Showing papers on "Insulator (electricity) published in 2011"

Apparatus and methods for transmission line based electric fence insulation

Abstract: Apparatus and methods for wire insulation in transmission line based electric fence are described in this invention. An insulator holds a wire pair that form the transmission line in its wire clamps. The insulator has a rain shed that sheds the wire clamps from getting wet by rain water. The insulator also has a pair of rain water divert guides that guide rain water accumulated on the wire to flow to the guide instead of to the wire clamps. This invention also describes a wire heating method that uses electric current to heat the fence wires such that the wire/wire clamp contact point will be kept dry and ice, snow accumulated on fence wires will be melted. Performance of the transmission line based electric fence can thus be greatly improved in advert weather conditions.

Analytical studies on holographic insulator/superconductor phase transitions

Abstract: We investigate the analytical properties of the s-wave and p-wave holographic insulator/superconductor phase transitions at zero temperature. In the probe limit, we analytically calculate the critical chemical potentials at which the insulator/superconductor phase transition occurs. Those resulting analytical values perfectly match the previous numerical values. We also study the relations between the condensation values and the chemical potentials near the critical point. We find that the critical exponent for condensation operator is 1/2 for both models. The linear relations between the charge density and the chemical potential near the critical point are also deduced in this paper, which are qualitatively consistent with the previous numerical results.

Externally gapped line arrester

Abstract: An arrester for preventing an insulator supporting a power line from experiencing an electrical flashover comprises an electrode, a varistor, and a separating device. The electrode is spaced apart from the power line or a conductor that is electrically tied to the power line so as to define an external gap therebetween. The separating device, in turn, comprises two portions operative to separate from one another when the varistor experiences an electrical condition sufficient to cause the varistor to fail. The electrode, the external gap, the separating device, and the varistor are arranged in electrical series with one another and in electrical parallel with the insulator.

Electrical control of terahertz nano antennas on VO2 thin film.

Abstract: We demonstrate an active metamaterial device that allows to electrically control terahertz transmission over more than one order of magnitude. Our device consists of a lithographically defined gold nano antenna array fabricated on a thin film of vanadium dioxide (VO2), a material that possesses an insulator to metal transition. The nano antennas let terahertz (THz) radiation funnel through when the VO2 film is in the insulating state. By applying a dc-bias voltage through our device, the VO2 becomes metallic. This electrically shorts the antennas and therefore switches off the transmission in two distinct regimes: reversible and irreversible switching.

Electric field computation of composite line insulators up to 1200 kV AC

Abstract: Satisfactory operation of composite insulators is intimately related to the surface electric field (stress) distribution. This paper presents results of calculation of the electric field distribution for composite insulators up to 1200 kV, using a 3D software package based on the Boundary Element Method. The impact of corona and grading rings, single and bundled conductors, insulator orientation (dead-end and suspension), single and double units, and surface condition (dry and wet) on the electric field distribution has been analyzed. For UHV systems (higher than 750 kV ac) the use of dual insulators with individual corona rings at the line and ground end and a common grading ring at the line end is beneficial. The existence of optimal dimensions of corona and grading arrangement has been illustrated on a 1000 kV insulator string. It was found that the dead end insulators experience higher electric stress when compared to their suspension counterparts and this difference gets more prominent as the system voltage increases.

Mica, a potential two-dimensional-crystal gate insulator for organic field-effect transistors.

Abstract: 2D mica crystals (with thickness < 100 nm) obtained by mechanical exfoliation are incorporated for the first time into the design of organic thin film field-effect transistor arrays and organic single crystal transistors as a gate insulator. The size of mica crystals could be up to the dimensions of an A4 piece of paper. All devices so fabricated exhibited high mobility and low operating voltage, indicating the high quality of the crystals and the great potential of mica crystals as a flexible, low-cost, transparent insulator for organic electronics.

Electro-absorption modulation in horizontal metal-insulator-silicon-insulator-metal nanoplasmonic slot waveguides

Abstract: An ultracompact, broadband, and fully complementary metal-oxide-semiconductor (CMOS) compatible Si nanoplasmonic electro-absorption modulator is proposed based on the recently developed horizontal metal-insulator-silicon-insulator-metal nanoplasmonic slot waveguide. The modulation relies on a highly accumulated electron layer at the insulator/Si interface induced by an applied voltage. Proof-of-concept devices are fabricated using standard Si CMOS technology. A 3-dB modulation around 1550 nm is measured under ∼6.5 V bias for a device with total length of only 4 μm. The design suggests that larger modulation could be achieved by using high-κ dielectrics as the insulator, thinning down the insulator thickness, and narrowing the Si core of the nanoplasmonic waveguide.

Differential signal transmission cable

Abstract: A differential signal transmission cable has a pair of conductors arranged to be distant from each other and parallel to each other, an insulator covering the pair of conductors, and a shield conductor wound around the insulator. The insulator has an outer periphery shape of a transversal cross section in that a plurality of curved lines with different curvature radiuses are combined. The shield conductor has an inner periphery shape of a transversal cross section in that the plurality of curved lines are combined in accordance with the outer periphery shape of the insulator.

Metal-insulator-silicon-insulator-metal waveguides compatible with standard CMOS technology

Abstract: Metal-insulator-silicon-insulator-metal (MISIM) waveguides are proposed and investigated theoretically. They are hybrid plasmonic waveguides, and light is highly confined to the insulator between the metal and silicon. As compared to previous ones, they are advantageous since they may be realized in a simple way by using current standard CMOS technology and their insulator is easily replaceable without affecting the metal and silicon. First, their structure and fabrication process are explained, both of which are compatible with standard CMOS technology. Then, the characteristics of the single MISIM waveguide whose insulator has its original or an adjusted refractive index are analyzed. The analysis demonstrates that its characteristics are comparable to those of previous hybrid plasmonic waveguides and that they are very effectively tuned by changing the refractive index of the insulator. Finally, the characteristics of the two coupled MISIM waveguides are analyzed. Through the analysis, it is obtained how close or far apart they are for efficient power transfer or low crosstalk. MISIM-waveguide-based devices may play an important role in connecting Si-based photonic and electronic circuits.

Electrical and optical devices incorporating topological materials including topological insulators

Abstract: An electrical device includes a current transport layer formed using a layer of a topological material selected from the group of a topological insulator, a quantum anomalous hall (QAH) insulator, a topological insulator variant, and a topological magnetic insulator. In one embodiment, the current transport layer forms a conductive wire on an integrated circuit where the conductive wire includes two spatially separated edge channels, each edge channel carrying charge carriers propagating in one direction only. In other embodiments, an optical device includes an optical layer formed using a layer of the topological material. The optical layer can be a light absorbing layer, a light emitting layer, a light transport layer, or a light modulation layer.

Surface discharge initiated by immobilized metallic particles attached to gas insulated substation insulators: process and features

Abstract: In order to study the developing process of surface discharges initiated by immobilized metallic particles attached to Gas Insulated Substation (GIS) insulators under gradually-raised applying voltages, long-term laboratory tests were conducted on a well-established 220 kV test assembly to observe the entire evaluation process of surface discharges from its inception to gradual expansion and the eventual occurrence of surface flashover Real-time detection was conducted to record conventional impulse current (CIC) signals, UHF signals, ultrasonic signals and light emission signals from PD Features of surface discharges at different developing stages were captured from the discharge trend curves, scatter diagrams, two-dimensional histograms, and grey-scale maps of PD The test findings indicate that i) surface discharge initiated by immobilized metallic particles attached to GIS insulators undergoes three developing stages from corona discharge domination in the incipient stage, to co-existence of corona discharge and surface discharge in the expansion stage, and finally the surface discharge domination in the final stage; ii) the shape and phase distribution shown in scatter diagram, histogram and grey-scale map could be used as effective criteria to infer different evolutionary stages of surface discharges produced by immobilized metallic particles attached to GIS insulators

Nonvolatile semiconductor memory device and method of fabricating the same

Abstract: According to one embodiment, a nonvolatile semiconductor memory device includes a semiconductor region, a tunnel insulator provided above the semiconductor region, a charge storage insulator provided above the tunnel insulator, a block insulator provided above the charge storage insulator, a control gate electrode provided above the block insulator, and an interface region including a metal element, the interface region being provided at one interface selected from between the semiconductor region and the tunnel insulator, the tunnel insulator and the charge storage insulator, the charge storage insulator and the block insulator, and the block insulator and the control gate electrode.

Separation of mixtures of particles in a multipart microdevice employing insulator‐based dielectrophoresis

Abstract: Dielectrophoresis is the electrokinetic movement of particles due to polarization effects in the presence of non-uniform electric fields. In insulator-based dielectrophoresis (iDEP) regions of low and high electric field intensity, i.e. non-uniformity of electric field, are produced when the cross-sectional area of a microchannel is decreased by the presence of electrical insulating structures between two electrodes. This technique is increasingly being studied for the manipulation of a wide variety of particles, and novel designs are continuously developed. Despite significant advances in the area, complex mixture separation and sample fractionation continue to be the most important challenges. In this work, a microchannel design is presented for carrying out direct current (DC)-iDEP for the separation of a mixture of particles. The device comprises a main channel, two side channels and two sections of cylindrical posts with different diameters, which will generate different non-uniformities in the electric field on the main channel, designed for the discrimination and separation of particles of two different sizes. By applying an electric potential of 1000 V, a mixture of 1 and 4 μm polystyrene microspheres were dielectrophoretically separated and concentrated at the same time and then redirected to different outlets. The results obtained here demonstrate that, by carefully designing the device geometry and selecting operating conditions, effective sorting of particle mixtures can be achieved in this type of multi-section DC-iDEP devices.

Electrical characteristics of natural and synthetic insulating fluids

Abstract: Mineral oil with high insulation performance and cooling capability is currently used for oil-immersed transformers. However, mineral oil is derived from petroleum and thus is a limited resource. In a search for mineral oil substitutes, we investigated the characteristics of silicone and ester oils. The electrical performance was assessed in terms of the breakdown and streaming electrification characteristics and the volume resistivity. The burning characteristics of each oil type were also investigated. The temperature dependence of the breakdown voltage in an oil unit and the surface breakdown characteristics in a composite insulating system comprising an insulating oil and an oil-immersed insulator were determined. We also investigated the temperature dependence of the charge density in oil. The charge density in silicone and mineral oils increased with temperature, with maximum values at ~ 100°C and ~ 60°C, respectively. By contrast, the charge density in ester oil decreased with increasing temperature and was maximum at ≤30°C.

Pattern analysis of discharge characteristics for hydrophobicity evaluation of polymer insulator

Abstract: Hydrophobicity is a prominent characteristic of silicone rubber for polymer insulators. However, due to the environmental influence, the decrease even the loss of hydrophobicity will take place, which causes the essential concern on the electrical accidents induced by the ageing of polymer insulators. The accurate evaluation on the insulator hydrophobicity is increasingly required for the long-term performance of outdoor insulators in service. In this paper, based on dynamic dropping test (DDT), pattern characteristic of surface discharges generated by the dynamic behavior of water droplet was investigated to evaluate the hydrophobic properties of silicone rubber insulator at different ageing levels. The specimens were prepared by using the method of corona degradation and determined by HC levels from HC1 to HC6. Both the dynamic behavior of water droplet and the induced discharge phenomena were captured by using a high-speed camera fixed vertically to the sample surface. In order to quantify the surface discharges, methods of image processing and fractal dimension were employed to establish the relationship between the pattern characteristic of discharge light and the HC levels. The morphology of discharge region and the distribution of luminous brightness in relationship with the lapse time can provide an optical evaluation method for the insulator hydrophobicity. It is found that the number and duration of discharge light increase with the increase of HC level. The increasing tendency in brightness intensity and fractal dimension of discharge pattern can reveal the decrease of hydrophobicity. Therefore, the results obtained indicate that the pattern characteristic of discharge light in DDT method is sensitive to the hydrophobic properties, which can be applied as a non-contact method for hydrophobicity evaluation of polymer insulators.

Simulation of Partial Discharge in High Voltage Power Equipment

Abstract: In high voltage (HV) electrical power system, variety of solid, liquid and gaseous materials are used for insulation purpose to protect the incipient failure inside the HV power equipment. Among these the solid insulation is widely used for high voltage power equipment HV electrical power system. Most of insulating materials are not perfect in all respect and contains always some impurities. The presence of air bubble is one of such impurities in insulating materials and highly undesirable for such type of insulation which causes a local weak zone inside the insulator. Insulation of the HV power equipment gradually degrades inside the insulator due to cumulative effect of electrical, chemical and thermal stress. Due to the high voltage stress the weak zone inside the insulator causes the partial discharge (PD) which is known as local electrical breakdown. As a result the insulation properties of such materials are enormously degrades its quality due to the PD. In this work, the simulation of PD activity due to presence of a small cylindrical void inside the solid insulation material of high voltage power equipment is studied with the MATLAB Simulink platform.

Method of fabricating a thin-film device

Abstract: A method of forming a thin-film device includes forming an oxide-semiconductor film formed on the first electrical insulator, and forming a second electrical insulator formed on the oxide-semiconductor film, the oxide-semiconductor film defining an active layer. The oxide-semiconductor film is comprised of a first interface layer located at an interface with the first electrical insulating insulator, a second interface layer located at an interface with the second electrical insulator, and a bulk layer other than the first and second interface layers. The method further includes oxidizing the oxide-semiconductor film to render a density of oxygen holes in at least one of the first and second interlayer layers is smaller than a density of oxygen holes in the bulk layer.

Impact of insulator shape, flow rate and electrical parameters on inactivation of E. coli using a continuous co-linear PEF system

Abstract: Pulsed electric field (PEF) application for the treatment of liquid media was investigated with focus on the improvement of the microbial inactivation. The paper aims to illustrate the various interdependencies of different treatment parameters such as electric field strength distribution, flow velocity profile, pulse energy, pulse frequency and electrical conductivity. Escherichia coli was used as an indicator microorganism to exemplify the impact of the previously mentioned parameters on the microbial inactivation results. The experimental set up was assisted by the numerical simulations of the electric field strength and flow velocity distribution. Two different configurations of insulator have been investigated related to the electric field strength and velocity distribution and their impact in the inactivation of E. coli. The convex insulator geometry was found to increase the average electric field strength from 37.6 to 38.5 kV/cm, but resulted in lower field homogeneity. Its use was therefore found to be favourable for the treatment media with lower conductivity. In that case, the application of a higher pulse number at maintained total specific energy input compensated field inhomogeneity effects by a longer treatment time. Industrial relevance: PEF as a non-thermal pasteurization technology requires an accurately defined treatment intensity in terms of electric field strength and treatment time. The microbial inactivation depends on the various interdependencies of different treatment parameters such as electric field strength distribution, flow velocity profile, pulse energy, pulse frequency and electrical conductivity. The presented investigation contributes to the understanding of these parameters for further successful industrial implementation of the PEF technology, such as, the proper selection of insulator shape, electric field strength and estimation of treatment time.

Influence of the linear non-uniformity of pollution layer on the insulator flashover under impulse voltage - estimation of the effective pollution thickness

Abstract: This paper is aimed at the influence of the linear non uniformity of pollution layer on critical current Icri and critical flashover voltage Vcri of polluted insulator under lightning impulse voltage. It is shown that the experimental values of Icri and Vcri of uniformly and non-uniformly polluted insulator depends on the configuration of pollution and the polarity of voltage. A mathematical model enabling to compute the flashover discharge characteristic constants (n and N) and the critical thickness of pollution layer and thence the critical characteristics of flashover (current and voltage) is presented. It's also shown that n and N are not static and they depend on the parameters of the equivalent electrical circuit, thermal characteristics of discharge and the condition of propagation. The computed critical voltages are found in a good accordance with the experimental ones while the computed critical currents are higher than the experimental ones. The recalculated critical currents and critical voltages assuming that only a part of the thickness of pollution layer contributes to the conduction phenomena at the interface between the discharge and electrolyte well match to the experimental values. Thus there is an effective thickness of pollution layer which varies linearly with the resistivity of pollution layer.

Anti-icing performance of RTV coatings on porcelain insulators by controlling the leakage current

Abstract: Considerable work has been done on preventing ice formation on insulators and the modification of the surface characteristics by increasing the contact angle and decreasing the adherent force have been tried with some degree of success. Heating by electric current has however proved to be an effective and practical method for de-icing transmission lines, but difficult to apply to insulators. A room temperature vulcanized (RTV) silicone rubber coating containing sufficient carbon black to render it partially conducting but not enough carbon to lose its surface hydrophobicity, has been investigated to determine if the heat generated would suffice to inhibit ice growth on the insulators. The heat exchange progress was analyzed and the leakage current through it to prevent ice forming was estimated and coatings developed accordingly. The anti-icing performances of these RTV silicone rubber coatings with different leakage current magnitudes were compared in a climate chamber. The results showed that the surface heating effect, together with the hydrophobicity, could significantly reduce the formation of ice on insulators.

Monolithic oxide–metal composite thermoelectric generators for energy harvesting

Abstract: Monolithic oxide–metal composite thermoelectric generators (TEGs) were fabricated using multilayer co-fired ceramic technology. These devices consisted of Ni0.9Mo0.1 and La0.035Sr0.965TiO3 as p- and n-type thermoelectric materials, and Y0.03Zr0.97O2 was used as an insulator, sandwiched between p- and n-type layers. To co-fire dissimilar materials, p-type layers contained 20 wt. % La0.035Sr0.965TiO3; thus, these were oxide–metal composite layers. The fabricated device had 50 pairs of p–i–n junctions of 5.9 mm × 7.0 mm × 2.6 mm. The calculated maximum value of the electric power output from the device was 450 mW/cm2 at ΔT = 360 K. Furthermore, this device generated 100 μW at ΔT = 10 K and operated a radio frequency (RF) transmitter circuit module assumed to be a sensor network system.

Conduction Mechanism and Reliability Characteristics of a Metal–Insulator–Metal Capacitor with Single ZrO2 Layer

Abstract: In this paper, the electrical characteristics and reliability of ZrO2-based metal–insulator–metal (MIM) capacitors are investigated. High capacitance density of 15.3 fF/µm2 was achieved for ZrO2 MIM capacitors, which is acceptable for the reported MIM capacitors. Schottky emission at the low field region is not a dominant mechanism, and Frenkel–Poole emission is the dominant mechanism at the high electric field region. The extracted dynamic constant and trap energy level were 4.013 and 0.963 eV, respectively. The reduced trap energy level with increasing electric field is due to a rise in the field-induced barrier-lowering effect. The variation of α as a function of stress time under constant voltage stress (CVS) gradually decreases, while the variation of ΔCstress/C0 under CVS increases because the generation of new dipoles in the high-κ dielectric under CVS may cause charge trapping in the high-κ dielectric.

Measuring and analyzing leakage current for outdoor insulators and specimens

Abstract: Outdoor insulation represents an important component of electric power transmission and distribution systems considering that a single insulator failure can result to an excessive outage of the power system. Different insulator designs and materials are employed by power corporations and their behavior is investigated and tested in lab and field tests as well as during service conditions. Specimens (rods and plates) are also tested when researchers focus on )bjYgh)(Uh)b(WYfhU)bd?YbcaYbUcZgifZUWYUWh)j)hmcfaUhYf)UCgwdYfZcfaUbWYk)h?cihVY)b( influenced by the insulator design. The performance of insulators is strongly linked with local conditions especially related to the accumulation of pollutants and the wetting mechanisms present. Leakage current is a well established tool to monitor and investigate surface electrical activity, which is strongly correlated to surface and material condition, experienced pollution and local conditions, and, thus, the overall performance of insulators. The scope of this paper is to review leakage current monitoring conducted by different researchers worldwide in respect to the variety of applications, the waveform shapes recorded, the correlation of waveform shapes and surface activity, the techniques applied on leakage current waveforms, the extracted and mea- sured values, the derived conclusions and overall significance of leakage current as a monitor- ing and investigating tool.

Method of operation of a multi-layer-multi-turn structure for high efficiency wireless communication

Abstract: A structure for wireless communication having a plurality of conductor layers, an insulator layer separating each of the conductor layers, and at least one connector connecting two of the conductor layers wherein an electrical resistance is reduced when an electrical signal is induced in the resonator at a predetermined frequency.

Three-dimensional cellular focusing utilizing a combination of insulator-based and metallic dielectrophoresis

Abstract: Particle focusing in microfluidic devices is a necessary step in medical applications, such as detection, sorting, counting, and flow cytometry. This study proposes a microdevice that combines insulator-based and metal-electrode dielectrophoresis for the three-dimensional focusing of biological cells. Four insulating structures, which form an X pattern, are employed to confine the electric field in a conducting solution, thereby creating localized field minima in the microchannel. These electrodes, 56-μm-wide at the top and bottom surfaces, are connected to one electric pole of the power source. The electrodes connected to the opposite pole, which are at the sides of the microchannel, have one of three patterns: planar, dual-planar, or three-dimensional. Therefore, low-electric-field regions at the center of the microchannel are generated to restrain the viable HeLa cells with negative dielectrophoretic response. The array of insulating structures aforementioned is used to enhance the performance of confinement. According to numerical simulations, three-dimensional electrodes exhibit the best focusing performance, followed by dual-planar and planar electrodes. Experimental results reveal that increasing the strength of the applied electric field or decreasing the inlet flow rate significantly enhances focusing performance. The smallest width of focusing is 17 μm for an applied voltage and an inlet flow rate of 35 V and 0.5 μl/min, respectively. The effect of the inlet flow rate on focusing is insignificant for an applied voltage of 35 V. The proposed design retains the advantages of insulator-based dielectrophoresis with a relatively low required voltage. Additionally, complicated flow controls are unnecessary for the three-dimensional focusing of cells.

Analysis of the relation between water and resistivity isotherms in concrete

Abstract: Concrete is a porous material, that contains an alkaline solution, whose pore network enables mass transport from the exterior. The concrete as composite material is quasi an insulator when it is dry and presents relatively low resistivities, in the order of few kΩ cm when it is fully saturated. Concrete resistivity reflects the degree of saturation and is therefore a useful indicator of the risk of chemical attack and of reinforcement corrosion. The dependence of resistivity on the degree of saturation has been studied, yet this subject has still not been fully elucidated. The present paper studies the evolution of concrete drying from the end of curing in order to analyze the water and resistivity isotherms. Four concrete mixes (w/c = 0.4 and 0.7 after 3 and 7 days of curing wrapped in plastic sheets) have been prepared and submitted to conditions of isothermic water desorption in controlled atmospheres with relative humidity (RH) of 55, 65, 75, 85, 95%. Resistivity measurements were simultaneously carried out which enabled to identify for the four mixes the water content and the RH which gives resistivity values higher than 105 Ω cm. The radii of water-filled pores calculated from Kelvin's law were found to be smaller than those calculated by integrating the mercury intrusion porosimetry (MIP) accumulated intrusion curve with the water lost during conditioning at different RHs. The water content measurement that seems to be most adequate for comparison with resistivity values is the volumetric fraction.

Non-thermal plasma ignition arc suppression

Abstract: An igniter (20) of a corona ignition system emits a non-thermal plasma in the form of a corona (30) to ionize and ignite a fuel mixture. The igniter (20) includes an electrode (32) and a ceramic insulator (22) surrounding the electrode (32). The insulator (22) surrounds a firing end (38) of the electrode (32) and blocks the electrode (32) from exposure to the combustion chamber (28). The insulator (22) presents a firing surface (56) exposed to the combustion chamber (28) and emitting the non-thermal plasma. A plurality of electrically conducting elements (24) are disposed in a matrix (26) of the ceramic material and along the firing surface (56) of the insulator (22), such as metal particles embedded in the ceramic material or holes in the ceramic material. The electrically conducting elements (24) reduce arc discharge during operation of the igniter (20) and thus improve the quality of ignition.

Effect of arc-levitating from polluted insulators' surface in the low air pressure on its DC flashover performance

Abstract: Part of DC arcs may levitate from the insulators' surface to form air-gap arcs in the process of insulator's flashover, especially in the low air pressure The air-gap arcs can cause the bridging between ribs (or sheds) of insulators easily, and the U–I characteristics of air-gap arcs and surface arcs are different Thus, the two aspects should be taken into account when evaluating the DC flashover performance of insulators at low air pressure This study analyses the effect of arc-levitating on the DC flashover voltage of polluted insulators and calculates the insulators' DC flashover voltages with and without considering the effect of air-gap arc The comparisons between calculated and experimental results show that the DC flashover voltages of polluted insulators are overestimated when the air-gap arcs are not taken into account