Sparks in a small gap between HV spherical metal electrode andcorona-charged organic film

Sparks between a spherical metal electrode and corona-charged organic film were studied in air at room temperature. dc and impulse high voltages (HV) were applied to the spherical metal electrode, the polarity of which was opposite to that of the charge on the film. The maximum surface voltage of the corona-charged film was ±2 kV. The gap length was studied in the range 0.2 to 2.5 mm. Films of PTFE, PP, PS and PET of thickness 30 to 50 μm, were tested. In the case of negatively charged films, the electric field strength depended on the film material; the spark field strength decreased in the following order: PTFE⩾PP>PS⩾PET. The dependence of spark field strength on the material of negatively charged film was observed under both dc and impulse voltage applications. In the case of the positively charged films, the spark field strength showed less dependence on the film material. The experimental results are explained in terms of the degree of electron emission from negatively charged PTFE being higher than that from negatively charged PET     

The impact of electrode dielectric coating on the insulationintegrity of GIS/GITL with metallic particle contaminants

Coating the inside surface of gas insulated switchgear (GIS) enclosures with a dielectric film reduces the deleterious effect of electrode surface roughness, impedes the development of metallic particle initiated microdischarges, increases the field required to lift particles, and reduces the charge acquired by particles, all of which help alleviate the adverse effect of contaminating metallic particles on insulation withstand. The performance of particle-contaminated compressed gas systems with dielectric coated electrodes is analyzed. Two mechanisms for the transfer of charge from electrodes to contaminating particles are considered, namely, conduction through the coating layer and microdischarges in the surrounding gas. The paper presents an electrostatic study of the particle lifting fields with dielectric covered electrodes. The overall breakdown strength of the system is evaluated and the results are discussed in the light of experimental findings     

A finite-element analysis of the electrostatic force on a uniformlycharged dielectric sphere resting on a dielectric-coated electrode in adetaching electric field

In the electrophotographic process, charged toner particles are transferred from one surface to another with an electric field. To enable electric field transfer of toner, the externally applied field strength must be greater than a threshold value, so that the Coulomb force can overcome the toner adhesion force at the supporting surface. In this paper, the threshold field strength to detach a charged dielectric particle is determined efficiently by using the Galerkin finite-element method to simultaneously solve the Laplace equation for the field distribution and an overall constraint equation for the force balance. This computational method also enables calculation of the electrostatic adhesion force and is applicable to various particle-electrode configurations. For illustrative purposes, however, we consider the axisymmetric problem of electric field detachment of a dielectric sphere with uniform surface charge resting on a planar dielectric-coated electrode. The analysis is particularly focused on the dependence of the electrostatic force upon the dielectric overcoating thickness and spacing between parallel plate electrodes. The electrostatic force on a uniformly charged particle in contact with a surface is found to be influenced significantly by the thickness of dielectric overcoating and the spacing between electrodes when either becomes less than five times the particle radius     

Charge acquired by a spherical ball bouncing on an electrode: comparison between theory and experiment

A conducting ball immersed in a poorly conducting liquid between two horizontal plates acquires a charge when subjected to a dc voltage. When the applied voltage is high enough for the electric force to overcome gravity, the ball rises, moves up through the liquid and falls down as its charge leaks away. The threshold of voltage, as well as the time of flight between contacts, depends on the charge acquired by the ball during the contact with the electrode. Experiments have been done using liquids of different conductivities and it was shown that the conductivity does not affect the lift-off voltage. When the ball gets close to the electrode a discharge occurs and a current pulse is registered by the external circuit. The charge carried by the pulse is an order of magnitude smaller than the charge transferred to the ball from the electrode. We have made a detailed study, with different balls and liquids, of the charge transferred to the external circuit. The dependence on the different parameters of the ratio charge transferred to the circuit-charge acquired by the ball is explained using the coefficients of capacity of the electrostatic system.     

Ozone generation in dry air using pulsed discharges with andwithout a solid dielectric layer

Energy efficient generation of ozone is very important because ozone is being used increasingly in a wide range of industrial applications. Ozonizers usually use dielectric barrier discharges and employ alternating current (ac) with consequent heat generation, which necessitates cooling. In the present study, very short duration pulsed voltage is employed resulting in reduced heating of the gas and discharge reactor. A comparison of ozone generation in dry air using a coaxial concentric electrode system with and without a solid dielectric layer is reported. Two types of dielectric layers were employed, ceramic and polyvinylchloride (pvc). The effects of peak pulsed voltage (12.5 to 62 kV), reactor length (0.1 to 1 m), pulse repetition rate (25 to 400 pulses per second, pps), gas flow rate (1.5 to 3.0 1/min) and variation of the pitch length of the spiral wire forming the central electrode (5 to 10 mm) on the concentration and production yield of ozone (g/kWh) are reported. A comparison is made between the performance of discharge reactors with (ceramic reactor Type IIC and pvc reactor Type IIP) and without (reactor Type I) a dielectric layer, using the same electrode gap separation (15 mm) and reactor lengths (0.157 and 1 m). High production yields of ozone in dry air of ~125 52 and 60 g/kWh were obtained when using, respectively ceramic, pvc, and no dielectric layer, for a fixed pulse rate of 100 pps, 15 1/min now rate and for a relatively short length of the reactor of 157 mm     

Iridium thin film as a bottom electrode for high dielectric (Ba,Sr)TiO3 capacitors

Abstract

We propose Ir thin films as new electrode materials for high dielectric BST capacitors. Ir was found to be superior to Pt in a number of aspects such as resistivity, adhesion and surface roughness. The Pt/BST/Ir/SiO₂/Si capacitors showed leakage currents as low as Pt/BST/Pt/SiO₂/Si ones, but higher capacitance resulted. For endurance properties with +5V unipolar pulse trains, the dielectric constant of BST films on Ir decreased by only 10% below its initial value after switching of 10⁹ cycles while that on Pt degraded by 30% after 10⁸ cycles. Ir bottom electrode effects on BST film properties were well explained by the formation of IrO₂ phases on the surface of Ir electrodes.     

Electric field and space charge of spherical electrode at highvoltage concentric with a grounded conductive sphere

The solution of the space-charge Poisson's equation is presented for a spherical electrode at high voltage concentric with a grounded conductive sphere. The obtained electric field is given in terms of the ion current emitted by the electrode and an integration constant. Both parameters are functions of boundary conditions. Using measured values of the ion current for a range of boundary conditions and applying these boundary conditions to determine the integration constant suggest a minimum value for the ion mobility of 1.9×10^-4 m² /V.s. Approximate formulas for the ion current and the electric field in terms of the independent parameters were also developed. Also, it was shown that this spherical system with its solution can be used to make accurate evaluation of the ion mobility. The obtained solutions can be applied with good approximation to many practical electrostatic systems involving point electrode at high voltage generating ions. Although the subject matter is very general and could have a fundamental research aspect, in this paper, it is meant to be applied to the area of electrostatic powder paint coating. Therefore, all the examples of boundary conditions and illustrations are typical of the electrostatic powder paint coating     

The structure and dielectric properties of thin PZT-type ferroelectric films with a diffuse phase transition

Abstract

By means of r.f. sputtering of the ceramic targets or pressed powder targets with the chemical constitution of Pb (Zr_0.52Ti_0.46W_0.01Cd_0.01) O₃ the polycrystalline thin ferroelectric films with the perovskite type structure and of thickness d_f = (1–2, 5) × 10^?6 m on metal (stainless steel, platinum) or ceramic (polycor) substrates have been obtained. In case of thin film deposition on steel substrate and on platinum at low temperatures (T_x < 723 K) the nonferroelectric intermediate layer with the same chemical constitution but with the pyrochlore type structure have been created. Results of the X-ray analysis and dielectric investigations (low frequency dispersion) have proved existence of such a structure. The structural phase transition (P4mm ? Pm3m) takes place in the thin ferroelectric films. This is a diffuse type transition and the degree of diffuseness depends on the structural perfection of the thin films. The measure of the structural perfection of the thin films was taken to be the mean value of the lattice strains (microdeformations) ? Δd/d ? where “d”-interplane distance and the mean dimension (D) of the areas of coherent X-rays scattering (crystallites). With increase in ? Δd/d ? and decrease in D the degree of diffuseness increases. For quantitative and qualitative describing of this dependence in thin PZT films the phenomenological model of diffused phase transition developed earlier by the authors for thin BaTiO₃ films has been applied. In this case a good agreement between theory and experiment have been achieved for low values of ? Δd/d ?.     

普鲁士蓝薄膜电极的制作及充放电研究

以多孔阳极氧化铝作电极活性物质的支撑体,制备了一种新型的普鲁士蓝薄膜电极。制备过程包括纯铝片在草酸溶液中阳极氧化成多孔阳极氧化铝,电化学法去多孔阳极氧化铝的阻挡层,磷酸中扩孔,无电沉积一层钯,再在孔中组装普鲁士蓝。用扫描电镜对支撑体和电极表面形貌进行了表征,用循环伏安法对电极进行了电化学研究。结果表明,这种支撑体孔隙率大于65%,组装的普鲁士蓝(PB)薄膜电极在-0.2～0.6V和0.6～1.2V两个电位窗口内呈现两对稳定的可逆峰,由这种薄膜电极组成的微型PB薄膜蓄电池,容量达到65mC/cm2,表现出良好的充放电性能。     

Partial discharge measurements in air and argon at low pressures with and without a dielectric barrier

Partial discharge (PD) characteristics in air and argon under low pressures down to 13.3 Pa (0,1 Torr) and 60 Hz AC energization are studied in an energized needle-plane electrode arrangement. The electrode configuration, vacuum chamber, facilities, and electrical connections for the experimental setup are described. Two cases are studied for each of two gases, air and argon, with 20 mm spacing between the two electrodes: (1) with and (2) without a Teflon/spl reg/ cap (dielectric barrier). Results for the four series of experiments and analysis of the discharge current pulse waveforms are presented. Topics discussed are the typical waveforms of the discharge current pulses at different pressures, and discharge current pulse rise time vs. pressure relationships.     

Analysis of the electric field and force in an arrangement of a conducting sphere and a plane electrode with a dielectric barrier

This paper presents an analysis of the electric field and dielectrophoretic force in an arrangement consisting of an uncharged conducting sphere and a plane electrode with a dielectric barrier. The electric field is calculated by using the method of multipole images using an iterative algorithm proposed for calculating the images of the dielectric barrier of finite thickness. The calculation results show electric field intensification due to the presence of the dielectric barrier having higher permittivity, /spl epsiv//sub S/, than that of the surrounding medium, /spl epsiv//sub E/; however, if the barrier is separated from the conducting sphere by at least the sphere radius, its influence is negligible. Inside the dielectric barrier, the electric field on the axis of symmetry becomes more uniform and the average field significantly increases with decreasing its thickness. For a case where dielectric barrier is sufficiently thin, the electric field at the contact point and the force on the conducting sphere vary approximately as power functions of /spl epsiv//sub S///spl epsiv//sub E/.     

Characteristics of thin film supercapacitor with ruthenium oxide electrode and Ta2O5+x solid oxide thin film electrolyte

We report findings related to a solid-state thin film supercapacitors (TFSCs) fabricated with ruthenium oxide electrodes and hydrogen doped tantalum oxide electrolyte in order to investigate a feasibility for solid oxide thin film electrolyte in all solid state micropower sources with hydrogen conducting electrolyte. The TFSCs in this study has a cell structure of RuO₂/Ta₂O₅/RuO₂/Pt. Radio frequency, off-axis r.f. sputtering deposition of a Ta₂O₅ thin film was performed on the bottom amorphous RuO₂ electrode which was deposited by an on-axis direct current reactive sputtering, within hydrogen atmosphere to enhance the concentration of mobile proton (H⁺) ions. Scanning electron microscopy (SEM) measurements reveal that the RuO₂/Ta₂O₅/RuO₂ hetero-interfaces have no inter-diffusion problems. Room temperature charge–discharge measurements with constant current clearly reveal typical supercapacitor behavior. Also, owing to the fast diffusion of H⁺ ions within the Ta₂O₅ lattice without any structural deterioration, the capacitance per volume of RuO₂/Ta₂O₅/RuO₂/Pt TFSCs was maintained to be constant during above 800 cycles. This result indicated that the solid oxide thin film has possibility as the solid proton conducting electrolyte for all solid state micropower sources.     

Structural and dielectric properties of epitaxial Ba0.6Sr0.4TiO3 thin films grown on Si substrates with thin SrO buffer layers

(100) epitaxial Ba_0.6Sr_0.4TiO₃ (BST) thin films were grown on Si substrates using a 9 nm thick SrO buffer layer. The phase shifter fabricated on BST films grown on a SrO buffered Si substrate showed a larger figure of merit (FOM) of 24.7°/dB as a result of improving the phase tuning while retaining an appropriate insertion loss compared to that (15.3°/dB) for the BST/MgO structure. This work demonstrates that a thin SrO buffer layer plays an important role in the successful integration of BST-based microwave tunable devices onto Si wafers.     

Corona and breakdown characteristics between sphere electrode with a protrusion and plane electrode under negative pulse voltage in N/sub 2/ gas

Corona and breakdown characteristics for a configuration of a sphere with a needle and a plane in N/sub 2/ gas are studied. The protrusion was used to simulate a metallic particle attached to a high voltage conductor surface in power apparatus. The corona and breakdown characteristics depend on the vertical distance between the needle tip and the bottom sphere. It was observed that the breakdown path changed from needle-to-plane to sphere-to-plane while increasing the vertical distance of the needle from the plane. Although corona was generated at the needle-tip at first and developed in the direction of the plane, both the needle-plane and the sphere-plane breakdown occurred at some short vertical distances. The sphere-plane breakdown in that distance was triggered by corona from the needle.     

接地材料在有无阴极保护环境下的选择分析

接地材料在土壤中腐蚀的速率与电气装置的安全运行关系密切.装置所在地区的土壤腐蚀条件以及接地材料是否被保护将直接影响接地材料的选择方案.阴极保护系统可以通过遏制金属内的电子迁移对接地材料进行保护,通常有外接电流及牺牲阳极两种方法,但并不是所有的装置条件都适用阴极保护防腐方法.在没有阴极保护的接地系统中,相同材料腐蚀速率明显增大,会对装置的使用年限和后期维护造成较大困难.所以在选择接地材料的过程中,若装置不使用阴极保护系统则有阴极保护时的常规材料将不适用.在此条件下接地材料的选择与规格都需要结合土壤条件进一步讨论.     

Microstructures and dielectric properties of Zn2SnO4 thin films by sputtering from a ZnO doped ceramic target

The dielectric properties of Zn₂SnO₄ thin films with various degrees of ZnO dopant concentration were investigated. Zn₂SnO₄ thin films were prepared using the radio frequency magnetron sputtering. The X-ray diffraction patterns of the 0 and 75 mole % ZnO doped Zn₂SnO₄ thin films revealed that Zn₂SnO₄ is the main crystalline phase, which is accompanied by a little SnO₂ as the second phase. The second phase SnO₂ in specimens vanished when the extent of ZnO additive was increased to 100 mole%. A dielectric constant of 15–40 and a loss factor of 0.10–0.14 of Zn₂SnO₄ thin films were measured at 1 MHz with ZnO dopant concentration in the range of 0–100 mole%.     

Abnormality of electric field at a wedgelike edge of a conductor or a dielectric interface and methods for its relaxation

Abnormal electric field appears at a wedgelike edge of a conductor (electrode) or a dielectric interface, which usually becomes infinitely high. This paper analyzes the electric field near such an edge by the analytical variable separation method and by the numerical one of the charge simulation method. The analysis focuses on the special conditions where the electric field becomes zero at an edge. These conditions are important for the insulation design to suppress the discharge inception at such edges of conductors and dielectric interfaces. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(1): 1–8, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20280     

烟气脱硫系统有旁路和无旁路的分析比较

脱硫无旁路设计在国外发展已经比较成熟,在国内才刚刚起步。国华三河发电有限责任公司一期工程脱硫为传统的有旁路设计,二期工程脱硫系统为无旁路设计,本文主要从设计、运行方面介绍了两者的不同点。     

Characteristics of creeping discharge developed in a narrow gap between insulators and effect of a backside electrode

Discharge characteristics have been investigated for a needle–plane electrode configuration containing insulating barriers with a narrow gap which has been placed between the needle and the plane. The characteristics of creeping discharge developed in the narrow gap of the barrier filled with SF₆ are especially considered. In the case of a configuration with a backside electrode below the needle, the corona generated from the needle easily extended to the gap. On the other hand, for a configuration without a backside electrode, the corona has hardly extended to the gap, and on increasing the applied voltage the corona developed greatly in the gap. This difference in corona extension should affect the flashover characteristics in the present system. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(2): 27–36, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10248     

Correlation between voltage holding capability and light emission in a 500 keV electrostatic accelerator utilized for fusion application

Voltage holding capability in a 500 keV electrostatic accelerator with large FRP insulators was examined without the beam acceleration. When high voltage was applied, the light with a broad peak at a wavelength of 420 nm was mostly emitted inside the accelerator even though breakdown did not occur. The voltage holding capability has a strong correlation with the light intensity. Stable voltage holding was realized under the conditions in which light emission was well suppressed.