High-voltage Field Research Articles

Surface Electrons: Theory and Electrohydrodynamic Applications

The paper presents the theory of surface electronic states induced by a high-voltage field and considers applications of the theory of surface electrons to electrohydrodynamic flows. Theoretical considerations were carried out within the framework of a one-electron quantum mechanical model. It is shown that surface electrons initiate the injection of negative charg-es from the cathode into a liquid dielectric containing an electron-withdrawing impurity, for example, molecular iodine. Comparison of the theoretic and experimental data is satisfacto-ry

Computed corrections for recollision effects on ionization and x-ray production cross sections obtained in positron-impact studies

The accurate experimental measurement of inner-shell ionization cross sections induced by positrons near the threshold energy is of great significance both for theory and practical application. So far, there are few published experimental data in this field, most of which involve a slow positron beam device and acceleration fields to achieve the desired collision energies. Most previous experimental studies, in which a negative acceleration potential was applied to the target, neglected to consider how backscattered positrons might be accelerated back to the target, generating surplus characteristic x-rays and inflating the cross-section estimates derived therefrom. Using Geant4 and Ansys Maxwell to simulate charged-particle transport, the experimental collision process in the negative high-voltage electromagnetic field of the target chamber is simulated realistically in this paper. Through the simulation process, the effect of the negative high-voltage electromagnetic field on backscattered positrons, hence on ionization and characteristic x-ray production cross sections, is obtained. We then estimate corrections for previously published experimental Ti K-shell ionization cross sections and Ag-Lαβγ, Bi-Mαβ, Pb-Mαβ x-ray production cross sections obtained by positron impact. In addition, we use simulation to demonstrate that such undesired effects can be suppressed by adjusting the size of the target and the tilt angle between the target normal and the positron beam axis.

Portable Non-Destructive Magnetic Resonance Sensor for Assessing the Aging Status of Silicon Rubber Insulators.

Silicone rubber insulators (SRIs) are widely used in high-voltage power grids. Due to high-voltage fields and harsh environmental conditions, SRIs eventually deteriorate with use in the power grid, decreasing their insulating performance and operational life and contributing to transmission line failures. Therefore, quantitatively assessing the aging status of SRIs is crucial. In this study, we evaluated the viability of the magnetic resonance method for assessing the age of SRIs at the level of chemical structure; we built and made a portable magnetic resonance sensor, and evaluated the sensor's functionality. By measuring the SRI sheds at various service times, it was discovered that the equivalent transverse relaxation time, T2eff, can describe the degree of aging of the SRIs. The results of the magnetic resonance measurements were also compared with those of the static contact angle method, and the two measurement methods yielded the same conclusions. However, the magnetic resonance method was more sensitive than the one using the static contact angle method.

Enhancing FBG Sensing in the Industrial Application by Optimizing the Grating Parameters Based on NSGA-II.

Fiber Bragg grating (FBG) technology has shown a mutation in developing fiber optic-based sensors because of their tiny size, high dielectric strength, distributed sensing, and immunity to high voltage and magnetic field interference. Therefore, FBG sensors significantly improve performance and accuracy in the world of measurements. The reflectivity and bandwidth are the main parameters that can dramatically affect the sensing performance and accuracy. Each industrial application has its requirements regarding the reflectivity and bandwidth of the reflected wavelength. Optimizing such problems with multi-objective functions that might t with each other based on applications' needs is a big challenge. Therefore, this paper presents an optimization method based on the nondominated sorting genetic algorithm II (NSGA-II), aiming at determining the optimum grating parameters to suit applications' needs. To sum up, the optimization process aims to convert industrial applications' requirements, including bandwidth and reflectivity, into the manufacturing setting of FBG sensors, including grating length and modulation refractive index. The method has been implemented using MATLAB and validated with other research work in the literature. Results proved the capability of the new way to determine the optimum grating parameters for fulfilling application requirements.

A novel LDMOS with optimized electric field distribution to eliminate substrate assisted depletion effect

A novel N-channel Super Junction Lateral double-diffused MOSFET (SJ LDMOS) with optimized electric field distribution is proposed. To eliminate substrate assisted depletion (SAD) effect, the source-drain electrodes of the proposed device are used to form a voltage in the substrate equal to the SJ layer. Then the surface of the substrate is depleted through the buffer layer. The substrate and the SJ layer are independently depleted, and form a similar electric field distribution. The influence of the substrate on the SJ layer is greatly removed. Finally, the influence of the substrate on SJ layer is completely eliminated. Under the same drift length of 20 μm, the specific on resistance (Ron,sp) and breakdown voltage (BV) of the proposed SJ LDMOS are reduced by 60.09% and 28.9% compared with those of the conventional SJ LDMOS, respectively. With the increase of the drift region length, the SJ LDMOS which eliminates the SAD effect has more obvious advantages in the high voltage field.

Effect of Negative High-Voltage Corona Field on Hydrophilicity and Vigor of Astragalus mongolicus Seeds

This work aims to study the effect of dc negative high-voltage corona electric field on the vigor and hydrophilicity of Astragalus membranceus (Fisch.) Bge. var. mongolicus (Bge.) Hsiao seeds. The ion wind generated by the multipin pole generator at −3, −4, −5, −6, and −7 kV and the electrostatic field acted together. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${A}$ </tex-math></inline-formula> . mongholicus seeds were exposed to the electric field for 30, 60, and 90 min. Results show that the ion wind velocity increases significantly with the increase of applied voltage. Malonaldehyde (MDA), electrical conductivity (EC), and apparent contact angle (APCA) in all treatment groups decreased to different degrees compared with the control samples. MDA, EC, and APCA decreased by 56.28%, 20.89%, and 31%, respectively. The hydrophilicity of seeds treated by negative corona field was improved, and the water absorption of seeds was increased by 1.34 times. Fourier infrared spectroscopy, scanning electron microscopy, and energy dispersive X-ray (EDX) spectroscopy were used to examine the spectra, apparent morphology, and surface elements of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${A}$ </tex-math></inline-formula> . mongholicus seed coats from different treatment groups. Results showed that the ionic wind generated by the negative high-voltage corona electric field had a significant etching effect on the seed coat and enhanced the water absorption and fiber strength of hydrophilic functional groups of the seed coat.

Modulating the surface potential of microspheres by phase transition in strontium doped barium titanate to restore the electric microenvironment for bone regeneration.

The endogenous electrical potential generated by native bone and periosteum plays a key role in maintaining bone mass and quality. Inspired by the electrical properties of bone, different negative surface potentials are built on microspheres to restore electric microenvironment for powerful bone regeneration, which was prepared by the combination of strontium-doped barium titanate (Sr-BTO) nanoparticles and poly (lactic-co-glycolic acid) (PLGA) with high electrostatic voltage field (HEV). The surface potential was modulated through regulating the phase composition of nanoparticles in microspheres by the doping amount of strontium ion (Sr2+). As a result, the 0.1Sr-BTO/PLGA group shows the lowest surface potential and its relative permittivity is closer to natural bone. As expected, the 0.1Sr-BTO/PLGA microspheres performed cytocompatibility, osteogenic activity in vitro and enhance bone regeneration in vivo. Furthermore, the potential mechanism of Sr-BTO/PLGA microspheres to promote osteogenic differentiation was further explored. The lower surface potential generated on Sr-BTO/PLGA microspheres regulates cell membrane potential and leads to an increase in the intracellular calcium ion (Ca2+) concentration, which could activate the Calcineurin (CaN)/Nuclear factor of activated T-cells (NFAT) signaling pathway to promote osteogenic differentiation. This study established an effective method to modulate the surface potential, which provides a prospective exploration for electrical stimulation therapy. The 0.1Sr-BTO/PLGA microsphere with lower surface potential and bone-matched dielectric constant is expected to have great potential in the field of bone regeneration.

Self-powered air purifier with coupling of non-thermal plasma and photocatalytic oxidation for formaldehyde degradation based on triboelectric nanogenerator

The emission of various volatile organic compounds (VOCs) caused by indoor decoration and furniture placement are the causes of health hazards in people's lives. Here, we demonstrate a self-powered air purifier for indoor organic pollutant removal based on triboelectric nanogenerator (TENG), coupling non-thermal plasma (NTP) with photocatalytic oxidation (PCO). An adjustable external high voltage field is generated by our homemade TENG, in which the output open-circuit voltage (Voc) ranges from 10 to 30 kV. After connecting the TENG with a non-thermal plasma generator (NTP-G), a maximum ozone concentration of 14.7 mg/m³ and NTP can be generated. The prepared three-dimensional porous framework is used as a photocatalytic layer, which can support more titanium oxide and increase the contact area between the photocatalyst and formaldehyde. This designed self-powered air purifier can reduce the formaldehyde concentration from 2.06 ppm to 0 ppm in 21 min in a 13 L closed air chamber. The design and concept proposed in this work has multiple ways for formaldehyde degradation and are not limited by sunlight, and can remove indoor formaldehyde around the clock, providing an effective way to create a cleaner and healthier indoor environment.

Influence of epitaxial layer structure and cell structure on electrical performance of 6.5 kV SiC MOSFET

Silicon carbide (SiC) material features a wide bandgap and high critical breakdown field intensity. It also plays an important role in the high efficiency and miniaturization of power electronic equipment. It is an ideal choice for new power electronic devices, especially in smart grids and high-speed trains. In the medium and high voltage fields, SiC devices with a blocking voltage of more than 6.5 kV will have a wide range of applications. In this paper, we study the influence of epitaxial material properties on the static characteristics of 6.5 kV SiC MOSFET. 6.5 kV SiC MOSFETs with different channel lengths and JFET region widths are manufactured on three wafers and analyzed. The FN tunneling of gate oxide, HTGB and HTRB tests are performed and provide data support for the industrialization process for medium/high voltage SiC MOSFETs.

Performance of a nanotextured superhydrophobic coating developed for high-voltage outdoor porcelain insulators

We live in an era of striking advancements in various domains of science and technology, where separate fields and specializations are overlapping into new horizons. This cooperative approach is emerging rapidly in polymer science by employing the organic and physical chemistry, materials science, as well as electrical and mechanical engineering to collaborate and develop uniquely innovative materials. In outdoor high voltage power equipment, various problems such as flashover, rain, icing, pollution, and UV can compromise the performance of insulators thereby distorting the reliability of the entire system. Superhydrophobic coatings are sought-after candidates owing to their ultra-non-wettable, easy-to-clean, and anti-ice character. However, the performance of superhydrophobic coatings when they are subjected to high-voltage fields is still lacking sufficient research. Here, we aimed at designing a robust and novel non-fluorinated superhydrophobic coating in order to increase the effective life-span of high-voltage insulators by preventing and/or delaying the possible arcing and flashover driven damages. The electrical properties of the coating were investigated through various and comprehensive test methods. The coating showed high thermal and desirable weathering stability. Compared with bare porcelain in dry, wet, and polluted conditions, the superhydrophobic coating successfully increased the flashover voltage. Moreover, the superhydrophobic coating exhibited low leakage currents through the condensation test when exposed to high humidity conditions. With leakage currents of as low as 20 mA after three continuous steps of voltage increase, the superhydrophobic coating showed less tracking and erosion lines than the pristine coating in an adapted inclined plane test for thin films.

High-resolution flexible electronic devices by electrohydrodynamic jet printing: From materials toward applications

High-resolution flexible electronic devices are widely used in the fields of soft robotics, smart human-machine interaction, and intelligent e-healthcare monitoring due to their mechanical flexibility, ductility, and compactness. The electrohydrodynamic jet printing (e-jet printing) technique is used for constructing high-resolution and cross-scale flexible electronic devices such as field-effect transistors (FETs), flexible sensors, and flexible displays. As a result, researchers are paying close attention to e-jet printing flexible electronic devices. In this review, we focused on the latest advancements in high-resolution flexible electronics made by e-jet printing technology, including various materials used in e-jet printing inks, the process control of e-jet printing, and their applications. First, we summarized various functional ink materials available for e-jet printing, including organic, inorganic, and hybrid materials. Then, the interface controlling the progress of e-jet printing was discussed in detail, including the physical and chemical properties of the functional ink, the interfacial wettability between the ink and substrate, and the micro-droplet injection behavior in a high-voltage field. Additionally, various applications of e-jet printing in the fields of flexible electrodes, FETs, flexible sensors, and flexible displays were demonstrated. Finally, the future problems and potential associated with the development of next generation e-jet printing technology for flexible electronic devices were also presented.

Effect of a high-voltage pulsed magnetic field on microstructure, mechanical properties and corrosion behavior of as-cast biodegradable Zn-Al alloy

Abstract Zn alloys as the body’s temporary implants, it have recently aroused widespread attention by researchers in recent years. In order to meet the requirement of biomedical application, biodegradable Zn alloys should possess certain mechanical properties. To this end, it is generally required that the grain structure can be uniform and refined. In this work, a high-voltage pulsed magnetic field (PMF) was employed to homogenize and refine the as-cast biodegradable Zn-Al binary alloy. The results showed that a 6 kV PMF changes the coarse columnar Zn dendrites (739±90.9 urn) to fine spherical grains (187±16.1 urn). Accompanying the microstructural change, the compression yield strength, ultimate compression strength, tensile yield strength, ultimate tensile strength and elongation of the alloy are increased by 48.9%, &gt;11.7%, 15.1%, 29.8% and 128%, respectively. Both the electrochemical and immersion tests show that PMF accelerates the corrosion rates of the Zn-Al alloy.

Structure Refinement and Homogenization of Zn-Cu Alloys Induced by a High-Voltage Pulsed Magnetic Field During the Solidification Process

Structure Refinement and Homogenization of Zn-Cu Alloys Induced by a High-Voltage Pulsed Magnetic Field During the Solidification Process

Research on the Bipolar Microsecond Pulse Generator Using the Multistage Resonant Charging

In this article, a bipolar pulse generator based on multistage resonant charging has been proposed, which can deliver microsecond-range pulses for medical and industrial applications. The main circuit consists of two sets of identical Marx generators connected back to back with the load between them. It can flexibly output bipolar pulses with adjustable amplitude, pulse width, and frequency. In this research, six eight-stage Marx generators have been employed to verify the performance of the proposed bipolar pulse generator. From the experimental results, the proposed generator can deliver pulses with the amplitude of ±10 kV to no-load and a resistive load of 50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{k}\Omega $ </tex-math></inline-formula> . The repetitive frequency can be adjusted from 1 Hz to 1 kHz, and pulse width can be adjusted from 0.2 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$400~\mu \text{s}$ </tex-math></inline-formula> with 50 ns rising and falling time. The relaxation time between the positive and negative pulses can be determined from 0.2 to 400 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> . In the high-voltage field, the proposed Marx generator can deliver higher output voltage pulses and has smaller voltage differences between stages than the traditional solid-state Marx generator.

Design and Implementation of Ultra-Wide Band Antenna for Partial Discharge Detection in High Voltage Power Equipment

Partial discharges (PD) are the most common and harmful threat to the health of electrical insulation of high voltage (HV) and high field (HF) equipment. The occurrence of PD activity in HV and MV equipment is at the same time a cause and a sign of insulation degradation that may eventually result in the breakdown of the HV power equipment. For the safe and reliable operation of HV power equipment, continuous PD monitoring needs to be conducted conveniently to prevent any unplanned power outages and damage to electrical power equipment. The ultra-high frequency (UHF) PD measurement method has been widely used as an effective technique to detect PD activity on HV power equipment due to its non-invasive principle. To enable PD detection accuracy, there is still a need for more sensitive PD sensors that can assist the UHF PD monitoring system by suppressing ambient background noise and low-frequency electromagnetic interferences from telecommunication such as GSM signals. To tackle the sensitivity issues, this article presents a new design of ultra-wideband (UWB) microstrip patch antenna that is capable of effective suppression of low-frequency interference signals. The proposed antenna, designed, simulated, and optimized using the CST Microwave Studio software, has a bandwidth of 3.3GHz, below -10dB, in the operating frequency range of 1.2GHz-4.5GHz. The prototype of this antenna, printed on an FR4 substrate of a thickness of 1.6mm and a dielectric constant of 4.4, featuring a compact size of 100mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times100$ </tex-math></inline-formula> mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times1.6$ </tex-math></inline-formula> mm, was implemented to detect PD through laboratory experiments. This paper shows that the designed UWB antenna has high sensitivity, good noise rejection and it is, therefore, a promising candidate sensor for PD detection on HV equipment.

Research the Effect of the Negative High-Voltage Electromagnetic Field in the Target Chamber on the Characteristic X-Ray Production Cross Sections by Positrons Impacting on the Thick-Target

Research the Effect of the Negative High-Voltage Electromagnetic Field in the Target Chamber on the Characteristic X-Ray Production Cross Sections by Positrons Impacting on the Thick-Target

Высоковольтная деградация электродов, обусловленная электрохимической инжекцией в жидких диэлектриках

The results of experimental studies of the electrode degradation caused by electrochemical reactions under the action of high-voltage fields are presented. Under study were technical hydrocarbon and polymethylsiloxane (PMS) liquids, their solutions with iodine (I2) at chemically active (Cu) and indifferent (Ti) electrodes. It is shown that in hydrocarbons the Cu electrodes interact intensively with I2, and the cathodic degradation is more intense than the anodic one. The Ti electrodes do not degrade, but physical adsorption of I2 occurs on them in hydrocarbons, and a polymer film forms on them in PMS. The kinetics of degradation in time was studied.

Simulation calculation and comparative analysis of three-dimensional temperature field of ultra high voltage through wall bushing under different current carrying capacity

As the key equipment of UHV transmission and transformation line, UHV bushing needs to carry the ultra-high voltage and large current of UHV power system at the same time. When the operating temperature of UHV bushing is too high, the operation failure rate will increase significantly, which will affect the stability and safety of UHV transmission line. Therefore, it is particularly important to analyze the temperature field characteristics of UHV bushing. This paper takes UHV bushing as the research object. The finite element software is used to calculate the electro thermal coupling. The three-dimensional thermal field distribution characteristics of UHV bushing are simulated and analyzed. This paper analyzes the influence of eddy current on the temperature distribution of UHV bushing under operation condition, and discusses the influence degree of eddy current on the temperature distribution of bushing, which provides an important basis for the temperature distribution, structure improvement and operation maintenance of bushing.

Cylindrical Vector Beam for Vector Magnetic Field Sensing Based on Magnetic Fluid

Based on the unique polarization characteristic of the cylindrical vector beam, a new-type vector magnetic field sensing technique is proposed. As the cylindrical vector beam passes through a magnetic fluid film, a polarization analyzer is used to detect the polarization state change of the output light after passing through a slit. Based on the birefringence effect, the direction of the magnetic field can be resolved by the direction of the maximum ellipticity, while the magnetic field strength can be obtained by the change of the maximum ellipticity. Both of the magnetic field strength and direction in the X-Y plane could be measured simultaneously. The experimental results show that the direction error is less than 2°, the strength error is less than 10 Gs, and the sensitivity of the strength of magnetic field is 0.12 °/Gs. Therefore, the proposed technique would be promising for two-dimensional magnetic field detection and safety detection, such as high-voltage discharge magnetic field detection.

Effects of frequency and thermal conductivity on dielectric breakdown characteristics of epoxy/cellulose/BN composites fabricated by ice-templated method

Epoxy resin has been extensively used in the electrical systems and electronic devices. However, it is still a challenge to fabricate highly thermally conductive but electrically insulating epoxy composites. In this work, epoxy/cellulose/BN (EP/C-BN) composites were fabricated by ice-templated method. More importantly, the effects of frequency and thermal conductivity on dielectric breakdown characteristics, supported by the experiments of dielectric breakdown characteristics, infrared thermal imaging and finite simulation analysis, were studied. The as-prepared EP/C-BN composites exhibit a maximum thermal conductivity of 1.19 W/(m·K), and notably improved breakdown time at high frequency (324% higher than that of EP at 44 kHz). This work gives significant insight into the design of the thermal management polymers working at high frequency and high voltage fields.