Showing papers on "Insulator (electricity) published in 2009"

Coax core insulator waveguide

Abstract: A communication device consistent with certain implementations has a coaxial cable having length and first and second ends. The coaxial cable further has a central conductor, a dielectric insulator surrounding the central conductor, and an electric shield conductor surrounding the dielectric insulator. The dielectric insulator serves as a dielectric waveguide having a characteristic impedance Z at an operating frequency range. A termination for electrical energy coupled into or out of the dielectric insulator at approximately the characteristic impedance Z at the operating frequency range to utilize the dielectric insulator as a waveguide for transmission of signals along the length of the coaxial cable, and wherein the center conductor is further used to communicate an electrical signal between the first and second ends. This abstract is not to be considered limiting, since other embodiments may deviate from the features described in this abstract.

Systems for efficient insulation of electrical structures

Abstract: An animal protectant power line electrical insulator to be placed on structures such as electrical apparatus to protect birds, wildlife and other animals. Specifically the insulator may include, a snap-fit insulating cover configured to fit over an energized part of an electrical structure of a power line, a resiliently flexible separable juncture for application onto the power line and secure closure; and perhaps even at least one formed eye on the cover. A cover may hold itself in place and may be made from plastic, fiberglass, PVC, or other semi-rigid, non-conductive material; molded, formed, or fabricated to fit a desired application.

Investigations on leakage current and phase angle characteristics of porcelain and polymeric insulator under contaminated conditions

Abstract: This paper deals with the analysis of leakage current and phase angle characteristics of porcelain and silicone rubber insulator in order to develop a better diagnostic tool to identify the pollution severity of outdoor insulators In this work, laboratory based pollution performance tests are carried out on porcelain and silicone rubber insulator under ac voltage at different pollution levels and relative humidity conditions with sodium chloride as a contaminant Multi resolution signal decomposition (MRSD) using discrete wavelet transform (DWT) is employed to understand the time-frequency characteristics of the leakage current signal Fast Fourier transform (FFT) spectral analysis is adopted to calculate the phase angle values of the applied voltage and leakage current signals Reported results on porcelain and silicone rubber insulators show that the pollution severity of outdoor insulators could be identified from the DWT STD-MRA (standard deviation multi resolution analysis) distortion ratio pattern analysis of leakage current signals

Dielectric properties and electric breakdown strength of a subpercolative composite of carbon black in thermoplastic copolymer

Abstract: We investigate the dielectric properties and electric breakdown strength of subpercolative composites of conductive carbon black particles in a rubber insulating matrix A significant increase in the permittivity in the vicinity of the insulator to conductor transition was observed, with relatively low increases in dielectric loss; however, a rapid decrease in electric breakdown strength was inevitable A steplike feature was ascribed to agglomeration effects The low ultimate values of the electric field strength of such composites appear to prohibit practical use

High performance AlGaN/GaN power switch with HfO2 insulation

Abstract: High performance AlGaN/GaN metal-insulator-semiconductor heterostructure field-effect transistor was fabricated using HfO2 as the surface passivation and gate insulator. The gate and drain leakage currents are drastically reduced to tens of nanoamperes before breakdown. Without field plates, for 10 μm of gate-drain spacing, the off-state breakdown voltage is 1035 V with a specific on resistance of 0.9 mΩ cm2. In addition, there is no current slump observed from the pulse measurements. This is the best performance reported on GaN-based power-switching devices on sapphire up to now, which efficiently combines excellent device forward, reverse, and switching characteristics.

Evaluation of Y2O3 gate insulators for a-IGZO thin film transistors

Abstract: In this work, Y 2 O 3 was evaluated as a gate insulator for thin film transistors fabricated using an amorphous InGaZnO 4 (a-IGZO) active layer. The properties of Y 2 O 3 were examined as a function of various processing parameters including plasma power, chamber gas conditions, and working pressure. The leakage current density for the Y 2 O 3 film prepared under the optimum conditions was observed to be -3.5 x 10 ―9 A/cm 2 at an electric field of 1 MV/cm. The RMS roughness of the Y 2 O 3 film was improved from 1.6 nm to 0.8 nm by employing an ALD (Atomic Layer Deposition) HfO 2 underlayer. Using the optimized Y 2 0 3 deposition conditions, thin film transistors (TFTs) were fabricated on a glass substrate. The important TFT device parameters of the on/off current ratio, sub-threshold swing, threshold voltage, and electric field mobility were measured to be 7.0 x 10 7 , 0.18 V/dec, 1.1 V, and 3.3 cm 2 /Vs, respectively. The stacked insulator consisting of Y 2 O 3 /HfO 2 was highly effective in enhancing the device properties.

Metal-insulator-semiconductor tunneling contacts

Abstract: A contact to a source or drain region. The contact has a conductive material, but that conductive material is separated from the source or drain region by an insulator.

Recurrent plot analysis of leakage current for monitoring outdoor insulator performance

Abstract: Outdoor insulators are widely accepted in power industry to maintain electrical insulation ranging from distribution to transmission lines. Such increasing development leads to a lack of appropriate diagnostic tools for assessing the performance of insulator in service, particularly in contaminated conditions. In order to monitor operating performance of contaminated outdoor insulators, a recurrent plot technique is proposed to analyze the leakage current passing through the insulator surface. Contamination tests were conducted in a laboratory by employing heavy salt fog with the deposition of non-soluble contamination. The leakage current was decomposed into different frequency components by using a wavelet transform technique. The temporal sequence of the extracted component was extended to m-dimensional phase space by using a phase-space reconstructed method. The recurrent plot is obtained to show that the topological structure of the high-frequency components is prominent to identify non-linear properties of discharge activities. Based on the analysis of the high-frequency components, the quantitative indicators of recurrent plot are obtained to reflect the underlying mechanism of flashover process. The results obtained indicate that the recurrent plot technique gives visual recurrent patterns of discharge activities for monitoring outdoor insulator performance. The dynamic behaviors on the insulator surface are graphically illustrated on the rectangular block structures with higher density of points. The structure changes indicate the switches of discharge states during the flashover process.

Semiconductor device and method of forming the same

Abstract: A semiconductor device and a method of forming thereof has a base body has a field stopping layer, a drift layer, a current spreading layer, a body region, and a source contact region layered in the order on a substrate. A trench that reaches the field stopping layer or the substrate is provided. A gate electrode is provided in the upper half section in the trench. In a section deeper than the position of the gate electrode in the trench, an insulator is buried that has a normal value of insulation breakdown electric field strength equal to or greater than the value of the insulation breakdown electric field strength of the semiconductor material of the base body. This inhibits short circuit between a gate and a drain due to insulation breakdown of an insulator film at the bottom of the trench to realize a high breakdown voltage in a semiconductor device using a semiconductor material such as SiC. The sidewall surfaces of the trench located below the gate electrode is inclined to form a trapezoidal profile.

Electro-Quasistatic High Voltage Field Simulations of Large Scale Insulator Structures Including 2-D Models for Nonlinear Field-Grading Material Layers

Abstract: Resistive field-grading material is applied to nonceramic insulators. For the design of insulator structures, these resistive field-dependent and thus nonlinear material layers are considered as 2-D layers within 3-D transient finite element method (FEM) simulations of electro-quasistatic fields. The 2-D layer modeling approach is validated and compared to conventional 3-D layer modeling for various layer thicknesses. Numerical results for realistic structures are shown herein.

High field-effect mobility pentacene thin-film transistors with nanoparticle polymer composite/polymer bilayer insulators

Abstract: High field-effect mobility organic thin-film transistors with nanoparticle polymer composite/polymer bilayer insulators were fabricated. A device composed of a polyvinylphenol (PVP) insulator filled with barium strontium titanate (BST) nanoparticles and coated with a thin polystyrene film was found to exhibit a field-effect mobility (1.2 cm2 V−1 s−1 for a pentacene device) and a field-induced current that are superior to those of devices with only a PVP insulator or a BST-filled PVP insulator. These improvements in the performance are due to an increase in the capacitance and a reduction in the interface roughness of the insulator.

Investigation of pollution flashover on high voltage insulators using artificial neural network

Abstract: High voltage insulators form an essential part of the high voltage electric power transmission systems. Any failure in the satisfactory performance of high voltage insulators will result in considerable loss of capital, as there are numerous industries that depend upon the availability of an uninterrupted power supply. The importance of the research on insulator pollution has been increased considerably with the rise of the voltage of transmission lines. In order to determine the flashover behavior of polluted high voltage insulators and to identify to physical mechanisms that govern this phenomenon, the researchers have been brought to establish a modeling. Artificial neural networks (ANN) have been used by various researches for modeling and predictions in the field of energy engineering systems. In this study, model of VC=f (H,D,L,?,n,d) based on ANN which compute flashover voltage of the insulators were performed. This model consider height (H), diameter (D), total leakage length (L), surface conductivity (?) and number of shed (d) of an insulator and number of chain (n) on the insulator.

Inspection of Insulators on High-Voltage Power Transmission Lines

Abstract: Porcelain insulators are widely used in overhead high-voltage power transmission lines in order to provide adequate insulation to withstand switching and lightning over voltages. Since the useful serviceable life of the individual insulator element and insulator strings is hard to predict, they must be verified periodically to insure that adequate reliability is maintained at all times. Over the years, many testing methods have been used for this purpose, each one with its own advantages and disadvantages. A novel insulator inspection method using low-frequency harmonics is proposed for human safety. Using this inspection device with a mobile robot can keep humans far away from power transmission lines. The working principle of this new method is based on the relationship between low-frequency harmonic components and the defective characteristic of the insulators. In this paper, the retrieval of low-frequency harmonics from complex noise is solved by using extended high-order cumulants (HOCs). The concept of cross mixing is newly proposed and the harmonic retrieval method using the slice of the sixth-order time-averaged moment poly-spectra is introduced based on this condition. It can be successfully used in the real environment where a full spectrum of multiplicative and colored noises exists. In the experiment, as one of our dedicated contributions, low-frequency harmonics and the defective characteristics of popular porcelain insulators are illustrated.

Electric field driven quantum phase transition between band insulator and topological insulator

Abstract: We demonstrate theoretically that electric field can drive a quantum phase transition between band insulator to topological insulator in CdTe/HgCdTe/CdTe quantum wells. The numerical results suggest that the electric field could be used as a switch to turn on or off the topological insulator phase, and temperature can affect significantly the phase diagram for different gate voltage and compositions. Our theoretical results provide us an efficient way to manipulate the quantum phase of HgTe quantum wells.

Experimental Study of Current Discharge Behavior and Hard X-ray Anisotropy by APF Plasma Focus Device

Abstract: Amirkabir (APF) is a new Mather-type plasma focus device (16 kV, 36 μf, and 115 nH). In this work we present some experimental results as variation of discharge current signal respect to applied voltage at the optimum pressure, focusing time of plasma versus gas pressure, and variations of current discharge with different insulator sleeve dimensions. As we prospected optimum pressure tending to increase as we tried to higher voltage levels. The time taken by the current sheath to lift-off the insulator surface and therefore quality of pinched plasma depends on the length of the insulator sleeve. The results show that the insulator diameter can influence on pinch quality. Behavior of hard X-ray (HXR) signals with the pressure and also anisotropy of HXR investigated by the use of two scintillation detectors. The distribution of HXR intensity shows a large anisotropy with a maximum intensity between 22.5° and 45° and also between −22.5° and −67.5°.

Local Bottom Gates for Graphene and Carbon Nanotube Devices

Abstract: Transistor devices having nanoscale material-based channels and techniques for the fabrication thereof are provided. In one aspect, a transistor device includes a substrate; an insulator on the substrate; a gate embedded in the insulator with a top surface of the gate being substantially coplanar with a surface of the insulator; a dielectric layer over the gate and insulator; a channel comprising a carbon nanostructure material formed on the dielectric layer over the gate, wherein the dielectric layer over the gate and the insulator provides a flat surface on which the channel is formed; and source and drain contacts connected by the channel. A method of fabricating a transistor device is also provided.

Influence of surface charges on impulse flashover characteristics of alumina dielectrics in vacuum

Abstract: For higher electrical insulator performance of vacuum circuit breakers (VCB), the surface flashover in vacuum should be improved. In particular, it is important to clarify how strongly surface charges influence the surface flashover mechanism. In this paper, we investigated the surface flashover characteristics based on the existence of surface charges on an alumina insulator in vacuum. We changed the location and magnitude of surface charges and measured surface flashover voltage. From our experimental results, an attempt was made to clarify the influence of charges on alumina dielectrics on impulse surface flashover characteristics in vacuum. From this, we concluded that (1) when surface charges were located near the cathode electrode, a positive charge made the surface flashover voltage lower and a negative charge made the surface flashover voltage higher; and, (2) when surface charges were located in the way of the discharge path, both positive and negative charges made the surface flashover voltage lower. We were able to explain these results by considering the influence of surface charges on the electric field at flashover and on the secondary electron emission avalanche.

Field-induced gap and quantized charge pumping in a nanoscale helical wire

Abstract: We propose several physical phenomena based on nanoscale helical wires. Applying a static electric field transverse to the helical wire induces a metal to insulator transition, with the band gap determined by the applied voltage. A similar idea can be applied to ``geometrically'' construct one-dimensional systems with arbitrary external potential. With a quadrupolar electrode configuration, the electric field could rotate in the transverse plane, leading to a quantized dc charge current proportional to the frequency of the rotation. Such a device could be used as a standard for the high-precession measurement of the electric current. The inverse effect implies that passing an electric current through a helical wire in the presence of a transverse static electric field can lead to a mechanical rotation of the helix. This effect can be used to construct nanoscale electromechanical motors. Finally, our methodology also enables ways of controlling and measuring the electronic properties of helical biological molecules such as the DNA.

Electric field driven quantum phase transition between band insulator and topological insulator

Abstract: We demonstrate theoretically that electric field can drive a quantum phase transition between band insulator to topological insulator in CdTe/HgCdTe/CdTe quantum wells. The numerical results suggest that the electric field could be used as a switch to turn on or off the topological insulator phase, and temperature can affect significantly the phase diagram for different gate voltage and compositions. Our theoretical results provide us an efficient way to manipulate the quantum phase of HgTe quantum wells.

Frequency Distribution of Leakage Current on Silicone Rubber Insulator in Salt-Fog Environments

Abstract: This paper presents an analysis result of using the frequency distribution of leakage current to monitor insulator performance in salt-fog environments. Experiments have been carried out on silicone rubber insulator by injecting salt fog into an artificial fog chamber with an ultrasonic vibration salt-fog generator and applying an AC voltage of 30 kVrms at 50 Hz as the test voltage. Based on the frequency distribution extracted by a wavelet transform technique, the measured leakage current is separated into the low-, intermediate-, and high-frequency components. Cumulative charge at each frequency component is obtained by a time-integral method and found to correlate the frequency components and the insulator performance. Obtained results show that high-frequency components are more effective than low-frequency components on monitoring insulator performance in salt-fog environments.

Electrical and optical properties of metal-insulator-transition VO2 thin films

Abstract: Vanadium dioxide thin films were deposited using in situ pulsed laser deposition technique on a-, c-, and r-plane Al2O3, and MgO(100) substrates. Microstructure of the films was varied between epitaxial VO2, polycrystalline VO2, mixtures of VO2 and V6O13 with VO2 as the main phase, and mixtures of VO2 and V6O13 with V6O13 as the main phase by controlling the deposition oxygen partial pressure. Detailed XRD, SPM, and FESEM measurements were performed in order to analyze the structure of the films. Resistivity as a function of temperature, current–voltage characteristics in electric current induced Joule heating transition process, and the optical transmittance both in insulator and metal states were measured. MIT effect led to 103–105 change in resistivity with varying transition temperature and hysteresis loop widths. The largest and the steepest transitions were found in the films with polycrystalline microstructure deposited at higher oxygen pressures. Epitaxial films had 2.5 times higher insulator state conductivity than polycrystalline films, which lead to a clearly smaller switching powers in MIT effect generated by Joule heating. However, the optical properties in both states were not considerable affected by conductivity or microstructure properties. The relationships between the microstructure, electrical and optical properties, as well as MIT switching effect together its dynamics in the films are discussed.

Measurement and simulation of the electric field of high voltage suspension insulators

Abstract: In this study, a method for the calculation of the electric field on high voltage insulators is presented. A model of the insulator string was set up using OPERA, an electromagnetic analysis program based on the Finite Element Method. In order to validate the accuracy of the method, simulated results have been compared with experimental results. Copyright © 2008 John Wiley & Sons, Ltd.

Effect of temperature on the streaming electrification characteristics of silicone oil

Abstract: We have investigated the performance of silicone oil as an insulating medium with the aim of developing environmentally-friendly, flame-retardant electric power equipment. We have studied the streaming electrification characteristics of silicone oil during flow, with regard to its use in the cooling of electric power equipment, at temperatures from 30 to 130degC. The effects of the insulator material on the charge density in the oil and on the accumulated charge density in the insulator were investigated. We use four kinds of insulators, including aramid paper, in these experiments. The silicone oil was negatively charged by streaming electrification, in contrast to conventional mineral oil. The magnitude of the accumulated charge density in the insulator was influenced by the kind of insulator. It was also found that the charge density in the silicone oil and the accumulated charge density in the insulator changed with increasing temperature. Moreover, we investigated the effect of the kinematic viscosity on the streaming electrification by performing experiments using oils with kinematic viscosities of 20 cSt and 50 cSt. We have considered the optimum combinations of silicone oil and insulator material.

Electric field controlled formation and dissociation of multiwalled carbon nanotube conductive pathways in a polymer melt

Abstract: Electric field controlled formation and dissociation of multiwalled carbon nanotube (MWCNT) conductive pathways in a polycarbonate (PC) melt are investigated by the dynamic percolation measurement. The results show that field-induced MWCNT alignment causes the decrease in the activation energy of conductive pathway formation. The directional or disordered alignment of MWCNTs in the PC melt results in the transition from a conductor to an insulator as the electric field changes from 500 to 1 V/cm. This electric-controllable directional or disordered alignment technology is promising for the fabrication of low-dimensional conductive materials and applications of voltage-switch devices.

Influence of relative humidity on surface charge decay on epoxy resin insulators

Abstract: The influence of relative air humidity on the surface charge decay on epoxy resin insulators initially charged by DC corona and on their surface resistivity is investigated at room temperature. It has been observed, that surface resistivity of the epoxy resin insulators decreases significantly at higher relative humidity. Thus, at higher relative humidity surface charge decay is dominated by electric conduction along the insulator surface. This effect has been verified by both, measurement and simulation of the surface charge decay.

Computation of AC flashover voltage of polluted HV insulators using a dynamic arc model

Abstract: Flashover of polluted insulators is still a serious threat to the safe operation of a power transmission system. Despite the extensive investigations carried out on the pollution performance of the insulators, the flashover characteristics are not well understood. Recent theoretical and experimental research on polluted insulators is yet to yield a perfect generalized mathematical model which can accurately predict critical flashover voltage. In this paper, the pollution flashover on the high voltage insulators has been investigated and a new dynamic arc model has been proposed. For this purpose, firstly the concerned insulators' scaled shapes were partitioned into triangular elements, then finite element method (FEM) was implemented for obtaining potential distribution on the surface of insulator and finally flashover voltages were determined by using the developed arc model. For a number of common insulators of different geometries the computed results of flashover voltages on the selected string insulators have been compared to experimental results of some other research. Pollution flashover behaviors of the insulators have been taken into consideration and the validity of the model was thus verified. Copyright © 2008 John Wiley & Sons, Ltd.

Smart link coupled to power line

Abstract: A smart link in a power delivery system includes an insulator, which electrically isolates a power line, and a switchable conductance placed in parallel with the insulator. The switchable conductance includes switchgear for sourcing, sinking, and/or dispatching real and/or reactive power on the power line to dynamically in response to dynamic loading, transient voltages and/or currents, and phase conditions or other conditions on the power line.

Designing a New Post Insulator Using 3-D Electric-Field Analysis

Abstract: Insulators are very important elements of electric power systems. This paper introduces an analysis of electrical conditions in the area between the conductor and the insulator's upperfitting. The designing of new a composite post insulator is presented with the upperfitting made of insulating material. Previous composite post insulators have had upperfittings made of conducting material metal. 3D analysis of electric-field strength in the insulator and its surroundings are also given. The computation was carried out by using the OPERA Vector Fields program tool. The results of this analysis are presented for both-new and old versions of a composite post insulator. 3D analysis shows that the new version has up to five times lower magnitudes of electric-field strength.

High-voltage insulator and a high-voltage electric power line using said insulator

Abstract: The high-voltage insulator for securing a high-voltage conductor in an electrical plant or in an electric power line comprises an insulating core, the first end of which is used for mechanically connecting to a high voltage conductor and/or to its coupling means, the second end being provided with a metal fastening element for fixing the insulator to a support, such as a tower. In order to impart lightning protection properties to the insulator, it is additionally provided with a multi-electrode system consisting of m electrodes which are mechanically attached to the insulating core and are arranged between the ends thereof. The electrodes are disposed in such a way as to support a formation of an electric discharge between the adjacent electrodes, between the electrode adjacent to the first end of the insulating core and to the high voltage conductor or to said coupling means, and between the electrode adjacent to the second end of the insulating core and the metal fastening element attached to the tower. The insulator is provided with means for compensating the reduction of the insulator creepage distance caused by the multi-electrode system. The electric power line using the insulator of this type does not require any lightning arresters.