Surface Electric Field Strength Research Articles

Experimental and theoretical study on the influence of bundle number on corona loss characteristics of ultra high voltage corona cage positive/negative DC conductors at high altitude

The corona loss generated by the conductor is one of the important factors in the design of ultra-high voltage (UHV) direct current transmission lines. This article is based on the high-altitude (2200 m) ultra-high voltage corona cage experimental platform built in Xining City, Qinghai Province. For the LGJ400-35 conductor used in the typical ± 800 kV DC transmission lines from Qinghai to Henan Province, positive and negative polarity corona experiments were conducted on LGJ400-35 conductors with 4, 6, 8, and 10 bundle under surface field strength conditions of 14–22 kV/cm. For the first time, corona loss data of bundle conductors in positive/negative polarity ultra-high voltage DC transmission lines were obtained, Fit the prediction formula for corona loss of transmission lines under different bundle numbers and surface electric field strengths of wires. And build a model in COMSOL Multiphysics software for simulation analysis, fitting the correction factor for the impact of wind speed on wire corona loss. The research results in the article can provide data reference and support for the construction of ultra-high voltage direct current transmission lines in high-altitude areas.

Tuning Surface Reactivity and Electric Field Strength via Intermetallic Alloying.

Many electrosynthesis reactions, such as CO2 reduction to multicarbon products, involve the formation of dipolar and polarizable transition states during the rate-determining step. Systematic and independent control over surface reactivity and electric field strength would accelerate the discovery of highly active electrocatalysts for these reactions by providing a means of reducing the transition state energy through field stabilization. Herein, we demonstrate that intermetallic alloying enables independent and systematic control over d-band energetics and work function through the variation of alloy composition and oxophilic constituent identity, respectively. We identify several intermetallic phases exhibiting properties that should collectively yield higher intrinsic activity for CO reduction compared to conventional Cu-based electrocatalysts. However, we also highlight the propensity of these alloys to segregate in air as a significant roadblock to investigating their electrocatalytic activity.

Aggregation kinetics of green tea nanoparticles: Effects of pH, metal ions, and temperature.

Colloidal nanoparticles in tea infusion are the link connecting micromolecular mechanism and macro-aggregation process of tea cream formation. In order to elucidate, the kinetics mechanism of green tea nanoparticles (gTNPs) aggregation, zeta-potentials, total average aggregation (TAA) rates, and critical coagulation concentration (CCC) in the presence of various pH and metal ions were investigated. Additionally, the effect of temperature on gTNPs aggregation was further explored. The results revealed that the TAA rate of gTNPs increased with decreasing pH values, the CCC of gTNPs increased in the order Mg2+ ≈Ca2+ <Na+ ≈K+ . The reason was that different positive ions changed the surface electric field strength of gTNPs to a different extent. Furthermore, it was indicated that low temperature could promote gTNPs aggregation in indirect way. Low temperature promoted the binding of epigallocatechin gallate (EGCG) and caffeine, and the combination between gTNPs and EGCG-caffeine complexes weakened the stability of gTNPs resulting from reduction in electrostatic repulsion. PRACTICAL APPLICATION: Tea is a popular beverage all over the world. This research revealed the mechanism of green tea nanoparticles aggregation and laid a theoretical foundation for the regulation of tea cream formation in tea beverage.

Highly sensitive fiber SPR sensor based on InSe nanosheets

Surface plasmon resonance (SPR) optical fiber sensors exhibit advantages such as small size, immunity to electromagnetic interference, and corrosion resistance, and are currently widely applied in the field of biodetection. However, their sensitivity and reusability are still limited in detecting biomolecules, trace concentrations, and weak signals. This paper proposes an approach by utilizing indium selenide (InSe) nanoflakes to enhance the surface electric field strength of the metal layer. InSe is a two-dimensional material that exhibits higher charge carrier mobility and refractive index compared to traditional two-dimensional materials, thereby promoting electron transfer and inducing a larger SPR effect. By testing the sensors composed of InSe nanosheets with different thicknesses, it is found that the sensitivity of InSe nanosheets with a thickness of 40 nm is up to 4655.76 nm/RIU, which is much higher than the sensitivity of traditional Au film sensors and 52 % higher than that of MoS2-Au film SPR sensors with the same structure. Moreover, the sensor has a higher FOM value of 33.25 RIU−1 and shows excellent characteristics in repeatability and stability experiments. In this paper, a new method is proposed to enhance the sensitivity of SPR sensors and realize the monitoring of lower biomolecule concentration and weak signal. In addition, the great potential of indium selenide nanosheets in optical applications is emphasized.

Voltage-Dependent FTIR and 2D Infrared Spectroscopies within the Electric Double Layer Using a Plasmonic and Conductive Electrode.

Strong electric fields exist between the electric double layer and charged surfaces. These fields impact molecular structures and chemistry at interfaces. We have developed a transparent electrode with infrared plasmonic enhancement sufficient to measure FTIR and two-dimensional infrared spectra at submonolayer coverages on the surface to which a voltage can be applied. Our device consists of an infrared transparent substrate, a 10-20 nm layer of conductive indium tin oxide (ITO), an electrically resistive layer of 3-5 nm Al2O3, and a 3 nm layer of nonconductive plasmonic gold. The materials and thicknesses are set to maximize the surface number density of the monolayer molecules, electrical conductivity, and plasmonic enhancement while minimizing background signals and avoiding Fano line shape distortions. The design was optimized by iteratively characterizing the material roughness and thickness with atomic force microscopy and electron microscopy and by monitoring the plasmon resonance enhancement with spectroscopy. The design is robust to repeated fabrication. This new electrode is tested on nitrile functional groups using a monolayer of 4-mercaptobenzonitrile as well as on CO and CC stretching modes using 4-mercaptobenzoic acid methyl ester. A voltage-dependent Stark shift is observed on both monolayers. We also observe that the transition dipole strength of the CN mode scales linearly with the applied voltage, providing a second way of measuring the surface electric field strength. We anticipate that this cell will enable many new voltage-dependent infrared experiments under applied voltages.

Behaviors of the water droplet impacting on subcooled superhydrophobic surfaces in the electrostatic field

The impact dynamic behavior of rainwater and the subsequent freezing process on the transmission line cause significant damage to the power grid. Therefore, a good understanding of the droplet impact and freezing process on a subcooled superhydrophobic surface under an electric field is crucial. In this study, the dynamic behavior of a droplet impacting a subcooled superhydrophobic surface at various surface temperatures and electric field strengths was visually studied. Moreover, the influence of the surface temperature and electric field strength on the contact time, maximum spread factor, rebound mode, and nucleation rate were investigated. Furthermore, the variation in rebound modes with electric field strength and surface temperature was clarified in the phase diagram. Eventually, the nucleation rate exponentially increases with an increase in the electric field strength and a decrease in the surface temperature. This study can aid in the anti-icing design of power grid systems.

Variation Characteristics of Particle Surface Electrochemical Properties during the Improvement of Reclaimed Soil from Hollow Village in Loess Area

Soil surface electrochemical properties, such as specific surface area and surface charge number, are important indexes to evaluate the agricultural soil quality change. However, there is not enough focus on the effect of different improved materials on the reclaimed soil surface electrochemical characteristics. Therefore, we selected maturing agent (TM), fly ash (TF), organic fertilizer (TO), maturing agent + organic fertilizer (TMO), fly ash + organic fertilizer (TFO), and no modified material (CK) treatment for 5 years of field location experiments to study the effects of different improved materials on the surface electrochemical properties of reclaimed soil from abandoned homestead. The results showed that, compared with CK treatment, the specific surface area, surface charge number, and surface charge density of reclaimed soil increased to 11.36–14.05 m2 g−1, 13.49–18.58 cmol kg−1, and 1.14–1.76 C m−2 after five years of application of different improved materials, respectively, and the number of surface charge under TFO, TMO, and TO treatment increased by 28.9%, 25.2%, and 37.7% compared with CK, respectively. Meanwhile, the specific surface area increased significantly (p &lt; 0.05), showing an order of TFO &gt; TMO &gt; TO &gt; TF &gt; TM &gt; CK. The surface electric field strength can reach the order of 108 V m−1. The statistical analysis results suggest that the contents of soil organic matter (SOM), silt, and clay were positively correlated with the soil surface electrochemical properties, which were the main factors for the changes of reclaimed soil surface electrochemical properties. Our research conclusion shows that in the process of reclamation of abandoned homestead in Loess Plateau, the application of different materials is helpful to improve the soil surface electrochemical properties, among which the organic–inorganic TFO treatment was a suitable improved material treatment for improving the surface electrochemical properties and fertility of reclaimed soil.

Specific cation effects on surface reactions of HgCl2 in clay-water systems

The significant complexity of the chemical forms and reactions of HgCl2 in clay-water systems make elucidating the corresponding interaction mechanisms and activities challenging. The specific ion effect and its mechanisms for HgCl2 adsorption at charged clay surfaces were investigated in this study. Experimental results showed that (1) at a fixed background concentration, the adsorption capacity and adsorption energy of HgCl2 on montmorillonite surface decreased in the order Li+> > Na+ > K+, and HgCl2 adsorption exhibited a strong specific cation effect. (2) For the same background cation (Li+, Na+ or K+), the adsorption capacity and energy of HgCl2 decreased as the cation concentration increased. An analysis of the origin of the adsorption energy for HgCl2 showed that this energy linearly increased with the surface electric field strength of montmorillonite. On the basis of orbital asymmetric hybridization theory, we speculated that specific adsorption of the HgCl2 molecule occurs via “polarization-induced covalent bonding” adsorption between O (clay surface) and Hg (HgCl2) atoms. The adsorption energy linearly increased with the surface electric field strength in the clay-water system. These findings provide useful information on modifying the physical, chemical and biological activities of HgCl2 in clay-water systems.

Effects of soil surface electrochemical properties on soil detachment regulated by soil types and plants

Soil surface electrochemical properties play an important role in soil detachment. However, the effects of soil surface electrochemical properties on soil detachment have received little attention. This study selected three typical soil types (sandy loam, silt loam and silt clay loam) and two typical herbaceous plants (Stipa bungeana Trin. and Artemisia gmelinii Web. ex Stechm., with an abandoned cropland) to quantify the effects of varied soil surface electrochemical properties caused by soil types and plants on soil detachment on the Loess Plateau, China. A hydraulic flume test was conducted under five flow discharges (0.1, 0.2, 0.3, 0.4 and 0.6 L s−1) on a 15° slope. The results showed that large differences in soil surface electrochemical properties occurred among different soil types and plant species. The exchangeable sodium percentage (ESP), cation exchange capacity (CEC), specific surface area (S), surface charge density (σ0), surface potential (φ0) and surface electric field strength (E0) ranged from 1.02% to 2.26%, from 7.26 to 24.34 cmolc kg−1, from 8.32 to 147.38 m2 g−1, from 0.09 to 2.02C m−2, from −81.33 to −149.92 mV and from 1.23 × 108 to 28.46 × 108 V m−1, respectively. The soil detachment capacity (Dc) was significantly correlated with ESP (P < 0.01), E0 (P < 0.01) and |φ0| (the absolute value) (P < 0.05). Moreover, Dc exponentially increased with |φ0| (R2 = 0.99) and linearly increased with ESP (R2 = 0.85) and E0 (R2 = 0.95). Therefore, soil surface electrochemical properties greatly varied with soil types and plants and had a significant effect on soil detachment.

Research on Electric Field Distribution and Voltage Equalization Characteristics of Tensile Insulator Strings in 750kV Substation

In the design process of the 750kV substation, the design of insulator strings is an important part. The design of insulator strings needs to ensure that the voltage borne by each insulator does not exceed its maximum voltage, the surface electric field strength does not exceed the discharge field strength, and the maximum economic benefits can be achieved simultaneously. In this paper, finite element calculation software is used to study the electric field distribution and voltage distribution of tensile insulator strings in 750kV substations. The relationship between the depth of the grading ring into the insulator string, the diameter of the grading ring, the diameter of the grading ring and the electric field distribution and voltage distribution of the insulator string is studied, and the recommended size of the grading ring for the 750kV insulator string is proposed to reduce the surface electric field strength of insulator strings and improve the voltage distribution of each piece of insulators. The research results have been applied to the 750kV substation designed by our institute.

Temperature and Electric Field Distribution Characteristics of a DC-GIL Basin-Type Spacer with 3D Modelling and Simulation

The temperature properties of real-type direct-current gas-insulated transmission lines (DC-GIL) with a basin-type spacer were investigated by the finite element method in this paper. A horizontally installed model was established and the temperature distribution was obtained with a 3D model. The specific heat capacity and thermal conductivity of the spacer were measured and applied in the simulation. The results show that the temperature of the convex surface was slightly higher than that of the concave surface. With an increase in the SF6 pressure, the temperature of the spacer decreased, which can be attributed to the improvement of convection due to increases in the heat capacity per unit volume. With an increase in the ambient temperature, the temperature of the spacer increased linearly. The temperature difference between the inner and outer parts of the spacer increased with increases in the load current. Besides, an obvious increase in the surface electric field strength appeared under the influence of the thermal gradient compared to the results without the thermal gradient. Thus, special attention should be paid to the insulation properties of the spacer considering the influence of temperature distribution. This study evaluates both the thermal and insulation characteristics of the GIL along with the spacer under various conditions.

Combined determination analysis of surface properties evolution towards bentonite by pH treatments

Bentonite possesses multiple physicochemical properties because of a large number of charges on the surface. Understanding charges-related surface characteristics at various aqueous solution conditions is critical for bentonite application in various fields, including material modification and environmental restoration. In this study, the evolution of surface properties (surface potential, surface electric field strength, specific surface area, and surface charge numbers) for bentonite samples was investigated using simple ion-exchange experiments and extended combined determination method at different pH conditions. Zeta potential, X-ray diffraction (XRD), and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) techniques were used to examine changes in bentonite structure and surface functional groups. The results demonstrated that surface potential was considerably negative (larger in absolute value) and more sensitive to pH variation than the zeta potential of bentonite under identical conditions. At multiple pH settings, the surface electric field strength and the numbers of bentonite’s surface charges were inversely proportional to hydrogen ion concentrations. Cations covalently bonded to clay’s surface might reduce negative surface charges and diminish surface electric field strength, particularly as ionic strength increased. Although moderate pH variation has no discernible effect on bentonite interlayer structural alterations, moderate clay dissolution and changes in mineralogical properties may increase the specific surface area of bentonite, particularly when the solvent chemical conditions are acidic. This study comprehensively sheds light on the evolution of surface properties of bentonite clay under acidic, neutral and alkaline conditions, which is helpful in understanding and optimizing its surface performance for material and environmental applications.

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.

Alteration of soil-surface electrochemical properties by organic fertilization to reduce dissolved inorganic nitrogen leaching in paddy fields

Dissolved inorganic nitrogen (DIN) adsorbed onto soil colloids plays an important role in soil N leaching, but previous studies have not clearly defined the mechanisms of this process in paddy soils under organic fertilization. In this study, we investigated how ongoing fertilization can change soil DIN leaching via affects on soil-surface electrochemical properties and physical properties, and the main influences of soil properties on DIN leaching were characterized. Five fertilization regimes applied during a 5-year field experiment were employed to study this mechanism, i.e., no fertilizer, chemical fertilizer, chemical fertilizer plus hog manure, hog manure, and chemical fertilizer plus oil cake. Increasing levels of applied manure decreased DIN leaching from the soil profile, especially for NH4+, the main form of DIN in the leachate and soil. Compared to chemical fertilizer, organic fertilization changed the surface electrochemical and physical properties more effectively with regards to decreased soil bulk density (9.84–20.49 %, P < 0.05) and specific surface area (26.38–44.88 %, P < 0.05), as well as enhanced water-holding capacity (19.05–42.86 %, P < 0.05) and the number and density of soil-surface charges (7.97.55–98.44 %, P < 0.05). Furthermore, organic fertilization significantly increased the NH4+ adsorbed by soil. Structural equation modeling showed that soil-surface electrochemical properties had the greatest impact (β = –0.88, P < 0.05) on the NH4+ content of the leachate when compared with the soil NH4+ adsorption capacity and physical properties. The increase in the soil-surface charge, surface charge density, surface potential, and surface electric field strength under organic fertilization increased soil NH4+ retention in soil (P < 0.001), and thus, these changes decreased the risk of NH4+ leaching. Our results suggest that continuous substantial organic fertilization may mainly decrease early DIN leaching from cultivated paddy soils in the Dongting Lake area by altering soil-surface electrochemical properties, where soil-surface electrochemical properties can be set as an internal factor to predict soil ion migration in agriculture systems, such as the Dongting Lake area or other similar regions.

Research on corona discharge suppression of high-voltage direct-current transmission lines based on dielectric-film-covered conductor

Corona discharge suppression for high-voltage direct-current (HVDC) transmission lines at line terminals such as converter stations is a subject that requires attention. In this paper, a method based on a conductor covered with dielectric film is proposed and implemented through a bench-scale setup. Compared with the bare conductor, the corona discharge suppression effect of the dielectric-film-covered conductor under positive polarity is studied from the composite field strength and ion current density using a line-plate experimental device. The influences of film thickness and film material on the corona discharge suppression effect are investigated. The charge accumulation and dissipation characteristics of different film materials are also studied. The results show that the conductor covered with dielectric film has excellent ability to inhibit corona discharge. The ground-level composite field strength of the conductor covered with dielectric film is lower than its nominal field strength, and its ion current density is at the nA m−2 level. The corona threshold voltage can be promoted by increasing the film thickness, but the ability to inhibit corona discharge becomes weak. The larger the surface electric field strength, the more charge accumulated, but the faster the charge dissipation rate. Compared with polyvinyl chloride film, cross-linked polyethylene film has stronger charge accumulation ability and slower charge dissipation rate, which can better restrain the corona discharge of HVDC transmission lines.

Effects of soil surface electric field on aggregates breakdown and water erosion in black soil region of Northeast China

Through quantitatively adjust soil electric field, we investigated the effect of soil electric field on aggregate stability and soil erosion in black soil region of Northeast China with the experiments of wet sieving and rainfall simulation. Results showed that: 1) Soil surface potential absolute value and electric field strength increased with the decreases of electrolyte concentration in bulk solution. Soil electric field strength could reach to 108 V·m-1. 2) With the increase of soil electric field strength, the degree of fragmentation of soil aggregates increased and the mean weight diameter (MWD) decreased sharply first and then kept constant. 3) With decreasing electrolyte concentration and increasing surface potential, the amount of soil loss increased. As the electrolyte concentration was &lt;0.01 mol·L-1, the corresponding soil surface potential was &gt; 210 and 209 mV for Bin-xian and Keshan, respectively, the cumulative amounts of soil loss with rainfall time almost overlapped, suggesting that the electrolyte concentration of 0.01 mol·L-1 was the threshold for soil erosion. 4) There was a linear relationship between soil cumulative loss and MWD. Our results indicated that soil electric field strength increased as the rain enters into the soil, which could induce soil aggregate breakdown and release amounts of fine soil particles. Finally, soil erosion occurred under the driving of flowing water. Our results provided insights into the mechanism underlying soil erosion in the black soil region of Northeast China.

Soil organic matter and silt contents determine soil particle surface electrochemical properties across a long-term natural restoration grassland

Vegetation restoration is an effective way to rebuild degraded ecosystems and restore soil function. Soil surface electrochemical properties, including specific surface area, cation exchange capacity, surface charge density, surface electric field strength, and surface potential, are often used as indicators to evaluate agricultural soil quality and fertility. However, little attention has been payed to the effect of natural revegetation on soil surface electrochemical properties. In this work, we selected a grassland restoration chronosequence (slope cropland, 0 years; natural grasslands restored for 3, 8, 22 and 24 years, i.e. NR3, NR8, NR22 and NR24, respectively) to investigate the changes of soil surface electrochemical properties along with vegetative restoration. Our results showed that surface charge density and surface potential for restored grassland ranged from 0.16 to 0.20 C m−2 and from −94 to −109 mV, with an average of 0.18 C m−2 and −101 mV, respectively. The value of surface electric field strength could reach to the order of magnitude of −107 V m−1 and showed a decreasing trend with increasing period of natural vegetation recovery. Cation exchange capacity and specific surface area significantly increased with the extension of natural restoration period except for NR3 (P < 0.05). It was found that soil organic matter (SOM) and silt content were the main factors to determine cation exchange capacity and specific surface area. Both cation exchange capacity and specific surface area were closely related to silt content but weakly related to clay content, possibly due to the high silt content in our studied soils. Moreover, cation exchange capacity and specific surface area showed a significant linear relationship with SOM, which may be ascribed to the diversity in cation substitution sites and high specific surface area of SOM. Our results indicated that the long-term natural restoration of grassland contributed to the improvement of cation exchange capacity and specific surface area.

Investigation of audible noise performance of HVAC conductor bundles at altitude of 2261 m

Extra or ultra-high voltage transmission lines can exhibit strong corona discharge and generate severe audible noise (AN) at high altitude areas, which has become a critical limiting factor for power lines construction. However, the AN data of bundle conductors at high altitude are very rare, which cannot support the power utilities adequately to make reasonable conductor selection. In this paper, sound pressure level (SPL) of 14 types of bundle conductors were investigated by using an ultra-high-voltage (UHV) corona cage (8 m × 8 m × 35 m) at altitude of 2216 m, where the bundle number between 4 and 12 and the conductor types may be used in 500 kV, 750 kV or 1000 kV power transmission project. Then many valuable AN data were obtained; the influence of bundle number and subconductor diameter on acoustic power density level (PWL) were analyzed; and an A-weighted PWL calculation method was proposed. Besides, by comparing the AN data obtained from the low-altitude area (altitude: 23 m), the AN altitude correction factor was concluded, and the influences of conductor parameters and the surface electric field strength on correction factors were discussed. The results obtained in this paper can provide important data for the construction of high-altitude alternating current (AC) power lines.

An insulation design rule for spacer in SF6/N2-filled DC gas insulated apparatus

A recurring challenge of a DC SF 6 /N 2 -filled GIS/GIL apparatus is the charge accumulation at DC stress. The conventional design rules and knowledge of AC spacers may not be applicable for this new type of apparatus. A novel design rule is proposed considering the effect of accumulated charge on the threshold of electric field strength resistant to the superposed voltage. A surface charge accumulation simulation model is introduced, and the key parameters in the simulation model are measured. In addition, an experimental platform for a 100 kV spacer flashover test is established. Spacer flashover tests under superimposed voltage with opposing polarities are carried out, and the withstanding voltage of the spacer is obtained. Finally, based on the proposed model, the threshold of the surface electric field strength (tangential component) on the DC spacer in SF 6 /N 2 mixed gases is discussed. For the reliable insulation design of a DC GIS/GIL apparatus filled with 0.7 MPa SF 6 /N 2 , the threshold of surface electric field strength on the DC spacer is 12 kV/mm. The insulation design rule can be referenced in the design of a high-voltage DC SF 6 /N 2 -filled GIS/GIL apparatus.

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.