Maximum Electric Field Strength Research Articles

A Novel Chip Surface Shielding Structure for Promoting Insulation Capability of High Voltage Semiconductor Chip

Partial discharge which often occurs at channel stopper of high voltage chip will cause insulation damage of chips which is harmful to the device application. Thus, it is important to improve the whole design to promote chip insulation capacity. In this brief, a novel chip surface shielding structure named U-protector is proposed which can promote the insulation capability of high voltage chips. Through the simulation, it can be found that the maximum electric field strength of chips can decrease 8% with adding U-protector. Moreover, verified by experiments, the partial discharge initial voltage (PDIV) of chips with U-protector can be promoted about 6.1%–12.7% of rated voltage. Furthermore, the universality and practicality of this structure are also investigated which can be used in multiple high voltage chips.

Modeling of polyvinylidene fluoride nanocomposite utilizing BaTiO3@SiO2 for energy storage

Polymer-based nano dielectrics are attracting great attention in the research world. Such materials, primarily for embedded capacitors, offer greater feasible energy storage alternatives. This research aims to analyze the distribution of electric field in binary and core–shell BaTiO3@SiO2 structures of polyvinylidene fluoride (PVDF) nanocomposites with various filler concentrations of nanofibers using COMSOL Multiphysics® software-based finite element method. The core–shell structures enhanced the electric field strength and polarization as compared to binary nanocomposites. The novelty of the work is the design of the interface layer on the surface of nanoparticles was beneficial in reducing the local electric field in the filler/ polymer matrix system. According to a finite element simulation, the SiO2 shell may effectively reduce the electric field contrast between the polymer matrix and the BaTiO3 filler. The PVDF/BaTiO3@SiO2 nanocomposites show a maximum electric field strength of 380 MV/m, which is about 2.5 times larger than PVDF/BT nanocomposites under both the same filler content of 2.5 wt% and applied voltage. This work provides a prosperous path to achieving large-performance capacitors.

Estimation of the maximum electric field strength in the cathode sheath of a Grimm-type glow discharge by end-on view optical emission spectroscopy in neon and argon

Looking “behind” the negative glow plasma: can we unveil the parameters describing the electric field distribution in the cathode sheath of the Grimm-type glow discharge source using standard end-on optical emission spectroscopy? We believe we can.

6G and beyond: Investigation of broadband terahertz interdigitated photoconductive antenna by exploiting laser parameters

AbstractPhotoconductive Antennas (PCA) are widely used for terahertz (THz) generation and detection. These PCAs build the basis for future 6G communication as they provide a high data rate and broad bandwidth. In this work, interdigitated photoconductive antenna (IPCA) has been designed and optimized for better performance in terms of THz radiation. The proposed IPCA is made of LT‐GaAs substrate material deposited on SI‐GaAs. Silver material has been assumed for the IPCA electrode structure. Moreover, the dependence of IPCA on the incident laser parameters such as its wavelength (λ = 800, 1060, and 1550 nm) and pulse duration (100–500 fs) has been investigated theoretically for different teeth widths (We = 500, 100, 50, and 20 nm). The performance of the IPCA with various parameters such as average carrier density, conductance, total photocurrent, THz radiated power, and electric field strength, has been analyzed. The results show maximum THz electric field strength of 20.85 V/m for a photo‐generated current of 1.887 A and enormous bandwidth beyond 14.9 THz with 20 nm teeth‐width‐based IPCA when illuminated with 100 fs 800 nm laser pulses. The proposed IPCA structure provides enhanced THz radiation compared to conventional PCA. This investigation helps the researchers to develop and integrate IPCA for future wireless communications as well as for a variety of applications, such as time‐domain spectroscopy (THz‐TDS), medical imaging, sensing, and security‐related applications.

Optimization of Corona Ring Design Used in UHV Composite Insulator by PSO Algorithm

The three-dimensional model for the V and I type composite insulators used in AC 1000kV single-circuit tangent power transmission tower has been established, and conducted E-field calculation in FEM software, the results show that maximum electric field strength of corona ring used in V type insulator is about 13.9% and insulator surface 29.2% higher than that of I type, thus corona ring structure should be further optimized. So PSO algorithm has been implemented, meanwhile, submodeling technique was also used to solve such large calculation amount problem due to complexity of used model which can effectively reduce calculation amount without lose of accuracy. Then the method combining FEM and PSO algorithm has been applied to corona ring structure multi-parameter optimization used in V and I type insulators, finally, maximum E-field located in surface of ring and insulator shed can meet the electric control value, and no corona discharges can be observed when corona rings were used in actual project. The method proposed in the paper can solve structure optimization problem for large field domain and multi-media complex model, meanwhile, have reference value for researching field of insulation structure optimization with PSO algorithm.

Electrostatic Simulation and Analysis of Transmission Line Corner Section for the CRAFT NNBI Test Platform

The gas-insulated transmission line (GITL), which is an important link between ion source and the power supply system, carries all the ion source and the extraction power supplies (ISEPS) conductors at −400 kV with respect to ground, from high voltage deck (HVD) to the ion source and the intermediate potentials of acceleration grids (AGs). In this article, three insulation schemes of the corner section of the GITL are put forward. Through the finite element analysis, only one scheme satisfies the design requirements. In this analysis, the relationships between the design parameters (the radius and angle of the corner section) and the design guiding principles (maximum electric field strength, equivalent distributed capacitance, and so on) are obtained. According to design requirements, the preliminary design parameters of the corner section are determined: the radius of the corner section can change from 50 to 150 mm and the angle of the corner section is chosen as 90°. In this case, the maximum electric field strength of the GITL decreases from 3.18 to 3.06 kV/mm, the maximum electric field strength of the inner surface of the grounding shell decreases from 1.08 to 0.73 kV/mm, the electric field non-uniformity coefficient decreases from 2.21 to 2.15, and the equivalent distributed capacitance increases from 82.12 to 94.70 pF. The simulation results provide a theoretical basis for the engineering design of the corner section of the GITL.

A Novel Method to Predict the Maximum Electric Fields in Different Body Parts Exposed to Uniform Low-Frequency Magnetic Field

Thepermissible external field strength described in international exposure guidelines and standards was derived under the assumption that humans are exposed to a uniform field in free space. However, realistic field distributions are partial body exposure to the nonuniform field. Thus, the permissible field strength has overconservative values when applying the spatial peak strength to practical compliance assessment. In this study, we discuss the relationship between the uniform external magnetic field strength and induced electric field in different body part models to help set the permissible field strength for nonuniform magnetic field exposure. We proposed a formula for estimating induced electric field from the electromotive force of cuboid models based on Faraday's law. Then, we applied the formula to homogeneous ellipsoidal and homogeneous realistically shaped models. Furthermore, we investigated the effect of model inhomogeneity to confirm the difference in the induced electric field in anatomical body models. The homogeneous ellipsoidal model was comparable to the homogeneous realistically shaped model, whereas the model inhomogeneity led to an approximately 1.5 times increase in the computed maximum electric field strength.

Optimization of corona ring for 230 kV polymeric insulator based on finite element method and PSO algorithm

The electric field distribution is a very important factor in the performance of polymeric insulators. This distribution varies under different operating conditions. Therefore, there are different approaches to reduce the electric field strength at the critical zones to acceptable values. One of these approaches is the use of corona rings. However, the design of corona rings is not standardized, and the geometric parameters affect the electric field distribution. This work analyzed the relationship between corona ring design parameters and the electric field strength near energized-end fitting in a real 230 kV polymeric insulator with a corona ring. First, it was used the Finite Element Method to evaluate the influence of three corona ring design parameters on the electric field strength: corona ring diameter, ring tube diameter, and corona ring position. Then, the PSO algorithm was used to optimize the original corona ring and reduce the electric field strength at three critical zones: triple point, the surface of the energized-end fitting, and the surface of the corona ring. The optimization process reduced the maximum electric field strength by 50.5% relative to the insulator with the original corona ring (82.4% without a corona ring).

Mathematical Parameters Calculation of Double Exponential Function by a New Numerical Method

Background: Lightning electromagnetic pulse (LEMP) and high-altitude electromagnetic pulse (HEMP) are widely described by three physical parameters (rise time tr, full-width at halfmaximum pulse width tw, and maximum electric field strength E0). These pulse shapes are often given by a double exponential form concerning four mathematical parameters, namely α, β, k and Ep. Objective: The transformation from physical parameters into mathematical parameters is necessary in waveform simulation and is traditionally accomplished by linear fit functions regarding the two groups of parameters. However, traditional methods commonly rely on data analysis and calculation. In order to obtain the mathematical parameters more concisely and clearly. Methods: In this paper, a numerical method to calculate the mathematical parameters by solving nonlinear equations with three key constraints is proposed. Firstly, we establish the nonlinear system of equations regarding four variables, namely t1, t2, α and β. Then, three constraints are given to converge the solutions of the equations. Lastly, select the minimal value of the convergent solution of each equation. Results: Comparing the solutions obtained by our proposed method to the iterated ones, the overall relative error is less than 2×10-8. Conclusion: The results show that our proposed method not only simplifies the transformation from physical parameters to mathematical parameters, but also keeps the solutions high accurate.

Free-carrier generation dynamics induced by ultrashort intense terahertz pulses in silicon.

We report the results of experimental studies and numerical simulation of the dynamics of the electron-hole pairs formation in silicon under the action of a two-period terahertz pulse with a maximum electric field strength of up to 23 MV/cm. It is shown that an inhomogeneous distribution of the charge carrier concentration over the depth of the silicon sample is formed, which persists for several microseconds. This inhomogeneity is formed due to a sharp increase in the rate of filling the conduction band with free carriers in the subsurface input layer of the silicon wafer, which occurs at a field strength above 15 MV/cm.

Effect of sinusoidal waveform and frequency on space charge characteristics of polyimide

The charge phenomena under sine and half-wave sine voltages within the frequency range of 500 Hz are studied here. Based on the pulsed electro-acoustic method, the traditional circuit design under high-frequency voltages is first analysed. It is found that the selection of a 186 pF protection capacitor and a 333 kΩ protection resistor can ensure that the actual voltage applied to the sample is consistent with the expected input. Based on this design, experimental results show that the polarity of the charge accumulated in the depth of the sample is determined by that of the upper electrode. Comparison results under special voltages with different amplitudes and frequencies indicate that the amount of accumulated charge under sine voltages are larger than those under positive and negative half-wave sine and DC conditions, and the samples under lower-frequency conditions show more charge accumulation. The maximum electric field strengths appear at 90 and 270 degrees of the sine voltage with a frequency of 10 Hz, and their values are 68.55 and 81.82 kV/mm, respectively. Therefore, the charge characteristics are easily affected by the voltage’s waveform and frequency parameters. The results obtained here can provide guidance for the application of insulating materials under special voltage environments.

Weight analysis and experimental study on influencing factors of high-voltage electro-pulse boring

Electro-pulse boring (EPB) has the advantages of high rock-breaking efficiency and good borehole wall quality, which is a new type of rock-breaking method with potential and close to industrialization. EPB is affected by many factors, such as voltage, electrode structure shape, rock composition, discharge times and so on. Firstly, according to the established simulation model of EPB and the previous research on electric breakdown model of rock, the maximum electric field strength in rock, the electric breakdown field strength of rock and its ratio with different influencing factors were simulated and calculated. Secondly, the probability of electric breakdown with different influencing factors was obtained. The extreme learning machine and average influence value (ELM-MIV) algorithm was proposed to analyze the weight of the six influencing factors on the probability of electric breakdown, such as peak voltage, electrode spacing, electrode angle, and so on. The correlation and contribution degree of the influencing factors on the electric breakdown probability were obtained. Then, the EPB experiment system based on the transformer-type pulse power supply was developed, and the coaxial cylindrical electrode bits with the spacing of 25 mm and 45 mm were developed. The drilling diameter of red sandstone was 100 mm and 60 mm, respectively. The results showed that the energy consumption of EPB was about 100–300 J/cm3 without slag discharge system. Finally, the influence experiments on EPB were carried out, and the influence rules of electrode spacing, discharge times and rock composition on EPB were obtained. It provided guidance and basis for the design of electrode bit and the selection of drilling technology parameters in different strata through the research on the influencing laws of EPB. It was of great significance to improve the efficiency and reduce the energy loss in the process of EPB.

Electric Field Investigations of a Compact Superconducting Three-Phase Single Conductor Cable Assembly

A new compact cable design was investigated using only liquid nitrogen (LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ), general used as coolant of superconductors, as sole electric insulation. First, it was analyzed which conductor arrangement is better suited in terms of maximum electric field strength to withstand the applied voltage of 123 kV. It was found that a three-phase single conductor arrangement with a maximum electric field strength of 10.5 kV/mm is more suitable than a triaxial arrangement with a maximum field strength of 16.5 kV/mm. Furthermore, a corresponding supporting insulator was developed to provide the highest possible mechanical and electrical withstand. A major focus was on selecting the most appropriate material and its permittivity in combination with the surrounding LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (ϵ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 1.43) to reduce the electric field strength to its possible minimum. The best relative permittivity for the supporting insulator is in the range between 1.4 and 3.4.

Inter-individual variations in electric fields induced in the brain by exposure to uniform magnetic fields at 50 Hz

The International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines and the Institute of Electrical and Electronics Engineers (IEEE) standard establish safety limits for human exposure to electromagnetic fields. At low frequencies, only a limited number of computational body models or simplified geometrical shapes are used to relate the internal induced electric fields and the external magnetic fields. As a consequence, both standard/guidelines derive the exposure reference levels for the external magnetic field without considering the variability between individuals. Here we provide quantitative data on the variation of the maximum electric field strengths induced in the brain of 118 individuals when exposed to uniform magnetic fields at 50 Hz. We found that individual characteristics, such as age and skull volume, as well as incident magnetic field direction, have a systematic effect on the peak electric field values. Older individuals show higher induced electric field strengths, possibly due to age-related anatomical changes in brain. Peak electric field strengths are found to increase for larger skull volumes, as well as for incident magnetic fields directed along the lateral direction. Moreover, the maximum electric fields provided by the anatomical models used by ICNIRP for deriving exposure limits are considerably higher than those obtained here. On the contrary, the IEEE elliptical exposure model produces a weaker peak electric field strength. Our findings are useful for the revision and harmonization of the current exposure standard and guidelines. The present investigation reduces the dosimetric uncertainty of the induced electric field among different anatomical induction models. The obtained results can be used as a basis for the selection of appropriate reduction factors when deriving exposure reference levels for human protection to low-frequency electromagnetic exposure.

Optimized design of DC shielding fittings for ±800kV UHV converter station

This paper studies the structure of the shielding device of DC device in the UHV converter station. Through simulation analysis, the electric field distribution on the surface of the shielding device is calculated to find the factors that affect the maximum field strength and the maximum electric field of the shielding device at different opening sizes and flange radius. By optimizing the structure and using a lantern-shaped shielding device, the maximum electric field strength on the surface of the shielding device of the same size can be reduced by more than 15%. The research of this project is of guiding significance for the design of shielding devices of UHV DC engineering in high altitude areas, and of great significance for promoting the progress and development of UHV DC transmission technology.

Double short vacuum gaps in series under lightning impulse voltage: Estimation of breakdown voltage

The objective of this paper is to propose a method for quantitatively estimating the breakdown voltage of double short vacuum gaps in series under the lightning impulse voltage. The study found a quantitative relationship between the breakdown voltage and the maximum electric field strength at the cathode. This relationship is validated by previous experimental works when the total gap distance is less than 20 mm.

Effect of Loudspeakers on the In Situ Electric Field in a Driver Body Model Exposed to an Electric Vehicle Wireless Power Transfer System

This study computationally evaluates the effect of loudspeakers on the in situ electric field in a driver body model exposed to the magnetic field from a wireless power transfer (WPT) system in an electric vehicle (EV), one with a body made of carbon fiber reinforced plastic (CFRP) and the other made with aluminum. A quasi-static two-step approach was applied to compute the in situ electric field. The computational results showed that the magnetic field distribution generated by the WPT is significantly altered around the loudspeakers, and shows obvious discontinuity and local enhancement. The maximum spatial-average magnetic field strength in the driver’s body was increased by 11% in the CFRP vehicle. It was 2.25 times larger than the reference levels (RL) prescribed in the International Commission of Non-Ionizing Radiation Protection (ICNIRP) guidelines in 2010. In addition, we found that the in situ electric field computed by the line- and volume-averaging methods were stable if the top 0.1% voxels are excluded. The maximum value was well below the basic restriction (BR) of the ICNIRP guidelines. Nevertheless, the presence of the loudspeaker led to increments in the electric field strength in parts of the human body, suggesting the potential influence of permissible transmitting power in the WPT system. The maximum electric field strength in the thigh and buttock with the woofer, increased by 27% in the CFRP vehicle. The arm value was up to 3 times higher than that obtained without the tweeter in the aluminum vehicle. Moreover, this study found that the maximum electric field strength depended on the location of the loudspeaker with respect to the WPT system and the separation from the driver model. Therefore, the loudspeaker should be considered when evaluating the maximum in situ electric field strength in the vehicle body design stage.

Tunneling Current in 4H-SiC p-n Junction Diodes

Heavily doped 4H-silicon carbide (SiC) epitaxial p-n junction diodes are fabricated, and their tunneling current under reverse-biased condition is investigated. Soft increase of the leakage current before avalanche breakdown is observed in the diodes with heavy reduced doping concentration. The temperature and electric field strength dependencies of the leakage current reveal that the leakage current is caused by a phonon-assisted tunneling process. An accurate parameter set for simulating the phonon-assisted tunneling current in 4H-SiC is obtained, which agrees well with the experimental results within a wide temperature range (100-500 K) regardless of the reduced doping concentration. In 4H-SiC p-n junction diodes, the Zener breakdown occurs at the maximum electric field strength of 5.7 MV/cm.

Study on Insulation Characteristics of Scratch Defects in 35kV XLPE Cable Terminals

In order to study the influence of different ring-shaped scratches on the insulation characteristics of 35kV Crosslinked polyethylene(XLPE) cable terminations, the model of air-gap defects caused by ring-shaped scratches was introduced at the end of the outer semi-conductor shielding layer, and the finite element simulation calculation was used to calculate the model. The electric field distribution characteristics inside the cable terminal were simultaneously made into cable end samples of different types of scratch defects, and the discharge characteristics were tested by a partial discharge test circuit. The results show that the air gap defect caused by the annular scratch defect increases the degree of electric field distortion. The maximum electric field strength is much larger than the breakdown field strength of the air, and it is prone to partial discharge activity. The Phase Resolved Partial Discharge(PRPD) of the cable terminal with ring scratch defects The spectrum shows a typical “rabbit ear” shape. As the scratch defects deepen, the PRPD spectrum begins to gradually transition to a short-feeling “cat ear” shape.

Lobule-Specific Dosage Considerations for Cerebellar Transcranial Direct Current Stimulation During Healthy Aging: A Computational Modeling Study Using Age-Specific Magnetic Resonance Imaging Templates

Aging is associated with a decline in cognitive and motor performances, which are a part of geriatric syndromes. Since aging is associated with morphological changes in the cerebellum and cerebellar morphology is a good predictor of cognitive and motor performances, so the study of cerebellar role in age-related decline in performance is necessary. Cerebellar transcranial direct current stimulation (ctDCS) has been proposed to study and facilitate the cerebellar function. However, lobule-specific dosing has not been investigated in healthy aging. This is important because the same electrode montage across different individuals for ctDCS (called the "one-size-fits-all" approach) can lead to inter-individual differences in the lobule-specific dosing of the electric field (EF). These differences can be due to the inter-individual variability and age-related changes in the cerebellar structure. To investigate such lobule-specific dosing differences in healthy aging, we modeled the lobular EF distribution across groups of 18 to 89 years for a commonly used "one-size-fits-all" ctDCS montage. A fully automated open-source pipeline performed age-group specific computational modeling of EF using 18 age-appropriate human brain magnetic resonance imaging (MRI) templates. The 18 age-appropriate human brain MRI templates were obtained from a database found online at https://jerlab.sc.edu/projects/neurodevelopmental-mri-database/. We extracted the EF magnitude (called EF strength) across the 28 cerebellar lobules based on a spatially unbiased cerebellar atlas. We investigated the aging effects on various measures of specificity including the ratio of the mean lobular EF at the lobules beneath the active electrode (ipsilateral [right] lobules VIIIa, VIIIb, IX) divided by the mean EF across both the targeted (ipsi) and the contralateral (contra) cerebellar hemisphere. Two-way ANOVA showed that the lobules as well as the age group (and their interaction term) had a significant effect (p < 0.01) on the EF strength. Specifically, EF strength increased significantly at the neighboring cerebellar lobules (e.g., ipsilateral [right] lobules VIIb, Crus I and Crus II) of the targeted cerebellar hemisphere at an old age (70-74, 75-79, and 85-89 years) that reduced the specificity of ctDCS at the ipsilateral (right) lobules VIIIa, VIIIb, IX beneath the active electrode. We also found that the maximum EF strength in the cerebellar hemispheres decreased with an increase in the volume of the cerebrospinal fluid (CSF) and a decrease in the cerebellar volume with aging in a linear manner. We found that cerebellar shrinkage and increasing thickness of the highly conductive CSF during healthy aging can lead to the dispersion of the current away from the lobules underlying the active electrode. We concluded that an individualized ctDCS approach for dosimetry is critical when ctDCS is used as an adjuvant treatment for active aging to address age-related lobule-specific cerebellar geriatric syndromes effectively. Future work is necessary to investigate age-related effects of lobule-specific ctDCS on the large-scale cognitive and motor networks using functional neuroimaging that is expected due to the cerebellum's extensive reciprocal connectivity with the cerebral cortex.