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Artykuły w czasopismach na temat "Distribution transformer thermal aging"
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Zhang, Xiaojing, Lu Ren, Haichuan Yu, Yang Xu, Qingquan Lei, Xin Li i Baojia Han. "Dual-Temperature Evaluation of a High-Temperature Insulation System for Liquid-Immersed Transformer". Energies 11, nr 8 (27.07.2018): 1957. http://dx.doi.org/10.3390/en11081957.
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A high-temperature oil–paper insulation system offers an opportunity to improve the overloading capability of distribution transformers facing seasonal load variation. A high-temperature electrical insulation system (EIS) was chosen due to thermal calculation based on a typical loading curve on the China Southern Power Grid. In order to evaluate candidate high-temperature insulation systems, Nomex® T910 (aramid-enhanced cellulose) immersed in FR3 (natural ester) was investigated by a dual-temperature thermal aging test compared with a conventional insulation system, Kraft paper impregnated with mineral oil. Throughout the thermal aging test, mechanical, chemical, and dielectric parameters of both paper and insulating oil were investigated in each aging cycle. The thermal aging results determined that the thermal class of the FR3-T910 insulation system meets the request of overloading transformer needs.
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Wei, Yanhui, Wang Han, Guochang Li, Xiaojian Liang, Zhenlu Gu i Kai Hu. "Aging Characteristics of Transformer Oil-Impregnated Insulation Paper Based on Trap Parameters". Polymers 13, nr 9 (22.04.2021): 1364. http://dx.doi.org/10.3390/polym13091364.
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Oil-impregnated insulation paper is an important part of transformers; its performance seriously affects the life of power equipment. It is of significance to study the aging characteristics and mechanism of oil-impregnated insulation paper under thermal stress for transformer status detection and evaluation. In the work, the accelerated thermal aging was carried out at 120 °C, and DP1490, DP787, and DP311 samples were selected to represent the new, mid-aging, and late-aging status of the transformer, respectively. The space charge distribution within the specimens was measured by the pulsed electro-acoustic (PEA) method and the trap parameters were extracted based on the measurement curves. Further, the aging mechanism was studied by molecular simulation technology. A typical molecular chain defect model was constructed to study the motion of cellulose molecules under thermal stress. The experimental results show that the corresponding trap energy levels are 0.54 eV, 0.73 eV, and 0.92 eV for the new specimen, the mid-aging specimen, and the late aging specimen, respectively. The simulation results show that the trapped energy at the beginning of aging is mainly determined by the loss of H atoms. The changes in trap energy in the middle stage of aging are mainly caused by the absence of some C atoms, and the trap energy level at the end of aging is mainly caused by the breakage of chemical bonds. This study is of great significance to reveal the aging mechanism of oil-impregnated insulation paper and the modification of insulation paper.
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Li, Min, Wei Yao, Xin Gao i Yan Ren. "Temperature simulation of oil-immersed transformerbased on fluid-thermal coupling". Journal of Physics: Conference Series 2503, nr 1 (1.05.2023): 012060. http://dx.doi.org/10.1088/1742-6596/2503/1/012060.
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Abstract The main components of the transformer face overheating and insulation aging caused by electromagnetic losses, which affect their service life. This paper analyzes an oil-immersed transformer with a rated voltage of 800kV based on heat transfer and fluid dynamics principles. The temperature distribution is carried out by magnetic-thermal coupling simulation. The influence of insulation oil flow rate on temperature is analyzed in the thermal field calculation, and the overall temperature rise of transformer and insulating oil is obtained. It turned out that the highest hot spot of the transformer occurs in the low-voltage winding, and the flow speed of insulation oil between the winding is the fastest.
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Poliakov, M. O., i V. V. Vasylevskyi. "Method for assessing unevenness of cellulose insulation layers aging of power transformers winding". Electrical Engineering & Electromechanics, nr 5 (6.09.2022): 47–54. http://dx.doi.org/10.20998/2074-272x.2022.5.08.
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Introduction. Improving the methods of estimating the insulation aging of the oil-immersed power transformer windings is an urgent task for transformer condition monitoring systems. The scientific novelty of the work is to take into account the uneven distribution of temperature and humidity along the vertical axis of the winding in modeling the aging of insulation and to develop methods for determining the conditions under which the aging rate of insulation in the intermediate layer will exceed aging rate in the hottest layer. The purpose of the work is to evaluate the wear unevenness of cellulose insulation based on modeling the distribution of temperature and humidity along the vertical axis of the power transformer winding. Methods. The transformer winding is mentally divided into horizontal layers of equal height, the reduction of service life is calculated in parallel for all horizontal layers. Layer with the maximum degree of aging for the entire period of operation and storage of the transformer is recognized as determining the reduction in the service life of the insulation of the transformer as a whole. A model of the interaction of winding layers is developed, with determination of temperatures, humidity, relative rate of aging of each layer due to temperature and humidity as a function of traditional design parameters such as load, cooling temperature, heat capacity and thermal resistance of transformer. The index of exceeding the aging rate by the layered method in comparison with this rate for the hottest layer is offered. The method of genetic algorithms determines the conditions for obtaining the maximum value of this index. Results. A computer model has been developed to predict the aging of the cellulose insulation of transformer windings. According to the proposed method, a layer with significantly shorter insulation aging time (in the example, time reduced by 39.18 %) than for the upper layer was determined, which confirms the feasibility of layer-by-layer monitoring and modeling of insulation aging processes of power oil-immersed transformer windings.
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Cao, Jian, Hao Jun Zhou i Su Xiang Qian. "Research on the 3D Temperature Field of Transformer Winding Based on Finite Element Analysis". Advanced Materials Research 129-131 (sierpień 2010): 353–57. http://dx.doi.org/10.4028/www.scientific.net/amr.129-131.353.
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Power transformer is one of the most important electric equipments in power network, its running state has a direct effect on its safe operation of power network. Fault’s occurrence of power transformer probably result in vast hazards or accidents. According to statistics, its over-temperature operation of winding often result in different fault patterns, such as aging, breakdown and its burnt, etc, which has a large proportion in its accidents of power transformer. In this paper, based on the thermal analysis theory, a 3D thermal field model of transformer’s winding and core is respectively established in ANSYS software environment. And its 3D temperature field distribution of power transformer, including winding and core is simulated. Numerical simulated results provide a reliable and convenient reference for its thermal performance analysis of power transformer.is simulated. Numerical simulated results provide a reliable and convenient reference for its thermal performance analysis of power transformer.
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Dong, Bingbing, Yu Gu, Changsheng Gao, Zhu Zhang, Tao Wen i Kejie Li. "Three-Dimensional Electro-Thermal Analysis of a New Type Current Transformer Design for Power Distribution Networks". Energies 14, nr 6 (23.03.2021): 1792. http://dx.doi.org/10.3390/en14061792.
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In recent years, the new type design of current transformer with bushing structure has been widely used in the distribution network system due to its advantages of miniaturization, high mechanical strength, maintenance-free, safety and environmental protection. The internal temperature field distribution is an important characteristic parameter to characterize the thermal insulation and aging performance of the transformer, and the internal temperature field distribution is mainly derived from the joule heat generated by the primary side guide rod after flowing through the current. Since the electric environment is a transient field and the thermal environment changes slowly with time as a steady field under the actual conditions, it is more complex and necessary to study the electrothermal coupling field of current transformer (CT). In this paper, a 3D simulation model of a new type design of current transformer for distribution network based on electric-thermal coupling is established by using finite element method (FEM) software. Considering that the actual thermal conduction process of CT is mainly by conduction, convection and radiation, three different kinds of boundary conditions such as solid heat transfer boundary condition, heat convection boundary condition and surface radiation boundary condition are applied to the CT. Through the model created above, the temperature rise process and the distribution characteristics of temperature gradient of the inner conductor under different current, different ambient temperatures and different core diameters conditions are studied. Meanwhile, the hottest temperature and the maximum temperature gradient difference are calculated. According to this, the position of weak insulation of the transformer is determined. The research results can provide a reference for the factory production of new type design of current transformer.
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Grabko, Volodymyr, Stanislav Tkachenko i Oleksandr Palaniuk. "Determination of temperature distribution on windings of oil transformer based on the laws of heat transfer". ScienceRise, nr 5 (29.10.2021): 3–13. http://dx.doi.org/10.21303/2313-8416.2021.002140.
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Object of research: development of a technology for determining the temperature of the winding of a power oil transformer, in particular, the analysis of thermal processes in the winding of a power transformer during short-term overloads, taking into account the influence of the environment.
Investigated problem: temperature distribution in the winding of a power oil transformer taking into account short-term load surges in the problem of assessing the residual life of the insulation of the transformer winding by temperature aging. The calculation of the temperature distribution in the winding was carried out using the passport data and characteristics of the power oil transformer, including the winding, transformer oil, load currents.
Main scientific results: a mathematical model was calculated, with the help of which the results of temperature distribution in the transformer winding were obtained during short-term load surges or constant work with an increased load. According to the presented model, the analysis of the cooling time of the transformer winding after short-term overloads is carried out. Comparing the results obtained on the simulation model with the known results of experimental studies of the temperature distribution in the winding of a power transformer, the adequacy of the mathematical model is proved. It is shown that the use of the laws of heat transfer in a homogeneous plate to analyze the temperature distribution in the transformer winding is not wrong, but requires clarifications and simplifications.
The area of practical use of the research results: enterprises of the machine-building industry and energy companies specializing in the production and operation of transformer equipment. Innovative technological product: simulation model of heat distribution in a transformer winding, which can take into account the load of the transformer, the effect of the environment on the insulation of the transformer windings.
An innovative technological product: a method for diagnosing the duration of the non-failure operation of a transformer, which makes it possible to ensure trouble-free operation and save money for the repair of transformer equipment.
Scope of application of the innovative technological product: design and development of diagnostic systems for windings of power oil transformers
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Prasojo, Rahman Azis, Rohmanita Duanaputri, Jamik Apriliasari, Rosina Ahda Dini i Devi Soviati Mahmudah. "Review pengaruh penetrasi photovoltaic terhadap loss of life dan kinerja transformator". JURNAL ELTEK 20, nr 2 (28.10.2022): 61. http://dx.doi.org/10.33795/eltek.v20i2.357.
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ABSTRAK
Salah satu peralatan yang penting dalam sistem distribusi tenaga listrik adalah transformator. Penuaan transformator disebabkan oleh kerusakan isolasi yang diakibatkan dari proses degradasi kimia yang terakselerasi oleh oksidasi dan peningkatan suhu. Maka dari itu, untuk menilai loss of life transformator yang paling umum digunakan adalah menggunakan karakteristik thermal transformator. Peningkatan penggunaan photovoltaic (PV) yang mulai menyebar di berbagai daerah adalah salah satu bukti mulai diandalkannya energi terbarukan. Hal ini membawa dampak positif maupun negatif, baik bagi sistem tenaga secara keseluruhan, maupun bagi peralatan listrik. Artikel ini membahas berbagai penelitian terdahulu yang meneliti tentang pengaruh penggunaan PV terhadap penurunan kondisi transformator distribusi. Artikel review ini dibagi menjadi tiga bagian. Yang pertama membahas tentang akibat pemasangan PV yang mempengaruhi kinerja dari isolasi transformator berdasarkan pembebanan yang dialami saat operasi. Yang kedua membahas tentang pengaruh harmonisa yang dihasilkan oleh sistem PV terhadap penuaan transformator. Yang terakhir membahas tentang beberapa penelitian terdahulu yang membahas pendekatan untuk mengatasi harmonisa pada sistem.
ABSTRACT
One of the most important equipment in an electric power distribution system is a transformer. Transformer aging is caused by insulation breakdown resulted from chemical degradation processes that are accelerated by oxidation and increasing temperature. To assess the loss of life of the transformer, the most commonly used is to use the thermal characteristics of the transformer. The increasing use of photovoltaic which is starting to spread in various regions is one proof that renewable energy is starting to be relied on. This has both positive and negative impacts, both for the power system as a whole and for electrical equipment. This article discusses various previous studies that examined the effect of the use of photovoltaic on the deterioration of the distribution transformer condition. This review article is divided into three parts. The first is the effect of PV penetration which affects the performance of the transformer insulation based on the loading during operation. The second is the effect of harmonics generated by the PV system on the transformer aging. The last is to discuss some of the previous studies that proposed methods in reducing harmonics in the system.
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Hong, Shin-Ki, Sung Gu Lee i Myungchin Kim. "Assessment and Mitigation of Electric Vehicle Charging Demand Impact to Transformer Aging for an Apartment Complex". Energies 13, nr 10 (19.05.2020): 2571. http://dx.doi.org/10.3390/en13102571.
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Due to the increasing use of Electric Vehicles (EVs), the effect of the EV charging power demand on the reliability of the power system infrastructure needs to be addressed. In apartment complexes, which have emerged as a common residential type in metropolitan areas and highly populated districts, high charging demand could result in substantial stress to distribution networks. In this work, the effect of EV charging power demand in an apartment complex on the aging of the Distribution Transformer (DT) is studied. A methodology based on the stochastic characterization of vehicle usage profiles and user charging patterns is developed to obtain realistic EV charging demand profiles. Based on the modeled EV charging profile and the transformer thermal model, the effect of different EV penetration ratios on DT aging for an apartment complex in the Republic of Korea is studied. Results for an EV penetration ratio of up to 30% indicated that DT aging could be accelerated by up to 40%, compared to the case without EV charging. To mitigate this accelerated DT aging caused by EV charging, the effectiveness of two integration approaches of Photovoltaic (PV) sources was studied. Based on a case study that included a realistic PV generation profile, it was demonstrated that a significant contribution to DT reliability could be achieved via the operation of PV sources. A more apparent contribution of PV integration was observed with an energy storage installation at higher EV penetration ratios. At an EV penetration ratio of 30%, a maximum decrease of 41.8% in the loss-of-life probability of the DT was achieved. The effects of different PV integration approaches and power management details on DT aging were also studied. The results demonstrate that the EV charging demand could introduce a significant level of stress to DTs and that this impact can be effectively mitigated by installing PV sources. These observations are expected to contribute toward the effective planning of power system infrastructures that support the design of sustainable cities with the widespread use of EVs.
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Jalbert, Rodriguez-Celis, Arroyo-Fernández, Duchesne i Morin. "Methanol Marker for the Detection of Insulating Paper Degradation in Transformer Insulating Oil". Energies 12, nr 20 (18.10.2019): 3969. http://dx.doi.org/10.3390/en12203969.
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This manuscript presents a comprehensive literature review with the aim to provide readers a reference document with up-to-date information on the field of methanol use as a chemical marker. It has been a little more than a decade since methanol was first introduced as a marker for assessing solid insulation condition in power transformers. It all started when methanol was identified in the laboratory during thermal ageing tests carried out with oil-immersed insulating papers and was subsequently also identified in transformer field samples. The first publication on the subject was released in 2007 by our research group. This review covers the methanol fundamentals such as the analytical methods for its determination in transformer oil, which is generally performed by headspace gas chromatography with mass spectrometry or flame ionization as a detector. Current standardization efforts for its determination include ASTM working group 30948 and IEC TC10. Kinetic studies have confirmed the relationship between methanol generation, the number of broken 1,4-β-glycosidic bonds of cellulose and changes in mechanical properties. Laboratory tests have confirmed its stability at different accelerated ageing temperatures. Several utilities have identified methanol during field measurements, case studies on power and some distribution transformers are presented, as well as transformer postmortem investigations. These field-testing results demonstrate its utility in monitoring cellulosic insulation degradation. Recently, a model of methanol interpretation has become available that allows for evaluation of the average degree of polymerization of core type transformer cellulose winding. Methanol has a role as an indicator of cellulosic solid insulation ageing in transformer mineral oil, and it is expected that in the future it will be in routine use by utilities.
Rozprawy doktorskie na temat "Distribution transformer thermal aging"
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Gao, Yuan. "Assessment of future adaptability of distribution transformer population under EV scenarios". Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/assessment-of-future-adaptability-of-distribution-transformer-population-under-ev-scenarios(f2aafdab-2161-4968-9568-2550a80d673e).html.
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As one of the most promising pathways in the transition period towards the low carbon economy, a large scale implementation of electric vehicles (EV) is expected in the near future. Concentration of EV charging in a small area or within a short time will dramatically affect the load demand profile, especially the peak load in the distribution network. As a result, distribution transformers are facing hazards of shortened lifetime due to extra loads, and direct failures caused by potential overloads. Considering the large number of distribution transformers and the massive investment involved, the adaptability of the population of distribution transformers under future EV scenarios should be assessed. In this thesis, an assessment strategy for the future adaptability of distribution transformer population under EV scenarios is introduced. Assessing the adaptability is to understand the impact of the hot-spot temperature, loss-of-life, expected lifetime and failure probability of each individual in the distribution transformer population. Determination of hot-spot temperature of distribution transformers is essential for the assessment. In order to achieve accurate prediction of hot-spot temperatures under EV scenarios, thermal parameters should be refined for individual distribution transformers so that their thermal characteristics can be reflected more accurately than using the generic values recommended for all distribution transformers in the IEC loading guide. Two methods for the refinement are proposed in this thesis. One method is to curve-fit hot-spot temperatures measured in the extended heat run test; and the other is to calculate each parameter with developed equations in the loading guide with standard heat run test results. The assessment strategy is introduced and demonstrated on a group of selected distribution transformers from the population under three EV scenarios, i.e. Business as usual (BAU), High-range and Extreme-range scenarios, which represent 0%, 32% and 58.9% EV penetration levels respectively. Results show that EV charging would be less concerned on the acceleration of thermal ageing than the direct failure due to breakdown caused by decrease of dielectric strength in an event of bubbling. Since the peak load and hot-spot temperature under EV scenarios only last for a short time and would be compensated by low values during the rest time of a day, which eventually leads to a moderate thermal ageing. Occasionally, severe over-ageing can be caused by extremely high hot-spot temperatures, and the lifetime will be reduced to an unacceptable level. However, on such occasions, hot-spot temperatures would be high enough to trigger bubbling and reduce the dielectric strength of transformer's insulation system to a level that is incapable of undertaking the voltage stress, which eventually causes breakdown of transformers. In terms of the failure probability, results show that no distribution transformers are facing failure risks due to bubbling under BAU scenario. Failure starts under High-range scenario. If transformers possessing a failure probability over 50% are identified as high risk, then 13% of investigated transformers are at high risk under High-range scenario, while it increases to 39% under Extreme-range scenario. It is found that the failure probability is dominantly controlled by the peak load, other factors such as transformer age and installation conditions are less influential. A threshold peak load of around 1.5 p.u. is observed that distinguishes transformers in high risk from others under Extreme-range scenario. This observation could be applied to assist the asset management under future EV scenarios that the peak load of distribution transformers should be restricted below 1.5 p.u. to prevent potential failure due to bubbling.
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Marko, Robert Michael. "Thermal modelling of a natural-convection-cooled, oil-immersed distribution transformer". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq23407.pdf.
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Mohamed, Ali Mohamed. "ANALYZING THE IMPACT OF PHOTOVOLTAIC AND BATTERIE SYSTEMS ON THE LIFE OF A DISTRIBUTION TRANSFORMER". Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-54952.
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This degree project presents a study case in Eskilstuna-Sweden, regarding the effect of the photovoltaic (PV) systems with battery energy storage system (BESS) on a power distribution transformer, and how they could change the transformer lifespan. For that, an extensive literature review has been conducted, and two MATLAB models were used to simulate the system. One model simulates the PV generation profile, with the option of including battery in the system, and the other one simulates the transformer loss of life (LOL) based on the thermal characteristics. Simulations were using hourly time steps over a year with provided load profile based on utility data and typical meteorological year weather data from SMHI and STRÅNG. In this study, three different scenarios have been put into consideration to study the change of LOL. The first scenario applies various levels of PV penetrations without energy storage, while, the other scenarios include energy storage under different operating strategies, self-consumption, and peak shaving. Similarly, different battery capacities have been applied for the purpose of studying the LOL change. Thus, under different PV penetrations and battery capacities, results included the variation of LOL, grid power, battery energy status, and battery power. Moreover, results concluded that the PV system has the maximum impact on LOL variation, as it could decrease it by 33.4 %, and this percentage could increase by applying different battery capacities to the system. Finally, LOL corresponding to the battery under peak shaving strategy varies according to the battery discharge target. As different peak shaving targets were used to control the battery discharge, and hence, study the impact on the transformer and estimate its LOL.
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Pradhan, Manoj Kumar. "Conformal Thermal Models for Optimal Loading and Elapsed Life Estimation of Power Transformers". Thesis, Indian Institute of Science, 2004. http://hdl.handle.net/2005/97.
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Power and Generator Transformers are important and expensive elements of a power system. Inadvertent failure of Power Transformers would cause long interruption in power supply with consequent loss of reliability and revenue to the supply utilities. The mineral oil impregnated paper, OIP, is an insulation of choice in large power transformers in view of its excellent dielectric and other properties, besides being relatively inexpensive.
During the normal working regime of the transformer, the insulation thereof is subjected to various stresses, the more important among them are, electrical, thermal, mechanical and chemical. Each of these stresses, appearing singly, or in combination, would lead to a time variant deterioration in the properties of insulation, called Ageing.
This normal and inevitable process of degradation in the several essential properties of the insulation is irreversible, is a non-Markov physico-chemical reaction kinetic process. The speed or the rapidity of insulation deterioration is a very strong function of the magnitude of the stresses and the duration over which they acted. This is further compounded, if the stresses are in synergy. During the processes of ageing, some, or all the vital properties undergo subtle changes, more often, not in step with the duration of time over which the damage has been accumulated. Often, these changes are non monotonic, thus presenting a random or a chaotic picture and understanding the processes leading to eventual failure becomes difficult. But, there is some order in this chaos, in that, the time average of the changes over short intervals of time, seems to indicate some degree of predictability.
The status of insulation at any given point in time is assessed by measuring such of those properties as are sensitive to the amount of ageing and comparing it with earlier measurements. This procedure, called the Diagnostic or nondestructive Testing, has been in vogue for some time now.
Of the many parameters used as sensitive indices of the dynamics of insulation degradation, temporal changes in temperatures at different locations in the body of the transformer, more precisely, the winding hot spots (HST) and top oil temperature (TOT) are believed to give a fairly accurate indication of the rate of degradation. Further, an accurate estimation of the temperatures would enable to determine the loading limit (loadability) of power transformer.
To estimate the temperature rise reasonably accurately, one has to resort to classical mathematical techniques involving formulation and solution of boundary value problem of heat conduction under carefully prescribed boundary conditions. Several complications are encountered in the development of the governing equations for the emergent heat transfer problems. The more important among them are, the inhomogeneous composition of the insulation structure and of the conductor, divergent flow patterns of the oil phase and inordinately varying thermal properties of conductor and insulation.
Validation and reconfirmation of the findings of the thermal models can be made using state of the art methods, such as, Artificial Intelligence (AI) techniques, Artificial Neural Network (ANN) and Genetic Algorithm (GA).
Over the years, different criteria have been prescribed for the prediction of terminal or end of life (EOL) of equipment from the standpoint of its insulation. But, thus far, no straightforward and unequivocal criterion is forth coming. Calculation of elapsed life in line with the existing methodology, given by IEEE, IEC, introduces unacceptable degrees of uncertainty. It is needless to say that, any conformal procedure proposed in the accurate prediction of EOL, has to be based on a technically feasible and economically viable consideration. A systematic study for understanding the dynamical nature of ageing in transformers in actual service is precluded for reasons very well known. Laboratory experiments on prototypes or pro-rated units fabricated based on similarity studies, are performed under controlled conditions and at accelerated stress levels to reduce experimental time. The results thereof can then be judiciously extrapolated to normal operating conditions and for full size equipment.
The terms of reference of the present work are as follows;
1. Computation of TOT and HST
Theoretical model based on Boundary Value Problem of Heat Conduction
Application of AI Techniques
2. Experimental Investigation for estimating the Elapsed Life of transformers
Based on the experimental investigation a semi-empirical expression has been developed to estimate the loss of life of power and station transformer by analyzing gas content and furfural dissolved in oil without performing off-line and destructive tests.
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Zhang, Xiang. "Dimensional analysis based CFD modelling for power transformers". Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/dimensional-analysis-based-cfd-modelling-for-power-transformers(49cac27d-38b9-4f23-a6ec-b5106422420c).html.
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Reliable thermal modelling approaches are crucial to transformer thermal design and operation. The highest temperature in the winding, usually referred to as the hot-spot temperature, is of the greatest interest because the insulation paper at the hot-spot undergoes the severest thermal ageing, and determines the life expectancy of the transformer insulation. Therefore, the primary objective of transformer thermal design is to control the hot-spot temperature rise over the ambient temperature within certain limit. For liquid-immersed power transformers, the hot-spot temperature rise over the ambient temperature is controlled by the winding geometry, power loss distribution, liquid flow rate and liquid properties. In order to obtain universally applicable thermal modelling results, dimensional analysis is adopted in this PhD thesis to guide computational fluid dynamics (CFD) simulations for disc-type transformer windings in steady state and their experimental verification. The modelling work is split into two parts on oil forced and directed (OD) cooling modes and oil natural (ON) cooling modes. COMSOL software is used for the CFD simulation work For OD cooling modes, volumetric oil flow proportion in each horizontal cooling duct (Pfi) and pressure drop coefficient over the winding (Cpd) are found mainly controlled by the Reynolds number at the winding pass inlet (Re) and the ratio of horizontal duct height to vertical duct width. The correlations for Pfi and Cpd with the dimensionless controlling parameters are derived from CFD parametric sweeps and verified by experimental tests. The effects of different liquid types on the flow distribution and pressure drop are investigated using the correlations derived. Reverse flows at the bottom part of winding passes are shown by both CFD simulations and experimental measurements. The hot-spot factor, H, is interpreted as a dimensionless temperature at the hot-spot and the effects of operational conditions e.g. ambient temperature and loading level on H are analysed. For ON cooling modes, the flow is driven by buoyancy forces and hot-streak dynamics play a vital role in determining fluid flow and temperature distributions. The dimensionless liquid flow and temperature distributions and H are all found to be controlled by Re, Pr and Gr/Re2. An optimal design and operational regime in terms of obtaining the minimum H, is identified from CFD parametric sweeps, where the effects of buoyancy forces are balanced by the effects of inertial forces. Reverse flows are found at the top part of winding passes, opposite to the OD results. The total liquid flow rates of different liquids for the same winding geometry with the same power loss distribution in an ON cooling mode are determined and with these determined total liquid flow rates, the effects of different liquids on fluid flow and temperature distributions are investigated by CFD simulations. The CFD modelling work on disc-type transformer windings in steady state present in this PhD thesis is based on the dimensional analyses on the fluid flow and heat transfer in the windings. Therefore, the results obtained are universally applicable and of the simplest form as well. In addition, the dimensional analyses have provided insight into how the flow and temperature distribution patterns are controlled by the dimensionless controlling parameters, regardless of the transformer operational conditions and the coolant liquid types used.
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Ureh, Henry Chigozie. "IMPACTS OF PLUG-IN ELECTRIC VEHICLE ON RESIDENTIAL ELECTRIC DISTRIBUTION SYSTEM USING STOCHASTIC AND SENSITIVITY APPROACH". DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/642.
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Plug-in Electric Vehicles (PEVs) are projected to become a viable means of transportation due to advances in technology and advocates for green and eco-friendly energy solutions. These vehicles are powered partially, or in some cases, solely by the energy stored in their battery packs. The large sizes of these battery packs require large amount of energy to charge, and as the demand for PEV increases, the increase in energy demand needed to recharge these PEV batteries could pose problems to the present electric distribution system. This study examines the potential impacts of PEV on a residential electric distribution system at various penetration levels.
An existing residential distribution network is modeled up to each household service point and various sensitivity scenarios and stochastic patterns of PEV loads are simulated. Impact studies that include voltage drop, service transformers overload, energy loss, and transformer thermal loss-of-life expectancy are analyzed. Results from the study are reported and recommendations to mitigate the impacts are presented.
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"Moving to a Smart Distribution Grid through Automatic Dynamic Loading of Substation Distribution Transformers". Master's thesis, 2011. http://hdl.handle.net/2286/R.I.9355.
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abstract: Dynamic loading is the term used for one way of optimally loading a transformer. Dynamic loading means the utility takes into account the thermal time constant of the transformer along with the cooling mode transitions, loading profile and ambient temperature when determining the time-varying loading capability of a transformer. Knowing the maximum dynamic loading rating can increase utilization of the transformer while not reducing life-expectancy, delaying the replacement of the transformer. This document presents the progress on the transformer dynamic loading project sponsored by Salt River Project (SRP). A software application which performs dynamic loading for substation distribution transformers with appropriate transformer thermal models is developed in this project. Two kinds of thermal hottest-spot temperature (HST) and top-oil temperature (TOT) models that will be used in the application--the ASU HST/TOT models and the ANSI models--are presented. Brief validations of the ASU models are presented, showing that the ASU models are accurate in simulating the thermal processes of the transformers. For this production grade application, both the ANSI and the ASU models are built and tested to select the most appropriate models to be used in the dynamic loading calculations. An existing application to build and select the TOT model was used as a starting point for the enhancements developed in this work. These enhancements include: Adding the ability to develop HST models to the existing application, Adding metrics to evaluate the models accuracy and selecting which model will be used in dynamic loading calculation Adding the capability to perform dynamic loading calculations, Production of a maximum dynamic load profile that the transformer can tolerate without acceleration of the insulation aging, Provide suitable output (plots and text) for the results of the dynamic loading calculation. Other challenges discussed include: modification to the input data format, data-quality control, cooling mode estimation. Efforts to overcome these challenges are discussed in this work.Dissertation/Thesis
M.S. Electrical Engineering 2011
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"Dynamic Loading of Substation Distribution Transformers: Detecting Unreliable Thermal Models and Improving the Accuracy of Predictions". Master's thesis, 2014. http://hdl.handle.net/2286/R.I.25809.
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abstract: t temperature (HST) and top-oil temperature (TOT) are reliable indicators of the insulation temperature. The objective of this project is to use thermal models to estimate the transformer's maximum dynamic loading capacity without violating the HST and TOT thermal limits set by the operator. In order to ensure the optimal loading, the temperature predictions of the thermal models need to be accurate. A number of transformer thermal models are available in the literature. In present practice, the IEEE Clause 7 model is used by the industry to make these predictions. However, a linear regression based thermal model has been observed to be more accurate than the IEEE model. These two models have been studied in this work.
This document presents the research conducted to discriminate between reliable and unreliable models with the help of certain metrics. This was done by first eyeballing the prediction performance and then evaluating a number of mathematical metrics. Efforts were made to recognize the cause behind an unreliable model. Also research was conducted to improve the accuracy of the performance of the existing models.
A new application, described in this document, has been developed to automate the process of building thermal models for multiple transformers. These thermal models can then be used for transformer dynamic loading.Dissertation/Thesis
Masters Thesis Engineering 2014
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"Dynamic Loading of Substation Distribution Transformers: An Application for use in a Production Grade Environment". Master's thesis, 2013. http://hdl.handle.net/2286/R.I.20804.
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abstract: Recent trends in the electric power industry have led to more attention to optimal operation of power transformers. In a deregulated environment, optimal operation means minimizing the maintenance and extending the life of this critical and costly equipment for the purpose of maximizing profits. Optimal utilization of a transformer can be achieved through the use of dynamic loading. A benefit of dynamic loading is that it allows better utilization of the transformer capacity, thus increasing the flexibility and reliability of the power system. This document presents the progress on a software application which can estimate the maximum time-varying loading capability of transformers. This information can be used to load devices closer to their limits without exceeding the manufacturer specified operating limits. The maximally efficient dynamic loading of transformers requires a model that can accurately predict both top-oil temperatures (TOTs) and hottest-spot temperatures (HSTs). In the previous work, two kinds of thermal TOT and HST models have been studied and used in the application: the IEEE TOT/HST models and the ASU TOT/HST models. And, several metrics have been applied to evaluate the model acceptability and determine the most appropriate models for using in the dynamic loading calculations. In this work, an investigation to improve the existing transformer thermal models performance is presented. Some factors that may affect the model performance such as improper fan status and the error caused by the poor performance of IEEE models are discussed. Additional methods to determine the reliability of transformer thermal models using metrics such as time constant and the model parameters are also provided. A new production grade application for real-time dynamic loading operating purpose is introduced. This application is developed by using an existing planning application, TTeMP, as a start point, which is designed for the dispatchers and load specialists. To overcome the limitations of TTeMP, the new application can perform dynamic loading under emergency conditions, such as loss-of transformer loading. It also has the capability to determine the emergency rating of the transformers for a real-time estimation.Dissertation/Thesis
M.S. Electrical Engineering 2013
Książki na temat "Distribution transformer thermal aging"
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1958-, Kramer Bill, Markel, A. J. (Anthony J.), National Renewable Energy Laboratory (U.S.) i International Electric Vehicle Symposium (25th : 2010 : Shenzhen, China), red. Application of distribution transformer thermal life models to electrified vehicle charging loads using Monte-Carlo method: Preprint. Golden, CO]: National Renewable Energy Laboratory, 2011.
Znajdź pełny tekst źródłaCzęści książek na temat "Distribution transformer thermal aging"
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An, Yi, Jianbing Pan, Beibei Li, Bei Liu i Kesheng Gai. "A Thermal Evaluation Method of Data-Driven Distribution Transformer". W Lecture Notes in Electrical Engineering, 1919–28. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-5959-4_233.
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Raith, Johannes, Christian Bonini i Mario Scala. "Simulation of Long-Term Transformer Operation with a Dynamic Thermal, Moisture and Aging Model". W Lecture Notes in Electrical Engineering, 211–26. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-5600-5_17.
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Roshan, Rajesh, Manisha Sharma i Raj Kumar Jarial. "Thermal Aging Analysis of Nomex Paper Solid Insulation Impregnated in Ester Insulation Oil for Possible Use in Transformer". W Intelligent Computing Applications for Sustainable Real-World Systems, 209–18. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-44758-8_18.
Pełny tekst źródłaStreszczenia konferencji na temat "Distribution transformer thermal aging"
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Sedighi, Alireza, Ali Kafiri, Mostafa Shahnazari, Mohammad reza Sehati i Faride Behdad. "Aging Assessment of Distribution Transformers Based on Thermal Imaging". W 2019 IEEE International Conference on Environment and Electrical Engineering and 2019 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe). IEEE, 2019. http://dx.doi.org/10.1109/eeeic.2019.8783439.
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Najdenkoski, K., G. Rafajlovski i V. Dimcev. "Thermal Aging of Distribution Transformers According to IEEE and IEC Standards". W 2007 IEEE Power Engineering Society General Meeting. IEEE, 2007. http://dx.doi.org/10.1109/pes.2007.385642.
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Watkins, Kenneth S. "Electrical Insulation System Degradation Sensors: Improving Reliability of Power Generation and Distribution". W 16th International Conference on Nuclear Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/icone16-48130.
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As insulation systems of power system components such as electrical motors, generators and transformers degrade, they become brittle, crack and, eventually, fail to perform their intended function. Failure of the insulation system of these components often leads to costly power interruptions that could be prevented if the actual condition of the insulation system is known. The degradation mechanisms of modern insulation systems are highly dependent on the actual environmental and operational conditions of the component. Current methods to measure insulation system condition are often complex, expensive and require specialized training to interpret. In contrast, conductive composite sensors made of the same polymeric components as the insulation system itself monitor the actual environmentally and operationally induced degradation of the component insulation and provide a quick, objective indication of the current condition and remaining design life of the insulation. This innovative technology utilizes low-cost, inert conductive particles compounded with a portion of the insulation polymer to provide a tiny degradation sensor embedded into the winding, core or stator of the component. Sensor output correlates with the degraded state of the insulation system relative to standard industry thermal endurance testing, giving advanced warning of a degraded condition of the insulation system before design conditions are exceeded. Maintenance personnel, utilizing a simple ohmmeter, can read sensor output quickly and reliably without specialized equipment or training. Alternately, threshold-warning devices connected to the sensor provide constant monitoring. Conductive composite degradation sensors provide advance warning of prematurely degraded insulation systems and reduce the need for complex, intrusive and sometimes destructive electrical testing. Because conductive composite degradation sensors require no electrical power during the aging process, they are ideally suited to wireless, passive radio frequency identification (RFID), and “smart label” technologies.
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Attestog, Sveinung, i Huynh Van Khang. "Electromagnetic and Thermal Modelling for Calculating Ageing Rate of Distribution Transformers". W 2018 21st International Conference on Electrical Machines and Systems (ICEMS). IEEE, 2018. http://dx.doi.org/10.23919/icems.2018.8549517.
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Hu, Zhi-feng, Kai-bo Ma, Wei Wang, Muhammad Rafiq, You Zhou, Qi Wang, Yue-fan Du, Cheng-rong Li i Yu-zhen Lv. "Thermal aging properties of transformer oil-based TiO2 nanofluids". W 2014 IEEE 18th International Conference on Dielectric Liquids (ICDL). IEEE, 2014. http://dx.doi.org/10.1109/icdl.2014.6893103.
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Jafari, Fereshteh Sadat, Fatemeh Kazemi i Javad Ahmadi Shokouh. "Non-destructive aging of transformer oil using electromagnetic waves". W 2015 20th Conference on Electrical Power Distribution Networks Conference (EPDC). IEEE, 2015. http://dx.doi.org/10.1109/epdc.2015.7330509.
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Khudonogov, I. A., E. Yu Puzina i A. G. Tuigunova. "Modeling Turn Insulation Thermal Aging Process for Traction Substation Transformer". W 2020 International Conference on Industrial Engineering, Applications and Manufacturing (ICIEAM). IEEE, 2020. http://dx.doi.org/10.1109/icieam48468.2020.9112021.
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Zhuravleva, Natalia, Alexandr Reznik i Dmitry Kiesewetter. "Study of thermal aging of mixture of transformer insulating liquids". W 2016 ELEKTRO. IEEE, 2016. http://dx.doi.org/10.1109/elektro.2016.7512159.
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Guerbas, F., L. Adjaout, A. Abada i D. Rahal. "New and Reclamation Transformer Oil Behavior under Accelerated Thermal Aging". W 2018 IEEE International Conference on High Voltage Engineering and Application (ICHVE). IEEE, 2018. http://dx.doi.org/10.1109/ichve.2018.8642062.
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Bagheri, M., A. Subramaniam, S. Bhandari, S. Chandar i S. K. Panda. "Residential lighting influence on cast-resin distribution transformer aging rate". W 2015 IEEE International Conference on Building Efficiency and Sustainable Technologies (ICBEST). IEEE, 2015. http://dx.doi.org/10.1109/icbest.2015.7435863.
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