Surface Electric Field Intensity Research Articles

Research on methods to increase the flashover voltage of supporting insulators in Tesla transformers.

This paper presents three methods aimed at enhancing the flashover voltage of the supporting insulator in a Tesla transformer. These methods include optimizing the maximum electric field on the insulator surface, adjusting the overall structure of the insulator, and changing the surface structure of the insulator. Ten insulator samples with different structures were designed based on electric field simulation. Subsequent experiments were conducted to validate the effectiveness of these methods in improving flashover voltage. On this basis, the supporting insulator of the Tesla transformer was redesigned, leading to an increased output voltage. The results are summarized in the following. First, optimization of the shielding rings of the cathode and anode reduces the electric field at the triple junction, which significantly increases the flashover voltage. Second, extending the inclination starting position of insulators with the same inclination angle effectively reduces the surface electric field intensity and increases the flashover voltage. Third, increasing the inclination angle within a certain range while keeping the inclination starting position constant extends the creepage distance and enhances the flashover voltage. However, excessively large inclination angles may lead to a decrease in flashover voltage due to excessive normal electric field. Fourth, grooving on the insulator surface at appropriate locations can inhibit the development of the streamer and improve flashover voltage. Finally, the supporting insulator of the Tesla transformer was redesigned based on these results, elevating the output voltage from 750kV to over 1 MV.

Effects of the Changes of Particle Surface Electric Field and Interaction Force on the Reclaimed Soil Aggregate Structural Stability under the Application of Different Soil Conditioners

Aggregate stability is a key factor in the evaluation of soil structure and erosion resistance, which is largely influenced by soil electric field and particle interaction. However, there are few studies on how different organic and inorganic soil conditioners change the surface electric field and interaction force of reclaimed soil to improve the aggregate stability. Therefore, a five-year field experiment was conducted to quantitatively study the effects of FeSO4 (TM), organic fertilizer (TO), fly ash (TF), maturing agent + organic fertilizer (TMO) and fly ash + organic fertilizer (TFO), compared with control (CK) treatment, on the reclaimed soil internal force and the aggregate crushing strength. The results showed that the reclaimed soil surface potential and electric field intensity increased after 5 years of application of organic and inorganic soil conditioners. Under the same electrolyte concentration and electric field conditions, the crushing strength of aggregates (<5 μm) treated with TFO, TMO, TO, TF and TM decreased by 43.70%, 35.51%, 25.97%, 8.28% and 5.49%, respectively, compared with the control treatment, and the combination of organic and inorganic treatment (TFO and TMO) had a better effect on improving the aggregate crushing resistance. With the application of soil conditioners, the reclaimed soil DLVO force and net resultant force gradually decreased, and the order of magnitude was TFO < TMO < TO < TF < TM < CK, indicating that the application of organic and inorganic soil conditioners enhanced the van der Waals attractive force and net attractive force between reclaimed soil particles, and reduced the net repulsive force between particles. The theoretical calculation results of the reclaimed soil internal force well explain the experimental results of aggregate stability against crushing, and the relationship between aggregate crushing strength and net resultant force is exponential (p < 0.01). Generally speaking, the soil conditioners increase the net attractive force between particles, reduce the possibility of violent crushing of aggregates due to the increase of electric field intensity and improve the aggregate structural stability, among which the combined application of organic and inorganic soil conditioners has a better improvement effect. The results of this study will lay a theoretical foundation for clarifying the improvement of different soil conditioners on the reclaimed soil structural stability and erosion resistance.

Analysis and design of overmoded coaxial Ku-band Cerenkov high power microwave oscillator with high efficiency

An overmoded coaxial Ku-band Cerenkov high power microwave oscillator with high efficiency is proposed. The distance between the inner and outer conductors of the slow wave structure (SWS) in the Cerenkov oscillator is smaller than the space wavelength of output microwave. The overmoded structure can increase the power capacity of the oscillator by increasing the transversal size of the device. The higher-order modes are introduced into the beam-wave interaction region intentionally, so that the intense relativistic electron beams (IREB) interacts with the fundamental and higher-order modes. Dual-mode operation leads impure mode component to output microwave, so the simple trapezoid inner conductor is designed to achieve mode purification and output pure TEM mode. The extractor is added at the end of the SWS, which enhances the axial electric field near the location and increases the modulation depth of the electron beam current passing through the region. The particle-in-cell (PIC) simulation results show that under the input power of 3.5 GW, the output microwave power is 1.8 GW, and the corresponding working efficiency is 51.4%, which is much higher than that of similar periodic devices. The mode of output microwave is pure TEM mode, and the maximum surface electric field intensity is 0.96 MV cm−1, which means that the probability of radio-frequency breakdown is low.

Analysis of interface mode localization in disordered photonic crystal structure

A disordered photonic crystal (D-PhC) structure is analyzed to study the interface mode localization characteristics. The design comprises a bilayer-disordered PhC structure, where layers are arranged in Thue–Morse sequence (TMS). The impact of local symmetric substructures on eigenstates coupling is also considered over a wider wavelength range. The mode hybridization study is carried out for varying refractive index contrast values of TMS structures at an operating wavelength of 550, 632.8, and 750 nm, respectively. The dispersion analysis confirms the localization of bulk guided, and edge-guided modes for different incidence angles at the structural local resonators. Further, increasing the RI contrast value leads to generation of hybrid interface modes of very high electric field intensity. Thus, showing its potential applications in both sensing and light guiding applications. Moreover, because of the higher surface electric field intensity this structure can also be used for fluorescence-based detection and surface-enhanced Raman spectroscopy as well.

Development of Future Compact and Eco-Friendly HVDC Gas Insulated Systems: Test Verification of Shape-Optimized DC Spacer Models

Spacers for the HVDC GIS/GIL play an important role in mechanically supporting conductors and separating compartments. At the same time, their insulation performance affects the stability and safety of system operation. Design rules and knowledge specific to AC spacers do not apply to those of DC spacers. Considering the shape influence on the surface electric field intensity of the spacer under HVDC applied voltage, as determined in our previous work, an optimized shape of a spacer model based on finite element electric field calculations and using standard HVAC alumina filled epoxy material and two novel types of materials were studied. The simulation’s results show that the DC shape optimization of the spacers can effectively reduce the electric field magnitudes along the spacer under different temperature gradients. To verify practically these findings, this paper presents the reduced scale gas insulated prototype that was constructed, the optimized DC spacers that were fabricated and the DC testing results using SF6-free surrounding gas: C4-Perfluoronitrile (C4-PFN, 3MTM NovecTM 4710)/CO2 and Trifluoroiodomethane (CF3I)/CO2. The results show that the shape-optimized spacer models made of conventional HVAC filled epoxy material have successfully passed the tests up to the maximum applicable ±123 kV DC exceeding thus ±119 kV DC that corresponds to the nominal voltage ±500 kV DC of the full scale.

Coupling plasmon-waveguide resonance and multiple plasma modes in hyperbolic metamaterials for high-performance sensing

A sensor based on plasmon-waveguide resonance (PWR) exhibits an impressive narrow linewidth and has attracted extensive attention in plasmon label-free sensing. However, the low surface electric field intensity limits the detection ability of biomolecules, where the refractive index changes are restricted at the sensor surface. In this study, we study the coupling of PWR and multiple plasma modes in a hyperbolic metamaterial (HMM), combining narrow linewidth and electric field enhancement advantages. The PWR-HMM sensor includes a gold film, lossless dielectric layer, and metal/dielectric multilayer HMM array composed of 2-layer Au/Al2O3 stacks. The evanescent field of PWR is used to excite multiple plasma modes in the HMM. The figure of merit of the proposed structure reaches 5417/RIU owing to the existence of lossless dielectric layer, which is 11.7 times than the conventional gold film structure. The maximum bulk sensitivity of the PWR-HMM sensor was 43 000 nm/RIU. In comparison with PWR, the surface electric field intensity and the surface sensitivity of PWR-HMM increase by four and two times, respectively. Furthermore, comparing the sensing performance of the PWR-HMM sensor and PWR-nanoparticle (NP) sensor (coupling PWR and localized surface plasmon resonance), it was found that PWR-HMM has 20% higher surface sensitivity than the PWR-NP. A sensing mechanism coupling PWR and multiple plasma modes in the HMMs opens a gate to significantly improve the PWR sensors performance, which is expected to be used to resolve urgent issues in biological, medical and clinical applications.

Study of laser-induced periodic surface structures on different coatings exhibit super hydrophilicity and reduce friction

This study aims to induce a laser-induced periodic surface structure (LIPSS) on different coatings using a picosecond laser. An energy dispersive X-ray (EDX) spectroscopy analysis was performed, and wettability and friction tests were performed. Additionally, the surface electric field intensity (EFI) distribution was analyzed using the finite element method (FEM) to study LIPSS generation on different coating morphologies. The EDX results demonstrated that the LIPSS induced on the TiN coatings did not destroy them; however, the TiCN coatings were oxidized in the LIPSS fabrication process. The numerical simulation results indicated that the surface EFI and depth of the surface roughness were significantly linear, and the EFI was significantly related to the refractive index and extinction coefficient of the coating material. The wettability and friction test results implied that the LIPSS on different coatings could exhibit super hydrophilicity and played a role in friction reduction.

Effect of Relative Humidity on the Surface Electric Field Intensity Characteristics under DC Voltage in a Corona Cage

The effect of relative humidity on the surface electric field (SEF) strength and a new non-contact assessment method based on space charge density were studied. The purpose of using space charge was to assess the SEF accurately, particularly after corona occurs. Space charge measurement and SEF evaluation were conducted at a relative humidity of 40% to 90%. The change law of SEF after corona occurs at different relative humidity was obtained. Results showed that under the same relative humidity, the space charge density increases with the applied voltage, while the SEF decreases with voltages after corona occurs. As the humidity condition aggravated, SEF first increases and then decreases, and the turning point is about 70%. The distribution of charge density has an opposite change trend. The variation of charge density and SEF demonstrates that the two have mutual inhibition. Meanwhile, the change formula of SEF shows that the electric field intensity on the wire surface is not constant after corona occurs. The corona discharge experiment and theoretical research can be further carried out based on the results in this paper.

Research of electric field strength on surface of conductor and its splitting type used in extra high voltage substation

Extra high voltage substation is an important part of the whole project locates in high altitude area, so corona audible noise exists around the operation equipment, mainly concentrated in the bundle conductor in the power station. This research on the split form and surface electric field intensity distribution of bundle conductor has a certain degree of theoretical and practical engineering application value. In this paper, an analysis of the classic formula illuminates the conductor split form, conductor diameter, bundle spacing and other factors how to affect the largest surface electric field intensity of the conductor. On this basis, we take a typical extra high voltage substation conductor as the research object. The three-dimensional model of the actual power station has been established with application of finite element simulation method in accordance with actual structure, and a preliminary calculation of surface electric field intensity also been obtained. According to the results, we analyze the reasons cause the serious corona. Then we design three-split conductor instead of two-split one, and make a comparative analysis between the two different forms. According to the three-split form mentioned above, the conductor diameter and bundle spacing are optimized. The research on the electrical field calculation and split form of bundle conductor provides references for the design of substation, and has practical value for the reduction of corona noise.

Electrostatic analysis and preliminary design of transmission line for the CRAFT NNBI test platform

Based on the development of Experimental Advanced Superconducting Tokamak (EAST), Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) has launched the project of China Fusion Engineering Test Reactor (CFETR). In order to explore and master fusion DEMO level key technologies, build key prototype systems for CFETR, a Comprehensive Research Facility for Fusion Technology(CRAFT)is being established. Negative-ion based Neutral Beam Injectors (NNBI), as one of the important parts of CRAFT, can provide neutral beam with 200∼400 keV beam energy and 2 MW beam power. Stable high voltage transmission is needed for the establishment and safe operation of NNBI. As one of the key components of high voltage transmission, transmission line (TL) plays an extremely important role. In this paper, four indexes, including the maximum electric field intensity (Emax), the inner surface electric field intensity (Esur) of the electromagnetism interference screening (EMIS), the equivalent distributed capacitance (Ceq) and the electric field non-uniformity coefficient (f), are used to evaluate the electric field performance of TL. And the relationship between these indexes and the position of acceleration grid (AG) conductor, the position of extraction grid (EG) conductor and the radius of EMIS is obtained by finite element (FE) analysis. Under the requirements of Esur and f, in order to reduce the maximum electric field intensity in the TL and equivalent distributed capacitance of the TL, the layout position of the TL is determined, which lays some theoretical foundations for the engineering design of the TL.

A method for measuring surface electric field intensity of insulators based on electroluminescent effect

The measurement for the surface electric field intensity of insulators based on electroluminescent effect is a non-contact measurement. By spraying a coating of epoxy paint mixed with ZnS:Cu electroluminescence powder on the surface of insulators, the part with high surface electric field intensity would be the first to glow. As the applied voltage increases, the area of luminous and the brightness increase. Therefore, the surface electric field distribution can be deduced by photographing and analyzing the luminescence of insulator surface coating. This method has successfully measured the surface electric field intensity distribution of disc insulators in GIL. Without the use of electric field probe, this method eliminates the electric field distortion caused by the probe completely. Besides, the permittivity of the coating can be decided according to the permittivity of the insulator material, and so eliminate the electric field distortion caused by the coating. The measure results of this method are in good agreement with reality.

Impact of In Situ Radome Lightning Diverter Strips on Antenna Performance

Lightning diverter strips are commonly used to protect the antenna and sensitive equipment within an airborne radome. This article compares the impact of solid metallic and segmented diverter strips on the radiation properties of the enclosed antenna. Solid metallic and segmented diverter strips of different segment profiles, i.e., square, circular, and diamond, are considered. This article reports how the placement of diverters on the radome and their geometric detail affect the antenna parameters, namely reflection coefficient and far-field pattern. Furthermore, the surface electric field intensity on segmented diverter strips is analyzed for different shapes, sizes, and separations between the metallic segments.

Study on atmospheric air glow discharge plasma generation and surface modification of carbon fiber fabric

AbstractOn the basis of a thin‐wire contact electrode structure, a nonuniform electric field is designed to realize diffuse discharge in atmospheric air. A new method of high‐efficiency treatment of carbon fiber fabrics by glow discharge plasmas at low discharge voltage is proposed. Through this method, carbon fiber fabrics are directly used as electrodes, the plasmas are directly formed on the surface, and a strong electric field region can be formed on the surface of carbon fiber fabrics. The high‐active plasmas generated in this study can not only introduce nitrogen functional groups that are difficult to be introduced by traditional air plasma treatment methods and a large number of oxygen functional groups on the surface of carbon fiber fabrics but also improve the surface roughness and wettability of the material. In addition, the important effects of surface electric field intensity and plasma treatment time on the modification effect were investigated. It lays a good technical foundation for the industrial application of carbon fiber surface modification with high efficiency and continuity in atmospheric air.

Cu@C core-shell nanoparticles with efficient optical absorption: DDA-based simulation and experimental validation

The cost-effective copper (Cu) nanoparticles and core/shell derived architectures with novel physicochemical properties have received tremendous attention in recent years. Herein, the effect of nanoparticle geometry (including diameter and core/shell ratio) on optical scattering and absorption of Cu@C core/shell nanoparticles has been investigated through a combination of DDA-based simulation and experimental validation. Simulated results have shown that the localized surface plasmon resonance (LSPR) peaks of Cu@C core-shell nanoparticles present slightly blue-shift with the increase of core/shell ratio, the core/shell ratio play the dominant role in the shift of the LSPR peak. Moreover, scattering efficiencies factors are inclined to be increasing faster with particle size and core/shell ratio increase, corresponding to enhanced surface electric field intensity which originated from excessive electron concentration on the interface between Cu core and C shell. Finally, experimental optical absorption performance has been performed with the aim at confirmation of size-sensitive light scattering behaviors of Cu@C core-shell nanoparticles via metal organic chemical vapor deposition technology. Results have found that the light absorption coefficient of up to 99.4% could be achieved for nanoparticles with an average particle diameter of 10 nm, while 98.9% for 23 nm. Further decrease in diameter on the nanometer scale is demonstrated to promote optical absorption to a certain extent, which agrees well with simulated results. All these findings have demonstrated ultra-small Cu@C core-shell nanoparticle to be a promising candidate for efficient optical absorption, and are beneficial for design and development of Cu@C core-shell nanoparticles enabled optical-based devices.

Corona onset criterion and surface electric field intensity characterized by space charge density

The accurate evaluation of corona onset criterion in air gap under high voltage has important theoretical and practical significance, but it is calculated and measured inaccurately at present because of the distortion caused by space charge. In this study, space charge density is measured by contactless acoustic device and it can directly determine the corona onset voltage and surface electrical field. The direct detection of space charge can eliminate the distortion of charge when other parameters are used to measure corona onset criterion. The experimental onset voltage in this work are compared with that calculated by Peek's formula, corona current and photon number. Results demonstrate the applicability and accuracy of this method. In the other hand, maximum space charge ratio is adopted to analyze the change rule of surface electrical field. It is found that the surface field strength is not constant after corona occurs and should be lower than the onset electrical field. This study provides a feasible approach to further study the effect of space charge on corona onset criterion in air gap.

Variation of surface electric field intensity determined by space charge density at different temperatures

Surface electric field (SEF) strength plays an important role in studying corona discharge and is widely utilized in the research of corona loss and ion flow field in transmission line projects. The electrical field invariant theory after corona occurs is widely adopted to describe the SEF, but it is not consistent with the actual corona discharge situation. Thus, how to accurately evaluate the change of SEF is crucial for the design of overhead lines. Space charge caused by corona around the wire surface is closely related to the SEF; therefore, it is feasible to use the space charge to characterize SEF. In this work, a system for space charge density measurement is established in the laboratory to analyze the distribution of space charge under different voltages and temperatures. The validity of the experimental results was verified by finite element method (FEM), and the maximum charge density ratio is proposed to correct the variation formula of SEF. The experimental results show that SEF is not equal to the onset field intensity, and displays a decreasing trend after corona initiates, which can be used to rectify the electrical field invariant theory.

Investigations into the mechanisms of electrohydrodynamic instability in free surface electrospinning

AbstractFree surface electrospinning is a continuous electrospinning method for low-cost, massive production of nanofibers. The interjet distanceλis a critical parameter in free surface electrospinning, which directly determines the nanofiber production efficiency. In this investigation, we studied the interjet distance during free surface electrospinning based on electrohydrodynamic instability theoretically and experimentally, with special interest focused on the effect of surface tension and electric field intensity on the interjet distance. The experimental results indicated that the critical parameters affecting the interjet distance were the surface tension and applied voltage, which was in good compliance with the theoretical prediction. The relationship between interjet distanceλand surface tension followed an allometric law with positive exponential function, and the relationship between interjet distanceλand applied voltage followed an allometric law with negative exponential function. The present results can be used to understand the basic parameters which determine the interjet distance in free surface electrospinning.

The effect of air pressure on the surface electric field intensity characteristics under negative DC corona discharge in a corona cage

The accuracy of surface electric field (SEF) is important for the research of corona discharge, both in numerical simulation and actual application. However, it is widely considered that the SEF is invariable after corona occurs (Kaptzov’s assumption). This theory makes corona study more convenient, but slightly inconsistent with the actual situation. In this work, the influence of air pressure on SEF intensity and distribution of space charge density under negative DC corona discharge is studied in corona cage via sound pulse method and maximum charge density ratio. The most important finding in this work is that when the voltage gradient is greater than the onset voltage, contrary to popular perception, SEF is not a fixed value and lower than the onset field intensity. And a linear negative correlation between the space charge density and the SEF intensity after the corona initiates is found for the first time. In addition, the SEF intensity has a decreasing trend with the applied voltage rising after corona initiates, and rises slightly with the increase of air pressure. The change of space charge density with applied voltage and air pressure is opposite to the change of electric field.

Determination of electric field intensity during microwave heating of selected vegetables and fruits

In microwave heating process, electric field intensity is the main parameter that controls the temperature rise in the material. With this parameter and available material properties, temperature changes are predictable. In this study, a new setup based on a domestic microwave oven was developed and uniform microwave radiation at 2450 MHz was lunched normal to the base of pre-prepared cylindrical samples. Different vegetable and fruit samples including apple, banana, carrot and potato were exposed to microwave radiation and their surface temperature changes were measured. Surface electric field intensity was determined by means of temperature rise, time and sample’s properties. Then, outside electric field intensity was obtained from the relation with surface value using a newly developed relation and compared with previous works. The calculated values were very close and reliable compared with previous methods.

Compositional accuracy of atom probe tomography measurements in GaN: Impact of experimental parameters and multiple evaporation events

A systematic study of the biases occurring in the measurement of the composition of GaN by Atom Probe Tomography was carried out, in which the role of surface electric field and laser pulse intensity has been investigated. Our data confirm that the electric field is the main factor influencing the measured composition, which exhibits a deficiency of N at low field and a deficiency of Ga at high field. The deficiency of Ga at high field is interpreted in terms of preferential evaporation of Ga. The detailed analysis of multiple evaporation events reveals that the measured composition is not affected by pile-up phenomena occurring in detection system. The analysis of correlation histograms yields the signature of the production of neutral N2 due to the dissociation of GaN32+ ions. However, the amount of N2 neutral molecules that can be detected cannot account for the N deficiency found at low field. Therefore, we propose that further mechanisms of neutral N evaporation could be represented by dissociation reactions such as GaN+→ Ga++ N and GaN2+→ Ga2++ N.