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1
Park, Herie, Dong-Young Lim e Sungwoo Bae. "Surface Discharge Mechanism on Epoxy Resin in Electronegative Gases and Its Application". Applied Sciences 10, n. 19 (24 settembre 2020): 6673. http://dx.doi.org/10.3390/app10196673.
Testo completoAbstract (sommario):
This study presents the surface discharge characteristics of insulating gases, including sulfur hexafluoride (SF6), dry air, and N2, under a non-uniform field. Surface discharge experiments were conducted, with the gas pressure ranging from 0.1 to 0.6 MPa, on samples of epoxy dielectrics under an AC voltage. The experimental results showed that the surface insulation performance significantly improved in insulating gases possessing electronegative gases, such as SF6 and dry air. Surface flashover voltages of SF6 were saturated with an increasing pressure, compared to dry air and N2. The surface discharge mechanism is proposed to explain the improvement and saturation of dielectric characteristics of the electronegative gas in complex dielectric insulations, as well as its influence on the surface flashover voltage. As an application, an insulation design method is discussed with regards to replacing SF6 gas in high-voltage power equipment based on the knowledge of the physics behind gas discharge.
2
Zhang, Guangquan, Xueqin Zhang, Bo Wang, Yujun Guo, Guoqiang Gao e Guangning Wu. "Study on the Discharge Characteristics along the Surface and Charge Movement Characteristics of Insulating Media in an Airflow Environment". Energies 15, n. 10 (18 maggio 2022): 3706. http://dx.doi.org/10.3390/en15103706.
Testo completoAbstract (sommario):
The gas–solid interface of high-voltage insulating equipment is a weaker part of insulating equipment insulation, and preventing the occurrence of discharge along the surface of insulating equipment is a critical problem for high-voltage insulation. This article investigates the discharge characteristics and charge movement characteristics of insulating media under an airflow environment. The surface discharge characteristics of the insulating medium in the airflow environment were obtained by using a high-velocity airflow test platform, and the surface discharge voltage characteristics, discharge path characteristics, and force conditions of the discharge process were analyzed. The surface charge motion characteristics of the insulating medium in the high-velocity airflow environment were also tested, and the distribution characteristics, dissipation characteristics and conduction mechanism of the surface charge of the insulating medium in the high-velocity airflow environment were revealed. The research results showed that: the discharge voltage along the insulating medium surface gradually increases with the increasing velocity of airflow; the discharge path along the surface of the insulating medium gradually shifts backward under the action of airflow; under the action of airflow, the charge on the insulating medium surface is blown away, thus reducing the charge concentration on the insulating medium surface; the trap level center of the insulating medium gradually decreases under the action of airflow, which provides the conditions for the charge blowing effect on the insulating medium surface. This investigation supplies the theory support for the protection of insulation equipment in an airflow environment and technical guidance for the insulation design of insulating equipment in an airflow environment to ensure the secure and steady running of insulating equipment in high-speed trains and high-voltage transmission lines.
3
Li, Chao, Lin Lin e Weidong Qu. "Study on insulation performance optimization of EMU high-voltage equipment box". Journal of Physics: Conference Series 2195, n. 1 (1 febbraio 2022): 012040. http://dx.doi.org/10.1088/1742-6596/2195/1/012040.
Testo completoAbstract (sommario):
Abstract The EMU high-voltage electrical equipment on the roof not only bears the erosion of various harsh and extreme environments, but also bears the impact of various over-voltage, and the insulation performance of the electrical equipment on the roof is seriously threatened. This paper studies the insulation optimization design method of EMU high-voltage electrical equipment, puts forward the method of adding a certain length of insulating sheath on the electrical equipment to improve the insulation performance of high-voltage equipment box, and tests the insulation optimization measures on high-voltage circuit breaker and EMU high-voltage cable. The result shows that the installation of insulating sheath is feasible to improve the insulation performance of EMU high-voltage equipment box.
4
Hayashi, Toshihiko, Toru Izumi, Tetsuro Hemmi e Katsunori Asano. "Insulating Properties of Package for Ultrahigh-Voltage, High-Temperature Devices". Materials Science Forum 740-742 (gennaio 2013): 1036–39. http://dx.doi.org/10.4028/www.scientific.net/msf.740-742.1036.
Testo completoAbstract (sommario):
Insulating properties of package for ultrahigh-voltage, high-temperature devices have been investigated. While all the packages have enough insulating strength at room temperature, deterioration of the insulating property at high temperature has been found with some packages. The authors have found that this deterioration is attributed to degrade the insulation property of AlN ceramics for DBC substrate at high temperature and that there is a various degree in the deterioration.
5
Rozga, Pawel, e Abderahhmane Beroual. "High Voltage Insulating Materials—Current State and Prospects". Energies 14, n. 13 (25 giugno 2021): 3799. http://dx.doi.org/10.3390/en14133799.
Testo completo
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Guo, Gang, Hongda Li, Mingcheng Gao e Long Che. "Numerical simulation of the breakdown process of dielectric in high voltage pulse discharge". Journal of Physics: Conference Series 2479, n. 1 (1 aprile 2023): 012009. http://dx.doi.org/10.1088/1742-6596/2479/1/012009.
Testo completoAbstract (sommario):
Abstract In order to study the breakdown process of the insulating medium of the needle-needle electrode under the action of high-voltage pulse discharge, the HV-LAB simulation software was used to study the discharge channel formed in the three kinds of insulating media, namely water, transformer oil, and air, and the three-dimensional model of the discharge breakdown insulating medium was designed. The process of discharge channel expansion, voltage, current, power, and energy loss in the discharge channel is analyzed. The results show that in the process of high-voltage pulse discharge breakdown of the insulating medium, the formation time of the discharge channel of transformer oil is long, the energy is accumulated, the number of discharge channels is less, the horizontal isopotential lines are dense, and the energy is concentrated. Under the same discharge conditions, the energy consumption of transformer oil in the process of high-voltage pulse discharge is the least. The results of this study can provide a reference for the selection of high-voltage crushing insulation medium.
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Tian, Chen, Zhiping Zhu, Jianping Liao, Zhifeng Liu, Fan Gao, Yufei Chen e Zhenggang Wang. "The study of the electrical properties of nano insulating oil for submarine cables". E3S Web of Conferences 522 (2024): 01019. http://dx.doi.org/10.1051/e3sconf/202452201019.
Testo completoAbstract (sommario):
At present, the alkylbenzene insulation oil for submarine cables of 220kV and above in China relies on imports, which poses high maintenance costs and supply interruption risks. Nano modified insulating oil has excellent electrical properties and broad application prospects in power systems. Therefore, nano SiO2 modified insulating oil was prepared, and the effects of APTES modified and unmodified nano SiO2 on the viscosity, breakdown voltage, and dielectric loss factor of the insulating oil were compared. The results showed that the viscosity of alkylbenzene insulating oil did not change significantly after the addition of nanoparticles, which met the operating standards for submarine cable oil; The breakdown voltage of the modified nano insulating oil has significantly increased, with a breakdown voltage of 0.12g/L being the highest. The breakdown voltage of the unmodified nano insulating oil has significantly decreased. The dielectric loss factors of modified and unmodified nano insulating oils do not vary significantly. This article provides theoretical and practical references for the domestic substitution research of submarine cable insulation oil.
8
Rafiq, Muhammad, Muhammad Shafique, Anam Azam, Muhammad Ateeq, Israr Ahmad Khan e Abid Hussain. "Sustainable, Renewable and Environmental-Friendly Insulation Systems for High Voltages Applications". Molecules 25, n. 17 (27 agosto 2020): 3901. http://dx.doi.org/10.3390/molecules25173901.
Testo completoAbstract (sommario):
With the inception of high voltage (HV), requisites on the insulating permanence of HV equipment is becoming increasingly crucial. Mineral/synthetic oil liquid insulation—together with solid insulation materials (paper, pressboard)—is the fundamental insulation constituent in HV apparatuses; their insulation attributes perform a substantial part in a reliable and steady performance. Meanwhile, implications on the environment, scarcity of petroleum oil supplies and discarding complications with waste oil have stimulated investigators to steer their attention towards sustainable, renewable, biodegradable and environmentally friendly insulating substances. The contemporary insulating constituent’s evolution is driven by numerous dynamics—in particular, environmental obligations and other security and economic issues. Consequently, HV equipment manufacturers must address novel specifications concerning to these new standards. Renewable, sustainable and environmentally friendly insulating materials are continuously substituting conventional insulating items in the market place. These are favorable to traditional insulating materials, due to their superior functionality. The also offer explicit security and eco-friendly advantages. This article discusses cutting-edge technology of environmentally friendly insulating materials, including their fabrication, processing and characterization. The new renewable, insulating systems used in HV equipment are submitted and their fundamental gains stated in comparison with conventional insulating materials. Several experimental efforts carried out in various parts of the world are presented, offering an outline of the existing research conducted on renewable insulating systems. The significance of this article lies in summarizing prior investigations, classifying research essence, inducements and predicting forthcoming research trends. Furthermore, opportunities and constraints being experienced in the field of exploration are evidently reported. Last but not least, imminent research proposals and applications are recommended.
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Zhorniak, Liudmyla, Alexej Afanasiev, Vitaliy Schus e Oleksandr Levchenko. "To the problem of the shielding systems efficiency in constructions of extra-high voltage electrical apparatus". Bulletin of NTU "KhPI". Series: Problems of Electrical Machines and Apparatus Perfection. The Theory and Practice, n. 1 (11) (23 luglio 2024): 3–9. http://dx.doi.org/10.20998/2079-3944.2024.1.01.
Testo completoAbstract (sommario):
In the article, the authors proposed a method for estimating the electric load parameters to calculate the distribution of the electric field strength of the solid insulating structure of gas-filled high-voltage devices with axial symmetry. This structure consists of a support and insulating busbar filled with SF6 gas as an internal insulating medium. This technique allows to evaluate the parameters of the electrical load (voltage and field strength) depen-ding on the design features of the device and the shielding system used to equalize the electric field. The proposed methodology allows to evaluate the effectiveness of the influence of design parameters of the protection system for gas-filled high-voltage equipment (instrument transformers, arresters, surge arresters, etc.) when designing and improving individual design solutions. The calculation results are in good agreement with the data of experimental studies and statistical information obtained as a result of monitoring the operation of insulating structures, taking into account actual operating conditions and the influence of external factors. The implementation of this technique allows us to take into account the influence of external factors and operational characteristics inherent in instrument transformers and surge suppressors. In the proposed methodology, as an example, we consider a supporting insulating coating that is in operation under the most unfavorable conditions, such as external pollution, moisture and their combination, overvoltage of various origins, etc. The theoretical conclusions are confirmed by the results of calculations using the example of the support-insulating cover of the surge suppressor of the OПН-500 series. A more accurate determination of the effectiveness of the proposed methodology for predicting the field strength distribution parameters under the influence of a shielding system can be achieved by conducting an additional series of calculations and experimental tests of specific insulating structures. Thus, it was concluded that the obtained results can be used to evaluate the external insulation characteristics of both surge suppressors and gas-filled instrument transformers, as well as similar high-voltage equipment of switchgears and transformer substations in conditions of ultra- and transformer substations ultra-high voltages
10
Mukherjee, Shubhankan, Adhir Baran Chattopadhyay e Sunil Thomas. "Electrostatic field theoretic approach to analyze the partial discharge phenomenon pertaining to insulation degradation". International Journal of Engineering & Technology 7, n. 2 (1 giugno 2018): 842. http://dx.doi.org/10.14419/ijet.v7i2.12095.
Testo completoAbstract (sommario):
This paper elucidates the application of electrostatic field theory to analyze partial discharge due to the void formation inside the insulating material. Formation of voids leads to accumulation of static charges leading to capacitance build-up. The most probable cause of insulation failure is due to the subjection of high voltage. Prolonged high voltage poses a threat and leads to insulation failure. Failures occur in the tip gap between the conductor and insulating material’s inner periphery. Probable causes of such failures are corona discharge, surface discharge and treeing, leading to formation of Lichtenberger figures in the material and cavity discharge. This paper presents a way of fabricating the inner lining of the insulator with a semiconductor layer obeying avalanche breakdown at breakdown voltage or voltages at which partial discharge is likely to occur. With the onset of high voltage which can cause a discharge, the semiconductor experiences avalanche breakdown giving out a single photon ejection by Geiger mode (principle). A superior prevention method of using Teflon for insulation instead of XLPE/PILC has been suggested and simulated using COMSOL. Detection using Avalanche photo-detector(LiDAR) may enable us to track the probable location of the occurrence of partial discharge and isolate the system.
11
Siddique, Abubakar, Muhammad Adnan, Waseem Aslam, Abdullah Mujahid e Tanzeela Khalid. "Enhancement of Dielectric Properties of Echo-Friendly Cottonseed Oil-based Nanofluids for High Voltages". Pakistan Journal of Engineering and Technology 7, n. 01 (15 aprile 2024): 6–12. http://dx.doi.org/10.51846/vol7iss01pp6-12.
Testo completoAbstract (sommario):
This study investigates the performance of nanofluid-based vegetable oil (VO) as an advanced dielectric medium for high-voltage equipment, with a specific focus on AC breakdown voltage (AC BDV). Nanofluids, comprising carefully selected nanoparticles (including Al2O3, TiO2, Fe2O3, SiO2, and Graphene) dispersed in cottonseed oil (CSO), offer a unique opportunity to enhance the dielectric properties of insulating fluids. Through a systematic experimental approach, AC BDV tests were conducted in Khwaja Fareed UEIT High Voltage Laboratory, and the results were compared to with traditional mineral oil (MO) for high-voltage equipment’s. The findings reveal significant improvements in the AC BDV of the nanofluid, demonstrating its enhanced electrical insulation capabilities. This study displays nanofluids based on VO as a promising alternative for enhancing high-voltage equipment's electrical performance while considering the environment. Implementing nanofluids effectively improves the dielectric properties of insulating fluids, contributing to advancements in high voltage equipment technology.
12
Nie, Yongjie, Meng Zhang, Yuanwei Zhu, Yu Jing, Wenli Shi, Guoping Li, Haopeng Chen et al. "Electrochromism of Viologen/Polymer Composite: From Gel to Insulating Bulk for High-Voltage Applications". Materials 14, n. 19 (8 ottobre 2021): 5901. http://dx.doi.org/10.3390/ma14195901.
Testo completoAbstract (sommario):
Power equipment operates under high voltages, inducing space charge accumulation on the surface of key insulating structures, which increases the risk of discharge/breakdown and the possibility of maintenance workers experiencing electric shock accidents. Hence, a visualized non-equipment space charge detection method is of great demand in the power industry. Typical electrochromic phenomenon is based on redox of the material, triggered by a voltage smaller than 5 V with a continuous current in μA~mA level, which is not applicable to high electric fields above 106 V/m with pA~nA operation current in power equipment. Until now, no naked-eye observation technique has been realized for space charge detection to ensure the operation of power systems as well as the safety of maintenance workers. In this work, a viologen/poly(vinylidene fluoride-co-hexafluoropropylene)(P(VDF–HFP)) composite is investigated from gel to insulating bulk configurations to achieve high-voltage electrical-insulating electrochromism. The results show that viologen/P(VDF–HFP) composite bulk can withstand high electric fields at the 107 V/m level, and its electrochromism is triggered by space charges. This electrochromism phenomenon can be visually extended by increasing viologen content towards 5 wt.% and shows a positive response to voltage amplitude and application duration. As viologen/P(VDF–HFP) composite bulk exhibits a typical electrical insulating performance, it could be attached to the surface of insulating structures or clamped between metal and insulating materials as a space charge accumulation indicator in high-voltage power equipment.
13
Zhorniak, Liudmyla, Alexej Afanasiev e Vitaliy Schus. "Analysis of design and structural features of the external insulation materials of high-voltage devices". Bulletin of NTU "KhPI". Series: Problems of Electrical Machines and Apparatus Perfection. The Theory and Practice, n. 2 (8) (27 dicembre 2022): 3–10. http://dx.doi.org/10.20998/2079-3944.2022.2.01.
Testo completoAbstract (sommario):
In the article, the authors have analysed the design and structural features of various materials for external insulation of high-voltage apparatuses, namely, high-voltage equipment of stations and substations. The operational reliability of the external insulation is determined mainly by the electrical load, which is characterized by the local values of the field strength. The field strength along the insulating cover is distributed very unevenly and has a maximum value near the electrode with high voltage. Electrical isolators are used in all high-voltage apparatus of electrical transmission and distribution circuits to separate the voltage from the ground. The materials used in the development and production of electrical insulators have certain unique characteristics. These materials prevent the free passage of internal electric charges in the material, which makes it practically impossible to conduct an electric current. The ability of a material to prevent electrical conductivity is characterized by its dielectric strength. Polymer insulators allow you to combine high mechanical strength with satisfactory electrical characteristics. In such combined structures, fiberglass rods or cylinders are used as an element that withstands mechanical load. Also, the design of the internal insulation of the capacitor type, impregnated and filled with hardened epoxy resin, allows for particularly precise winding of the synthetic material and the placement of aluminium foils, which provide the capacitive levelling of the graduation and are necessary for the control and formation of the electric field. Such a field is controlled in such a way as to optimize the dimensions, mass and electrical characteristics of the high-voltage apparatus depending on the voltage class and other parameters. The protective polymer coating provides high electrical characteristics of insulators under operating conditions. It is known that during the operation of the high-voltage device, the aging rate of the external insulation is additionally enhanced due to the complex and heterogeneous structure of the insulating cover itself, as well as the influence of the surrounding environment and weather conditions. The main element of external insulation is the supporting insulating cover, in the middle of which the elements of the active part of a certain electrical device are placed. Its basis is usually a glass-epoxy cylinder (this ensures the mechanical stability of the structure), on which ribs made of organosilicon rubber are placed, which in turn ensures the electrical strength of the external insulation.
14
Ridel, Aleksander, e Alexander Bychkov. "Optical Recording of Bubble Dissolution of Diagnostic Gases in Electrical Insulating Liquids". Applied Mechanics and Materials 792 (settembre 2015): 602–5. http://dx.doi.org/10.4028/www.scientific.net/amm.792.602.
Testo completoAbstract (sommario):
The diffusion coefficients of the basic diagnostic gases were determined by optical recording of the bubble dissolving dynamics in degassed insulating liquid. It is necessary to understand the diffusion of diagnostic gases in insulating liquids for obtaining high-quality diagnostic conclusions obtained during the analysis of high voltage electrical equipment with paper-oil insulation using gas methods.
15
Chul Kim, Ki. "Degradation evaluation of high voltage insulating oils by terahertz spectroscopy". International Journal of Engineering & Technology 7, n. 2.12 (3 aprile 2018): 8. http://dx.doi.org/10.14419/ijet.v7i2.12.11025.
Testo completoAbstract (sommario):
Background/Objectives: The stable electrical power supply is the most important issue for modern industrial society employing various electrical appliance. The power transformer is one of the most important component in the electrical power supply system.Methods/Statistical analysis: The common diagnosis method of insulating oil of transformer is gas-chromatograph. The gas-chromatograph is performed to detect dissolved gas ininsulating oil of transformerduring the stop-period of transformer unit. In this research, the optical properties of insulating oils of transformer (unused new oil, used oil of normal operation, and waste oil of malfunction) are analyzed using a terahertz time-domain spectroscopy in the range of 0.1 ~ 3.0 THz.Findings: The new insulating oil is colorless and transparent. The used insulating oil and waste insulating oil exhibit dark yellow and brown color. The THz sample pulses are delayed of phase and reduced of amplitude compare to passing through the free space. The reduce of amplitude is attributed to increasing of absorption due to aging effect of oils. The refractive index and absorption coefficient of insulating oils are calculated from measured THz pulses. The refractive index of ‘new or used oil’ exhibits a constant value of 1.455 and 1.463 in the full frequency range. But refractive index of ‘waste oil’ exhibits various values of 1.466 ~ 1.485 with the frequency, which is relatively high. The normalized amplitude of waste insulating oil is reduced. The absorption coefficient of waste insulating oil is increased linearly with the increase of frequency. The reducing of THz amplitude is attributed to increase of absorption due to aging effect of oils.Improvements/Applications: The aging effect of insulating oils of transformer is characterized by the portable THz-TDS system. It can be applied to in situ monitoring of insulating oil conditions.
16
Baghelkar, Neetu, e Abhishek Dubey. "STUDY AND PERFORMANCE OF PARTIAL DISCHARGE OF MODEL FOR DIFFERENT TYPE INSULATION MATERIALS WITH CAPACITANCE VALUE". International Journal of Research -GRANTHAALAYAH 8, n. 12 (20 gennaio 2021): 323–27. http://dx.doi.org/10.29121/granthaalayah.v8.i12.2020.2975.
Testo completoAbstract (sommario):
The properties of the insulating material must be the best to avoid failure of electrical equipment. Partial discharges act as electrical sparks that occur within insulation and the high-voltage electrical system. The different types of voltage and current pulses are produced, which last for a very short time. Partial discharge is taking place in high voltage power equipment such as cables, transmission lines and transformers, etc.
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Ahsan, Matiullah, Md Nor Ramdon Bin Baharom, Zainab Zainal, Luqman Hakim Mahmod, Irshad Ullah, Mohd Fairouz Mohd Yousof, Nor Akmal Mohd Jamail, Muhammad Saufi Kamarudin e Rahisham Abd Rahman. "Historical Review of Advancements in Insulated Cross-Arm Technology". Energies 15, n. 21 (3 novembre 2022): 8221. http://dx.doi.org/10.3390/en15218221.
Testo completoAbstract (sommario):
High-voltage transmission technology has advanced quickly with the overall development and increased use of renewable energy. More demands on the insulating system are made when high-voltage power systems evolve. One of the significant factors is the sharp rise in population density, which led to the high demand for electricity. Right-of-way infringement is a problem that frequently occurs these days. Transmission is done over a rated capacity; as a result, the transmission line heats up, the insulation ages, and the electric field becomes distorted. The insulating system is prone to fail too soon when the operating voltage inverses or when there is a significant temperature differential. Environmentally friendly insulating materials have received much attention recently. A synergistic optimisation of heat resistance properties, mechanical properties, and dielectric properties must be accomplished before these materials can be used in high-voltage transmission systems. They must also withstand harsh electrical and thermal shocks such as overvoltage and short-circuit faults. One of the developments that has become a popular research topic is the constantly evolving tower design. This review article presents advancements in cross-arm technology in high-voltage transmission systems to elaborate on the limitations and contributions of different research work.
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Suwarno, Suwarno. "Partial Discharge in High Voltage Insulating Materials". International Journal on Electrical Engineering and Informatics 8, n. 1 (30 marzo 2016): 147–63. http://dx.doi.org/10.15676/ijeei.2016.8.1.11.
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Hadi, Nabipour Afrouzi, Zulkurnain Abdul-Malek, Saeed Vahabi Mashak e A. R. Naderipour. "Three-Dimensional Potential and Electric Field Distributions in HV Cable Insulation Containing Multiple Cavities". Advanced Materials Research 845 (dicembre 2013): 372–77. http://dx.doi.org/10.4028/www.scientific.net/amr.845.372.
Testo completoAbstract (sommario):
Cross-linked polyethylene is widely used as electrical insulation because of its excellent electrical properties such as low dielectric constant, low dielectric loss and also due to its excellent chemical resistance and mechanical flexibility. Nevertheless, the most important reason for failure of high voltage equipment is due to its insulation failure. The electrical properties of an insulator are affected by the presence of cavities within the insulating material, in particular with regard to the electric field and potential distributions. In this paper, the electric field and potential distributions in high voltage cables containing single and multiple cavities are studied. Three different insulating media, namely PE, XLPE, and PVC was modeled. COMSOL software which utilises the finite element method (FEM) was used to carry out the simulation. An 11kV underground cable was modeled in 3D for better observation and analyses of the generated voltage and field distributions. The results show that the electric field is affected by the presence of cavities in the insulation. Furthermore, the field strength and uniformity are also affected by whether cavities are radially or axially aligned, as well as the type of the insulating solid. The effect of insulator type due the presence of cavities was seen most prevalent in PVC followed by PE and then XLPE.
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Rafiq, Muhammad, Yuzhen Lv e Chengrong Li. "A Review on Properties, Opportunities, and Challenges of Transformer Oil-Based Nanofluids". Journal of Nanomaterials 2016 (2016): 1–23. http://dx.doi.org/10.1155/2016/8371560.
Testo completoAbstract (sommario):
The mineral oil or synthetic oil in conjunction with paper is mainly being applied as dielectric medium in many of the high voltage apparatus. However, the advent of high voltage levels such high voltage alternating current (HVAC) and high voltage direct current (HVDC) has prompted researchers to direct their focus onto an insulation system which can bear the rising high voltage levels. The modern insulating liquid material development is guided by various factors such as high electrical insulation requirements and other safety and economic considerations. Therefore transformer manufacturer companies have to design transformers with these new specific requirements. The transformer oil-based nanofluids with improved dielectric and thermal properties have the potential to replace mineral oil base products in the market place. They are favorable because they function more superior than mineral oil and they contribute definite insulating and thermal gains. This paper reviews recent status of nanofluids use as transformer oils. The nanofluids used as transformer oils are presented and their advantages are described in comparison with mineral oil. The multiple experimental works carried out by different researchers are described, providing an overview of the current research conducted on nanofluids. In addition scope and challenges being confronted in this area of research are clearly presented.
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Zhorniak, Liudmyla, Alexej Afanasiev e Vitaliy Schus. "Analysis of the features of the shielding system of polymer insulation structures of high voltage electrical equipment". Bulletin of the National Technical University "KhPI". Series: Energy: Reliability and Energy Efficiency, n. 1 (8) (5 luglio 2024): 41–48. http://dx.doi.org/10.20998/2224-0349.2024.01.18.
Testo completoAbstract (sommario):
In the article, the authors analysed the existing shielding systems of insulating structures of high-voltage devices together with electrodes under high potential. At the same time, the possibilities of using toroidal screens of various designs and the conditions of their installation in gas-filled equipment structures (gas-filled current and voltage measuring transformers, arresters, etc.) using polymer insulating materials are considered. Based on the analysis of literary sources, the most effective method of estimating the electric load parameters for determining the electric field strength distribution along the continuous insulating structure of gas-filled high-voltage devices with axial symmetry is proposed. This design is a support-insulating shell filled with SF6 as an internal insulating medium. Methodical materials are recommended that allow you to estimate the electrical load parameters (voltage and field strength) depending on the design features of the device and the shielding system used to level the electric field. Based on them, it is possible to evaluate the effectiveness of the calculation coefficients of the shielding system of gas-filled high-voltage equipment in the design process and during the improvement of individual design solutions. The results of the analytical evaluation by such methods are in good agreement with the data of experimental studies and statistical information obtained as a result of monitoring the work of insulating structures, taking into account real operating conditions and the influence of external factors. The introduction of the obtained materials allows you to take into account the influence of external factors and operational characteristics inherent in measuring transformers and overvoltage limiters. To explain the results of the analysis of methodical materials carried out in the article, as an example, the results of calculations of the support-insulation shell of the gas-filled current transformer of the TOG series, which was the most affected during operation, are given. in adverse conditions, given under such conditions as external pollution, humidity and their combination, as well as under conditions of overvoltage of various origins, etc. On the basis of the presented materials, it is possible to more accurately determine the effectiveness of various screenings. system, as well as how to predict the field strength distribution parameters under the influence of the shielding system, taking into account its design features. In addition, on the basis of the conclusions formed in the work, it is possible to plan and conduct an additional series of calculations and experimental tests taking into account the features of specific structures. Thus, the obtained results can be used to evaluate the external insulation parameters of both gas-filled measuring transformers and similar high-voltage equipment of distribution devices and transformer substations.
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Du, Bin, Yu Shi e Qian Liu. "Fabrication of Fe3O4@SiO2 Nanofluids with High Breakdown Voltage and Low Dielectric Loss". Coatings 9, n. 11 (1 novembre 2019): 716. http://dx.doi.org/10.3390/coatings9110716.
Testo completoAbstract (sommario):
Insulating oil modified by nanoparticle (often called nanofluids) has recently drawn considerable attention, especially concerning the improvement of electrical breakdown and thermal conductivity of the nanofluids. However, traditional insulating nanofluid often tends to high dielectric loss, which accelerates the ageing of nanofluids and limits its application in electrical equipment. In this paper, three core-shell Fe3O4@SiO2 nanoparticles with different SiO2 shell thickness were prepared and subsequently dispersed into insulating oil to achieve nanofluids. The dispersion stability, breakdown voltages and dielectric properties of these nanofluids were comparatively investigated. Experimental results show the alternating current (AC) and positive lightning breakdown voltage of nanofluids increased by 30.5% and 61%, respectively. Moreover, the SiO2 shell thickness of Fe3O4@SiO2 nanoparticle had significant effects on the dielectric loss of nanofluids.
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Ye, Xiangyang, e Mahesh Dhotre. "CFD Simulation of Transonic Flow in High-Voltage Circuit Breaker". International Journal of Chemical Engineering 2012 (2012): 1–9. http://dx.doi.org/10.1155/2012/609486.
Testo completoAbstract (sommario):
A high-voltage circuit breaker is an indispensable piece of equipment in the electric transmission and distribution systems. Transonic flow typically occurs inside breaking chamber during the current interruption, which determines the insulating characteristics of gas. Therefore, accurate compressible flow simulations are required to improve the prediction of the breakdown voltages in various test duties of high-voltage circuit breakers. In this work, investigation of the impact of the solvers on the prediction capability of the breakdown voltages in capacitive switching is presented. For this purpose, a number of compressible nozzle flow validation cases have been presented. The investigation is then further extended for a real high-voltage circuit breaker geometry. The correlation between the flow prediction accuracy and the breakdown voltage prediction capability is identified.
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Lyutikova, M. N., S. M. Korobeynikov e A. A. Konovalov. "Electrophysical properties of mixtures of mineral oil and synthetic ester dielectric liquid". Safety and Reliability of Power Industry 14, n. 2 (28 luglio 2021): 132–41. http://dx.doi.org/10.24223/1999-5555-2021-14-2-132-141.
Testo completoAbstract (sommario):
Power transformers are key equipment in power generation, transmission, and distribution systems. The reliability of power transformers is based on the performance of the insulation system, which includes solid cellulose insulation and a liquid dielectric. Modern power engineering requires liquid insulation to have excellent insulating properties, high fire resistance, and biodegradability. Mineral oil that has been in use for over 100 years does not meet certain requirements. Therefore, various methods of enhancing the insulating properties of the oil are currently being considered, including mixing it with other liquid dielectrics, which have excellent properties. Synthetic and natural esters are considered as alternative fluids.This article discusses the possibility of enhancing the insulating characteristics of mineral oil with a high content of aromatic hydrocarbons (for example, T-750 oil) by mixing it with synthetic ester Midel 7131. Assessment is given of insulating parameters of the resulting mixtures with an ester fraction in mineral oil from 0% to fifty%. The main characteristics of the mixtures are described, such as density, kinematic viscosity, flash point, dielectric loss tangent, relative dielectric permittivity, breakdown voltage, and moisture content. It is shown that with an increase in the proportion of ester, some parameters of the obtained insulating liquid improve (flash point, dielectric constant, breakdown voltage), while values of other parameters (density, kinematic viscosity, dielectric loss tangent) with an ester content of more than 10% in the mixture do not meet the requirements for mineral oils.
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Wajanasoonthon, Kanin, e Amnart Suksri. "Long Term Thermal Performance of Palm Oil and Nano Graphene Filler in Nanofluids Application on Transformer Insulating Oil and Electrical Breakdown Voltage". Key Engineering Materials 931 (9 settembre 2022): 9–15. http://dx.doi.org/10.4028/p-bhz05b.
Testo completoAbstract (sommario):
Mineral oil has been used as electrical insulation for a long time due to its availability, excellent cooling and dielectric property. However, petroleum sources are nonrenewable, and it is depleting. Vegetable insulating oil is an alternative since it is renewable, environment-friendly, biodegradable, high fire-point, and has a good electrical breakdown voltage level. These properties can make vegetable insulating oil as a replacement for mineral oil that is going to be limited in availability. Nevertheless, vegetable insulating oil have high viscosity, leading to a slow flow rate on the cooling performance. This research is to investigate the breakdown voltage of palm oil-based liquid insulators. This liquid is palm oil methyl esters-based nanofluids (NPME) that was converted from the transesterification process to reduce viscosity and mixed with graphene nanoparticles. These nanofluids were also aged by thermal aging at 100 °C for 168, 336 and 504 hours before testing for their electrical breakdown voltage. The results show that the transesterification process can reduce the viscosity of palm oil by about 6.6 times. Also, the breakdown voltage of nanofluids is higher than bare palm oil methyl ester after thermal aging for 504 hours.
26
Bu, Qinhao, Sheng Liu, Le Feng, Haowei Xu e Qiaogen Zhang. "High Frequency Breakdown Characteristics of Alumina Filler Content Epoxy Resin". Advances in Engineering Technology Research 11, n. 1 (24 luglio 2024): 399. http://dx.doi.org/10.56028/aetr.11.1.399.2024.
Testo completoAbstract (sommario):
Power electronic transformers have high insulation frequency and compact insulation structure, and insulation performance is one of the main factors restricting their further development. Epoxy resin is an important insulating material in the electrical industry, its thermal conductivity and mechanical properties can not meet the needs of high-frequency transformers, usually metal oxide (Al2O3, etc.) is added to form composite insulation material. It is of great reference value for the insulation design of power electronic transformer to study the insulation performance of composite insulation materials with different filler content ratio under high-frequency AC. The effects of power supply frequency and alumina filler content on the breakdown performance of the composite were investigated experimentally. The results show that the breakdown voltage of pure epoxy resin decreases exponentially with frequency. At any filler content, the breakdown voltage of epoxy resin decreases with the increase of frequency, and the decreasing trend gradually slows down when the frequency increases from 50Hz to 1000Hz, and the decreasing trend gradually increases when the frequency increases to 2000Hz. The breakdown voltage of epoxy resin showed a down-rise-down trend with the increase of filler content, and the effect of filler content on breakdown voltage gradually weakened with the increase of frequency.
27
Yamamoto, Osamu. "EXPERIENCES IN NUMERICAL ANALYSES OF SURFACE CHARGE ON INSULATORS EXPOSED TO HIGH VOLTAGE IN VACUUM". ASEAN Engineering Journal 5, n. 1 (20 marzo 2015): 9–21. http://dx.doi.org/10.11113/aej.v5.15452.
Testo completoAbstract (sommario):
This paper deals with the electrical insulation of a gap bridged by a solid dielectric between a pair of electrodes in a vacuum, where the dielectric is a model of an insulating spacer holding electrodes in various vacuum devices. Such gap configuration is typical as a model for studying physical mechanisms of an electrical breakdown or a flashover in a vacuum, in which the insulation ability is considerably lower than a gap without any insulating spacers. Many researchers have long investigated the mechanisms of flashover, and it is believed that the charging of the insulator surface is the primary drive of such weakness. One of the effective approaches for studying mechanisms is to analyze the characteristic of charge accumulated on the insulator surface both by experiments and by numerical analyses. This paper reviews previous works conducted by the author’s research group and demonstrates the difficulties we have encountered upon conducting the numerical analyses.
28
Ghani, Sharin Ab, Mohd Shahril Ahmad Khiar, Imran Sutan Chairul e Muhammad Imran Zamir. "Effect of repeated electrical breakdowns on mineral and natural ester insulating oils". Bulletin of Electrical Engineering and Informatics 10, n. 6 (1 dicembre 2021): 2989–96. http://dx.doi.org/10.11591/eei.v10i6.3258.
Testo completoAbstract (sommario):
Transformer insulating oils are exposed to repeated electrical discharge or breakdowns inside power transformers. Durability tests are conducted to analyze the ability of oil to resist decomposition due to such high electrical stresses. With the increasing demand for alternative insulating oils for oil-immersed transformers, it is worthy to compare the performance of different types of insulating oils (conventional mineral-based insulating oil and natural ester-based insulating oil) under repeated electrical breakdown. In this paper, the AC breakdown voltage of different mineral-based and natural ester-based insulating oils is reported. Durability tests were conducted based on the AC breakdown voltage behavior of insulating oils after 50 electrical breakdown shots. The AC breakdown voltage of each insulating oil sample was assessed according to the ASTM D1816 standard test method. Based on the results, it can be concluded that the dissimilarity in chemical composition of the insulating oils has a significant effect on the AC breakdown voltage behavior of these oils under repeated electrical breakdowns.
29
NIWA, Toshio, Izumi ISHIKAWA, Hiroyuki MIYATA e Tohru TAKAHASHI. "Development of Insulating Materials for High Voltage Cables." International Journal of the Society of Materials Engineering for Resources 3, n. 1 (1995): 160–66. http://dx.doi.org/10.5188/ijsmer.3.160.
Testo completo
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Frolov, S. T., N. Ya Gusak, V. P. Mukhin, L. Ya Yantovskii e A. D. Smolyar. "Improved qhenching of glass high-voltage insulating components". Glass and Ceramics 46, n. 9 (settembre 1989): 371–72. http://dx.doi.org/10.1007/bf00677804.
Testo completo
31
Huang, Fang. "Technology of Heat-Resistant & High Voltage-Resistant Insulation Materials Based on Polymer Composite". Advanced Materials Research 391-392 (dicembre 2011): 340–44. http://dx.doi.org/10.4028/www.scientific.net/amr.391-392.340.
Testo completoAbstract (sommario):
High voltage insulation of the heat-resistant polymer composite material mainly composed of synthetic resin matrix, reinforcing materials, inorganic fillers, pigments and other components. In addition, according to the technical and performance requirements will be added in the resin matrix curing agent, thickener, mold release agents, solvents and so on. By different proportions of the resin matrix and filler and other additives, under conditions in certain insulating polymer composites were prepared to explore the relationship between components, the best formula and the ideal insulation material.
32
Lühring, Ulrich, Daniel Wienold e Frank Jenau. "Investigation on the Applicability of the Time Domain Analysis of Discharges in Gases for the Defect Identification at AC Voltage". Transactions on Environment and Electrical Engineering 2, n. 1 (8 gennaio 2017): 35. http://dx.doi.org/10.22149/teee.v2i1.57.
Testo completoAbstract (sommario):
The partial discharge diagnosis is an established instrument for the condition assessment of high voltage insulations and equipment. Under AC voltage stress the phase resolved pattern is of great significance in order to become aware of the type of fault. As a result of the inapplicability for DC voltage stress, approaches for alternative interpretation techniques such as the time domain analysis of partial discharges were identified in recent investigations. In these different types of fault are taken into account as well as different insulating media. The purpose of this paper is to investigate whether an analysis of the pulse shape is also applicable for the defect identification under AC voltage stress. By focussing on gaseous insulating media, contact noise and surface discharges are emulated in ambient air, whereas corona discharges are emulated in ambient air and oxygen. A method for analysing discharges, occurring in the negative and the positive half-wave of the test voltage, is proposed and discussed.
33
Lyutikova, M. N., S. M. Korobeynikov, S. I. Sotnikov e A. A. Konovalov. "Study of chemical properties of insulation mixtures to be used in high-voltage equipment". Safety and Reliability of Power Industry 15, n. 2 (27 luglio 2022): 81–89. http://dx.doi.org/10.24223/1999-5555-2022-15-2-81-89.
Testo completoAbstract (sommario):
Reliable operation of high-voltage oil-filled equipment directly depends on the condition of the insulation. One of the main components of the insulation system is transformer oil, which has been used for more than 120 years. However, in the light of modern requirements for insulating materials, oil is significantly inferior to synthetic esters in terms of such properties as chemical stability, environmental safety and high fire resistance. At present, the mixing of synthetic ester and transformer oil can be considered as one of the ways to improve the properties of the latter. A change in the chemical properties of an insulating liquid during its aging, and, consequently, the formation of various impurities and a change in the structure of its component composition will also affect the electrical insulating characteristics of the liquid dielectric. And the more the liquid is oxidized, the more significantly the electrophysical parameters worsen, including the main parameter — electrical strength (or breakdown voltage).This paper presents the results of a study of the chemical properties of mixtures of oil and synthetic ester during prolonged exposure to elevated temperatures. The assessment of the quality of insulating mixtures was carried out by changing such indicators as optical turbidity, acid value, ester value, peroxide value, surface tension and corrosiveness. Fluid testing results in this study indicate that blending of synthetic ester with aromatic oil at 10% and 20% (v/v) results in mixtures that show signs of a colloidal system. This is evidenced by atypical trends in the diagrams indicating the change in peroxide value, acid value and optical turbidity during their aging at a temperature of 110ºС with free access of air to the surface of the mixture. Increasing the proportion of ester in the mixture to 30% and above leads to stabilization or slowdown of chemical reactions occurring due to thermal-oxidative effects. Under thermal exposure (without air access), the addition of synthetic ester to the aromatic oil in a volume of 30% or more significantly reduces the likelihood of sediment formation due to the destruction and polycondensation of aromatic hydrocarbons in mineral oil.
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Mohd Salleh, Nor Izzati, Nor Akmal Mohd Jamail, Nishanti Suntharasaka, Nor Shahida Mohd Jamail, Mohamad Farid Sies, Qamarul Ezani Kamarudin e Mohamed Afendi Mohamed Piah. "Analysis of HVDC breakdown characteristic of LLDPE-natural rubber added with biofiller as high voltage insulating material". Indonesian Journal of Electrical Engineering and Computer Science 20, n. 3 (1 dicembre 2020): 1203. http://dx.doi.org/10.11591/ijeecs.v20.i3.pp1203-1209.
Testo completoAbstract (sommario):
<p>The influence of solid insulation has been investigated by few researchers.<br />The mechanism of solid breakdown is important in insulation studies. In this<br />research, testing on Linear-Low Density Polythylene (LLDPE) with Natural<br />Rubber (NR) and different weight concentration of biofiller are conducted<br />under High Voltage Direct Voltage (HVDC) by using needle and sphere<br />types of electrode arrangements. Oil Palm Empty Fruit Bunch (OPEFB) and<br />Pineapple Leaf Fiber (PALF) are the biofillers used for the samples<br />development. The LLDPE-NR samples consists of different weight<br />percentages of biofiller which are 0%, 2.5%. 5.0%. 7.5% and 10% with 3mm<br />thickness. The voltage has been increased until the breakdown occurs. Based<br />on the results obtained, OPEFB and PALF with the highest weight<br />percentages of 10% showed the highest damage voltages of 59.09kV and<br />59.36kV. It has been proven that both samples with the highest filler content<br />have appropriate insulating properties. In conclusion, the addition of biofiber<br />to LLDPE-NR has improved the breakdown properties compared to pure<br />LLDPE.</p>
35
Wolny, Stefan. "Analysis of High-Frequency Dispersion Characteristics of Capacitance and Loss Factor of Aramid Paper Impregnated with Various Dielectric Liquids". Energies 12, n. 6 (19 marzo 2019): 1063. http://dx.doi.org/10.3390/en12061063.
Testo completoAbstract (sommario):
This paper presents research results of the loss factor of high voltage insulation samples made of aramid paper impregnated with various types of insulating oil. The analysis was carried out in the high frequency domain in the range of 50 Hz to 1 MHz. The experiments were carried out for three impregnation types: mineral oil, synthetic ester and natural ester. The influence of temperature in the range of 20 °C to 100 °C, which is typical when using this type of insulation in power transformers, was taken into account. In addition, the process of influence of initial aging of aramid paper was simulated by heat soaking the samples before their impregnation at a temperature of 250 °C in multiple time intervals. Based on the analyses of dispersion characteristics of insulation sample loss factors, conclusions and recommendations for further diagnostics of aramid-oil insulations using the method described were delineated.
36
Ma, Cheng, Meilin Wu, Wennan Wang, Yaqiong Jia e Wei Shi. "Electrical Characterizations of 35-kV Semi-Insulating Gallium Arsenide Photoconductive Switch". Photonics 8, n. 9 (10 settembre 2021): 385. http://dx.doi.org/10.3390/photonics8090385.
Testo completoAbstract (sommario):
In this paper, a three-layer GaAs photoconductive semiconductor switch (GaAs PCSS) is designed to withstand high voltage from 20 to 35 kV. The maximum avalanche gain and minimum on-state resistance of GaAs PCSS are 1385 and 0.58 Ω, respectively, which are the highest values reported to date. Finally, the influence of the bias voltage on the avalanche stability is analyzed. The stability of the GaAs PCSS is evaluated and calculated. The results show that the jitter values at the bias voltages of 30 kV and 35 kV are 164.3 ps and 106.9 ps, respectively. This work provides guidance for the design of semiconductor switches with high voltage and high gain.
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Zhang, Xu, Chuan Li, Yu Hui Li, Hong Wei Yang e Jian Fa Li. "The Electrical Insulation Property of PTFE Cannula in High Elevation". Advanced Materials Research 516-517 (maggio 2012): 1545–50. http://dx.doi.org/10.4028/www.scientific.net/amr.516-517.1545.
Testo completoAbstract (sommario):
The polytetrafluoroethylene (PTFE) with the good dielectric property is a kind of nonpolar material. Made from the PTFE, the cannula has the high electrical insulation performance. This cannula can be applied to the equipment which requires for the high electrical insulation. There are 3 kinds of power-frequency voltage resistant experiments on PTFE cannulas with the inner diameter and outer diameter of 0.55/1.35, 0.7/1.5, 0.96/1.6, 0.46/0.96, 1.5/3.0 in the 1970m elevation. The PTFE cannulas are tested at the 85kV power-frequency voltage with the pure condition, the humidity condition, and the polluted condition separately in 1 minute. The result induced that the PTFE cannula did not be destroyed in all of the above experiments with no puncture sound, no smoke, no flashover and no burning. The insulating quality of the PTFE cannula is satisfied with the insulation requirement of the 85kV, i.e., the pollution level I.
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Cheng, Yujia, Guang Yu e Zhuohua Duan. "Breakdown Properties of Cables with Different Inorganic, Insulating Nanomaterials". Inorganics 9, n. 12 (20 dicembre 2021): 90. http://dx.doi.org/10.3390/inorganics9120090.
Testo completoAbstract (sommario):
The insulation performance of cable insulating materials can be optimised via matrix modification. Typically, low-density polyethylene (LDPE) is used as the matrix, and a certain proportion of nanoparticles are added to this matrix. To explore the effects of nanoparticles with different forms on the structural interface and crystal morphology of the material, nano-MMT and nano-ZnO were added to LDPE, and comparative experiments were carried out. Based on microscopic test results, material insulation performance changes before and after optimisation were observed. Then, simulation cable models with different insulating materials were developed. Based on the simulated electrical measurements, the thermal breakdown performance of the different insulating materials was tested. According to infrared stereo vision detection results, anomalous temperature points in the cables can be located accurately. Finally, based on macroscopic test results, we verified whether the inorganic, insulating nanomaterials meet the requirements for high-voltage transmission.
39
Yoo, Jeong-Sang, Yong-Man Gil e Tae-Young Ahn. "High-Power-Density DC–DC Converter Using a Fixed-Type Wireless Power Transmission Transformer with Ceramic Insulation Layer". Energies 15, n. 23 (28 novembre 2022): 9006. http://dx.doi.org/10.3390/en15239006.
Testo completoAbstract (sommario):
In this study, we propose the use of a short-distance and fixed-type wireless power transmission transformer via a half-bridge LLC resonant converter. A ceramic insulating layer was used instead of an air gap, meaning that the heat generated from the transformer core and the PCB winding was quickly transferred to the external metal case, with the ceramic insulating layer acting as a heat pipe. In order to stabilize the output voltage, we proposed the use of IR photo tunnel technology, and it was applied to two ceramic insulating layers so that the voltage error signal of the secondary output voltage could be transmitted as light to the primary side. As a result, it was possible to physically separate the primary and secondary sides of the power circuit centering on the ceramic insulating layer. The experiment was carried out with the input voltage of 400 V, the output voltage of 54 V, the maximum output power of 1 kW, and the switching frequency of 1.3 MHz or higher. As a result, the maximum operating frequency was 1.83 MHz, and the output voltage stability to the load was 0.49% or lower. The power density of the experimental circuit was 380 W/in3 or higher, and the maximum power conversion efficiency was approximately 93% or higher.
40
O'Neal, Chad B., Matthew Feurtado, Jennifer Stabach, Ty McNutt e Brandon Passmore. "Temperature Dependence of High Dielectric Strength Potting Materials for Medium Voltage Power Modules". Journal of Microelectronics and Electronic Packaging 12, n. 4 (1 ottobre 2015): 212–18. http://dx.doi.org/10.4071/imaps.472.
Testo completoAbstract (sommario):
Voltage insulation inside power modules is paramount for functional and reliable operation. Dielectric potting materials are stressed as the overall size of these modules is reduced due to size, weight, and cost considerations while the operating voltage of these modules continue to increase. In particular, voltage ratings of silicon carbide (SiC) device technologies will continue to increase above 6.5 kV into the tens of kilovolts in the future. SiC devices are also often operated at higher junction temperatures to take advantage of the high-temperature capabilities of the material. As the module temperature increases, the dielectric strength of insulating materials in the module tends to decrease, which is a serious concern for a compact power module operating at many kilovolts. A plurality of high-temperature-rated, high dielectric strength potting materials was tested for voltage breakdown and leakage current up to 30 kV and 250°C. A range of different materials, both conventional and novel, were tested, including silicones and Parylene. Materials were selected with a dielectric strength >20 kV/mm, an operating temperature range of 200°C or higher, and low hardness and modulus of elasticity with the intent of demonstrating the capability of blocking 20 kV or more in a reasonable thickness. A custom test setup was constructed to apply the voltage to test samples while measuring the breakdown voltage and simultaneously recording the leakage current. Test coupons were designed to provide a range of dielectric thicknesses over which to test the dielectric strength. Although voltage isolation may increase with increased dielectric thickness, the volt per millimeter isolation rate often decreases. The performance degradation of these materials over temperature is plotted, and insulation thicknesses are suggested for use with medium voltages at operating temperatures above 175°C.
41
Andrade, Arthur F., Edson G. Costa, Filipe L. M. Andrade, Clarice S. H. Soares e George R. S. Lira. "Design of Cable Termination for AC Breakdown Voltage Tests". Energies 12, n. 16 (9 agosto 2019): 3075. http://dx.doi.org/10.3390/en12163075.
Testo completoAbstract (sommario):
International standards prescribe overvoltage tests to evaluate the insulating material performance of high-voltage cables. However, it is difficult to manage the electric fields at the cable ends when laboratory measurements are carried out because surface and external discharges occur at the cable termination. Therefore, this paper presents a procedure for designing cable terminations to reduce the electric field at the cable ends to appropriate levels even in the case of overvoltage tests. For this purpose, computer simulations of electric field distribution using the finite element method (FEM) were performed. A 35 kV cable model was employed as a sample. An voltage with RMS (root mean square) value of 300 kV was used as an overestimate of breakdown voltage for the internal insulating material. The cable termination model obtained through the proposed methodology allows an electric field reduction in air, preventing the occurrence of external discharges, and thus permitting the breakdown voltage measurement of the cable’s inner insulation.
42
Yao, Wei, Zhengyong Huang, Jian Li, Liya Wu e Chenmeng Xiang. "Enhanced Electrical Insulation and Heat Transfer Performance of Vegetable Oil Based Nanofluids". Journal of Nanomaterials 2018 (2018): 1–12. http://dx.doi.org/10.1155/2018/4504208.
Testo completoAbstract (sommario):
Nanoparticles enhance the electrical insulation and thermal properties of vegetable oil, and such improvements are desirable for its application as an alternative to traditional insulating oil for power transformers. However, the traditional method of insulating nanofluids typically achieves high electrical insulation but low thermal conductivity. This work reports an environmentally friendly vegetable oil using exfoliated hexagonal boron nitride (h-BN) showing high thermal conductivity and high electrical insulation. Stable nanofluids were prepared by liquid exfoliation of h-BN in isopropyl alcohol. With 0.1 vol.% of the nano-oil, the AC breakdown voltage increased by 18% at 25°C and 15% at 90°C. Both the positive and negative lightning impulse breakdown voltages of the nano-oil were also enhanced compared with those of the pure oil. Moreover, the thermal conductivity of the nano-oil increased by 11.9% at 25°C and 14% at 90°C. Given its high thermal conductivity, the nano-oil exhibited faster heating and cooling effects than the pure oil. Nano-oils with an electric field (either DC or AC) displayed a faster thermal response than that without an electric field. The reason is that h-BN is oriented under the electric field and formed a thermal network to increase the heat transfer.
43
Liu, Fan, Xian Tao Tao, Lin Yang, Ping Liu e Kai Zhou. "XLPE Cable Insulation Enhancement Mechanism Based on Isopropoxide Catalyzed Siloxane". Advanced Materials Research 554-556 (luglio 2012): 277–81. http://dx.doi.org/10.4028/www.scientific.net/amr.554-556.277.
Testo completoAbstract (sommario):
In this paper, needle-shape insulation defect was made in XLPE cable samples. With high-voltage and high-frequency accelerated aging, water tree was formed inside XLPE layer. One group of the samples was injected siloxane catalyzed by isopropoxide for rejuvenation, and the breakdown voltage was significantly greater than new samples. Nano-inorganic particles were observed by scanning electron microscope (SEM) inside the breakdown channels of rejuvenated samples. The insulation enhancement mechanism is described in this paper based on the new discovery, that the insulating property of cables is enhanced by the nano-inorganic particles, because of its ability to inhibit the partial discharge damage inside the water tree channel.
44
Fal, Jacek, Omid Mahian e Gaweł Żyła. "Nanofluids in the Service of High Voltage Transformers: Breakdown Properties of Transformer Oils with Nanoparticles, a Review". Energies 11, n. 11 (28 ottobre 2018): 2942. http://dx.doi.org/10.3390/en11112942.
Testo completoAbstract (sommario):
The continuous development of electrical systems and high voltage transformers builds the need for looking for new insulating media or to improve the insulating properties of commercially available transformer oils (TO) by various modification techniques. One of these techniques is the modification of existing mineral oils by the addition of different types of nanoparticles in various concentrations. These types of materials, suspensions of nanoparticles called nanofluids, have found numerous applications in the energy industry, especially in heat exchanger systems and solar cells. Much research has been done on attempts to replace mineral oils (MO), which are harmful for the environment, with natural ester oils (NE), but to make this possible, it is necessary to improve the insulating properties of these oils, for example by adding nanoparticles. This paper presents an extensive overview of the insulating properties; including for AC, DC and the lightning impulse breakdown voltage; for both mineral and natural ester oils containing various type of nanoparticles (NP). It is presented that the use of nanofluids could improve the efficiency of existing high voltage infrastructures with a low financial cost.
45
Islam, Sanjida, Md Selim Hossain, Md Farhamdur Reza e Md Mamunur Rashid. "Experimental Investigation of Insulating Properties of Vegetable Oil under High Voltage". European Journal of Engineering Research and Science 4, n. 1 (9 gennaio 2019): 17–23. http://dx.doi.org/10.24018/ejers.2019.4.1.1047.
Testo completoAbstract (sommario):
Due to concerns over the world’s energy necessity and environmental impact of mineral oil, these conditions induce many researchers to search for substitute sources for insulating oil. Alternatives insulating oil with biodegradable characteristics, environment friendly and presented in different countries including Bangladesh such as vegetable oils have been proposed for high voltage applications. In this paper, a relative measurement of breakdown voltage through experimental investigation of coconut, mustard, soybean, and palm oil and their blend (which is available in Bangladesh and cost effective) is presented. Break down voltage was measure with different electrode configuration by changing gap distance. The results show that the blend of (50% coconut oil + 50% palm oil) got high breakdown voltage in mushroom-mushroom electrode, and other side in plane-plane type pure soybean oil got high breakdown voltage, compared with transformer oil. The presented result illustrate that the proposed mixed oil provides better performance than the rise husk oil.
46
Islam, Sanjida, Md Selim Hossain, Md Farhamdur Reza e Md Mamunur Rashid. "Experimental Investigation of Insulating Properties of Vegetable Oil under High Voltage". European Journal of Engineering and Technology Research 4, n. 1 (9 gennaio 2019): 17–23. http://dx.doi.org/10.24018/ejeng.2019.4.1.1047.
Testo completoAbstract (sommario):
Due to concerns over the world’s energy necessity and environmental impact of mineral oil, these conditions induce many researchers to search for substitute sources for insulating oil. Alternatives insulating oil with biodegradable characteristics, environment friendly and presented in different countries including Bangladesh such as vegetable oils have been proposed for high voltage applications. In this paper, a relative measurement of breakdown voltage through experimental investigation of coconut, mustard, soybean, and palm oil and their blend (which is available in Bangladesh and cost effective) is presented. Break down voltage was measure with different electrode configuration by changing gap distance. The results show that the blend of (50% coconut oil + 50% palm oil) got high breakdown voltage in mushroom-mushroom electrode, and other side in plane-plane type pure soybean oil got high breakdown voltage, compared with transformer oil. The presented result illustrate that the proposed mixed oil provides better performance than the rise husk oil.
47
Jörgens, Christoph, e Markus Clemens. "Modeling the electric field at interfaces and surfaces in high-voltage cable systems". COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 39, n. 5 (8 maggio 2020): 1099–111. http://dx.doi.org/10.1108/compel-01-2020-0041.
Testo completoAbstract (sommario):
Purpose In high-voltage direct current (HVDC) cable systems, space charges accumulate because of the constant applied voltage and the nonlinear electric conductivity of the insulating material. The change in the charge distribution results in a slowly time-varying electric field. Space charges accumulate within the insulation bulk and at interfaces. With an operation time of several years of HVDC systems, typically the stationary electric field is of interest. The purpose of this study is to investigate the influence of interfaces on the stationary electric field stress and space charge density. Design/methodology/approach An analytic description of the stationary electric field inside cable insulation is developed and numerical simulations of a cable joint geometry are applied, considering spatial variations of the conductivity in the vicinity of the electrodes and interfaces. Findings With increasing conductivity values toward the electrodes, the resulting field stress decreases, whereas a decreasing conductivity results in an increasing electric field. The increased electric field may cause partial discharge, resulting in accelerated aging of the insulation material. Thus, interfaces and surfaces are characterized as critical areas for the reliability of HVDC cable systems. Research limitations/implications This study is restricted to stationary electric field and temperature distributions. The electric field variations during a polarity reversal or a time-varying temperature may result in an increased electric conductivity and electric field at interfaces and surfaces. Originality/value An analytical description of the electric field, considering surface effects, is developed. The used conductivity model is applicable for cable and cable-joint insulations, where homo- and hetero-charge effects are simulated. These simulations compare well against measurements.
48
BUZNIKOV, N. A., I. T. IAKUBOV, A. L. RAKHMANOV, K. I. KUGEL e A. O. SBOYCHAKOV. "HIGH-FREQUENCY RESPONSE AND VOLTAGE NOISE IN MAGNETIC NANOCOMPOSITES". International Journal of Modern Physics B 23, n. 20n21 (20 agosto 2009): 4216–33. http://dx.doi.org/10.1142/s0217979209063389.
Testo completoAbstract (sommario):
We study the noise spectra and high-frequency permeability of inhomogeneous magnetic materials consisting of single-domain magnetic nanoparticles embedded into an insulating matrix. Possible mechanisms of 1/f voltage noise in phase-separated manganites is analyzed. The material is modelled by a system of small ferromagnetic metallic droplets (magnetic polarons or ferrons) in insulating antiferromagnetic or paramagnetic matrix. The electron transport is related to tunnelling of charge carriers between droplets. One of the sources of the 1/f noise in such a system stems from fluctuations of the number of droplets with extra electron. In the case of strong magnetic anisotropy, the 1/f noise can arise also due to the fluctuations of the magnetic moments of ferrons. The high frequency magnetic permeability of nanocomposite film with magnetic particles in insulating non-magnetic matrix is studied in detail. The case of strong magnetic dipole interaction and strong magnetic anisotropy of ferromagnetic granules is considered. The composite is modelled by a cubic regular array of ferromagnetic particles. The high-frequency permeability tensor components are found as a functions of frequency, temperature, ferromagnetic phase content, and magnetic anisotropy. The results demonstrate that magnetic dipole interaction leads to a shift of the resonance frequencies towards higher values, and nanocomposite film could have rather high value of magnetic permeability in the microwave range.
49
Roger, Daniel, e Ewa Napieralska-Juszczak. "Voltage distribution in the windings of high temperature inverter-fed motors". COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 37, n. 5 (3 settembre 2018): 1824–36. http://dx.doi.org/10.1108/compel-01-2018-0024.
Testo completoAbstract (sommario):
Purpose High-temperature (HT°) motors are made with inorganic coils wound with a ceramic-coated wire. They must be carefully designed because the HT° insulating materials have a lower breakdown voltages than the polymers used for insulating standard machines. Design/methodology/approach The voltage distribution between stator coils is computed with high-frequency (HF) equivalent circuits that consider the magnetic couplings and the stray capacitances. Two time scales are used for getting a fast computation of very short voltage spikes. For the first step, a medium time scale analysis is performed considering a simplified equivalent circuit made without any stray capacitance but with the full PWM pattern and the magnetic couplings. For the second step, a more detailed HF equivalent circuit computes voltage spikes during short critical time windows. Findings The computation made during the first step provides the critical time windows and the initial values of the state variables to the second one. The rise and fall time of the electronic switches have a minor influence on the maximum voltage stress. Conversely, the connection cable length and the common-mode capacitances have a large influence. Research limitations/implications HF equivalent circuits cannot be used with random windings but only to formed coils that have a deterministic position of turns. Practical implications The proposed method can be used designing of HT° machine windings fed by PWM inverter and for improving the coils of standard machine used in aircraft’s low-pressure environments. Originality/value The influence of grounding system of the DC link is considered for computing the voltage spikes in the motor windings.
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Aakre, Torstein Grav, Erling Ildstad e Sverre Hvidsten. "Time Development of Voltage Frequency Dependence of Partial Discharge Activity in Voids". Proceedings of the Nordic Insulation Symposium, n. 26 (8 agosto 2019): 139–44. http://dx.doi.org/10.5324/nordis.v0i26.3294.
Testo completoAbstract (sommario):
Condition assessment of high voltage equipment based on partial discharge measurements is often performed after a voltage pre-conditioning period. The aim of this paper is to present results from experimental examinations of time variance of partial discharge activity and to propose physical explanations of the phenomena observed. Experiments were performed on laboratory made 3 mm thick discs of generator bar insulation, consisting of mica and glass fiber reinforced epoxy with a 0.5 mm thick cylindrical void surfaces of 10 mm in diameter. The effect of conducting and insulating void surfaces was examined using copper tape as upper and lower electrodes of the voids. All objects were tested by 12 one-minute long AC voltage frequency sweeps at frequencies from 50 Hz to 0.1 Hz distributed in time from start of the experiment, after initial one-hour constant 50 Hz voltage application and during object short-circuiting for 20 h. The main result shows that in case of insulating voids the apparent charges vanished after the one-hour constant 50 Hz voltage application. After a grounding period of 5 minutes, the charge magnitudes slowly increased with time until reaching steady state after about 4-8 hours. Test objects with conductive void surfaces showed such reduction in case of PD testing at 0.1 Hz only. At voltage frequencies above 10 Hz the measured PD magnitudes were found to be nearly constant, close to the expected high theoretical value. This indicate that PD by-products strongly affected the void resistivity and thereby affect the PD activity of insulating voids. These by-products are temporary and disappear with time.