Normal Component Of Electric Field Research Articles

Discharge Randomness and Attraction Process of Epoxy Surface on Discharge Channel in SF6 Gas Under Uniform Electric Field

It is generally believed that due to the electric field distortion effect and the photoemission process of the solid surface, the discharge channel near the solid surface trends to develop along the surface than that in bulk gas. One way to improve insulation performance is to avoid the solid surface from participating in the gas discharge process. However, the mechanism of the solid surface’s effect on the gas discharge process is still unclear. In this paper, we recorded high-speed framing pictures of the discharge process in SF6 gas near the epoxy surface under lightning impulse voltage in the uniform electric field. The arc pictures show that the attraction effect of the solid surface to the discharge channel is related to the surface shape, gas gap height, and distance from the discharge channel to the solid surface. Besides, discharge randomness also plays a role, which is more obvious in the cylinder insulator than in the conical insulator, for the surface with conical shape could easily attract and arrest the discharge channel to its surface. According to the pictures of discharge process near the cylinder surface, we found that the photoemission process occurs in the streamer stage but has little effect on the attraction effect. The leader initiates after the streamer bridges the gas gap, and its random stepped walk could induce the attraction effect from the solid surface: only when the random stepped leader deflects close to the solid surface, the discharge channel could be further attracted to the solid surface by the electrostatic force, especially its normal component. The result indicates that there are three points to prevent the solid surface from participating in the gas discharge process and further improve insulation performance: choose a cylinder shape (avoid a conical shape), keep the surface away from the high electric field area where discharge may start, and reduce the normal component of the surface electric field.

Effect of Electric-Field Components on the Flashover Characteristics of Oil-Paper Insulation Under Combined AC-DC Voltage

Flashover characteristics are closely related to the electrical field distribution on the surface of oil-paper insulation. In this study, the effects of electrical field and DC voltage components on the creepage flashover characteristics of oil-paper insulation under combined AC-DC voltage (CADV) are investigated using two electrode models. The results demonstrate that when the DC voltage component is large, the flashover voltage under the influence of strong parallel electric field component is approximately 1.2 times higher than that under the influence of strong normal electric field component. When the DC voltage component value increases under the influence of strong normal electric field component, the value of corresponding AC voltage component of the creepage flashover voltage exhibits a decreasing trend. It is believed that due to the strong normal electric field component, the electrons intensify the collision on the surface of the insulating pressboard. Under the influence of the DC voltage component and due to the presence of space charge on the insulating pressboard, the distribution shape of carbonized particles on the surface of the insulating pressboard after creepage flashover is different. Furthermore, the instantaneous energy release during creepage flashover under CADV is higher than that under AC voltage, and the greater the DC voltage component value, more severe is the damage to the fibers on the insulating pressboard surface.

An Electrohydrodynamic analysis for the characterisation of fluid flow within conducting and non-conducting channels

This paper presents a generalized non-dimensional theoretical formulation with boundary conditions to analyze the EHD flow within the conducting and non-conducting channels. The substantial effect of normal and tangential components of electric field on fluid flow within the channel is presented through simulation results based on the non-dimensional parameters of strength, penetration, and repulsion of electric forces. The simulation results reveal that the normal component of induced electric field transits the flow regime within surfaces of a channel. The tangential component of applied electric field increases the thickness of viscous boundary layer, leading to skewed velocity profiles.

Nonreciprocal Epsilon-Near-Zero-Dielectric Bilayers: Enhancement of Nonreciprocity from a Nonlinear Transparent Conducting Oxide Thin Film at Epsilon-Near-Zero Frequency

We envision the use of an indium tin oxide (ITO) thin film as part of a bilayered silicon-photonics subwavelength device to boost nonlinearity-assisted all-passive and ultrafast nonreciprocal behavior. Asymmetric $p$-polarized oblique excitation of a mode near the epsilon-near-zero frequency, with a highly confined and enhanced normal electric field component and large absorption, allows one to harness the strong subpicosecond nonlinear response of ITO for the generation of notable nonreciprocal performance in an ultracompact two-port element. Although the results are limited by loss, we find the optimal operational point and the maximum attainable nonreciprocal transmittance ratio of the metasurface versus light intensity---including an apparent upper bound slightly over 2---and we perform exhaustive numerical simulations considering nonlinear processes of both anharmonic and thermal nature that validate our predictions, including steady-state and pulsed-laser excitation.

Numerical Studies of the Electric Field of a Power Cable with Sector Strands and Impregnated Paper–Plastic Insulation for a Voltage of 20 kV

In power cables with sector current-carrying strands (SCSs), impregnated with paper insulation, there is a tangential electric field component along the layers. The permissible electric strength along the paper tapes is about ten times less than in the normal direction, which is taken into account when developing three-wire power cables impregnated with paper insulation for voltages of 20 and 35 kV. The use of modern paper—plastic-impregnated insulation having higher performance characteristics than conventional impregnated paper insulation, can promote the creation of more efficient cable designs with individually shielded sector-shape conductors in a common lead sheath for a voltage of 20 kV. Each insulated strand of such cables has a copper shield, and so it is enough to consider the electric field in the cross section of the insulation of one SCS. The electric potential distribution is described by the Laplace differential equation, the solution of which is implemented by the finite element method using the Ansys Maxwell software package. A numerical study of the electric fields has been carried out for power cables with SCSs that have a cross section of 400 mm2 for a voltage of 20 kV. The curvature radius of the cable sectors varied from 5 to 7 mm with an insulation thickness of 7 to 9 mm. Based on the research results, the maximum values of the normal and tangential electric field components depending on the curvature radius of the sector strand and insulation thickness have been obtained. Insulation areas have been allocated in which the maximum absolute values of the tangential electric field strength components have been observed. The allowable values of the sector curvature radius and the thickness of insulation for power cables with paper-impregnated insulation for 20 kV have been determined.

An Analytical Model of One-Sided Multipactor on a Dielectric of a Metal Surface for Spacecraft Application

The aim of this article is to establish a general and practical analytical model of the one-sided multipactor on a dielectric of a metal surface and analyze the resonant multipactor effect for the recent growing interest in spacecrafts. A theoretical multipactor model involving a normal static electric field, a radio frequency (RF) electric field with both tangential and normal components, and the influence of the desorption gas is proposed. The kinetic properties and the resonant condition of the electron are studied by analytical calculations. The results show that the transit time of the electron decreases with the increase in the normal static electric field and the pressure of the desorption gas. The emission phase of the electron is the paramount factor that has a direct influence on the occurrence of the resonant multipactor. If the resonant multipactor effect could appear, the emission phase of the electron should be larger than a critical phase, and the ratio between the amplitude of the normal component of the RF electric field and the normal static electric field should be larger than a specific value as well.

Investigation on surface electric field distribution features related to insulator flashover in SF6 gas

The gas-solid interface is generally considered to be the weakest part in gas-insulated systems. The flashover voltage of a gas-solid interface is difficult to predict because it involves an extremely complex physical process affected by multiple factors. In this paper, we employ the support vector regression (SVR) method based on mass data on the features of the electric field that are indicators of the flashover voltage. We cast 48 kinds of epoxy resin post insulators as samples, and 61 features are extracted to characterize the surface electric field distribution and the flashover voltage under standard lightning impulse voltage. Four indicators that may be useful in predicting the flashover voltage were obtained; the maximum electric field along the surface of the insulator (E max ), the normal electric field components of E max (E n_Emax ), the maximum gradient of the surface tangential electric field component (E t_gm ), and the integral of the area in which the E value exceeds x% of E max along the insulator surface (V t60 ). We establish an SVR flashover voltage prediction model with these four features, whose average deviation is 7% in 10,000 predictions. It is expected that this study may provide a reference for the continued study of the gas-solid surface flashover mechanism.

Calculation of Accumulated Charge on Surface of Insulated House Near DC Transmission Lines by Method of Characteristics

Charges resulting from corona on dc transmission lines will be driven by the electric field to the space and form the ion flow field. Some space charges will accumulate on the surface of the insulated buildings in the vicinity of high-voltage direct current transmission lines and may lead to human body shock. An improved iterative method is used to solve the ion flow field and accumulated charges according to the boundary condition that the normal component of electric field on the insulated building surface is zero. The accumulated charges are calculated by a 3-D method of characteristics based on the known ion flow field, which avoids large-scale numerical calculation. The calculation results are in a good agreement with the measured data of reduced-scale test under laboratory conditions.

Microwave Near-Field Focusing Beam Generation by Zeroth-Order Inward Cylindrical Traveling Leaky Wave

In this letter, a method is proposed to generate the near-field focusing beam in microwaves by using the TM-polarized zeroth-order inward cylindrical traveling leaky wave (ZICTLW), whose normal electric-field component is a truncated zeroth-order Hankel function of the first kind. The focusing property of ZICTLW is analyzed. Furthermore, the relation between the focusing property and the truncation region, which is used to remove the singularity, is investigated. In order to generate a focusing beam, a ZICTLW antenna is designed based on a three-layer radial waveguide with both a capacitive sheet and a planar high-impedance sheet covered. The simulation and the measurement validate that the proposed antenna can generate a focusing zone, which can be controlled by the operating frequency.

On the Proper Generalized Decomposition applied to microwave processes involving multilayered components

Many electrical and structural components are constituted of a stacking of multiple thin layers with different electromagnetic, mechanical and thermal properties. When 3D descriptions become compulsory the approximation of the fields along the thickness direction could involve thousands of nodes. To circumvent the numerical difficulties that such a rich description imply, we recently propose an in-plane–out-of-plane separated representation with the aim of computing fully 3D solutions as a sequence of 2D problems defined in the plane and others (1D) in the thickness. The main contribution of the present work is the proposal of an efficient in-plane–out-of-plane separated representation of the double-curl formulation of Maxwell equations able to address thin-layer laminates while ensuring the continuity and discontinuity of the tangential and normal electric field components respectively at the plies interface.

Effect of nano-TiO2/EP composite coating on dynamic characteristics of surface charge in epoxy resin

As a modification method, surface coating is considered to be an effective method in regulating the surface state of the epoxy resin, thus suppressing the accumulation of surface charge. In this paper, epoxy resin coated with nano-TiO 2 /EP composite coating was prepared and two electrode systems which were respectively dominated by normal and tangential electric field component were designed. Surface potential distributions of samples at different time under two electrode systems were studied by electrostatic probe method, volume and surface conductivities of the samples were tested by capacitance probe method. The effects of nano-TiO 2 particle content (1, 3, 5, and 7%) on the surface charge dynamic characteristics of epoxy resin were obtained. The results showed that the surface charge was mainly accumulated near the electrode when the normal electric field component was dominant, and the accumulation region was related to the material. When the content of nano-TiO 2 particles in the coating was 1 and 3%, the charge mainly accumulated near the high voltage electrode. When the content of nano-TiO 2 particles in the coating was 5 and 7%, the charge was mainly accumulated near the ground electrode. On the other hand, when the tangential electric field component was dominant, the surface charge would be dissipated, and the dissipation rate of the surface charge near the high voltage electrode was faster than the surface charge accumulated near the ground electrode. Taking the dynamic process of surface charge into account, it was found that the coating of which nano-TiO 2 particle content was 5% showed the most significant effect on restraining charge accumulation.

Strategies for improved global representation of magnetospheric electric potential structure on a polar-capped ionosphere

In some simple models of magnetospheric electrodynamics [e.g., Volland, Ann. Géophys., 31, 154–173, 1975], the normal component of the convection electric field is discontinuous across the boundary between closed and open magnetic field lines, and this discontinuity facilitates the formation of auroral arcs there. The requisite discontinuity in E is achieved by making the scalar potential proportional to a positive power (typically 1 or 2) of L on closed field lines and to a negative power (typically −1/2) of L on open (i.e., polar-cap) field lines. This suggests it may be advantageous to construct more realistic (and thus more complicated) empirical magnetospheric and ionospheric electric-field models from superpositions of mutually orthogonal (or not) vector basis functions having this same analytical property (i.e., discontinuity at L = L*, the boundary surface between closed and open magnetic field lines). The present work offers a few examples of ways to make such constructions. A major challenge in this project has been to devise a coordinate system that simplifies the required analytical expansions of electric scalar potentials and accommodates the anti-sunward offset of each polar cap's centroid relative to the corresponding magnetic pole. For circular northern and southern polar caps containing equal amounts of magnetic flux, one can imagine a geometrical construction of coordinate contours such that arcs of great circles connect points of equal quasi-longitude (analogous to MLT) on the northern and southern polar-cap boundaries. For more general polar-cap shapes and (in any case) to assure mutual orthogonality of respective coordinate surfaces on the ionosphere, a formulation based on harmonic coordinate functions (expanded in solutions of the two-dimensional Laplace equation) may be preferable.

Microwave Imaging Using Normal Electric-Field Components Inside Metallic Resonant Chambers

A novel 3-D microwave imaging approach performed within a resonant air-filled metallic chamber is introduced and investigated. The new method utilizes the measurements of normal electric-field components at discrete points along the metallic chamber’s wall—near the chamber-wall boundary, the normal-field components are dominant, while the tangential components vanish. The inversion algorithm fully incorporates the resonant features of the low-loss chamber. A numerical study is used to quantify the imaging performance of using this technique compared with the traditional unbounded domain imaging. An experimental system is presented where the electric field is collected using 24 antennas distributed in three circumferential layers around an object of interest located inside the circular-cylindrical metallic chamber. For collecting the normal component of the field, two types of linearly polarized antennas are investigated: $\lambda /4$ monopole antennas and specially designed reconfigurable antennas (RAs), both projecting perpendicularly out from the chamber walls into the enclosure. The measured data are calibrated and then inverted using a multiplicatively regularized finite-element contrast source inversion algorithm. Using 3-D reconstructions of simple dielectric targets, it is shown that utilizing the RAs improves imaging performance due to a reduction in the modeling error introduced in the inversion algorithm.

Local subsystems in gauge theory and gravity

We consider the problem of defining localized subsystems in gauge theory and gravity. Such systems are associated to spacelike hypersurfaces with boundaries and provide the natural setting for studying entanglement entropy of regions of space. We present a general formalism to associate a gauge-invariant classical phase space to a spatial slice with boundary by introducing new degrees of freedom on the boundary. In Yang-Mills theory the new degrees of freedom are a choice of gauge on the boundary, transformations of which are generated by the normal component of the nonabelian electric field. In general relativity the new degrees of freedom are the location of a codimension-2 surface and a choice of conformal normal frame. These degrees of freedom transform under a group of surface symmetries, consisting of diffeomorphisms of the codimension-2 boundary, and position-dependent linear deformations of its normal plane. We find the observables which generate these symmetries, consisting of the conformal normal metric and curvature of the normal connection. We discuss the implications for the problem of defining entanglement entropy in quantum gravity. Our work suggests that the Bekenstein-Hawking entropy may arise from the different ways of gluing together two partial Cauchy surfaces at a cross-section of the horizon.

Experimental Validation of Bessel Beam Generation Using an Inward Hankel Aperture Distribution

In this paper, we prove experimentally that nondiffractive Bessel beams can be generated by using inward cylindrical traveling wave aperture distributions. An azimuthally invariant inward traveling wave distribution is defined over the aperture of a radial line slot array (RLSA) to launch a Bessel beam whose normal electric-field component assumes a truncated, zeroth-order Bessel function. An optimization procedure based on a holographic approach is used for tuning the position and size of the slots of the RLSA. The antenna is centrally fed by a coaxial probe transition. The final structure operates at 12.5 GHz. Full-wave simulations and measurements of the vertical component of the electric field show that a non-diffractive radiation is obtained within a range larger than 12 wavelengths in front of the antenna. The generated Bessel beam presents a stable half-power beamwidth of about 20 mm within this range. The proposed system may open new opportunities for planar, low-profile Bessel beam generators at millimeter waves, Terahertz, and optics.

Trapping and chaining self-assembly of colloidal polystyrene particles over a floating electrode by using combined induced-charge electroosmosis and attractive dipole-dipole interactions.

We propose a novel low-frequency strategy to trap 10 μm colloidal polystyrene (PS) particles of small buoyancy velocity on the surface of a floating electrode, on the basis of combined induced-charge electroosmotic (ICEO) flow and dipole-dipole chaining phenomenon. For field frequencies of 5-50 Hz, much lower than the reciprocal RC time scale, double-layer polarization makes electric field lines pass around the 'insulating' surface of the ideally polarizable floating electrode. Once the long-range ICEO convective micro-vortexes transport particles quickly from the bulk fluid to the electrode surface, neighbouring particles aligned along the local horizontal electric field attract one another by attractive dipolar interactions, and form arrays of particle chains that are almost parallel with the applied electric field. Most importantly, this low-frequency trapping method takes advantage of the dielectrophoretic (DEP) particle-particle interaction to enhance the downward buoyancy force of this dipolar chaining assembly structure, in order to overcome the upward ICEO fluidic drag and realize stable particle trapping around the flow stagnation region. For the sake of comparison, the field frequency is further raised far above the DC limit. At the intermediate frequencies of 200 Hz-2 kHz, this trapping method fails to work, since the normal electric field component emanates from the conducting electrode surface. Besides, at high field frequencies (>3 kHz), particles can be once again effectively trapped at the electrode center, though with a compact (3 kHz) or disordered (10 kHz) 2D packing state on the electrode surface and mainly governed by the short-range negative DEP force field, resulting in requiring a much longer trapping time. To gain a better interpretation of the various particle behaviours observed in experiments, we develop a theoretical framework that takes into account both Maxwell-Wagner interfacial charge relaxation at the particle/electrolyte interface and the field-induced double-layer polarization at the electrode/electrolyte interface, and apply it to quantify the particle-particle electrokinetic interactions. With this simple geometrical configuration of a floating electrode, our results provide a new way to realize trapping of colloidal particles with a small buoyancy velocity under the combined action of ICEO flow and an attractive dipole-dipole interaction.

Elongating the Air Working Distance of Near-Field Plasmonic Lens by Surface Plasmon Illumination

A method is proposed and demonstrated to elongate the air working distance of near-field plasmonic lens with deep subwavelength resolution. It is done by employing surface plasmon illumination (SPI) with a high transverse wavevector and a plasmonic lens with a metal-dielectric-metal structure. Specially designed SPI source with subwavelength grating and multiple metal-dielectric films delivers the shifted spatial spectra components of mask patterns, which help to enhance plasmonic lens optical transfer ability of patterns’ information even with a large air working distance. Moreover, a metal reflector serves to modulate the magnitude of the tangential and normal electric field components in the imaging region and brings the considerable improvement of imaging quality. Numerical simulations show that the maximum air working distance could reach 60 for 32 nm half-pitch resolution at 365 nm wavelength about six times that for the conventional superlens under normal illumination (NI). An approximate model of the air working distance elongation under SPI is given and agrees well with simulations.

Influence of Poisson equation boundary conditions and quantum corrections to carrier concentrations at material interfaces in TCAD process simulation

AbstractIn TCAD process simulation, the Poisson equation for electrostatic potential is usually solved in silicon and polysilicon regions, assuming a zero normal component of electric field (ZEF) boundary conditions (BCs) at material interfaces. This is correct for a free (or covered only with dielectric) flat surface of silicon, which is typical for 1D SIMS profile simulations. However, it is inaccurate in other important cases, in particular, under the gate of submicron MOS transistors, where more general BCs preserving the continuity of the flux of electric displacement should be applied. In a simulation, the choice of BCs changes the electrostatic potential near material interfaces and, thereby, impacts simulated dopant distributions and transistor characteristics. We introduced such general BCs in Sentaurus Process and applied them to the 2D simulation of CMOS transistors with polysilicon or metal gate. A noticeable (but moderate) increase of simulated threshold voltage in comparison to the ZEF BCs is demonstrated. In addition, the effect of carrier concentration reduction at silicon/dielectric interfaces due to quantum‐mechanical repulsion was introduced into a continuum process simulation using the modified local‐density approximation. This changes the dopant distributions in a nanometre thin layer in semiconductors at both sides of the gate oxide, resulting in a reduced concentration of the main dopant near the interface, which is most pronounced at high dopant concentrations. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A Wire Electrode inside Parallelepipedicaly-Shaped Ground Inhomogeneity: Comparison of Two Solutions

The results for the resistance of the wire electrode inside parallelepipedicaly-shaped domain surrounded with homogeneous ground obtained by one recently proposed procedure for modeling described structure are compared with recently published results realized applying one new hybrid boundary element method. The first approach is based on the approximating system wire-parallelepiped with one wire conductor off equivalent length and cross-section radius. The hybrid method is based on equivalent electrodes method and point matching method applied on matching values for potential of wire electrode and normal component of electric field on the boundary surface between conductive media. The quasi-stationary approach is applied. DOI: http://dx.doi.org/10.5755/j01.eee.19.5.1845

Generation of Propagating Bessel Beams Using Leaky-Wave Modes

The generation of Bessel beams using a leaky radial waveguide is presented. The radial waveguide consists of a capacitive sheet over a ground plane. It supports an azimuthally invariant leaky-wave mode whose normal electric-field component is a truncated, zeroth-order Bessel function. The annular spectrum and nondiffractive extent of the Bessel beam is clearly linked to the complex wavenumber of the leaky-wave mode. The fields inside the radial waveguide are derived using classical vector potential techniques. A vector approach is employed to avoid paraxial approximations of earlier works and the associated limitations on shaping the Bessel beam. Design rules are provided to synthesize a desired propagating Bessel beam. A simple coaxial feed is proposed for the radial waveguide and its input impedance is derived analytically. The analytical results are also validated numerically. The proposed structure and design procedure can be used for generating arbitrary zeroth-order propagating Bessel beams at microwave and millimeter-wave frequencies.