Power Frequency Electric Field Research Articles

A granularity data method for power frequency electric and electromagnetic fields forecasting based on T–S fuzzy model

The impact of electromagnetic radiation generated by signal transmission base stations and power stations to meet the needs of communication equipment and energy consumption on the environment has caused people concerns. Monitoring and prediction of electric and magnetic fields have become critical tasks for researchers. In this paper, we propose a granularity data method based on T–S (Takagi–Sugeno) fuzzy model, named fuzzy rule-based model, which utilizing finite rules that are determined by the deviations between the predicted values and the true values after the data goes through a granulation-degranulation mechanism, to predict the intensity of power frequency electric field and electromagnetic field. A series of experiments show that fuzzy rule-based models have better robustness and higher prediction accuracy in comparison with several existing prediction models. The improvement of the performance of the fuzzy rule-based model quantified in terms of Root Mean Squared Error is 20.86%, 51.91%, 62.28%, 65.10%, and 71.92% in comparison with that of the Ridge model, Lasso model, and a family of support vector machine model with different kernel functions, including linear kernel (SVM-linear), radial basis function (SVM-BRF), polynomial kernel (SVM-polynomial) respectively, on the electromagnetic field testing data, and 37.42%, 55.16%, 58.79%, 59.28%, 64.27% lower than that of the Ridge model, Lasso model, SVM-linear model, SVM-BRF model and SVM-polynomial model on the power frequency electric field testing data.

Design and application of a power frequency electric field measuring device for a high‐humidity environment

AbstractThe power frequency electric field is the most important electromagnetic environmental factor in alternating current power transmission projects. The humidity has a negative influence on available electric field measuring devices, which may lead to discrepancies of up to seven times the actual value at a relative humidity exceeding 80%. The changes in the support and probe shell impedance may be the reason for the error. The optimization measures include modifying the communication mode, designing a suitable structure and circuit for the probe, and using composite insulating material with strong hydrophobicity for the support. A three‐axis omnidirectional electric field measuring device was developed based on wireless communication and composite support. The variation of the measured electric field strength value is less than 1% at relative humidities ranging from 45% to 90% in the laboratory, and the measured results obtained in high humidity at the high‐voltage test site and under the transmission line demonstrated high accuracy. The research demonstrates that the composite support can be used to improve the performance of conventional devices. The proposed device can better meet the needs for accurate measurement of electric field strength in a high‐humidity environment and overcome the technical problems raised by the IEC standard.

Research on the influence of power frequency electric field of pantograph on passengers’ health in high-speed EMU

Research on the influence of power frequency electric field of pantograph on passengers’ health in high-speed EMU

Research on hand-held power frequency electric field measurement safety warning system

Research on hand-held power frequency electric field measurement safety warning system

A Ti: LiNbO3 optical waveguide sensor for measurement of intensive electric field

In this paper, a Ti: LN optical waveguide intensive electric field sensor without metal structure is designed and fabricated. By using the finite element simulation, the refractive index difference Δno and Δne of the waveguide are designed as 0.0105 and 0.0305 respectively when the prediffusion depth d is 5 μm, which results in the static operating point of the sensor is 86.4° when the length L is 45 mm and the prediffusion width w is 10 μm. The simulation results show that when the design of LN substrate is 6 mm (x) × 1 mm (y) × 45 mm (z), the ratio of the external and internal electric fields is 4.216, and the half-wave electric field is 10053 kV/m. The sensor is measured by the power-frequency electric field measurement system, and the half-wave electric field is about 10135 kV/m, and the maximum detectable electric field is about 3041 kV/m.

Heart rate variability assessment during work in personal protective equipment under environmental thermal load

Introduction. When performing work in open areas in the summer, electrical engineering personnel use shunt shielding kits to protect against industrial frequency electric fields. However, the use of personal protective equipment has an additional thermal load on the human body, which is assessed, among other things, by changes in the indicators of the functional state of the cardiovascular system.
 The study aims to assess the variability of the heart rate when working in shunting screening kits under conditions of modeling the thermal load of the environment.
 Materials and methods. The study carried out in seven volunteers using power frequency electric field personal protective equipment. Heart rate variability assessed for simulated elevated thermal load environment. The volunteers worked with physical activity (walking) of 60 minutes treadmill and 15 minutes rest in the same climatic conditions (recovery period) after. Temperature and humidity inside shunting shielding personal suit recorded. The determination and statistical analysis of heart rate variability based in electrocardiogram were performed. Based on the recording of an electrocardiogram, the authors carried out the determination and statistical analysis of heart rate variability indicators.
 Results. Volunteers heart rate variability analysis showed that stress index median values during work and recovery periods were 345 cu and 96 cu without shunting shielding personal suit. Work in shunting shielding personal suit showed that stress index median values were 196 cu and in recovery period 152 cu. RR-interval median values under work in personal protective equipment were lower (0.552 s) than without personal protective equipment (0.617 s). The results revealed the tendency to body thermoregulatory mechanisms strain increase in work time, characterized by RR-intervals differences with personal protective equipment use and without (ΔRR) — 0.057 s, and organism partial recovery during rest time (ΔRR — 0.113 s) with personal protective equipment.
 Limitations. The number of volunteers was due to the limited duration of the study.
 Conclusion. The results of cardiovascular system functional state assessment by heart rate variability indicate stress with regulatory systems overstrain with and without personal protective equipment. Power frequency electric field personal protective equipment makes additional external thermal load to human body as stress index (196 cu), RR-intervals (0.552 s) in work period and slight decrease in recovery period (152 cu and 0.566 s). Stress index high values in the recovery period associated with prolonged environment thermal load exposure due to climatic parameters and volunteers staying in PPE after the end of physical work.
 Ethics. The Local Ethics Committee of the Izmerov Research Institute of Occupational Health approved this study carried out under the WMA Declaration of Helsinki (record № 3 from 23.03.2022).

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.

Influence of phase sequence arrangement on the electromagnetic environment of four-circuit AC line on the same tower

The paper predicts the power frequency electric field (PFEF), audible noise (AN), and radio interference (RI) of double-circuit 220kV and double-circuit 110kV four-circuit lines on the same tower erected on the same tower through the numerical calculation method of electromagnetic environment (EME) of AC transmission lines (TLs). Through a typical tower structure, the influence of the phase sequence (PS) on the EME is analysed, and the optimal and worst PSs are obtained. The optimal PS can significantly improve the EME, especially with a good confinement effect on the electric field’s power frequency. In addition, it also focuses on analyzing the influence degree of PS when the phase spacing, conductor-to-ground height and layer spacing change and establishes the applicable range of the optimal PS.

Measurement and Test of Electromagnetic Environment of Power Transmission and Transformation Project Based on Full Humidity Condition

Currently, the power transmission engineering electromagnetic environment monitoring instrument is widely used but cannot realize the power frequency electric field monitoring if the humidity is above 80%. By analyzing the influence factors of the humidity on the measuring instrument, this paper puts forward the power frequency electromagnetic field measurement method in the full humidity condition. The comparison test and data analysis are carried out under different humidity conditions. The distribution characteristic curve of the power frequency electric field is calculated by Maxwell software, and the accuracy of the measured data is verified from the theoretical calculation. The analysis proves that the power frequency electromagnetic field is independent of the environmental humidity, which strongly supports the electromagnetic environment measurement on rainy days of high humidity weather conditions.

Analysis of monitoring effect on Hybrid Electric Field for AC/DC Cross Line

Electrostatic induction charge which generated by the coupling effect of hybrid electric field of AC/DC cross line and metal object under the transmission line can cause different levels of electric shock injury to human. In order to find out the distribution law of the hybrid electric field and reduce the effect of electrostatic induction, this paper set up shielding lines which paralleled to the AC and DC lines respectively on the outside of the side conductors and along the diagonal of parallelogram at crossing point, then measured the electric field distribution in shielding areas of 750kV AC and 500kV DC lines and the induced voltages of shielding lines in different states, analyzed the effect of shielding line on power frequency electric field and DC composite electric field. The results showed that shielding lines have a reducing effect on the hybrid electric field of the cross lines, the average power frequency field strength is reduced by 12.6%, the DC composite field and power frequency electric field at the crossing position was far less than the limits specified in the respective standards. Both induced voltage of bare lines and shielding lines wrapped with adhesive tape increase with the raise of erection height. Under the same conditions, the average induction voltage of bare conductor is 9.3% higher than that of shielding lines wrapped with adhesive tape. There is no obvious difference between parallel and vertical erection methods of the same number of shielding lines in the degree of reduction of induced voltage.

Atom-based power-frequency electric field measurement using the radio-frequency-modulated Rydberg spectroscopy

The radio-frequency modulated electromagnetically induced transparency (EIT) in a ladder three-level system with Rydberg state is studied. Under the influence of a fast radio-frequency field, the EIT peak splits into a series of sidebands. When attaching a power-frequency electric field directly to the fast radio-frequency field, the odd-order sidebands of the Rydberg-EIT oscillate sensitively with the power-frequency field. The oscillation frequency is equal to twice the power frequency; the oscillation amplitude is monotonically increasing with the amplitude of the power-frequency field when the change of Stark-shift is smaller than the radio frequency. Our work paves the way for measurement of power-frequency electric field based on Rydberg atoms.

Non - contact voltage estimation method based on power frequency electric field sensor

The existing non-contact voltage measurement methods are advanced because of their high insulation, safety and reliability, but the distance between the sensor and the transmission line is difficult to measure. Therefore, a non-contact voltage estimation method based on power frequency electric field sensor is proposed. The two factors that lead to the estimation error, sensor consistency and sensor arrangement, are studied by finite element simulation and experiment based on this method. The development of the prototype has also been completed, and its feasibility has been verified through experiments. The experimental results show that the device can be applied to single transmission line voltage measurement. And the maximum estimation error is only 4.12 kV at 38 kV voltage, which proves that this method has high accuracy.

Investigation on occupational hazard factors in teaching and research places of a university

Objective: To investigate and monitor the occupational hazards in the Teaching and Research Laboratory (hereinafter referred to as the place) of a university, so as to provide basis for the occupational health work in the university. Methods: November 2014, 46 places in a university were selected by stratified random sampling, and the occupational health risk factors were investigated. Results: Indoor temperature, humidity, sulfur dioxide, nitrogen dioxide, carbon monoxide and carbon dioxide were detected in 21 sites, xylene and hydrofluoric acid were detected in 6 sites, and colony count was detected in 18 sites, the power frequency electric field intensity was measured in 23 places, and the x-ray radiation dose was measured in 4 places. Noise was measured at 21 sites, with 7 sites exceeding the standards accounting for 33.3% (7/21) ; 21 sites were detected for illumination and 10 sites for nonconformity accounting for 47.6% (10/21) ; 10 sites for Microwave Radiation and 3 sites exceeding the standards accounting for 30% (3/10) ; and 25 sites were detected for outdoor air volume and air velocity, the percentage of unqualified was 72% (18/25) in 18 sites, among which the wind velocity was statistically significant in teaching, research and experimental sites (P=0.010) . Conclusion: The occupational hazards in the teaching and research places of a university should be paid attention to, and the engineering protection and personal protection should be strengthened in the experiment.

Научно-методические основы физиолого-гигиенической оценки термической нагрузки среды с учетом использования средств индивидуальной защиты от электрических полей промышленной частоты на высоковольтных объектах

Due to the new technologies and power networks development, the number of extremely high-voltage power frequency sources increases. These sources may affect the human nervous, cardio-vascular systems as well as vision. Maintenance, repair, and adjustment of high-voltage equipment is carried out by the electricotechnical staff. Electrotechnical staff is exposed to power frequency electric field from the switchyards and overhead transmission lines where permissible limit values are exceeded. Human health protection from the harmful power frequency electromagnetic field effects is an actual issue of the occupational safety. Staff safety work must be provided by use of the personal protective equipment from unfavorable and hazard occupational factors. Usual personal protective equipment is the conductive suit, which includes conductive clothes, facescreen, gloves and footwear. Screening property of the personal protective equipment are based on the principle of Faraday cage, which is realized by the conductive materials. These materials and personal protective equipment need to have optimal air permeability and water vapor transmission properties. In accordance with the possible work outdoors, in the warm season especially, electrotechnical staff is exposed not only to the main harmful occupational factor, and climatic environments too, such as air temperature, its movement speed, humidity. Personal protective equipment development requires complex multifactorial assessment with special attention to the human body physical load value, his functional state, metabolic parameters, as well as suit thermal insulation.

A high-resolution electric field sensor based on piezoelectric bimorph composite

The rapid development of the internet of things technology has led to great demand for intelligent electric field sensor (EFS). Several working principles have been proposed, however major challenges remain existed for the requirements of EFS with low-cost, large-range, and high-resolution. In this paper, an EFS based on piezoelectric (PE) bending effect using d 31 mode is developed, where a bending strain is induced on the sandwiched bimorph structure of PZT/PDMS/PZT under an applied electric field, and the capacitance value of the PDMS layer reveals detectable variation. We demonstrate an EFS operating at the stress-mediated coupling between PE ceramic and elastic dielectric polymer, which reveals advantages such as simple fabrication process, low-cost and low power consumption. Due to the sandwiched bimorph structure, the strain caused by the electric field can be effectively transferred to improve the resolution of the device. The constitutive equations for the sandwiched bimorph structure are built, and the working principle of the proposed EFS is demonstrated. The EFS exhibits high sensitivity under both AC and DC electric fields, with a resolution of 0.1 V cm−1 in the range of −3 to 3 kV cm−1. The proposed sensor provides an alternative solution for power equipment fault diagnosis, power frequency electric field detection, etc.

Analysis of power frequency electric field distortion caused by substation inspection robot

In the era of intellectualization, many substation inspection robots are being put into operation, but they will cause electric field distortion in the surrounding space during operation. This paper establishes a three-dimensional simplified simulation calculation model for 500kV substations and inspection robots. Based on the boundary element method, we simulate the power frequency electric field of the substation switchyard and analysis the distortion electric field when the inspection robot is in the station. The results show that when the electric field intensity is strong, the distortion coefficient caused by the robot will be larger, and the maximum can reach 2.25 times, and when the electric field intensity is small, the distortion coefficient will be smaller, and the distortion coefficient is 1.42 times on average.

Investigation of occupational hazard of 750 kV extra high voltage substations

Objective: To understand the current status of major occupational hazards in 750 kV extra high voltage (EHV) substations. Methods: In July 2019, through investigating and detecting the sulfur hexafluoride, power frequency electric field and noise occupational hazards of 750 kV EHV substations in substation 1, substation 2, substation 3, substation 4, substation 5, substation 6 and substation 7, the exposure intensity of the sulfur hexafluoride, power frequency electric field and noise intensity that the operators are exposed to during the inspection process were analyzed. Results: The qualified rate of 358 sulfur hexafluoride test results was 100.0% of the seven 750 kV EHV substations. The qualified rate of 8 h time-weighted average of the power frequency electric field of those 750 kV EHV substations contacted by operators was 100.0%. Among the 847 power frequency electric field detection points, the exceeding standard rate of power frequency electric field was 64.3%, and the differences in the power frequency electric field detection exceeding standard rates of different substations and inspection areas were statistically significant (χ2=87.52, 50.86, P<0.01) . The highest exceeding standard rate of power frequency electric field was the circuit breaker inspection area (94.4%, 34/36) . The noise intensity test results of the seven EHV substations were 41.1-79.7 dB (A) , and the qualified rate was 100.0%. Conclusion: The sulfur hexafluoride, power frequency electric field and noise that the operators contacted in 750 kV EHV substations meet the requirements of occupational exposure limits. The inspection areas of main transformers, capacitors, reactors, bus bars and switches have high power frequency electric field radiation, should be select equipment iand give priority to robot inspection, and reasonably adjust the inspection time to reduce the intensity level of substation operators' exposure to power frequency electric field.

Target Positioning Optimization Method in Power System

This thesis presents a method that a position measurement method for moving targets is proposed based on the positioning method based on the time difference of arrival (TDOA) which is based on the research on the positioning problem of station inspection operators and equipment in complex working conditions. The probability error method is introduced to optimize the traditional positioning method that realizes the target node positioning by optimizing the distance difference between the target node to be located in the network domain environment and different base stations, which can effectively improve the positioning accuracy of staff and equipment in the station. Through experiments in a complex power frequency electric field environment, the test results show that the results calculated by the optimization method are better than the existing traditional positioning methods, and can effectively improve the positioning accuracy under the condition of line-of-sight, and realize the substation space Mobile target positioning to ensure the safety of operators.

Electric field generated by high-voltage transmission system is beneficial to cotton growth

With the increasing popularity of high-voltage transmission systems, the potential effects of environmental electric fields (EFs) generated by these systems to surrounding organisms is gradually becoming a source of public concern. Cotton is planted on a large scale all over the world and is exposed inevitably to environmental EF. In this study, cotton was exposed continuously to power frequency electric field (PF EF) of different intensities (0 kV/m, 2 kV/m, and 10 kV/m) and evaluated on agronomic traits, yield, organic matter contents, protective enzyme activities, and genes expression over time and at different stages of plant growth. We found that cotton was impressionable by EF at the seedling stage, while it was relatively insensitive at the maturity stage. Exposure to PF EF is safe and beneficial to growth and yield for cotton in our experiment. Data collected from growing cotton of plant height, functional leaf number, dry weight of plant and boll, contents of soluble sugar and total protein, and activities of superoxide dismutase and catalase exhibited a tendency to increase under the EF treatment. Transcriptional analyses showed that EF caused significant changes in the expression levels of 86 genes of cotton, and most of which were up-regulated. These differentially expressed genes are involved in carbohydrate metabolic process and various transfer proteins synthesis, and are associated with the activity of some transferases and hydrolases, providing a novel perspective for understanding molecular mechanisms underpinning the yield increase of EF to cotton.

Study on Measurement Error of Power Frequency Electric Field Intensity Caused by Change of Air Dielectric Constant with Humidity

People are paying more and more attention to the influence of power frequency electric field on their living environment, so the measured value of power frequency electric field under AC transmission line becomes an important reference for judging whether the surrounding environment is polluted or not. In actual measurement, it is found that the measured value of electric field intensity in high humidity areas is often relatively large. This paper will investigate the influence of the change of air dielectric constant on electric field measurement. Through experiments and simulations, it is found that air dielectric constant increases with the increase of humidity, which increases rapidly before the ambient humidity reaches 75%, and increases slowly after the ambient humidity exceeds 75%. However, it was found by simulation that the change of air dielectric constant has no obvious influence on the surrounding electric field intensity. Therefore, the change of air dielectric constant is not the main factor leading to relatively large measured value of field intensity in high humidity areas.