.

Study on detection method of power frequency magnetic field disturbance signal for underwater target

Study on detection method of power frequency magnetic field disturbance signal for underwater target

Analysis and design of an immunity test platform against D.C. and power-frequency magnetic field

The magnetic field environment around tokamak devices is very strong, which affects the working characteristics of electrical and electronic devices. For the study of magnetic field interference problems and the qualification test of sensitive devices, an immunity test platform against both D.C. and power-frequency magnetic fields is designed in this paper, including the analysis and design of magnetic field generating coil and the power supply. The rated D.C. and power-frequency magnetic fields of the test coil are 200 mT and 50 mT, respectively, and the field inhomogeneity is 1.1. The electromagnetic design and the thermal design of the test coil are presented. The power supply adopts the three-stage series structure of rectifier, D.C. bus and H-bridge to enable the output of both D.C. and power-frequency currents. As the test requires a wide output current range with a high accuracy, an improved topology is proposed to ensure the stability and accuracy at all test levels. The operation principle and control strategy of the topology are analyzed and presented. The simulation results show that the topology and control strategy meet the design requirements.

A Self-Sustained Current Sensor for Smart Grid Application

Along with the ever-increasing attraction of the internet of things, self-sustainable smart sensor is receiving more and more attention. However, in some industrial sensing applications, such as the monitoring system of the transmission line in power grid, there are still a lot of critical technical issues that remain to be addressed. On the one hand, the power issue has long been an obstacle of the sensors in power grid because the routine maintenance in this case is almost impossible considering its high cost. On the other hand, highly integrated current sensing techniques with large linear range for measuring the transmission current in power line are still limited. To date, in the power grid, autonomous current sensor nodes with free-standing designs are in great demand. In this article, a complete solution for addressing these two issues has been proposed. First, a magnetic energy harvester that can scavenge the ambient power-frequency magnetic field around the transmission line is proposed. The proposed electrodynamic design is based on nonlinear resonance, which is demonstrated to have a higher power density. The power density of the prototype can be as high as 3.42 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (tested at merely 3 Oe applied magnetic field). Second, a power management circuit is specially designed for the energy harvester. The minimum input voltage of the circuit can be as low as 0.33 V. Finally, an anisotropic magnetoresistance (AMR) sensor head with large linear range is customized for sensing the current in power grid. The largest linear range of the AMR sensor can be as large as ±170 Oe. The specially designed sensing system can be a promising solution to realize the new generation of self-sustainable current sensor network in power grid.

Association of personal exposure to power-frequency magnetic fields with pregnancy outcomes among women seeking fertility treatment in a longitudinal cohort study

To assess for the first time the potential relationships of personal exposure to magnetic fields (MF) with pregnancy outcomes among a cohort of women from a fertility clinic, addressing, through study design, some of the primary limitations of previous studies on this topic. Longitudinal preconception prospective cohort. Fertility center. Our analysis included 119 women recruited from 2012 to 2018, who underwent invitro fertilization (IVF) (n = 163 cycles) and/or intrauterine insemination (IUI) (n = 123 cycles). Women wore personal exposure monitors continuously for up to three consecutive 24-hour time periods separated by several weeks. Implantation, clinical pregnancy, live birth, and pregnancy loss. The median and maximum of the overall daily mean (daily peak) MF exposure levels were 1.10 mG (2.14 mG) and 15.54 mG (58.73 mG), respectively. MF exposure metrics were highest among women who changed environments four or more times per day. Overall, no statistically significant associations between MF exposure metrics and fertility treatment or pregnancy outcomes were observed in crude or adjusted models. Effect estimates, both positive and negative, varied by outcome and the exposure metric, including the way in which exposure was modeled. Personal MF exposures were not associated with fertility treatment outcomes or pregnancy outcomes. Despite its limited size, strengths of the study include a longitudinal repeated-measures design, the collection of personal MF exposure data across multiple days, and carefully documented outcome and covariate information among a potentially susceptible study population.