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An extended Markov model to determine the reliability of protective system
, Article 2006 IEEE Power India Conference, New Delhi, 10 April 2006 through 12 April 2006 ; Volume 2005 , 2005 , Pages 428-432 ; 0780395255 (ISBN); 9780780395251 (ISBN) ; Fotuhi, M ; Sanaye Pasand, M ; Sharif University of Technology
2005
Abstract
In this paper a reliability model for power transformer protection is proposed. The model is an extension of a previously proposed Markov model for transmission line protection. Optimum routine test and self checking intervals of the power transformer protection system are determined using the extended Markov model. © 2006 IEEE
Design of dual- and quad-band E-CRLH-TLs with arbitrary phase characteristics
, Article Progress In Electromagnetics Research M ; Vol. 35, issue , 2014 , p. 141-149 ; Nikmehr, S ; Ghurt-Tappeh, M.V ; Bemani, M ; Sharif University of Technology
Abstract
In this paper, extended composite right/left-handed (E-CRLH) transmission line (TL) metamaterial structures, with two left-handed (backward) and two right-handed (forward) pass bands, are investigated. Also, design procedures in order to design dual- and quad-band E-CRLH-TLs are presented in detail and the parameters of these structures are extracted by clean formulas, while satisfying arbitrary phase shifts at the operating frequencies. Finally, the dispersion and characteristic impedances of these transmission lines are derived and plotted. The results of this paper can be applied to any type of TL-based dual- and quad-band microwave component
Comparison of transformer detailed models for fast and very fast transient studies
, Article IEEE Transactions on Power Delivery ; Volume 23, Issue 2 , 2008 , Pages 733-741 ; 08858977 (ISSN) ; Vakilian, M ; Gharehpetian, G. B ; Sharif University of Technology
2008
Abstract
The fast and very fast transient overvoltages can endanger the insulation of transformer windings. Therefore, it is necessary to develop models, to study these transients. This paper compares the two well-known multiconductor transmission line (MTL) and lumped parameter detailed (RLC ladder network) models. The high-voltage (HV) winding of a 220/35-kV, 50-MVA transformer has been modeled using these models. The simulation results of the MTL and the RLC ladder network models have been compared with the measurements results in the frequency domain, by application of the Pearson's correlation coefficients. It is shown that the RLC Ladder Network model should be used for fast transient...
Modeling of D-STATCOM in distribution systems load flow
, Article Journal of Zhejiang University: Science A ; Volume 8, Issue 10 , 2007 , Pages 1532-1542 ; 1673565X (ISSN) ; Shayanfar, H. A ; Fotuhi Firuzabad, M ; Sharif University of Technology
2007
Abstract
This paper presents modeling of Distribution STATCOM (D-STATCOM) in load flow calculations for the steady-state voltage compensation. An accurate model for D-STATCOM is derived to use in load flow calculations. The rating of this device as well as the direction of required reactive power injection for voltage compensation in the desired value (1 p.u.) is derived and discussed analytically and mathematically by the phasor diagram method. Furthermore, an efficient method for node and line identification used in load flow calculations is presented. The validity of the proposed model is examined by using two standard distribution systems consisting of 33 and 69 nodes, respectively. The best...
A hybrid transformer model for determination of partial discharge location in transformer winding
, Article IEEE Transactions on Dielectrics and Electrical Insulation ; Volume 14, Issue 2 , 2007 , Pages 436-443 ; 10709878 (ISSN) ; Vakilian, M ; Blackburn, T. R ; Phung, B. T ; Naderi, M. S ; Nasiri, A ; Sharif University of Technology
2007
Abstract
Partial discharges are well known as a source for insulation degradation in power transformers. A hybrid transformer model is introduced to simulate the transformer winding transient response. Transformer structural data is used to determine the hybrid model parameters. Calculations of the hybrid transient model parameters are based on the parameters of the lumped parameter equivalent transformer model and electromagnetic rules. Modern computation techniques and optimizations are employed beside this model for PD location using the multi conductor transmission line model and also to analyze its propagation aimed at achieving (i) more reliable simulation results (ii) less computational time...
Analytical approach for analysis of nonuniform lossy/lossless transmission lines and tapered microstrips
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 54, Issue 12 , 2006 , Pages 4122-4129 ; 00189480 (ISSN) ; Mehrany, K ; Rashidian, B ; Sharif University of Technology
2006
Abstract
In this paper, distribution of voltage along a general nonuniform transmission line is expanded in an appropriate form, and by employing an approach similar to conventional and modified differential transfer matrix methods already proposed for optical structures, analytical expressions are obtained for voltage/current distributions and reflection/transmission coefficients. This method shows great accuracy in different test cases and has been found to be superior to the well-known analytical method of small reflections. Notwithstanding, the overall accuracy of proposed approach is further improved by introducing the technique of multiple divisions. In particular, lossy/lossless tapered...
A novel dual-band transmission line with equal-phase responses
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 69, Issue 2 , 2021 , Pages 1265-1272 ; 00189480 (ISSN) ; Tajik, A ; Fakharzadeh, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
This article presents a novel dual-band transmission line (TL), consisting of a multibranch stub, which can provide equal unwrapped phases at two different frequencies. The frequency ratio can be close to one without any significant degradation in the device performance. Besides, the bandwidth of the proposed line can be manipulated at both frequencies by adjusting the design parameters. The behavior of the structure over the frequency bands is investigated theoretically, and the design procedure and relations are derived. The simulation and measurement results of a quarter-wavelength open-ended stub and a branch-line coupler (BLC) are presented and compared to verify the performance of the...
Reactive compensation techniques for increasing loadability of long primary distribution lines
, Article 37th Annual North American Power Symposium, 2005, Ames, IA, 23 October 2005 through 25 October 2005 ; Volume 2005 , 2005 , Pages 233-237 ; 0780392558 (ISBN); 9780780392557 (ISBN) ; Stefopoulos, G. K ; Parniani, M ; Sharif University of Technology
2005
Abstract
Electric networks often consist of remote cities or villages with low population densities, which consume a considerably small amount of energy. This can be in the order of a few megawatts for places that are up to 100 km away from the source. Typical uncompensated primary distribution lines are not an effective option for these situations, since line loadability drastically decreases as the line length is increased. Increasing the voltage level, on the other hand, is not cost effective. This paper investigates different reactive compensation techniques for increasing the loadability of these lines. Effect of series capacitors, shunt capacitors and voltage regulating transformers in such...
General solution of linear differential equations by using differential transfer matrix method
, Article 2005 European Conference on Circuit Theory and Design, Cork, 28 August 2005 through 2 September 2005 ; Volume 3 , 2005 , Pages 113-116 ; 0780390660 (ISBN); 9780780390669 (ISBN) ; Mehrany, K ; Rashidian, B ; Sharif University of Technology
2005
Abstract
A new analytical method for finding the general solution of the nth-order linear differential equation with variable coefficients is given based on generalizing the idea of differential transfer matrix method already proposed for solving the second order Helmholtz equation. Our generalization has two aspects. First, the given formulation copes with the nth-order linear differential equations, rather than the special case of second order wave equations. Second, the proposed approach is generalized in several different ways each yielding different types of differential transfer matrices with correspondingly different numerical accuracies. The presented methods can be applied to problems such...
Semi-active control of forced oscillations in power transmission lines via optimum tuneable vibration absorbers: With review on linear dynamic aspects
, Article International Journal of Mechanical Sciences ; Vol. 87, issue , 2014 , p. 163-178 ; Moradi, H ; Vossoughi, G ; Sharif University of Technology
Abstract
Due to flexibility, relatively small weight and low energy-dissipative characteristics of cables, they are vulnerable to external excitations such as wind, wind-rain, earthquake and traffic loadings. Among them, galloping phenomenon is one of the most important sources of electrical/mechanical failures in power transmission lines. In this paper, tuneable vibration absorbers (TVAs) are used to suppress galloping forced vibrations (as a semi-active control approach). Using mode summation technique, mathematical model of the hybrid problem including the transmission line and an arbitrary number of absorbers is presented. Developing a sophisticated multi-loops optimization algorithm, best values...
Comparison of different electrocardiogram signal power line denoising methods based on SNR improvement
, Article 2012 19th Iranian Conference of Biomedical Engineering, ICBME 2012 ; 2012 , Pages 159-162 ; 9781467331302 (ISBN) ; Afzali, M ; Vahdat, B. V ; Sharif University of Technology
2012
Abstract
In order to access to an accurate detection of electrocardiogram signal in medical approaches especially mobile health and wearable medical devices, development of noise cancellation algorithms seems essential. In this study, the power line noise in ECG signal is filtered using several methods including DFT based, IIR, FIR, adaptive, Kalman, Wavelet and higher order statistics filters. Signal-to-noise ratio (SNR) improvements of the filters are then compared. It is found that FIR and IIR filtering show higher SNR improvement
Digital distance protection of transmission lines in the presence of SSSC
, Article International Journal of Electrical Power and Energy Systems ; Volume 43, Issue 1 , December , 2012 , Pages 712-719 ; 01420615 (ISSN) ; Mozafari, B ; Ranjbar, A. M ; Sharif University of Technology
2012
Abstract
In this paper the impact of Static Synchronous Series Compensator (SSSC) on the impedance calculated by distance relay is investigated. Analytical results are presented and verified by detailed simulations. Six different phase to phase and phase to ground measuring units of the distance relay are simulated to resemble the behavior of the relay. It is shown in this paper that zero sequence of the injected voltage by 48 pulse SSSC converter has the most impact on the apparent impedance seen by the phase to ground fault measuring unit and cause under reaching of distance relay. It can be concluded from the results that SSSC located in the middle of the transmission line cause to divide trip...
A method for optimal coordinated insulation design of transmission line
, Article Australian Journal of Electrical and Electronics Engineering ; Volume 7, Issue 3 , 2010 , Pages 211-223 ; 1448837X (ISSN) ; Vakilian, M ; Blackburn, T. R ; Sharif University of Technology
Abstract
The first step in the accepted methods of overhead transmission line insulation coordination is to specify a reliability criterion, and then based on this constraint the most economic insulation design is sought. While the objective of an optimal insulation design method is to find an insulation design that minimises the total cost (the sum of the installation cost, operational cost and cost of failure), each of the cost components can be determined on a per-year basis taking into account the equipment's lifetimes. In this paper, through application of ATP software and realising the total cost of different transmission line designs, a set of alternative insulation designs using various surge...
Transmission line model for one-dimensional metallic grating in TE polarization
, Article 2010 International Conference on Photonics, ICP2010, 5 July 2010 through 7 July 2010 ; July , 2010 ; 9781424471874 (ISBN) ; Mehrany, K ; Sharif University of Technology
2010
Abstract
A simple transmission line model is presented to emulate field behavior in a one dimensional metallic grating in TE polarization. The proposed model is based on the fact that pairs of adjacent metallic strips in the structure act as a parallel plate waveguide supporting TE guided modes for low enough frequencies. The effect of fringing fields is also included and a very good approximate model is obtained to simulate metallic gratings in TE polarization
Spurious-free analysis of two-dimensional low-loss metallic gratings
, Article Journal of Optics (United Kingdom) ; Volume 18, Issue 3 , 2016 ; 20408978 (ISSN) ; Nezhad, A. Z ; Borji, A ; Shahabadi, M ; Sharif University of Technology
Institute of Physics Publishing
Abstract
Transmission line formulation is used to analyze two-dimensional low-loss metallic gratings at optical frequencies when plasmonic waves propagate in the structure. This method, like the Fourier modal method, suffers from numerical instabilities when applied to such structures. A systematic approach to avoid these instabilities is presented. These numerical artifacts are attributed to the violation of Li's inverse rule and the appearance of higher-order spurious modes. In this paper, a new approach is proposed to identify and to greatly reduce the effect of these spurious modes based on the accuracy by which these modes are satisfying the conservation of momentum. Furthermore, the proposed...
Analysis of the power transfer to a nonlinear transmission line
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 65, Issue 11 , 2017 , Pages 4073-4083 ; 00189480 (ISSN) ; Hashemi, S. M. A ; Sharif University of Technology
Abstract
The input current of a nonlinear transmission line (NLTL), driven by a step voltage pulse, was analyzed theoretically. As specific results of the analysis, two basic parameters of NLTLs were formulated for the first time: the energy injected to NLTLs and their characteristic impedance. The energy delivered to an NLTL by a square voltage source, with a series resistance of RS, is given by a closed-form formula, which depends on the NLTL parameters and the input pulse characteristics. Considering the importance of the problem of the determining the injected energy content in a wide variety of the different applications of NLTLs, the obtained result will be of great importance, facilitating the...
Theory of RF pulse generation through nonlinear transmission lines
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 66, Issue 7 , 2018 , Pages 3234-3244 ; 00189480 (ISSN) ; Hashemi, S. M. A ; Farzaneh, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
Nonlinear transmission lines (NLTLs) are one of the most prominent solid-state sources of high-power RF pulses. However, there is no integrated mathematical basis, which predicts adequately the generated waveforms on an NLTL and those delivered to the load. This analysis is required for designing and optimizing these transmission lines. Most works in this area are related to experimental studies and results. In this paper, we have developed a theoretical basis, which predicts all the required characteristics of the generated RF pulses on a lossy NLTL. The RF amplitude, the maximum voltage, and the central frequency of the generated pulses at each node of an NLTL are formulated. All the...
A New cavity resonance assisted by anisotropic metasurfaces
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 66, Issue 7 , 2018 , Pages 3224-3233 ; 00189480 (ISSN) ; Memarian, M ; Itoh, T ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
A new resonance phenomenon is demonstrated in waveguide cavities, which simultaneously uses two orthogonal modes (polarizations). This resonance is formed by bouncing waves with similar handedness, between two simple anisotropic metasurfaces having a relative rotation angle. The rotated anisotropic metasurfaces can cross couple the waves from one polarization to the other at the cavity end. The field profile of the resonant mode does not exhibit nodes and antinodes, thus the resonant frequency is not solely determined by the cavity length, unlike common resonators. The resonance condition is theoretically demonstrated from both field and transmission line perspectives, and is validated by...
Automatic superimposed droop frequency control scheme for dc microgrids
, Article 2019 International Aegean Conference on Electrical Machines and Power Electronics, ACEMP 2019 and 2019 International Conference on Optimization of Electrical and Electronic Equipment, OPTIM 2019, 27 August 2019 through 29 August 2019 ; 2019 , Pages 120-125 ; 9781538676875 (ISBN) ; Mokhtari, H ; Poshtan, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
This paper proposes a control strategy to improve the superimposed droop frequency control scheme in DC microgrids. Conventional droop-based schemes for DC microgrids control suffer from issues such as inaccurate power sharing among the sources, voltage control with insufficient quality, and adverse effect of the line resistance on the droop characteristic. To overcome these challenges, the superimposed droop frequency method has been introduced. However, the stable operation in terms of the load variations and improper voltage quality are still the challenges with this prior-art method due to the injected AC voltages. In this paper, a method is proposed to solve the stability problem and...
Dielectrophoretic interaction of two particles in a uniform electric field
, Article Microsystem Technologies ; Volume 25, Issue 7 , 2019 , Pages 2699-2711 ; 09467076 (ISSN) ; Moghimi Zand, M ; Dastani, K ; Sharif University of Technology
Springer Verlag
2019
Abstract
The local electric field distorsion induced by a dielectric particle leads to particle–particle interactions and assembly which is very interesting for their useful applications on microfluidic devices. Particles behavior becomes more complicated if several particles interact at the same time. This paper presents a comprehensive numerical analysis of the assembly and particle–particle interactions for two similar and dissimilar dielectric particles immersed in a dielectric fluid using the immersed interface method based on two-dimensional direct-current dielectrophoresis. The immersed interface method is a finite-difference (or finite element) based numerical method which its key advantage...