Dielectric Breakdown Voltage Research Articles

Numerical Study on Alternating Current Breakdown Mechanism Between Sphere-Sphere Electrodes in Transformer Oil-Based Magnetic Nanofluids.

A numerical simulation was developed for magnetic nanoparticles in a liquid dielectric to investigate the AC breakdown voltage of the magnetic nanofluids according to the volume concentration of the magnetic nanoparticles. In prior research, we found that the dielectric breakdown voltage of the transformer oil-based magnetic nanofluids was positively or negatively affected according to the amount of magnetic nanoparticles under a testing condition of dielectric fluids, and the trajectory of the magnetic nanoparticles in a fabricated chip was visualized to verify the related phenomena via measurements and computations. In this study, a numerical simulation of magnetic nanoparticles in an insulating fluid was developed to model particle tracing for AC breakdown mechanisms happened to a sphere-sphere electrode configuration and to propose a possible mechanism regarding the change in the breakdown strength due to the behavior of the magnetic nanoparticles with different applied voltages.

Application of Markov Model to Estimate Individual Condition Parameters for Transformers

This paper presents a study to estimate individual condition parameters of the transformer population based on Markov Model (MM). The condition parameters under study were hydrogen (H2), methane (CH4), acetylene (C2H2), ethylene (C2H4), ethane (C2H6), carbon monoxide (CO), carbon dioxide (CO2), dielectric breakdown voltage, interfacial tension, colour, acidity, water content, and 2-furfuraldehyde (2-FAL). First, the individual condition parameter of the transformer population was ranked and sorted based on recommended limits as per IEEE Std. C57. 104-2008 and IEEE Std. C57.106-2015. Next, the mean for each of the condition parameters was computed and the transition probabilities for each condition parameters were obtained based on non-linear optimization technique. Next, the future states probability distribution was computed based on the MM prediction model. Chi-square test and percentage of absolute error analysis were carried out to find the goodness-of-fit between predicted and computed condition parameters. It is found that estimation for majority of the individual condition parameter of the transformer population can be carried out by MM. The Chi-square test reveals that apart from CH4 and C2H4, the condition parameters are outside the rejection region that indicates agreement between predicted and computed values. It is also observed that the lowest and highest percentages of differences between predicted and computed values of all the condition parameters are 81.46% and 98.52%, respectively.

The study on limited asynchronous breaking based on the adjustment of breaking time

Multi-interrupter in series is the only way for high voltage circuit breaker to develop Ultra high voltage levels. It is especially important for multi-interrupter in series to keep synchronization in breaking, but synchronous breaking of multi-interrupter is relative, and asynchronous breaking is absolute, so the conception of limited asynchronous breaking is brought up in this paper. Research on the compensation of dynamic dielectric recovery based on active asynchronous, and make each vacuum circuit breaker (VCB) has a different instantaneous gap length at current zero-crossing, to realize active compensation for dynamic dielectric recovery. In this paper, the model of post arc resistance will be established by ATP DRAW within the research of VCB with triple-interrupters as background, research the limited asynchronous breaking and the dynamic dielectric recovery characteristics of the various interrupter by adjusting the breaking time of the VCB, and the gain analysis of insulation breakdown voltage is analyzed. At last, the module of double-break VCB is established, and the correctness of simulation results is proved by tests.

Simultaneous Production of Transformer Insulating Oil and Value-Added Glycerol Carbonates from Soybean Oil by Lipase-Catalyzed Transesterification in Dimethyl Carbonate

Fatty acid methyl esters (FAMEs), as a transformer insulating oil, and value-added glycerol derivatives were simultaneously synthesized from soybean oil by transesterification using Lipozyme 435 in dimethyl carbonate (DMC). The conversion of transformer insulating oil and glycerol derivatives reached 92% and 72%, respectively, under optimum conditions (DMC-to-oil molar ratio of 4.5:1 with 0.5 v/v % water and 15 wt. % Lipozyme 435 at 70 °C) in one-pot batch reactions. The purified transformer insulating oil possessed a dielectric breakdown voltage of 82.0 kV, which is sufficiently high for transformer insulation oil applications. Other properties such as density, dielectric breakdown voltage, and viscosity were comparable or superior to those of mineral oil, confirming that achieved material could be used as an alternative transformer insulating oil. Additionally, the glycerol was simultaneously converted into glycerol derivatives, which can be utilized as ingredients for cosmetics or monomers for bio-based plastics. This study clearly demonstrates that transformer insulating oil and value-added glycerol derivatives were simultaneously produced based on the zero-waste utilization of soybean oil.

Study of dielectric and insulation properties of nano-additives doped epoxy resin

This paper aims to reveal the high voltage insulation and dielectric properties of epoxy resin samples with various nano-particle of Al2O3 and SiO2. In addition, experimental results were measured for dielectric properties (permittivity and tanδ at 1 kHz and 10 kHz), breakdown voltage and dielectric strength. The dielectric and high voltage insulation properties of nano-composites are analyzed in detail with respect to different experimental parameters such as frequency, particle size of additives, additive contents, additive permittivity and thickness of the samples. The results show the effects of nano-additives in permittivity, dissipation factor, breakdown strength and voltage for nano-composites.

Layer-by-layer engineering of two-dimensional perovskite nanosheets for tailored microwave dielectrics

We report an approach for constructing ultrathin microwave dielectrics using two-dimensional (2D) perovskite nanosheets (Ca2Nb3O10). The solution-based layer-by-layer assembly of Ca2Nb3O10 nanosheets enables the tailoring of dielectric responses and breakdown voltage in order to realize miniaturized capacitors with improved performances. Multilayer stacked nanosheet films showed a stable dielectric response of up to 10 GHz; the dielectric constant of ∼200 is the highest among high-κ perovskites in the ultrathin region (<30 nm). Moreover, the nanosheet films realized a high capacitance density (∼20 µF/cm2) with a robust thermal stability up to 250 °C. These superior dielectric properties of perovskite nanosheets offer a new solution for high-performance microwave devices.

Fabrication, performance and applications of integrated nanodielectric properties of materials – a review

The design and development of modern technological composites for the electrical and electronic applications are highly crucial. The minitualization, performance and durability of nanocomposites are achieved by integrating the nanodielectric properties of materials. In this review article, the entire upcoming trends in the domain of nanodielectric illustrated with important applications co-related to the various fabrication techniques of integrated nanodielectric composites are provided. The factors affecting the nanodielectric due to operating electric field and material interface which exhibit the high dielectric constant, low loss and moderate breakdown voltage. The complete sketch from concept, fabrication, factors co-related and applications of nanodielectric properties with the future scope are taken into consideration for further developments.

Preparation and characterization of multi shape ZnO/PVDF composite materials

Two different morphologies of ZnO (lotus-shaped, rod-shaped) and ZnO/PVDF composite materials were prepared. The morphologies of ZnO and composite materials were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Fourier transform infrared spectroscopy (FT-IR), thermal gravimetry (TG), and X-ray diffraction (XRD) were also used to characterize the chemical structures and phase composites of ZnO and ZnO/PVDF composite materials. Breakdown voltage, dielectric constant and dielectric loss of ZnO/PVDF composite materials were also tested. Microstructure analysis showed that ZnO nanoparticles dispersed uniformly in the matrix. And the dielectric constant expresses a significantly improvement while the dielectric loss and breakdown voltage expresses no significant change. Moreover, dielectric constant keeps an improvement tendency with increasing content of ZnO.

An electrical super-insulator prototype of 1D gas-solid Al2O3 nanocell

High electric breakdown strength of insulating materials is essential to improving the reliability of the electricity grid, reducing the size of electric devices, saving energy, protecting the environment, and reducing costs. Traditionally, dielectric breakdown strength is increased by exploiting its dependence on the thickness of the dielectric material, based on the electron impact ionization and avalanche theory by Townsend (1900) and Seitz (1949) [9]. However, at present there has been little research addressing the role of the transverse dimension (perpendicular to the direction of the electric field) in the avalanche breakdown process, and no results about research in nanoscale. An insulation breakdown prototype of a 1D nanocell was constructed. It consisted of an air-column and Al2O3 solid wall. Based on the analysis and comparison between nanocell geometrical dimensions and avalanche physical dimensions, it was found that the properties of the 1D nanocell diverges from the gas/solid discharge theories of Townsend and Seitz. Along with the I-V results of 1D nanocell by C-AFM (Conductive-Atomic Force Microscope), it was demonstrated that electrical breakdown cannot be caused by electron avalanche in 1D nanocell. The discharge properties of Al2O3 NPT (nano pore template) with nanocells array and when it inserted into the air gap as a barrier were studied to further demonstrate the capability of 1D nanocells on the electrical characteristic of macroscale material. Results showed that the scale effect of nanocells have an obvious role in improving the dielectric breakdown voltage, with singular discharge phenomena identified. This study proposes a new super-insulator prototype of 1D nanocell and supplies a novel thought for constructing high performance nanostructured dielectrics for more wide applications, and provides a scientific basis on the interconnection among Micro-Meso-Macro scales.

Evaluation of thermal degradation in isotactic polypropylene films used in power capacitors

Power capacitors are widely used by electric power utilities in electrical systems to improve power quality for their consumers. However, problems with physical installation, ambient temperature and electrical disturbances can raise the internal operating temperature above the ideal designed for the component, which can accelerate the degradation of the dielectric material. Since polypropylene film is the main part of the capacitor dielectric system, it is important to know about the effects of thermal aging on the physicochemical properties of the material. This work presents results of physical–chemical characterization tests of thermal aged isotactic polypropylene (iPP) film used in power capacitors. Tensile strength tests, dynamic mechanical thermal analysis, differential scanning calorimetry, X-ray diffraction (WAXS) and dielectric strength were performed. The results showed that the thermal aging causes morphological changes and reduction in the dielectric breakdown voltage of the iPP film.

A Study of Oxide Etch Angle of Edge Termination Field Plate for Fabrication of SiC SBD

The silicon carbide (SiC) material is being spotlighted as a next-generation power semiconductor material due to the characteristic limitations of the existing silicon materials. SiC has a wider band gap, higher breakdown voltage, higher thermal conductivity, and higher saturation electron mobility than Si. However, actual SiC SBDs exhibit a lower dielectric breakdown voltage than the theoretical breakdown voltage that causes the electric field concentration, a phenomenon that occurs on the edge of the contact surface as in the conventional power semiconductor devices. In this paper, we designed an edge termination structure using a field plate structure through oxide etch angle control, and optimized the structure to obtain a high breakdown voltage. The experiment results indicated that oxide etch angle was 45° when the breakdown voltage characteristics of the SiC SBD were optimized and a breakdown voltage of 681V was obtained.

Performance Analysis of Nanomaterials based Transformer Oil

The nanomaterials based transformer oil can be considered as next-generation insulation fluids because they offer exciting new possibilities to enhance dielectric breakdown voltage as well as heat transfer performance compared to pure transformer oils. Transformer oil (TOL) is a liquid dielectric which acts as an insulating medium as well as coolant. A colloidal mixture of nano-sized particles in base fluid is called nanofluids. Nanofluids are prepared by mixing the nanomaterials for different volume concentrations with TOL as base fluid. Nanofluids are significant potential heat transfer fluids with enhanced thermo physical properties can be applied in many devices for better performances. Nanofluids play an important role in cooling of transformer oil, engine cooling, in nuclear reactor, defense and space. Our effort focused on increasing dielectric breakdown voltage of transformer oil-based nanofluids with different volume concentrations of nanoparticles.

Impact of oxygen plasma on nitrided and annealed atomic layer deposited SiO2/high-k/metal gate for high-voltage input and output fin-shaped field effect transistor devices

In this study, the authors investigate the impact of radical oxygen plasma on nitrided and annealed atomic layer deposited (ALD) SiO2 as a thick gate oxide (1.65–3 V) with a high-k/metal gate transistor. Time-dependent-dielectric-breakdown voltage, secondary ion mass spectroscopy (SIMS), and x-ray photoelectron spectroscopy (XPS) studies were conducted, and the results are discussed for nitrided and annealed ALD SiO2 with and without radical oxygen plasma exposure. Atomistic material simulations were performed to understand the reactions between oxygen radicals and silicon oxynitride (SiON). Our key findings from SIMS and XPS show that radical oxygen plasma exposure led to a 34% nitrogen loss from the thick SiON gate oxide and damaged the gate oxide, resulting in a 1 V reduction in the dielectric breakdown voltage. Atomistic material simulation results also show that atomic oxygen can react with Si-(ON)-Si to form Si–O–Si bonds and mobilize NO into the interstitial space. Similarly, when O atoms and O2 molecules are placed near N clusters, spontaneous diffusion of N2 into the interstitial space occurs. Diffusion barrier calculations further indicate a barrier energy of less than 0.5 eV in SiO2 and SiON, which can lead to the out-diffusion of NO and N2 from SiO2 and SiON. These compositional changes may result in increased leakage and a degraded breakdown voltage. The increased gate leakage and degraded breakdown voltage is attributed to the compositional changes in SiON.

Oxide Growth Mechanism on Mg AZ91 Alloy by Anodizing: Combination of Electrochemical and Ellipsometric In-Situ Measurements

The sparking initiation during the anodizing of metals in passivating electrolytic media is highly dependent on the physico-chemical properties of the evolving dielectric interface. The present paper focuses on magnesium alloy AZ91 and describes its anodizing in KOH 3 M over the potential range 0 to 40 V by combining in situ ellipsometric and electrochemical methods. In a first step, a thin and compact MgO anodic film is formed by ionic migration with a rate of 0.4 nm V−1. At 4 V to 5 V, the growth stresses lead to a sharp cracking of this MgO layer and the precipitation of a porous external Mg(OH)2 layer. Under this overlayer acting as a membrane, a defective MgO film grows with a higher growth rate (1.1 nm V−1), inducing a new passivation state. This inner MgO layer is characterized by a relatively high dielectric constant and a large thickness (100 nm at 40 V) and is probably responsible for the low dielectric breakdown voltage observed during the anodizing process of magnesium alloy.

Development of a New Bio-Based Insulating Fluid from &amp;lt;i&amp;gt;Jatropha curcas&amp;lt;/i&amp;gt; Oil for Power Transformers

The present work aims to develop a new vegetable insulating fluid for power transformers based on Jatropha curcas oil. Besides its technical benefits, Jatropha curcas oil has a socio-economic role by promoting income to rural families, contributing to the countryside development and avoiding rural exodus. Thus, the entire transformer oil production (extraction, processing, characterization and accelerated aging) was covered and a new process was developed. For oil extraction, the most suitable process was the solvent extraction (5 mL of hexane per gram of crushed non-peeled seeds during 30 minutes) with an oil yield of 32%. In raw oil processing stage, the degumming, with 0.4 g of phosphoric acid per 100 g of oil, at 70°C, was used to remove phosphatides. Then, free fatty acids were 96% neutralized with a sodium hydroxide solution (0.5% w/w) at room temperature. For the oil clarification, the combination of 5% w/woil of activated carbon and 1% w/woil of MgO resulted in a bright, odorless and clear oil with an acid number of 0.04 mgKOH·g﹣1. The oil drying in a vacuum rotary evaporator, at 70°C, for 2 hours reduced the water content to 177 ppm. The processed oil was characterized following ASTM D6871 methods. This oil presented higher dielectric breakdown voltage (55 kV) than commercial transformer fluids (BIOTEMP®, EnvirotempFR3®, and Bivolt®), which increases transformer safety, capacity and lifetime. In addition, the processed oil has a lower viscosity than BIOTEMP® fluid, which can enhance the heat dissipation efficiency in the transformer. Moreover, the processed oil flash and fire points of 310°C and >340°C, respectively, confirm the great security of vegetable insulating fluids. The analyzed properties of the processed oil fulfill all the ASTM D6871, ABNT NBR 15422 and IEC 62770 specifications. Therefore, Jatropha curcas oil is a potential substitute formineral insulating fluids.

Enhanced breakdown performance of Anatase and Rutile titania based nano-oils

Nano-oils synthesized by dispersing dielectric nanostructures counter common intuition as such nano-oils possess substantially higher positive dielectric breakdown voltage with reduced streamer velocities than the base oils. Nano-oils comprising stable and dilute homogeneous dispersions of two forms of titanium (IV) oxide (TiO 2 ) nanoparticles (Anatase and Rutile) have been experimentally examined and observed to exhibit highly enhanced dielectric breakdown strength compared to the conventional transformer oils. The present study involves titania dispersed in two different grades of transformer oils, both with varied levels of thermal treatment, to obtain consistent and high degrees of enhancement in the breakdown strength, as well as high degrees of increment in the survival of the oils at elevated electrical stressing compared to the base oils, as obtained via detailed twin parameter Weibull distribution analysis of the experimental observations. The experimental results demonstrate higher augmented breakdown strength for Anatase compared to the Rutile phase of titania. In-depth survey of literature indicates that mostly Rutile based oils are used. However, the present study shows that they exhibit relatively less breakdown strength enhancement compared to the Anatase based oils. It is also observed that heat treatment of the nano-oils further enhances the dielectric breakdown performance. The differences in the performance of Anatase and Rutile has been explained based on the electronic structure of the two and the affinity towards electron scavenging and the theory has been found to validate the experimental observations.

Relaxor behavior of BaTiO3-BiYO3 perovskite materials for high energy density capacitors

Dielectric materials with high dielectric constant and breakdown voltage are very promising for pulsed energy storage applications. In this paper, (1-x) BaTiO3-xBiYO3 (x=0–0.5) ceramics were synthesized using conventional solid-state reaction method. The ceramic structure transformed from ferroelectric tetragonal phases (x≤0.5) to pseudo-cubic phases (x≥0.1). When x=0.2, beyond the solid solubility limit of BaTiO3-BiYO3, the second phase and glassy phases were formed, accompanying lattice parameter excursion. It revealed a gradual change from classic ferroelectric behavior in pure BaTiO3 to highly diffusive and dispersive relaxor-like characteristics with BiYO3 content increasing. It exhibited high polarization maximum and low remnant polarization, which was favorable for energy storage in (1-x)BaTiO3-xBiYO3 ceramics, due to the disrupted long polarization, the created weak coupling and the formed second phase. Furthermore, the nonlinearity of the (1-x)BaTiO3-xBiYO3 ceramics were weakened obviously. A maximum energy storage density of 0.316J/cm3 at 66kV/cm with relative high energy efficiency of 82.7% was achieved in 0.8BaTiO3-0.2BiYO3 ceramic, which indicated that (1-x)BaTiO3-xBiYO3 ceramics were promising lead-free relaxor materials for energy storage applications.

Effects of silicate ion concentration on the formation of ceramic oxide layers produced by plasma electrolytic oxidation on Al alloy

Plasma electrolytic oxidation (PEO) coatings were fabricated on 5083 Al alloy in KOH electrolyte solution with adding various concentrations of Na2SiO3. Changes in voltage–time response and micro-discharge evolution were analyzed, and the surface and cross-section of the resulting coating layer were further characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The results showed that discharge characteristics were evidently changed with different Na2SiO3 concentrations, particularly higher Na2SiO3 concentrations leading to lower dielectric breakdown voltages. It was found that porous surface structure became prevalent with increasing Na2SiO3 concentration. The EDS analysis confirmed the incorporation of Si element in the PEO coatings. The result of XRD analysis revealed that metastable phases such as γ- and η-alumina were produced as a result of PEO, while amorphous phases appeared with excessive Na2SiO3 concentrations (10 and 14 g/L). The coating thickness was significantly increased about 2–8 times with increasing Na2SiO3, almost depending on Na2SiO3 concentration.

인버터 서지와 온도 스트레스 하에서 Magnet Wire 절연 수명평가

Coil specimen was prepared by coating a copper wire with two varnish thin layers: the first was polyamideimide (PAI)/nanosilica (5 wt%) varnish and the second was anti-corona PAI/nanosilica (15 wt%) varnish. Insulation breakdown voltage was investigated under inverter surge condition at <TEX>$20^{\circ}C$</TEX>, <TEX>$70^{\circ}C$</TEX>, <TEX>$100^{\circ}C$</TEX>, <TEX>$150^{\circ}C$</TEX>, <TEX>$200^{\circ}C$</TEX>, <TEX>$250^{\circ}C$</TEX>, respectively. The insulation lifetime of the two layered coil was tens of times longer than that of original PAI coil. And the insulation lifetime decreased with increasing ambient temperature because there was weak binding strength between copper and varnish layer.

Effect of filler particle size on electric energy density of epoxy-aluminum nanocomposites

The size effect of filler particles on the dielectric properties and maximum electric energy density of epoxy-aluminum composites are evaluated. Aluminum particles encapsulated with aluminum oxide layers are used as the fillers to enhance the dielectric constant of the composite and also to maintain the breakdown strength. Experiments were conducted to evaluate the dielectric constant, dissipation factor, breakdown voltage and maximum electric energy density of the composites as a function of filler loading. Dielectric property measurements demonstrated that, for composites containing 70 nm (average particle size) aluminum the dielectric constant is increased by a factor of 7 at 18 wt% filler loading as compared with that of pure epoxy matrix. Even if there is a reduction in breakdown strength, the addition of nanoparticles resulted in potential gain in electric energy density. To analyze the size effect of filler particles on the performance of the composites, samples with a different filler size of 40 nm (APS) were prepared and dielectric properties were evaluated. It is observed that the enhancement in dielectric constant is 6 times that of pure epoxy at a lower filler concentration of 14 wt% for 40 nm (APS) filler samples. The improvement in maximum energy density is 4 times at 18 wt% filler loading and 3.5 times at 14 wt% filler loading for 70 nm (APS) and 40 nm (APS) composites respectively. Material characteristics were analyzed using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC) and Thermogravimetric (TGA) techniques.