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Author: Kashif Imdad
Publisher:
ISBN:
Category :
Languages : en
Pages : 86
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Book Description
This thesis presents the results related to high frequency modeling of power transformers. First, a 25kVA distribution transformer under lightning surges is tested in the laboratory and its high frequency model is proposed. The transfer function method is used to estimate its parameters. In the second part, an advanced high frequency model of a distribution transformer is introduced. In this research, the dual resonant frequency distribution transformer model introduced by Sabiha and the single resonant frequency distribution transformer model under lightning proposed by Piantini at unloaded conditions are investigated and a modified model is proposed that is capable to work on both single and dual resonant frequencies. The simulated results of the model are validated with the results of Sabiha and Piantini that have been taken as reference. Simulations have shown that the results of the modified model such as, secondary effective transfer voltages, transferred impedances and transformer loading agree well with the previous models in both time and frequency domains. The obtained objectives of this research are: * Methodology for determining the parameters of a power transformer. * High frequency modeling of a transformer in order to simulate its transient behavior under surges. * Modification of high frequency model for single and dual resonance frequency. The originality and methodology of this research are: * High frequency transformer model is derived by means of the transfer function method. In the literature, the transfer function method has been used in many applications such as the determination of the mechanical deformations or insulation failure of interturn windings of transformers. In this thesis, the parameters of the proposed model are estimated using the transfer function method. * Modification of high frequency model for single/dual resonance frequency using the transfer function method. The transfer function can also be used to determine the state of the transformer. The modification in the developed model using the proposed technique has been validated. The high frequency transformer model was presented by Sabiha at two resonance frequency under both condition loading and unloading was used as reference model for modification and further enhancement. A transformer with 25kVA capacity was tested in UPC Terrassa Spain in High voltage lab under the effect of impulse voltage and the digital data was stored via oscilloscope in computer. An algorithm was developed to estimate the transformer parameters by transfer function method using fast Fourier transform analysis. In this scheme the two port network theory concept was taken for black box analysis of transformer. The series of transient¿s frequencies of experimental digital data was noted. The transformer parameters such as Z11, Z12, Z21, and Z22 calculated on all these frequencies in order to generate a narrow band of correct frequency at which the transients was developed experimentally and therefore it has to be developed on that specific frequencies. Earlier the transfer function method was used for the mechanical deformation analysis in the transformer, now similar method of modeling used to estimate the parameters of transformer and propose accurate transformer model for two resonance frequencies only and the parameters estimation was based simply placing RLC elements. The proposed model also tested and validated for accuracy and reliability. In the second phase of research high frequency models of transformer for protection from the transients based on experimental data are presented. Which were tested and validated for unloading and loading for Single and Two resonant frequencies, and modeled using transfer function method. The proposed single model leads to others two models which are verified by two port network theory, unloaded transfer under time domain and frequency domain analysis, transformer loading under different loads and transfer function.
Author: Kashif Imdad
Publisher:
ISBN:
Category :
Languages : en
Pages : 86
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Book Description
This thesis presents the results related to high frequency modeling of power transformers. First, a 25kVA distribution transformer under lightning surges is tested in the laboratory and its high frequency model is proposed. The transfer function method is used to estimate its parameters. In the second part, an advanced high frequency model of a distribution transformer is introduced. In this research, the dual resonant frequency distribution transformer model introduced by Sabiha and the single resonant frequency distribution transformer model under lightning proposed by Piantini at unloaded conditions are investigated and a modified model is proposed that is capable to work on both single and dual resonant frequencies. The simulated results of the model are validated with the results of Sabiha and Piantini that have been taken as reference. Simulations have shown that the results of the modified model such as, secondary effective transfer voltages, transferred impedances and transformer loading agree well with the previous models in both time and frequency domains. The obtained objectives of this research are: * Methodology for determining the parameters of a power transformer. * High frequency modeling of a transformer in order to simulate its transient behavior under surges. * Modification of high frequency model for single and dual resonance frequency. The originality and methodology of this research are: * High frequency transformer model is derived by means of the transfer function method. In the literature, the transfer function method has been used in many applications such as the determination of the mechanical deformations or insulation failure of interturn windings of transformers. In this thesis, the parameters of the proposed model are estimated using the transfer function method. * Modification of high frequency model for single/dual resonance frequency using the transfer function method. The transfer function can also be used to determine the state of the transformer. The modification in the developed model using the proposed technique has been validated. The high frequency transformer model was presented by Sabiha at two resonance frequency under both condition loading and unloading was used as reference model for modification and further enhancement. A transformer with 25kVA capacity was tested in UPC Terrassa Spain in High voltage lab under the effect of impulse voltage and the digital data was stored via oscilloscope in computer. An algorithm was developed to estimate the transformer parameters by transfer function method using fast Fourier transform analysis. In this scheme the two port network theory concept was taken for black box analysis of transformer. The series of transient¿s frequencies of experimental digital data was noted. The transformer parameters such as Z11, Z12, Z21, and Z22 calculated on all these frequencies in order to generate a narrow band of correct frequency at which the transients was developed experimentally and therefore it has to be developed on that specific frequencies. Earlier the transfer function method was used for the mechanical deformation analysis in the transformer, now similar method of modeling used to estimate the parameters of transformer and propose accurate transformer model for two resonance frequencies only and the parameters estimation was based simply placing RLC elements. The proposed model also tested and validated for accuracy and reliability. In the second phase of research high frequency models of transformer for protection from the transients based on experimental data are presented. Which were tested and validated for unloading and loading for Single and Two resonant frequencies, and modeled using transfer function method. The proposed single model leads to others two models which are verified by two port network theory, unloaded transfer under time domain and frequency domain analysis, transformer loading under different loads and transfer function.
Author: Su, Charles Q.
Publisher: IGI Global
ISBN: 1466619228
Category : Technology & Engineering
Languages : en
Pages : 587
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Book Description
"This book explores relevant theoretical frameworks, the latest empirical research findings, and industry-approved techniques in this field of electromagnetic transient phenomena"--Provided by publisher.
Author: Jaime Avila-Rosales
Publisher:
ISBN:
Category : Electric transformers
Languages : en
Pages : 466
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Book Description
Author: Behrooz Vahidi
Publisher: Springer Nature
ISBN: 9819957966
Category : Technology & Engineering
Languages : en
Pages : 142
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Book Description
This book describes many aspects of power transformers. And it mainly provides valuable knowledges such as two deals with power transformer construction, different types of transformers and connections, power transformer core modelling, and the low-frequency and mid-frequency modelling of transformers. Moreover, it also introduces a new method for high-frequency modelling of transformer which can attract many students learning the power transformer research field. The goal of this book is to educate the postgraduate students and engineers about principals and modeling of the transformers .
Author: Feras Fattal
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Transients encountered by transformers in power stations during normal operation can have complex oscillatory overvoltages containing a large spectrum of frequency components. These transients can coincide with the natural frequencies of the transformers windings, leading to voltages that can be greater or more severe than the current factory proof tests. This may lead to insulation breakdown and catastrophic failures. Existing lumped parameter RLCG transformer models have been proven to be less accurate for very fast transient overvoltages (VFTO) with frequencies over 1 MHz. A white box model for transient analysis of transformer windings has been developed using Multiconductor Transmission Line (MTL) Theory. This model enables the simulation of natural frequencies of the transformer windings up to frequencies of several MHz, and can be used to compute voltages between turns by representing each turn as a separate transmission line. Both continuous and interleaved disk windings have been modelled and a comparison and validation of the results is presented.
Author: Juan A. Martinez-Velasco
Publisher: John Wiley & Sons
ISBN: 1119480531
Category : Technology & Engineering
Languages : en
Pages : 618
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Book Description
A hands-on introduction to advanced applications of power system transients with practical examples Transient Analysis of Power Systems: A Practical Approach offers an authoritative guide to the traditional capabilities and the new software and hardware approaches that can be used to carry out transient studies and make possible new and more complex research. The book explores a wide range of topics from an introduction to the subject to a review of the many advanced applications, involving the creation of custom-made models and tools and the application of multicore environments for advanced studies. The authors cover the general aspects of the transient analysis such as modelling guidelines, solution techniques and capabilities of a transient tool. The book also explores the usual application of a transient tool including over-voltages, power quality studies and simulation of power electronics devices. In addition, it contains an introduction to the transient analysis using the ATP. All the studies are supported by practical examples and simulation results. This important book: Summarises modelling guidelines and solution techniques used in transient analysis of power systems Provides a collection of practical examples with a detailed introduction and a discussion of results Includes a collection of case studies that illustrate how a simulation tool can be used for building environments that can be applied to both analysis and design of power systems Offers guidelines for building custom-made models and libraries of modules, supported by some practical examples Facilitates application of a transients tool to fields hardly covered with other time-domain simulation tools Includes a companion website with data (input) files of examples presented, case studies and power point presentations used to support cases studies Written for EMTP users, electrical engineers, Transient Analysis of Power Systems is a hands-on and practical guide to advanced applications of power system transients that includes a range of practical examples.
Author: Yazid Alkraimeen
Publisher:
ISBN:
Category : Electric generators
Languages : en
Pages : 77
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Book Description
Power transformers are static devices capable of transferring energy from one electrical circuit to another by means of electromagnetic induction at the same frequency. The most common application of transformers in an electric power system is to step up or down the voltage level of an electric grid. This is essential for the efficient transmission and distribution of electricity from generating plants to different types of consumers. Electrical energy used in residential, commercial and industrial settings is delivered to consumers by means of transformers, which normally operate 24 hours a day, 365 days a year. Therefore, design improvements that result in an increase of efficiency and reliability of these devices will be reflected in an enhanced overall performance of electric power systems. Modern transformers are subjected not only to fast front excitations due to lightning and switching conditions, but also to fast and repetitive pulses related to the widespread connection of power electronic components. These phenomena can produce large transient overvoltages and dielectric stresses that can damage the transformer or significantly reduce its life expectancy. The definition of models able to accurately and effectively predict these phenomena is essential for the insulation design of transformers. In this dissertation, a winding model to predict the transient voltage distribution in a disk-type transformer is described. The presented model is a function of frequency, with electrical parameters computed using the Finite Element Method and analytical formulas. In order to increase the accuracy of the presented model, frequency-dependent core and proximity losses are calculated and validated using the Finite Element Method. In addition, this dissertation introduces a simple and accurate formula for the computation of frequency-dependent proximity impedance. Furthermore, a complete model of a prototype disk-type transformer with 2000 turns is implemented and verified experimentally.
Author: Xiangning Lin
Publisher: John Wiley & Sons
ISBN: 1118653823
Category : Technology & Engineering
Languages : en
Pages : 340
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Book Description
An advanced level examination of the latest developments in power transformer protection This book addresses the technical challenges of transformer malfunction analysis as well as protection. One of the current research directions is the malfunction mechanism analysis due to nonlinearity of transformer core and comprehensive countermeasures on improving the performance of transformer differential protection. Here, the authors summarize their research outcomes and present a set of recent research advances in the electromagnetic transient analysis, the application on power transformer protections, and present a more systematic investigation and review in this field. This research area is still progressing, especially with the fast development of Smart Grid. This book is an important addition to the literature and will enhance significant advancement in research. It is a good reference book for researchers in power transformer protection research and a good text book for graduate and undergraduate students in electrical engineering. Chapter headings include: Transformer differential protection principle and existing problem analysis; Malfunction mechanism analysis due to nonlinearity of transformer core; Novel analysis tools on operating characteristics of Transformer differential protection; Novel magnetizing inrush identification schemes; Comprehensive countermeasures on improving the performance of transformer differential protection An advanced level examination of the latest developments in power transformer protection Presents a new and systematic view of power transformer protection, enabling readers to design new models and consider fresher design approaches Offers a set of approaches to optimize the power system from a microeconomic point of view
Author: Ye Liu
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The transformer is one of the most difficult power devices to model accurately, especially in the high frequency range. A transformer model which is suitable for simulating high frequency behavior in the Electromagnetic Transients Program (EMTP) is available. This model is based on the frequency characteristics of the transformer terminal admittance matrix over a given range of frequencies. Normally, the terminal admittance matrix is obtained from measurements. However, this procedure is very costly and, in addition, it is not useful to predict the current/voltage profile inside the transformer windings. In order to avoid these disadvantages, in this thesis a finite element method to model the transformer is proposed. This model can be used to obtain the electromagnetic field inside the windings and the circuit parameters such as R, L, C to derive the equivalent circuit network. The terminal admittance matrix is then obtained which can be used by EMTP.
Author: Mantosh Devgan
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Pre-mature failures of wind turbine step up (WTSU) transformers have been reported in the wind farms although, the failed transformers had previously passed all quality assurance tests and had assembled all standard requirements. Vacuum circuit breaker (VCB) initiated steep front transient impact is one of the potential causes of such insulation failures. The use of VCB as switching devices and intense cable network increases the likelihood for high frequency transient overvoltages (TOVs) in wind farms. Multiple prestrikes and restrikes of VCB in conjunction with cable capacitance and inductance of transformer give rise to fast steep front voltage transients which eventually cause insulation failures in WTSU transformer. This emphasizes the need to conduct switching transient analysis studies for wind power plants, to investigate the severe switching overvoltages experienced by WTSU transformers. In this work, high frequency modeling in a broad frequency range for major components of the wind farms and an investigation of switching transients on WTSU transformer are presented. An adaptive model of VCB capable of simulating statistical phenomena and overvoltages on circuit breaker and the components that it interacts with is developed in PSCAD/EMTDC. A high frequency phase model of single core cable, taking into account the high frequency effect of cable, i.e., electromagnetic transient propagation, skin effect and reflections is simulated in PSCAD/EMTDC. A linear wideband frequency-dependent black box model of an actual WTSU transformer based on the experimental determination of admittance matrix in a wide frequency range and subjecting the measured admittance matrix to an approximation by means of a rational function through vector fitting is used to simulate WTSU transformer. The rational function obtained for WTSU transformer can then be realized into an RLC network for time domain simulations in PSCAD/EMTDC. A test bench is simulated using the above mentioned high frequency models and replicating Type-IV wind turbine generator synchronized with the grid. Transient scenarios are investigated to understand the most severe switching transients experienced by WTSU transformers, considering the worst repeated switching transient overvoltages and the steep rate of voltage rise experienced by the WTSU transformer. Six different attributes of voltage waveforms across the WTSU transformer are used to investigate the transient behavior in the cases carried out on the proposed test bench.
