Showing papers on "Insulator (electricity) published in 2017"
TL;DR: In this paper, a depletion/enhancement-mode β-Ga2O3 on insulator field effect transistors can achieve a record high drain current density of 1.5/1.0
Abstract: We have demonstrated that depletion/enhancement-mode β-Ga2O3 on insulator field-effect transistors can achieve a record high drain current density of 1.5/1.0 A/mm by utilizing a highly doped β-Ga2O3 nano-membrane as the channel. β-Ga2O3 on insulator field-effect transistor (GOOI FET) shows a high on/off ratio of 1010 and low subthreshold slope of 150 mV/dec even with 300 nm thick SiO2. The enhancement-mode GOOI FET is achieved through surface depletion. An ultra-fast, high resolution thermo-reflectance imaging technique is applied to study the self-heating effect by directly measuring the local surface temperature. High drain current, low Rc, and wide bandgap make the β-Ga2O3 on insulator field-effect transistor a promising candidate for future power electronics applications.
153 citations
TL;DR: In this paper, the effect of direct fluorination on surface charge migration and flashover voltage was verified, and it was shown that the surface charge decay of epoxy-based model insulators is a slow process, but the decay rate increases when an outer dc electric field is applied.
Abstract: Epoxy-based model insulators were manufactured and fluorinated under a F2/N2 mixture (12.5% F2) at 50 °C and 0.1 MPa for 15 min and 60 min. Surface charge accumulation and decay behavior were studied with and without dc voltage application. The effect of direct fluorination on surface charge migration as well as on flashover voltage was verified. The obtained results show that the charge decay of epoxy-based insulators is a slow process, but the decay rate increases when an outer dc electric field is applied. The surface charge distribution is changed when a streamer is triggered on the insulator surface. The existence of heteropolarity surface charges can decrease the dc surface flashover voltage to some extent, while the surface flashover voltage is almost unchanged when charges of the same polarity accumulate on the insulator surface. The short time fluorinated insulator can modify the surface resistivity, and the rate of surface charge dissipation is greatly increased under a dc electric field.
141 citations
TL;DR: In this article, a depletion/enhancement mode b-Ga2O3 on insulator field-effect transistors can achieve a record high drain current density of 1.5/1.0 A/mm by utilizing a highly doped b-GA 2O3 nano-membrane as the channel.
Abstract: We have demonstrated that depletion/enhancement-mode b-Ga2O3 on insulator field-effect transistors can achieve a record high drain current density of 1.5/1.0 A/mm by utilizing a highly doped b-Ga2O3 nano-membrane as the channel. b-Ga2O3 on insulator field-effect transistor (GOOI FET) shows a high on/off ratio of 1010 and low subthreshold slope of 150 mV/dec even with 300 nm thick SiO2. The enhancement-mode GOOI FET is achieved through surface depletion. An ultra-fast, high resolution thermo-reflectance imaging technique is applied to study the self-heating effect by directly measuring the local surface temperature. High drain current, low Rc, and wide bandgap make the b-Ga2O3 on insulator field-effect transistor a promising candidate for future power electronics applications.
121 citations
TL;DR: In this article, the heat transfer surface charge accumulation model of operating DC-GIL was developed, including the nonlinear relationship between volume current in gas and electric field, and the space charge was also considered in the model.
Abstract: With this expected future advance of HVDC, the use of gas insulated transmission lines (GIL) for dc application are getting increasingly interesting. For now, the problem of surface charge accumulation on gas-insulator interface is one of the critical factors for the development of DC-GIL. In many previous works, the model of surface charge accumulation on insulator was investigated. However, the quantitative relationship between temperature and surface charge accumulation on insulator was not exactly obtained since the lack of complicated heat transfer progress in the model. In this paper, the heat transfer surface charge accumulation model of operating DC-GIL was developed, including the nonlinear relationship between volume current in gas and electric field. Moreover, the space charge was also considered in the model. Based on the developed model, temperature distributions in DC-GIL insulator under different current are obtained. Afterwards, the temperature impact on space charge density in the insulator, the saturation time of surface charge accumulation, the surface charge on the insulator surface, and the electric field distribution on the insulator were investigated. It was proven that the tangential component of the electric field reaches to 5.3 kV/mm on lower interface and 5.0 kV/mm on upper interface for Ti=378 K. This value increase 17.8% on lower interface and 17.6% on upper interface along with the conductor temperature from 298 K to 378 K. The data can be referred in the insulation design of DC-GIL.
78 citations
TL;DR: Poly(ethylene oxide) is demonstrated to be a suitable matrix polymer for the solution‐doped conjugated polymer poly(3‐hexylthiophene) and free‐standing, mechanically robust tapes illustrate the versatility of the developed dopant:semiconductor:insulator ternary blends.
Abstract: Poly(ethylene oxide) is demonstrated to be a suitable matrix polymer for the solution-doped conjugated polymer poly(3-hexylthiophene). The polarity of the insulator combined with carefully chosen processing conditions permits the fabrication of tens of micrometer-thick films that feature a fine distribution of the F4TCNQ dopant:semiconductor complex. Changes in electrical conductivity from 0.1 to 0.3 S cm−1 and Seebeck coefficient from 100 to 60 μV K−1 upon addition of the insulator correlate with an increase in doping efficiency from 20% to 40% for heavily doped ternary blends. An invariant bulk thermal conductivity of about 0.3 W m−1 K−1 gives rise to a thermoelectric Figure of merit ZT ∼ 10−4 that remains unaltered for an insulator content of more than 60 wt%. Free-standing, mechanically robust tapes illustrate the versatility of the developed dopant:semiconductor:insulator ternary blends.
70 citations
TL;DR: Techniques were introduced for the acoustic detection of insulator faults by acoustic radiation noises to classify the fault state insulators without human inspection by considering the amount of total noises and 120-Hz harmonic components.
Abstract: Insulators are important equipment used to electrically isolate and mechanically hold wires in high-voltage power transmission systems. Faults caused by the deterioration of the insulators induce very serious problems to the power transmission line. Techniques were introduced for the acoustic detection of insulator faults by acoustic radiation noises. Radiation noises were measured from normal state insulators and fault state insulators in an anechoic chamber. The insulators used were two porcelain insulators, a cut-out switch, two line posters, and a lightning arrester. A new acoustic technique determines the direction of the insulator faults using source localization with three-dimensional microphone arrays. The advantage is to classify the fault state insulators without human inspection by considering the amount of total noises and 120-Hz harmonic components. The fault detection was determined by neural network to diagnose the state automatically. The proposed technique was evaluated by distinct, real datasets and the efficacy was validated. The noise source was detected with 100.0% accuracy and the classification ratio achieved 96.7% for three typical conditions.
59 citations
TL;DR: This work proposes and demonstrates a general method to decouple the two roles of the insulator by employing localized dielectric breakdown, which allows the insulators to be thick, which enhances stability, while enabling low-resistance carrier transport as required for efficiency.
Abstract: Silicon-based photoelectrodes for solar fuel production have attracted great interest over the past decade, with the major challenge being silicon's vulnerability to corrosion. A metal-insulator-semiconductor architecture, in which an insulator film serves as a protection layer, can prevent corrosion but must also allow low-resistance carrier transport, generally leading to a trade-off between stability and efficiency. In this work, we propose and demonstrate a general method to decouple the two roles of the insulator by employing localized dielectric breakdown. This approach allows the insulator to be thick, which enhances stability, while enabling low-resistance carrier transport as required for efficiency. This method can be applied to various oxides, such as SiO2 and Al2O3. In addition, it is suitable for silicon, III-V compounds, and other optical absorbers for both photocathodes and photoanodes. Finally, the thick metal-oxide layer can serve as a thin-film antireflection coating, which increases light absorption efficiency.
57 citations
TL;DR: It is found that under electrical stress, local charge accumulation and charge trapping/detrapping are the onset mechanisms for dielectric BD formation, which avoids self-accelerated and thermally driven catastrophic BD.
Abstract: Insulating films are essential in multiple electronic devices because they can provide essential functionalities, such as capacitance effects and electrical fields. Two dimensional (2D) layered materials have superb electronic, physical, chemical, thermal and optical properties, and they can be effectively used to provide additional performances (flexibility, transparency). 2D layered insulators are called to be essential in future electronic devices, but their reliability, degradation kinetics and dielectric breakdown process are still not understood. In this work the dielectric breakdown process of multilayer hexagonal boron nitride (h-BN) is analyzed at the nanoscale and the device level, and the experimental results are studied via theoretical models. It is found that, under an electrical stress, local charge accumulation and charge trapping/de-trapping are the onset mechanisms for dielectric breakdown (BD) formation. By means of conductive atomic force microscopy (CAFM) the BD event is triggered at s...
53 citations
TL;DR: In this article, an online RF-based partial discharge (PD) technique for monitoring ceramic disc insulators is presented. But the method is limited to the case of broken, cracked and punctured insulators.
Abstract: Defects in ceramic insulators like broken, cracked and punctured discs give rise to the initiation of partial discharge (PD) activities within the samples which has a detrimental effect on the insulator life. Hence it is important for the utilities to identify such defective samples as early as possible so that appropriate replacement strategies can be devised. The work presented in this paper involves the investigation of a number of cases of insulator defects, with the goal of developing an online RF-based PD technique for monitoring ceramic disc insulators. The three classes examined are a cracked ceramic insulator disc; a disc with a hole through the cap, and a completely broken insulator disc. The defective discs are considered individually and are also incorporated into strings of 2, 3, and 4 insulators. The captured RF pulses are processed by extracting wavelet packet based features. Feature reduction and selection is carried out and classification results are obtained. To classify the discharges arising from different types of defects, an artificial neural network (ANN) algorithm is applied to the extracted features, and recognition rates of more than 95% were reported for each class. The results of preliminary field tests carried out on a 40 feet high test transmission tower are also reported and their analysis showed good discrimination between the different defect types.
42 citations
TL;DR: A thermodynamic formulation to quantify defect formation energetics in an insulator under a high electric field and analysis of neutral oxygen vacancies in alkaline-earth-metal binary oxides have implications for understanding the behavior of insulating oxides in electronic, magnetic, catalytic, and electrocaloric devices under ahigh electric field.
Abstract: We demonstrate a thermodynamic formulation to quantify defect formation energetics in an insulator under a high electric field. As a model system, we analyzed neutral oxygen vacancies (color centers) in alkaline-earth-metal binary oxides using density functional theory, Berry phase calculations, and maximally localized Wannier functions. The work of polarization lowers the field-dependent electric Gibbs energy of formation of this defect. This is attributed mainly to the ease of polarizing the two electrons trapped in the vacant site, and secondarily to the defect induced reduction in bond stiffness and softening of phonon modes. The formulation and analysis have implications for understanding the behavior of insulating oxides in electronic, magnetic, catalytic, and electrocaloric devices under a high electric field.
39 citations
TL;DR: In this article, the insulation characteristics of GIS under combined voltage of DC and lightning impulse were investigated and the results of the experiments show that residual DC voltage in GIS could deteriorate its insulation ability and the combined voltage was found to be a critical condition for GIS insulation.
Abstract: Operating experience shows that residual DC voltage remains in GIS bus bar for a long time after opening of disconnectors. This DC voltage will not only cause accumulation of charges and contaminants on the insulator surface, but will also easily lead to motion of free metallic particles in SF6 gas gap, weakening the insulation ability of GIS. At the time of disconnectors reclosing, impulse voltage could be generated in the bus bar and superimpose on the pre-existing DC voltage. As a result, GIS will be under combined voltage of DC and impulse. This paper experimentally studies the insulation characteristics of GIS under combined voltage of DC and lightning impulse. It is found that, for non-contaminated insulators, when DC and LI voltage are of the same polarity, flashover voltage under combined voltage is nearly the same as the flashover voltage under LI alone. However, when they are of the opposite polarity, flashover voltage decreases with increasing DC voltage. In cases there are metallic particle or powder around insulator, pre-stressed DC voltage will cause adhesion of contaminants on the insulator surface and lead to decrease of flashover voltage. Specially, for the particle-contaminated insulator, it is found that the surface charge accumulation caused by DC voltage will have big influence on the flashover voltage, and the most critical condition is when DC and LI voltage are of the opposite polarity. In addition, the breakdown characteristics of SF6 gas gap with free metallic particle are investigated. It is found that under pre-stressed DC voltage, particle will do standing motion or bouncing motion. And breakdown voltage becomes lowest when particle is doing standing motion. The results of the experiments show that residual DC voltage in GIS could deteriorate its insulation ability and the combined voltage of DC and impulse is found to be a critical condition for GIS insulation. Moreover, the combined voltage is shown to be more sensitive to detect some insulation defects in GIS than applying impulse voltage alone, especially for free metallic particles, which are commonly found in GIS but up to now no effective detection method is proposed. Therefore combined voltage of DC and impulse could be considered to serve as a supplement of field test for GIS.
TL;DR: In this paper, the effect of temperature on pollution performance of SIR insulators is studied, and a novel and simple methodology to achieve uniform contamination layer on inherently hydrophobic HTV SIR samples is presented.
Abstract: In recent times, high temperature vulcanized (HTV) silicone rubber insulators (SIR) are being widely used for overhead high voltage transmission and distribution systems. However, over a period, the insulator surface will be exposed to high temperature in several places, particularly in desert areas; further accumulation of pollutants can alter the temperature distribution along the insulator. In the present work, long-term electrothermal experimentation is carried out on various types of full-scale insulator units. The effect of temperature on pollution performance of SIR insulators is studied, and a novel and simple methodology to achieve uniform contamination layer on inherently hydrophobic HTV SIR insulator samples is presented. A specially fabricated oven having a provision for high voltage connection and facility for measurement of leakage currents is provided. Furthermore, study of migration of low molecular weight, recovery trends of hydrophobicity, and changes in material properties using scanning electron microscopy Fourier transform infrared spectroscopy is carried out.
TL;DR: In this article, two different methods under uniform and non-uniform pollution layer were presented to measure and calculate the leakage current (LC) of silicone rubber insulators, and the surface conductivity used in the calculations was extracted from the measured LC after wetting rate.
Abstract: This study presents two different methods under uniform and non-uniform pollution layer in order to measure and calculate the leakage current (LC) of silicone rubber insulators. Experimental test for evaluating the LC analysis of polluted insulator have been done in a laboratory clean fog chamber. The electric field and potential distributions were obtained from finite element method software for 3D models. The mathematical background and circuit theory are described in details by a section of insulator and using the extended form factor formula. The surface conductivity used in the calculations was extracted from the measured LC after wetting rate. LC characteristics under 1 : 1, 1 : 2, 1 : 5 and 1 : 10 ratios of top to bottom surface salt deposit density on polymeric insulators are studied. To verify the proposed models of this study, the results of experimental data and two other approaches are compared with together before dry-band formation. Moreover, a dynamic LC model under uniform pollution layer has been introduced and extended in order to calculate the LC when the formation of dry-bands along the insulator surface occurs. The dynamic model is drawn from experimental data and measured surface conductivity.
01 Dec 2017
TL;DR: The model of convolutional neural network from recent studies on deep learning is adopted to achieve end-to-end intelligent detection of insulators, which helps computers to identify the insulators from the footage faster and obtain fault detection more accurate of the insulator.
Abstract: Insulator is an extremely important component of the power transmission system. This article adopts the model of convolutional neural network from recent studies on deep learning to achieve end-to-end intelligent detection of insulators, which helps computers to identify the insulator from the footage faster and obtain fault detection more accurate of the insulator. Firstly, the method of object detection is used to determine the location of the insulator; then the insulator is extrapolated using fully convolutional networks; lastly, based on insulator's fault explosion characteristic, the coordinates of the fault explosion can be detected. The experimental results indicate that the method can effectively detect the faulted insulators in highly cluttered images, and our insulator fault detection outperforms existing methods.
TL;DR: In this paper, the authors provide a comprehensive overview of the many factors that may enhance the level of electric field along the high voltage (HV) insulators, review of existing stress control methods and new promising technologies in stress control using advanced materials.
TL;DR: In this article, the authors reported the fabrication of polymer field effect transistors operating under a bias of |1 V| in which the insulator and semiconductor are gravure-printed on plastic at the high speed of 0.7 m s−1.
Abstract: This study reports the fabrication of polymer field-effect transistors operating under a bias of |1 V| in which the insulator and semiconductor are gravure-printed on plastic at the high speed of 0.7 m s−1. Remarkably, the process does not necessitate any surface modification and relies solely on the careful selection and optimization of formulations based on solvent blends. In addition to demonstrating high-throughput fabrication, this study fulfills another requirement for organic electronics and achieves low-voltage operation in ambient air by using a polyelectrolyte insulator, poly(4-styrenesulfonic acid) (PSSH). PSSH is a proton conductor that forms electrical double layers at the interfaces with the gate electrode and the semiconductor channel upon application of a small gate voltage (≤ |1 V|). Printed PSSH exhibits a high capacitance of 10 µF cm−2, leading to a printed poly(3-hexylthiophene) hole mobility above 0.1 cm2 V−1 s−1 in a bottom-gate, top-contact configuration.
Journal Article•
TL;DR: In this article, forced convection flow and heat transfer of MWCNTs-water nanofluid in heat sink collector equipped with mixers are studied, and the three-dimensional governing equations are numerically solved in the domain by the control volume approach based on the SIMPLE algorithm.
Abstract: In this paper, forced convection flow and heat transfer of MWCNTs-water nanofluid in heat sink collector equipped with mixers are studied. The three-dimensional governing equations are numerically solved in the domain by the control volume approach based on the SIMPLE algorithm. Reynolds numbers are considered in laminar-turbulent range of 50
TL;DR: In this paper, the breakdown mechanism in the Micro-Cathode Arc Thruster has been studied to better understand the nature of the discharge ignition and to extend the ignition system lifetime.
Abstract: The breakdown mechanism in the Micro-Cathode Arc Thruster has been studied to better understand the nature of the discharge ignition and to extend the ignition system lifetime. It has been found that optimal material selection of the insulator is an important factor during breakdown. Two opposite processes have been found to cycle during operation. The processes are degradation of the conductive film from the inter-electrode interface and re-deposition of the conductive film due to cathode spot erosion. Initial resistances were found to vary from hundreds of ohms to thousands of ohms based on the initial connectivity of the film to the electrodes. After initial breakdown however, resistances have been found to stabilize in a typical pattern. Materials capable of withstanding high temperatures, high pressures, and smooth surfaces are shown to be beneficial for extending thruster lifetime.
TL;DR: In this article, a surface charge measurement system which could achieve temperature control was constructed, and a model insulator with truncated cone type was employed, as well as two types of high-voltage electrodes, i.e. plate and needle electrodes.
Abstract: During the operation of gas insulated switchgear (GIS) and gas insulated line (GIL), the conducting bar generates joule heat, and a non-uniform distribution of temperature forms in the bulk of the insulators. As the load varies, the temperature distribution changes, and it has an influence on the bulk conductivity of the insulators. Moreover, the surface charge accumulation can be affected. In order to clarify this, a surface charge measurement system which could achieve temperature control was constructed, and a model insulator with truncated cone type was employed, as well as two types of high-voltage electrodes, i.e. plate and needle electrodes. It is found that both polarities of charges existed on the insulator surface when a dc high voltage was applied to the plate or needle electrode, and homo-charge density was much higher than that of hetero-one. As for the plate electrode, homo-charges resulted from micro-discharges, while generated by corona in the case with needle electrode. As temperature increased, homo-charge density decreased, kept unchanged and increased for three cases, respectively, i.e. when dc voltage was applied to the plate electrode, and when voltage of 3 and 20 kV was applied to the needle electrode. Moreover, a simulation model involving multi-physics was established, which included heat conduction in solid and transient field changing from the initial capacitive to stationary resistive field distribution. It is proved that the electric conduction of the insulator bulk contributed to the accumulation of hetero-charges, and temperature could enhance this. Besides, when temperature increased, the corona inception voltage reduced, and hence the homo-charge density increased. Due to the effect of neutralization and the differences in the sensitivity of corona with different intensity to temperature, the tendency of homo-charge density changing with temperature for the three cases showed distinct in the experiments.
TL;DR: In this paper, the effect of pollution severity, leakage distance and dry band location on the flashover characteristics of silicone rubber insulator was investigated, and the electric field and potential along a silicone rubber sample were studied under different pollution severity and dry bands conditions.
Abstract: This paper investigates the flashover and ageing behavior of silicone rubber insulators under various contamination and dry band conditions. Effect of pollution severity, leakage distance and dry band location on the flashover characteristics of silicone rubber insulator was investigated. Flashover voltage and electric field distribution were measured under different pollution severity levels and dry band conditions. Effect of leakage distance on flashover voltage was also studied. Tests were carried out in a climate chamber and specific values of humidity and ambient temperature were used. A commercially available simulation package, COMSOL Multiphysics, was used to validate the experimental results. Electric field and potential along a silicone rubber sample were studied under different pollution severity and dry band conditions. Fourier transform infrared spectroscopy was used to analyze the chemical changes on the insulator surface and investigate the hydrophobicity recovery property of silicone rubber after flashover tests. The results of this study will further our knowledge regarding the flashover of silicone rubber outdoor insulators under contaminated and dry band conditions and could be used to improve the existing flashover models.
TL;DR: By dual gating a few-layer MoS_{2} flake, spatially separated electronic states showing superconductivity and Shubnikov-de Haas (SdH) oscillations are induced that enables "bipolarlike" superconducting transistor operation.
Abstract: Electric fields applied on either side of a thin, semiconducting transition-metal dichalcogenide create a superconducting layer atop a metallic layer within the material.
TL;DR: In this paper, the authors proposed to integrate composite insulators in a three phase 400 kV AC double circuit line situated in the northwest of Algeria for better electrical performances, and compared the already existing glass and porcelain insulators and the proposed composite insulator in terms of electric field distribution.
Abstract: Because of their advantages over glass and porcelain insulators, composite insulators are being used now in power transmission lines for different voltage rating levels. Recently, the 400 kV level is introduced by Societe Nationale de l'Electricite et du Gaz, SONELGAZ (Algerian Company of Electric Power and Gas) where glass insulators are installed. For better electrical performances, we propose in this paper to integrate composite insulators in a three phase 400 kV AC double circuit line situated in the northwest of Algeria. A comparison is done between the already existing glass insulators and the proposed composite insulator in terms of electric field distribution. The electric field is studied along the leakage paths of the insulators under different surface conditions (dry and clean, uniformly and non uniformly polluted, and in presence of water droplets). Three composite insulators with different shed configurations are proposed. From these three configurations, we selected the insulator presenting lower electric field magnitude in critical areas mainly on the triple point junction (air — HV end — housing material interface). On the double circuit line, we focused our study on the phase insulator that presents the highest electrical stress. Impact of hardware fittings, tower, phases and conductors on the electric field distribution has been analyzed. Effects of bundled conductors have been also studied. Simulations were carried out by employing 2D Finite Element Method (FEM) using COMSOL Multiphysics® 4.3 software. Results show that electric field is lower in the case of composite insulators. Furthermore, we found that the calculation model can be simplified by not considering all circuit phases. Note that appropriate corona rings are considered on both HV and ground ends for glass and composite insulators and their geometrical parameters (corona ring diameter, corona ring tube diameter and corona ring height) are kept constant throughout the whole study.
TL;DR: In this paper, a 3D high-resolution surface charge measurement system was established on actual 220 kV basin insulator, which captured the surface charge distribution characteristics of the insulator under DC and AC voltage through high-precision probe scanning.
Abstract: The Gas Insulated Switchgear (GIS) equipment observes surface charge accumulation under DC or AC voltage in real operation, which could distort the electric field and incur flashover eventually. With a 3D high-resolution surface charge measurement system established on actual 220 kV GIS basin insulator, the present research captured the surface charge distribution characteristics of the insulator under DC and AC voltage through high-precision probe scanning on the insulator surface. The test results show that: 1) Surface charge demonstrates obvious polarity effect under DC voltage. Under positive DC voltage, there accumulated mainly positive surface charges. Under negative DC voltage, the polarity of accumulated surface charges is all negative. Regardless of charge polarities, the surface charge density increases as the voltage amplitudes mounts and the voltage application duration prolongs. 2) Surface charge accumulation also takes place under AC voltage application. All charges are negative and distribute in a uniformed manner but in smaller density comparing to the DC scenario. As the voltage amplitudes increase, the surface charge density first increases, then decreases and finally reaches a near saturation state. As voltage application goes on, the surface charge accumulation becomes more obvious. Above all, the insulation issues in relation to surface charge accumulation require due attention in the application and maintenance of GIS equipment, and the present research attempts to provide useful reference for the optimal design of GIS/GIL insulators.
14 May 2017
TL;DR: In this article, a novel +45° insulator is proposed, which has a conductivity graded structure in which the high conductivity part performs as a shield to reduce the electric field concentration at anode triple point and along surface.
Abstract: In this paper, a novel +45° insulator is proposed. The insulator has a conductivity graded structure in which the high conductivity part performs as a shield to reduce the electric field concentration at anode triple point and along surface. Hence, the surface electrical withstanding strength would be enhanced. Computer aided simulation is performed to investigate the electric field distribution with different shape parameters of high-conductivity area and an electric field optimized insulator design is thus obtained. A Fused Deposition Modeling 3D printing technique is adopted to fabricate the conductivity graded insulator. The wide application of 3D printing in insulator fabrication is expected for its ability to fabricate special functional structure and high fabricating efficiency. Flashover tests are to be conducted to investigate the electrical withstanding performance of such insulators.
TL;DR: In this article, the role of insulator dimensions (shank diameter, shed diameter and number of sheds) on flashover performance has been discussed and it is shown that the increased probability of flashover due to the presence of water particles when compared to insulators with only wet surfaces can be quantified.
Abstract: This paper describes a method based on electric field calculation and random walk theory for evaluating insulator performance in a wet environment. Arc bridging of sheds via water particles suspended in close proximity to the insulator has been considered. The role of insulator dimensions (shank diameter, shed diameter and number of sheds) on the flashover performance has been discussed. It is shown that the increased probability of flashover due to the presence of water particles when compared to insulators with only wet surfaces can be quantified. With low to moderate levels of contamination commonly encountered in service, the relative increase in flashover probability is higher due to the presence of suspended water particles than that obtained under heavy contamination.
TL;DR: In this paper, a spouted bed process used for combining of particles and a polymer matrix in order to fabricate highly filled composite materials is described, as well as the apparatus for this aim and the flow regime of fine particles.
TL;DR: A DC step test and a number of DC life endurance tests have been performed at a temperature of 20°C on 200 μm thick samples of a commercial (AC grade) XLPE and its nanocomposite which is intended for DC use.
Abstract: A DC step test and a number of DC life endurance tests have been performed at a temperature of 20°C on 200 μm thick samples of a commercial (AC grade) XLPE and its nanocomposite which is intended for DC use. It was found that the breakdown strength of the nano-composite on the DC step test was considerably larger than that of the unfilled XLPE. However, the endurance tests showed that the difference between the characteristic lifetime of the nano-composite and its unfilled base polymer reduced as the applied field was reduced and the lifetimes became essentially the same when the applied field was 130 kV/mm, which is the lowest for which we have data at present. The life line was analyzed as an inverse power law and gave median life exponents of n = 10.76 for the nano-composite and n = 13.58 for the XLPE. These values are consistent with estimates from step tests on the same materials that have been recently published, and imply that the nano-composite will perform worse than the AC grade XLPE as a DC insulator if the inverse power law continues to be obeyed down to service fields.
01 Jul 2017
TL;DR: A novel method is proposed based on Faster R-CNN in which Region Proposal Network (RPN) is used to generate high-quality insulator candidates and the convolution features are shared with Fast R- CNN to detect the insulator.
Abstract: Insulators are the most common equipment in the power system, the failure of insulators will cause heavy economic loss to electric power companies, so it is very important to detect insulators effectively for inspecting their working states. This paper proposes a novel method to detect the insulators based on Faster R-CNN in which Region Proposal Network (RPN) is used to generate high-quality insulator candidates and the convolution features are shared with Fast R-CNN to detect the insulator. A large number of visible light images are used as experimental data in experiment, and the results show that this method can detect insulators in complex background with high precision as well as low time cost.
TL;DR: In this article, the surface potential decay characteristics of specimens extracted from in-service aged and reference HVDC composite insulator sheds are reported and analyzed using a noncontact technique, and surface and bulk conductivities of the specimens were determined and used for analyzing by means of computer simulations their impact on the potential distribution profiles and its decay.
Abstract: Surface potential decay characteristics of specimens extracted from in-service aged and reference HVDC composite insulator sheds are reported and analyzed in this paper. In the experiments, surfaces of the insulator samples were charged by dc corona and the decay was recorded utilizing a non-contact technique. In addition, surface and bulk conductivities of the specimens were determined and used for analyzing by means of computer simulations their impact on the potential distribution profiles and its decay. Based on the performed experiments, trap density distributions, mobility of charge carriers and field dependent bulk conductivities are deduced for the investigated samples with the aim to evaluate the ageing severity.
TL;DR: In this article, a low-k/high-k bilayer polymer dielectric was used for solution-processed semiconducting single-walled carbon nanotube (s-SWNT) field effect transistors with efficient charge transport and operation at low voltage.
Abstract: Solution-processed semiconducting carbon nanotube transistors with a high mobility and an ON/OFF ratio are the most promising for use in flexible electronics. In this paper, we report low-k/high-k bilayer polymer dielectrics for solution-processed semiconducting single-walled carbon nanotube (s-SWNT) field-effect transistors (s-SWNT-FETs) with efficient charge transport and operation at low voltage. Thin low-k polystyrene (10 nm) is used for the first contact insulator with a channel in order to passivate the dipolar disorder induced by high-k insulators. The second gate insulator for low voltage operation is cyanoethyl pullulan (CEP), which is an environmentally friendly high-k insulator based on cellulose. Moreover, poly[(vinylidenefluoride-co-trifluoroethylene) is chosen as a single layer dielectric for comparison. A reasonably low operational voltage (<10 V) and high operational stability are achieved by the s-SWNT-FETs with polystyrene/CEP bilayer gate dielectrics. In addition, this indicates that th...