Artículos en Periódicos

Búsqueda Rápida:   Artículos Encontrados: 0.

tr id="tpd_2012" class="entry">
AutoresTítuloPeriódico Fecha Archivo
A. S. Bretas, K. C. O. Salim, R. H. Salim Hybrid Fault Diagnosis Formulation For Unbalanced Underground Distribution Feeders.(Resumen) International Journal of Power and Energy Systems 2012  
Resumo: This paper presents further formulation details of an implemented hybrid fault diagnosis method for unbalanced underground distribution systems (UDS). The proposed formulation is hybrid approach based, using both arti?cial neural networks (ANNs) and wavelet transforms (WTs) for the fault diagnosis process. Traditional fault location and detection approaches are digital Fourier transforms based, which have an inverse time–frequency resolution relationship that provides a low level of robustness to the fault diagnosis process.UDS are characterized by having a signi?cant shunt capacitance component, non-symmetrical and non-transposed lines, time-varying loads and single or double phase laterals. These characteristics make UDS feeders operation highly unbalanced, which compromises the traditional digital Fourier transforms based fault diagnosis methods performance. This paper describes further formulation details of an implemented hybrid fault diagnosis method and discusses the obtained test results. The test results demonstrate the techniques capability and robustness and its potential for on-line applications.
R. H. Salim, D. P. Marzec, A. S. Bretas Phase Distance Relaying With Fault Resistance Compensation for Unbalanced Systems.(Resumen) IEEE Transactions on Power Delivery 2011  
Resumen: This letter presents an extension of an existing ground distance relay algorithm to include phase distance relays. The algorithm uses a fault resistance estimation process in the phase domain, improving efficiency in the distance protection process. The results show that the algorithm is suitable for online applications, and that it has an independent performance from the fault resistance magnitude, the fault location, and the line asymmetry.
R. H. Salim, K. R. C. Oliveira, A. S. Bretas Further Improvements on Impedance-Based Fault Location for Power Distribution Systems.(Resumen) IET Proceedings. Generation, Transmission & Distribution 2011  
Resumen: In this study, further improvements regarding the fault location problem for power distribution systems are presented. The proposed improvements relate to the capacitive effect consideration on impedance-based fault location methods, by considering an exact line segment model for the distribution line. The proposed developments, which consist of a new formulation for the fault location problem and a new algorithm that considers the line shunt admittance matrix, are presented. The proposed equations are developed for any fault type and result in one single equation for all ground fault types, and another equation for line-to-line faults. Results obtained with the proposed improvements are presented. Also, in order to compare the improvements performance and demonstrate how the line shunt admittance affects the state-of-the-art impedance-based fault location methodologies for distribution systems, the results obtained with two ot her existing methods are presented. Comparative results show that, in overhead distribution systems with laterals and intermediate loads, the line shunt admittance can significantly affect the state-of-the-art methodologies response, whereas in this case the proposed developments present great improvements by considering this effect.
N. G. Bretas, A. S. Bretas, S. A. R. Piereti Innovation Concept for Measurement Gross Error Detection and Identification in Power System State Estimation.(Resumen) IET Proceedings. Generation, Transmission & Distribution 2011  
Resumen: In this study, the innovation approach is used to estimate the measurement total error associated with power system state estimation. This is required because the power system equations are very much correlated with each ot her and as a consequence part of the measurements errors is masked. For that purpose an index, innovation index (II), which provides the quantity of new information a measurement contains is proposed. A critical measurement is the limit case of a measurement with low II, it has a zero II index and its error is totally masked. In other words, that measurement does not bring any innovation for the gross error test. Using the II of a measurement, the masked gross error by the state estimation is recovered; then the total gross error of that measurement is composed. Instead of the classical normalised measurement residual amplitude, the corresponding normalised composed measurement residual amplitude is used in the gross error detection and identification test, but with m degrees of freedom. The gross error processing turns out to be very simple to implement, requiring only few adaptations to the existing state estimation software. The IEEE-14 bus system is used to validate the proposed gross error detection and identification test.
A.D. Filomena, M. Resener, R. H. Salim, A. S. Bretas Distribution Systems Fault Analysis Considering Fault Resistance Estimation (Resumen) International Journal of Electrical Power & Energy Systems 2011  
Resumen: Fault resistance is a critical component of electric power systems operation due to its stochastic nature. If not considered, this parameter may interfere in fault analysis studies. This paper presents an iterative fault analysis algorithm for unbalanced three-phase distribution systems that considers a fault resistance estimate. The proposed algorithm is composed by two sub-routines, namely the fault resistance and the bus impedance. The fault resistance sub-routine, based on local fault records, estimates the fault resistance. The bus impedance sub-routine, based on the previously estimated fault resistance, estimates the system voltages and currents. Numeric simulations on the IEEE 37-bus distribution system demonstrate the algorithm’s robustness and potential for offline applications, providing additional fault information to Distribution Operation Centers and enhancing the system restoration process.
M. C. R. Paz, R. G. Ferraz, A. S. Bretas, R. C. Leborgne System Unbalance and Fault Impedance Effect on Faulted Distribution Networks (Resumen) Computer & Mathematics with Applications 2010  
Resumen: This paper presents a numerical study of the system unbalance and the fault impedance effect on faulted power system analysis. Two short circuit techniques, the symmetrical components and phase components algorithms are implemented and analyzed based on numerical simulations of the IEEE 13 bus test feeder. Test cases include voltage unbalance effect and fault impedance effect on during-fault voltages and currents. The results show that the during-fault voltages and currents are greatly affected by both voltage unbalance and fault impedance.
A. D. Filomena, M. Resener, R. H. Salim, A. S. Bretas Fault Location for Underground Distribution Feeders: An Extended Impedance-Based Formulation with Capacitive Current Compensation (Resumen) International Journal of Electrical Power & Energy Systems 2009  
Resumen: Underground distribution systems are normally exposed to permanent faults, due to speci?c construction characteristics. In these systems, visual inspection cannot be performed. In order to enhance service restoration, accurate fault location techniques must be applied. This paper describes an extended impedance-based fault location algorithm for underground distribution systems. The formulation is developed on phase frame and calculates the apparent impedance using only local voltage and current data. The technique also provides an iterative algorithm to compensate the typical capacitive component current of underground cables. Test results are obtained from numerical simulations using a real underground distribution feeder data from the Electrical Energy Distribution State Company of Rio Grande do Sul (CEEE-D), southern Brazil. Comparative results show the techniques accuracy and robustness in respect to fault type, distance and resistance.
R. H. Salim, M. Resener, A. D. Filomena, K. R. Caino de Oliveira, A. S. Bretas Extended Fault Location Formulation for Power Distribution Systems (Resumen) IEEE Transactions on Power Delivery (Aceptado para Publicación) 2009  
Resumen: In this paper an extended impedance based fault location formulation for generalized distribution systems is presented. The majority of distribution feeders are characterized by having several laterals, non-symmetrical lines, highly unbalanced operation, and time-varying loads. These characteristics compromise traditional fault location methods performance. The proposed method uses only local voltages and currents as input data. The current load profile is obtained through these measurements. The formulation considers load variation effects and different fault types. Results are obtained from numerical simulations using a real distribution system of the Electrical Energy Distribution State Company of Rio Grande do Sul (CEEE-D), southern Brazil. Comparative results show the technique robustness in respect to fault type and traditional fault location problems such as fault distance, resistance, inception angle, and load variation. The formulation was implemented as an embedded software and is nowadays used at CEEE-D's distribution operation center.
R. H. Salim, K. R. Caino de Oliveira, M. Resener, A. D. Filomena, A. S. Bretas Hybrid Fault Diagnosis Scheme Implementation for Power Distribution Systems Automation (Resumen) IEEE Transactions on Power Delivery vol. 23, n. 4, pp. 1846-1856. 2008  
Resumen: Power distribution automation and control are important tools in the nowadays restructured electricity markets. Unfortunately, due to its stochastic nature, distribution systems faults are hardly avoidable. This paper proposes a novel fault diagnosis scheme for power distribution systems, composed by three different processes: fault detection and classification, fault location, and fault section determination. The fault detection and classification technique is wavelet based. The fault location technique is impedance-based and uses local voltage and current fundamental phasors. The fault section determination method is artificial neural networks based and also uses the local current and voltage signals to estimate the faulted section. The proposed hybrid scheme was validated through ATP/EMTP simulations and was implemented as embedded software. It is currently used as a fault diagnosis tool in a southern Brazilian power distribution company.
A. D. Filomena, R. H. Salim, M. Resener, A. S. Bretas Ground Distance Relaying With Fault Resistance Compensation for Unbalanced Systems (Resumen) IEEE Transactions on Power Delivery, vol. 23, n. 3. pp. 1319-1326 2008  
Resumen: Fault resistance is a critical variable in distance relaying. If not considered, due to underreaching phenomenon, it may cause misoperation of ground distance relays for internal faults. Still, as a consequence of the overreaching phenomenon, the unbalanced nature of loads and asymmetry of lines can affect the distance protection operation efficiency. Mainly, due to these aspects, there is low precision in protection zone limits of ground distance relays. In this paper it is proposed a new algorithm to increase the precision of these limits, improving efficiency in the distance protection process. The proposed method is based in phase-coordinates and uses a fault resistance estimate to develop the trip decision procedure. The results show that the algorithm is suitable for online applications, and that it has an independent performance from the fault resistance magnitude, the fault location and the line asymmetry.
K. R. C. de Oliveira, R. H. Salim, M. Resener, A. D. Filomena, A. S. Bretas Unbalanced Underground Distribution Systems Fault Detection and Section Estimation (Resumen) Lecture Notes in Computer Science, vol. 4682, pp. 1054-1065 2007  
Resumen: This paper presents a novel fault detection and section estimation method for unbalanced underground distribution systems (UDS). The method proposed is based on artificial neural networks (ANNs) and wavelet transforms (WTs). The majority of UDS are characterized by having several single/double phase laterals and non-symmetrical lines. Also, Digital Fourier Transforms (DFT), used in the majority of traditional protection relays, supplies a low level of robustness to the fault diagnosis process due to its inversely proportional time-frequency characteristic. These characteristics compromise the traditional fault diagnosis methods performance. ANNs are capable of learning and generalizing, whereas WTs are robust tools capable of evaluating a signal’s frequency range that can characterize the fault phenomenon. This paper describes the proposed diagnosis method and discusses the results obtained from simulated implementation. The obtained results demonstrate the capability and robustness of the technique indicating its potential for on-line applications.
A. S. Bretas, L. O. Pires, M. Moreto, R. H. Salim A BP Neural Network Based Technique for HIF Detection and Location on Distribution Systems with Distributed Generation (Resumen) Lecture Notes in Computer Science, vol. 4114, pp. 608-613 2006  
Resumen: High Impedance Faults (HIF) are faults of difficult detection and location while using traditional digital relaying. In this article it is presented a new proposal for detection and location of HIF’s in distribution systems with distributed generation (DG), based on artificial neural networks. The methodology inputs are the local measured voltage and current phase components, supplying as output the detection, classification and location of the fault, when it occurs. The basic characteristics, the algorithm and comparative tests with other detection and location methodologies are presented in this article. The proposed scheme was tested in a simulation platform of a distribution system with DG. The comparative results of the technique with usual fault detection and location schemes show the high efficiency and robustness of the method.
A. S. Bretas, R. H. Salim A New Fault Location Technique for Distribution Feeders with Distributed Generation (Resumen) WSEAS Transactions on Power Systems, Grécia, vol. 1, n. 5, pp. 894-900 2006  
Resumen: The fault location techniques for power distribution systems (PDS) in use nowadays assume that the system has a radial power °ow. Since new technologies in development, such as the distributed generation (DG), change this characteristic, it is necessary to adjust the already existing methods for fault location, since they show to be ine±cient. In this paper, it is presented a new fault location method based on positive sequence apparent impedance. Computational simulations were made and the method was tested in two systems and compared with other existing fault location techniques in order to validate it. The basic characteristics of the method, the new algorithm and a variety of case studies are presented in the paper in order to illustrate its e±ciency in distribution systems with DG.
N. G. Bretas, J. B. A. London Júnior, L. F. C. Alberto, A. S. Bretas A Topological Approach to the Identification of Critical Measurements in Power-System State Estimation (Resumen) IEEE Transactions on Circuits and Systems I-Fundamental Theory and Applications, Estados Unidos, vol. 52, n. 1, pp. 139-147 2005  
Resumen: This paper presents a new topological methodology for critical measurements identification in observable networks. A measurement is said to be critical, in an observability sense, if its removal from the measurement set makes the associated system lose observability. The proposed methodology is based on the properties of both, observable measurement subnetworks (OMS) and redundant branch sets (RBS), for the first time proposed. To reduce the combinatorial bluster, the proposed method divides the measurements into two groups and classifies them into two phases. It allows identifying the critical measurements without any numerical calculation. Indeed, it is simple and fast. To clarify the proposed method and to demonstrate its simplicity, two examples are provided. The proposed method is successfully tested in the IEEE-14 bus system as well as in two realistic systems of Brazilian utilities. The first is a 121-bus system by ELETROSUL, and the other is a 383-bus system by Companhia Hidroelétrica do São Francisco (CHESF).
A. S. Bazanella, C. L. Conceição Transient stability improvement through excitation control (Resumen) International Journal of Robust and Nonlinear Control, Inglaterra, vol. 14, pp. 891-910 2004  
Resumen: In this paper we present, discuss, extend and compare di®erent design methods for excitation control aiming at improving transient and steady- state stability.
J. B. A. London Júnior, A. S. Bretas, N. G. Bretas Algorithms to Solve Qualitative Problems in Power Systems State Estimation (Resumen) International Journal of Electrical Power & Energy Systems, Inglaterra, vol. 8, pp. 583-592 2004  
Resumen: This paper presents two algorithms. The first one allows the identification of critical measurements and critical sets. The second algorithm allows, in a straight and fast way, observability analysis and restoration as well as the updating of the measurements qualitative characteristics in the situation of measurements losses. For such purpose, a Base Case Measurement Set is considered. This measurement set contains all the installed and virtual measurements. The proposed algorithms work in a straightforward manner, using a new way based on the relationship between measurements and equivalent states. These states are obtained via triangular factorization of the Jacobian matrix, characterizing the algorithms as numerical. The sparse structure of such matrix allows the use of sparse techniques speeding up the process. The algorithms were tested in the IEEE-14-bus system, as well as in two realistic systems of Brazilian utilities. The results proved the algorithms are reliable, easy to implement and fast. q 2004 Elsevier Ltd. All rights reserved.
M. G. Larios, R. Ortega, A. S. Bazanella, A. Stankovic An energy-shaping approach to the design of excitation control of synchronous generators (Resumen) Automatica, vol. 39, n. 1, pp. 111-119 2003  
Resumen: In this paper we discuss the estimation of the domain of attraction of equilibria in power systems and propose a new passivity-based controller design methodology for excitation control of synchronous generators. The methodology goes beyond the widely popular damping injection (LgV) schemes, to actually shape the total energy function via modification of the energy transfer between the mechanical and electrical components of the system. Applying the procedure it is shown that a, properly tuned, linear state feedback enlarges both the estimates and the actual domain of attraction, thus increasing critical clearing time for faults. This is illustrated in two case studies, including a benchmark comparison with the classical control scheme.
A. S. Bretas, A. G. Phadke Artificial Neural Networks in Power System Restoration (Resumen) IEEE Transactions on Power Delivery, Estados Unidos, vol. 18, pp. 1181-1186 2003  
Resumen: Power system restoration (PSR) has been a subject of study for many years. In recent years, many techniques were proposed to solve the limitations of the predetermined restoration guidelines and procedures used by a majority of system operators to restore a system following the occurrence of a wide area disturbance. This paper discusses limitations encountered in some currently used PSR techniques and a proposed improvement based on artificial neural networks (ANNs). The proposed scheme is tested on a 162-bus transmission system and compared with a breadthsearch restoration scheme. The results indicate that the use of ANN in power system restoration is a feasible option that should be considered for real-time applications.


Artículos en Revistas

Busca Rápida:   Número de artigos encontrados: 0.

AutoresTítuloRevistaFechaArchivo
M. O. Oliveira, J. H. Reversat, A. S. Bretas, L. U. Iurinic, V. H. Iurinic Gestión del Mantenimineto en el Sector Eléctrico.(Resumen) Ingeniería Eléctrica, Buenos Aires, vol. 1, pp. 122-130 2011  
Resumen: Este artículo presenta un enfoque estratégico sobre la gestión del mantenimiento en los Sistemas Eléctricos de Distribución (SED). En este sentido, el objetivo de este trabajo es mostrar el impacto que ejerce el Mantenimiento Centrado en Confiabilidad (Reliability Centered Manteinance -RCM) sobre los diferentes elementos que conforman los SED. Los resultados obtenidos a través del análisis de un sistema de distribución real demuestran las ventajas obtenidas a través de una gestión de mantenimiento estratégicamente planificada.
A. S. Bretas, A. G. Phadke Power System Restoration Methodologies and Implementation Strategies(Resumen) IEEE Computer Applications in Power, vol. 14, pp. 58-59 2001  
Resumen: Este artigo apresenta uma revisão sobre as principais estratégias e metodologias de implementação de restauração de sistemas elétricos de potência. Neste sentido, este artigo faz uma apresentação do livro "Power System Restoration: Methodologies & Implementation Strategies.


Artículos en Congresos/Conferencias

1
AutoresTítuloEvento Fecha
G. D. Ferreira, A. S. Bretas, M. O. Oliveira Establishing Trade-Offs between Sustained and Momentary Reliability Indices in Electric Distribution Protection Design: A Goal Programming Approach (Resumen) 17th Power Systems Computation Conference 2011
Resumen: In this paper, electric distribution reliability is considered under both aspects of customer interruptions: sustained and momentary. A contingency simulation-based technique is used to develop nonlinear models for the SAIFI and MAIFI reliability indices, taking into account the protective devices locations and reclosing schemes used in the substation breaker and line reclosers. The models are aggregated to a set of linear constraints to constitute a nonlinear goal programming model, used to establish the tradeoff between SAIFI and MAIFI reliability indices. As a result, the methodology enables deterministic optimization of distribution feeder protection design by identifying types and locations for protective devices, and the protection schemes to be employed in the line reclosers and substation breaker: fuse saving or fuse blowing. A case study considering a real distribution feeder with 51 buses is presented to illustrate the application and evaluate the performance of the proposed optimization methodology.
J. U. N. Nunes, A. S. Bretas Impact of Distributed Generation on Automatic Fault Location in Unbalanced Distribution Networks. An Extended Impedance Based Fault Location Formulation (Resumen) 17th Power Systems Computation Conference 2011
Resumen: This paper .
R. J. Cabral, R. C. Leborgne, A. S. Bretas Obtenção de Índices de Afundamentos de Tensão Devido a Faltas Monofásicas em Sistemas de Distribuição (Resumen) Conferência Brasileira sobre Qualidade da Energia Elétrica 2011
Resumen: This paper .
F. H. Garcia, R. G. Ferraz, R. C. Leborgne, A. S. Bretas Single Line-to-Ground Faults on Distribution Systems: Effect of Pre-Fault Voltages on Fault Currents (Resumen) IEEE Power Engineering Society General Meeting 2011
Resumen: This paper .
J. U. N. Nunes, A. S. Bretas An Impedance-Based Fault Location Technique for Unbalanced Distributed Generation Systems (Resumen) PowerTech Trondheim-2011 2011
Resumen: This paper presents an analytical method for fault location in unbalanced distribution systems with the presence of distributed generation. In recent years, distributed generation has become an efficient and economical energy production. However, the high penetration of distributed generators change the nature of the electric power distribution systems, passive networks with a single direction of power flow for active networks, with a power flow in various directions. Thus, the presence of generators in distribution systems affect the accuracy of impedance-based fault location methods. This method proposes the extension of a mathematical formulation based on the apparent impedance in order to make it suitable for unbalanced systems.
N. G. Bretas, A. S. Bretas, S. A. R. Piereti Masked Errors in Power Systems State Estimation and Measurement Gross Errors Detection and Identification (Resumen) PowerTech Trondheim-2011 2011
Resumen: In this paper, a topological and geometrical based approach is used to define an index, undetectability index (UI), which provides the distance of a measurement from the range space of the Jacobean matrix of the power system. The higher the value of this index, for a measurement, the closer it will be to the range space of that matrix, that is, the error in measurements with high UI is not reflected in their residuals, thus masking a possible gross error those measurements might have. Using the UI of a measurement, the possible gross error the state estimation process might mask is recovered; then the total gross error of that measurement is composed and used to the gross error detection and identification test. A two bus system is used to show how this geometrical view of gross error analysis works. The classical three bus system used in many papers of the state estimation field is used as an example of a small application of the proposed methodology.
M. O. Oliveira, D. P. Marzec, G. Bordin, A. S. Bretas, D. P. Bernardon Climate Change Effect on Very Short-Term Electric Load Forecasting (Resumen) PowerTech Trondheim-2011 2011
Resumen: Climate changes are related to air temperature, relative humidity, wind speed, precipitation level, among others. These variables have a large effect on very short-term electricity demand (minutes or hour ahead). In this context, this paper presents a methodology for very short-term load forecasting considering the climatic change impact. Therefore, air temperature and relative humidity are related through the Discomfort Index, and the first with the wind speed are linked through the Wind Chill. These climate indexes are used in this paper for electric load forecasting together with a multiple regression model. The proposed projection methodology was tested computationally and compared with real date obtained from a distribution utility located in southern Brazil. The results demonstrate the strong dependence of the evolution of electricity demand with climatic change in the very short-term.
D. S. Gazzana, A. S. Bretas, G. A. D. Dias, M. Tello, V. Dienstmann Grounding Meshes Performance Evaluation in Sand Soil due Lightning Surges (Resumen) The 9th International Conference on Power Systems Transients 2011
Resumen: This paper presents a study related to the Lightning Protection System (LPS). The work includes practical aspects and computational simulation in order to evaluate the performance of a proper LPS with focus on the grounding system in sand soil. The Alternative Transients Program (ATP) is used to model the whole protection scheme including air termination system, down conductor system and earth termination system. An electric model representing a human body is considered to verify the step and touch potentials generated due a lightning surge. Initially, an introduction is made emphasizing the security problem constantly present in sentry boxes located in beaches. In the following, the proposed LPS is presented with discussion about modeling in ATP. Finally, simulation results are presented and conclusions are made .
G. A. D. Dias, D. S. Gazzana, A. S. Bretas, M. Tello, A. Vogel, A. Born, V. Dienstmann Death in the Bech Sentry Box How to Avoid (Resumen) International Conference on Grounding and Earthing 2010
Resumen: In this paper the Author intend to present a real case with fatalities produced by a lightning bolt in two people and show what was done to avoid this event repetition in terms of lightning protection system and impulsive grounding system that minimize step and contact voltages under and around a Xangri-lá beach Sentry Box. The method used to evaluate the proposed solution in terms of grounding system and lightning protection system was a simplified one using the ATP - Alternative Transient Program due to the need of a fast solution to the problem. Nowadays, the Authors are working in one more precise method to compare with the simplified method used and to refine the solution, if necessary.
D. S. Gazzana, M. O. Oliveira, A. S. Bretas, A. Lerm, A. Bettiol A Hybrid Expert System Based on Neural Networks and Fuzzy Logic for Fault Identification in Electric Power Substations (Resumen) International Conference on Fuzzy and Neural Computation 2010
Resumen: This paper presents a novel approach for on-line fault identification in an Electric Power Substation (EPS). The proposed methodology is based on signal processing techniques allied with a Fuzzy Logic and Artificial Neural Network. The test electric system was rigorously built in an electromagnetic transient numerical simulator, named Alternative Transient Program (ATP), conformably to the needs presented by a Thermoelectric Generation Plant of 711 MW - 230 kV, located in southern Brazil. Simulated test cases demonstrate the generalization capability of the developed hybrid Expert System based on Neural Networks and Fuzzy Logic, now utilized in a Southern Brazilian Utility.
G. D. Ferreira, M. O. Oliveira, A. S. Bretas, G. Cardoso Jr., A. P. Morais Seleção e Alocação Otimizada de Dispositivo de Proteção e Manobras em Sistemas Eletricos de Distribuição Utilizando o algoritmo Colônia de Formigas(Resumen) International Congress on Electricity Distribution 2010
Resumen: Neste trabalho é proposta uma abordagem para melhoria da confiabilidade de sistemas de distribuição de energia elétrica, considerando a determinação de forma otimizada dos tipos e locais de instalação dos dispositivos de proteção contra sobrecorrente e manobras em alimentadores de distribuição. O objetivo específico do processo de otimização é minimizar os indicadores de confiabilidade SAIDI e ASIDI. Na busca pelas melhores soluções é empregada uma variação do algoritmo Colônia de Formigas, o Max-Min Ant System.
M. O. Oliveira, A. S. Bretas, G. D. Ferreira Differential Protection of Three-Phase Transformer Based on Transient Signal Analysis(Resumen) International Congress on Electricity Distribution 2010
Resumen: This paper presents a new methodology to detect and discriminate disturbances in three-phase transformers. The proposed method is based on the Discrete Wavelets Transform (DWT) use. The spectral energy of the low frequency components is calculated and the change in these energies is used as decision criteria. The performance of this methodology is tested through simulation of several fault events made with BPA's ATP/EMTP (Electro Magnetic Transient Program). The proposed algorithm was implemented in MATLAB® environment. Test results show that the new algorithm is highly accurate and independent of the fault conditions.
J. U. N. Nunes, A. S. Bretas Impedance-Based Fault Location Formulation for Unbalance Primary Distribution systems with Distributed Generation(Resumen) International Conference on Power System Technology 2010
Resumen: This paper presents a revision of the state-of-the-art methodologies currently used for simulation and evaluation of Electromagnetic Compatibility (EMC) transients in high frequency grounding systems. The most applicable numerical techniques as Moments Method, Finite Element Method, Finite Difference Time Domain Method and Transmission Line Modeling Method are discussed with focus in its characteristics, advantages and disadvantages Later, practical aspects of the computational implementation of Transmission Line Modeling Method are presented with emphasis in the grounding impedance study.
D. S. Gazzana, A. S. Bretas, G. A. D. Dias, M. Tello Transmission Line Modelling Method (TLM) Based Model for Impulsive Grpunding Transient Evaluation(Resumen) International Conference on Lightning Protection 2010
Resumen This paper presents practical aspects of a computational implementation based on the Transmission Line Modeling Method in one dimension (TLM-1D) for the transient analysis of grounding electrodes. Initially, an introduction on the subject with a brief revision of the state-of-the-art methodologies currently used for impulsive grounding transient evaluation is made, emphasizing TLM. In the following, aspects related to the representation of the grounding conductors are reported considering the soil ionization phenomenon in the transitory analysis. Finally, simulation results are presented and discussed
F. H. Garcia, A. S. Bretas, R. G. Ferraz, R. C. Leborgne Método para a Determinação de Correntes de Falta Fase-Terra em Sistemas Elétricos de Potência(Resumen) IX Induscon 2010
Resumen: Os sistemas elétricos de potência representam uma complexa estrutura e possuem fundamental importância para a sociedade moderna. As perturbações nos sistemas elétricos, causadas por faltas ou curtos-circuitos, provocam desde curtas interrupções no fornecimento a blecautes, em casos extremos. Um sistema elétrico pode ser representado por uma matriz, denominada matriz impedância de barra, que permite obter de forma direta e simples a magnitude das correntes de faltas. Entretanto, frequentemente a obtenção desta matriz é feita a partir da inversão da matriz admitância de barra. O objetivo deste trabalho é apresentar um método para determinação das correntes de falta a partir da inversão parcial da matriz admitância de barra.
D. O. F. Pereira, A. S. Bretas Extended Ground Distance Relaying with Fault Resistance Compensation (Resumen) Moderm Electric Power System - MEPS 2010
Resumen: Fault resistance introduces an error in traditional ground distance relay apparent impedance measurement process. If not accordingly considerated it produces primary protection zone underreach. Line asymmetry also affects relay operation producing overreaching. So due to these two aspects protection zone limits of ground distance relays present low precision. In order to increase these precision limits, a new protection algorithm is proposed. The proposed method is based in phase coordinates and uses a fault resistance estimate to develop the trip decision procedure. The estimation procedure uses one-terminal voltage and current data in an iterative process. The proposed algorithm results are compared to traditional ground distance relay for method validation.
G. D. Ferreira, A. S. Bretas, G. Cardoso Jr. Optional Distribution Protection Design Considering Momentary and Sustained Reliability Indices (Resumen) Moderm Electric Power System - MEPS 2010
Resumen: Today momentary interruptions are an important customer issue and most distribution engineers consider them a reliability issue. This paper considers reliability as all aspects of customer interruptions, including momentary interruptions. A methodology for multiobjective optimization is proposed to minimize SAIFI, SAIDI and MAIFIE indices simultaneously. This goal is achieved considering both the optimized allocation of protective devices and switches, and the definition of the protection scheme to be employed in the reclosers and substation breaker, fuse saving or fuse blowing. The constraints considered include technical and economic limitations. In the search for the better solutions is employed the Nondominated Sorting Genetic Algorithm - II. The methodology was tested in a real distribution system with 51 buses, and the results compared with the current configuration of the protection system.
J. U. N. Nunes, A. S. Bretas An Extended Fault Location Formulation for Unbalanced Distribution Feeders with Distributed Generation (Resumen) Moderm Electric Power System - MEPS 2010
Resumen: This paper presents an extended impedance-based formulation for fault location on deregulated electric power distribution systems. Distribution feeders are inherently unbalanced and traditionally radial. Deregulated distribution systems can have distributed generation, which changes the fault period power flow and decreases the accuracy of current state-of-the-art impedance based fault location formulations. Therefore, in this paper an extended impedance-based formulation is proposed. The work includes the formulation analytical development as simulation test results. Comparative test results are also presented, highlighting the formulations increased accuracy compared with current impedance-based fault location techniques.
D. S. Gazzana, M. O. Oliveira, A. S. Bretas, A. Lerm, A. Bettiol An Expert System for Substation Fault Detection in Thermoelectric Generation Plants (Resumen) Moderm Electric Power System - MEPS 2010
Resumen: This paper presents a methodology to develop a Fault Diagnosis Integrated System in a Thermoelectric Generation Plant (TGP). The proposed methodology is based on three methods: Discrete Fourier Transform (DFT), Fuzzy Logic and Artificial Neural Network (ANN). The test electric system was built in BPA's ATP/EMTP software, conformably to the needs presented by a Thermoelectric Generation Plant (TGP) of 711 MW - 230 kV, located in southern Brazil. Simulated test cases demonstrate the generalization capability of the protection system developed, now used in a Southern Brazilian Utility.
M. O. Oliveira, D. S. Gazzana, A. S. Bretas, A. Lerm, A. Bettiol Sistema Especialista para Detecção e Diagnóstico de Faltas em Sistemas de Geração Termoelétrica (Resumen) XVIII Congresso Brasileiro de Automática - CBA 2010
Resumen: In many Thermoelectric Generation Plants (TGP) fault location is performed only on the basis of monitoring system data analysis, as for example, the state of switches and circuit breakers. However, this procedure can lead to misidentification of the faulty component, especially when the substation is large. Accordingly, it must be taken into account other variables such as the magnitude and phase of voltages and currents as well as system oscillography data. Moreover, the evaluation of a greater number of variables leads to the necessity of using an expert system to support decision making. In this context, this paper presents a methodology used to develop a Fault Diagnosis Integrated System in a TGP. The proposed methodology in this work is based on the idealization of three integrated subsystems: Pre-Processing Data System, Fault Identification System, and Expert System. The simulated system was built, rigorously, conformably to the needs presented by a TGP of 711 MW -230 kV, located in southern Brazil. Simulated test cases demonstrate the generalization capability of the developed program. The developed software is nowadays installed in a Southern Brazilian Utility.
M. O. Oliveira, D. P. Marzec, G. Bordin, A. S. Bretas, D. P. Bernardon Análise do Efeito de Variáveis Climáticas sobre a Evolução de Demanda de Energia Elétrica (Resumen) XVIII Congresso Brasileiro de Automática - CBA 2010
Resumen: The projection of electricity demand on the horizon for long, medium and short term are crucial to the planned expansion and operation of the electric power systems. In this context, this paper presents a methodology for projection of demand for electricity in the very short term considering the effect of climatic variables. Therefore, Ambient Temperature (TA) and Relative Humidity (RH) are related through the Discomfort Index (DI) in both the TA with the Wind Velocity (WV), are linked through Wind Chill (WC). These relations climate were used in this paper to obtain a projection model of demand using multiple linear regressions. The projection model proposed was tested computationally and compared with based on actual data obtained from a utility generating electricity located in Rio Grande do Sul, Brazil. The results demonstrate the dependence of the evolution of electricity demand with climatic variables in the very short term.
J. U. N. Nunes, A. S. Bretas Localização de Faltas Estendida para Alimentadores de Distribuição (Resumen) XVIII Congresso Brasileiro de Automática - CBA 2010
Resumen: This paper presents an impedance-based fault location formulation for distribution systems with the presence of dis- tributed generation. Distribution feeders are characterized by the asymmetry of the lines and the single direction of power flow. However, on systems that have distributed generation, the nature of power flow is changed, becoming non-radial. Therefore, it is necessary to study and develop a novel formulation for fault location that considers the contributions of the distributed generation. This method is based on steady state analysis. The work illustrates the extensions made to an existing method to estimate the fault location.
R. J. Cabral, R. G. Ferraz, R. C. Leborgne, A. S. Bazanella, A. S. Bretas Análise Numérica do Efeito dos Desequilibrios em Sistemas de Distribuição Faltosos (Resumen) XVIII Congresso Brasileiro de Automática - CBA 2010
Resumen: This paper presents a numerical study of the effects of the system unbalance and fault impedance on the calculation of voltages and currents in faulted systems. Two methods of fault calculation are tested: the symmetrical components method and the phase components method. Simulation using ATP/EMTP are considered as a benchmark to calculate the errors for each method. The fault calculation methods are implemented in MATLAB. The IEEE 13 bus test feeder is used in the case study where asymmetrical faults are simulated. Two different operational conditions that are tested considering three levels of voltage imbalance at the substation bus (3.65%) and several fault impedances between 0 and 25 ?. The results show the accuracy of each fault calculation method and the error sensitivity to the pre-fault voltage imbalance and the fault impedance.
D. O. F. Pereira, A. S. Bretas Relé de Distância tipo Terra Compensado (Resumen) XVIII Congresso Brasileiro de Automática - CBA 2010
Resumen: This work presents a new fault resistance estimation procedure for digital distance relaying application. The fault resistance is estimated through an iterative procedure using one-terminal voltage and current fasors from the faulted line. The method is based in phase coordinates, allowing its application to untransposed lines. The results of this new method are compared with the tradicional ground distance relay to show its efficience.
G. D. Ferreira, A. S. Bretas, G. Cardoso Jr. Seleção e Alocação Otimizada de Dispositivos de Proteção de Sobrecorrente e Manobras: Uma Proposta para Melhoria da Confiabilidade de Sistemas Elétricos de Distribuição (Resumen) XVIII Congresso Brasileiro de Automática - CBA 2010
Resumen: In this work a mathematical formulation for the problem of optimal allocation of protective and switching devices in distribution systems is proposed, in order to minimize the reliability indexes SAIDI and ASIDI. The mathematical model of the objective function considers the determination of protection zones of protective devices, and the possibility of restoration of power supply. The constraints considered include technical limitations, economic and safe operation of the system. This approach results in a combinatorial optimization problem with nonlinear, discontinuous and nondifferentiable objective function, with in- teger variables and nonlinear constraints. In the search for better solutions to the problem is employed the Genetic Algorithm, with a local search mechanism and a specialized mutation operator. The methodology was tested in a real distribution system with 51 buses, and the results compared with the current configuration of the protection system.
F. H. Garcia, R. G. Ferraz, A. S. Bretas Análise de Faltas Fase-Terra em Sistemas Elétricos de Potência Desequilibrados: Método de Componentes Simétricas Modificado(Resumen) XVIII Congresso Brasileiro de Automática - CBA 2010
Resumen: Currently unsymmetrical faults are analyzed using phase components or symmetrical components methods. The method of phase components has a good precision, but requires more processing time and computational resources. The method of symmetrical components is simpler, but has limited precision when applied to unbalanced systems, as in the case of distribution networks. This work presents initially a numerical comparative study between the symmetrical components short- circuit (SS) technique and the Alternative Transient Program (ATP). After, a modified symmetrical component method for SS studies is presented. The study is exemplified for a 4 buses system, whose operational data are obtained using the ATP program. Short-circuit and faults through various impedances values are simulated. The proposed method for short-circuit is implemented in Matlab.
F. H. Garcia, R. J. Cabral, A. S. Bretas, R. C. Leborgne Estudio Numérico de Cortocircuito Monofásico en Presencia de Generación Distribuida: Métodos de Análisis y Huecos de Tensión(Resumen) VI Conferencia Científica Eléctrica 2010
Resumen: This paper analyzes the influence of the distributed generation on voltage sags on an unbalanced distribution system. The system was simulated using the ATP program and two fault calculation methods: the symmetrical components method (SCM) and the phase components method (PCM). The paper compares the short circuit currents obtained by using the three simulation methods. The simulations on ATP are used as reference values. The paper shows that distributed generation improves the immunity of the distribution system against voltage sags and that the phase components method is more accurate than the symmetrical components method when the system unbalance increasesos.
N. G. Bretas, A. S. Bretas Bad Data Analysis Using the Composed Measurements Errors for Power System State Estimation (Resumen) VIII Bulk Power System Dynamics and Control 2010
Resumen: In this paper, a topological/geometrical based approach is used to define the undetectability index (UI), which provides the position of a measurement related to the range space of the Jacobean matrix of the power system. The higher the value of this index, for a measurement, the closer it will be to the range space of that matrix, that is, the error in measurements with high UI is not reflected in their residuals, thus masking a possible gross error those measurements might have. Using the UI of a measurement, the possible gross error the state estimation process might mask is recovered; then the total gross error of that measurement is composed and used to the gross error detection and identification test. The gross error processing turns out to be very simple to implement, requiring only a few adaptations to the existing state estimation software. The IEEE-14 bus system is used to validate the proposed gross error detection and identification test.
R. G. Ferraz, R. J. Cabral, A. S. Bretas, A. S. Bazanella, R. C. Leborgne System Unbalance Effect on Faulted Distribution Systems: A Numerical Study (Resumen) IEEE Power Engineering Society General Meeting 2010
Resumen: This paper presents a numerical study of the system unbalance effect on system voltage and current calculation during asymmetrical faults. Two different system operational conditions are tested considering a voltage imbalance at the substation bus: balanced system loads and voltage imbalance equal to 3.65% due to system loads. Five fault impedances are simulated. Two fault analysis methods, the symmetrical components and phase component algorithms are implemented and analyzed based on numerical simulations of asymmetrical faults on the IEEE 13 bus test feeder. The results show the accuracy of each fault analysis method and how the errors may vary according to the system pre-fault unbalance operation condition and the fault impedance.
F. H. Garcia, R. G. Ferraz, A. S. Bretas Influência da Redução de Matrizes nas Tensões e Correntes de Sistemas Elétricos Trifásicos Desequilibrados Utilizando o Método de Kron (Resumen) Simpósio Brasileiro de Sistemas Elétricos - SBSE 2010
Resumen: Este trabalho analisa o impacto da utilização do método de redução de Kron aplicado aos sistemas elétricos de potência, especificamente nos sistemas de distribuição de baixa tensão. A redução é aplicada ao modelo da linha elétrica para eliminar a equação correspondente ao neutro da mesma. O programa ATP é empregado para simular dez cenários distintos, onde é considerado o desequilíbrio do sistema como referência para a comparação dos resultados. Os resultados numéricos apresentados mostram que em determinadas condições a redução de Kron pode originar erros significativos.
M. Resener, R. H. Salim, A. S. Bretas Alocação e Ajuste Ótimo de Reguladores de Tensão em Sistemas de Distribuição (Resumen) Simpósio Brasileiro de Sistemas Elétricos - SBSE 2010
Resumen: Neste artigo é apresentada uma metodologia para alocação e ajuste ótimo de reguladores de tensão em sistemas de distribuição. Como objetivo principal tem-se a melhoria da qualidade da energia entregue ao consumidor e a redução dos custos da distribuidora. Através de análises utilizando um fluxo de potência trifásico e da avaliação de funções objetivo, são determinados a localização e os ajustes do(s) regulador(es) de tensão. Ainda, são consideradas as características específicas dos sistemas de distribuição, como presença de ramificações, acoplamento entre as fases e o uso de diferentes condutores ao longo do alimentador.
M. O. Oliveira, D. P. Marzec, G. Bordin, A. S. Bretas, V. M. Madeira, D. P. Bernardon Projeção de Demanda de Energia Elétrica a Curtíssimo Prazo Considerando o Índice de Desconforto (Resumen) Simpósio Brasileiro de Sistemas Elétricos - SBSE 2010
Resumen: Projeções de demanda de energia elétrica nos horizontes de curto e curtíssimo prazo são determinantes para o planejamento e programação da operação de sistemas elétricos de potência. Neste sentido, o presente trabalho apresenta um modelo para projeção de demanda de energia elétrica a curtíssimo prazo considerando variáveis climáticas e comportamentais, tratadas através de relações causa-efeito. A temperatura ambiente e a umidade relativa do ar são relacionadas através do índice de desconforto, utilizado no modelo desenvolvido. O modelo foi testado através de simulações computacionais, baseadas em dados reais obtidos junto a uma concessionária de geração de energia elétrica do Rio Grande do Sul. Os resultados obtidos demostram que o índice de desconforto é um indicador explicativo da evolução da demanda.
M. O. Oliveira, A. S. Bretas Modelagem de Transformadores para Estudos de Transitórios Eletromagnéticos (Resumen) VI Worskpot: International Workshop on Power Transformers 2010
Resumen: Os Sistemas Elétricos de Potência (SEP) estão constantemente expostos à ocorrência de fenômenos transitórios originados por eventos como, por exemplo, faltas elétricas, manobras de operação e fenômenos atmosféricos. Esses transitórios eletromagnéticos geram sinais que abrangem um amplo espectro de freqüências e que influencia de forma relevante tanto no desempenho dos sistemas de proteção quanto no correto funcionamento dos equipamentos dos SEP (transformadores, geradores, reatores, banco de capacitores, etc.). Nesse sentido, a representação de transformadores para estudos de transitórios eletromagnéticos pode ser bastante complicada, tendo em vista o grande número de projetos de núcleos e o fato de que alguns parâmetros do transformador são não-lineares e dependentes da freqüência. Neste contexto, este trabalho visa apresentar uma revisão sobre os principais modelos de transformadores de potência utilizados para estudos de transitórios eletromagnéticos. Assim, neste artigo são apresentadas as principais considerações para a modelagem de transformadores junto aos critérios utilizados para a classificação dos modelos existentes. Apresentam-se também as abordagens utilizadas para a modelagem de transformadores em estudos de transitórios eletromagnéticos de baixa, média e alta freqüência. A modelagem do transformador em função do tipo de representação também é abordada neste trabalho onde se descreve o comportamento linear e não-linear do transformador. O objetivo principal deste trabalho é apresentar uma revisão detalhada das principais abordagens sobre a modelagem dos transformadores de potência visando contribuir e facilitar a representação desta máquina em futuros estudos de transitórios eletromagnéticos.
M. O. Oliveira, A. S. Bretas Metodologias para Proteção Diferencial Digital de Transformadores de Potência: Revisão do Estado-da-Arte (Resumen) VI Worskpot: International Workshop on Power Transformers 2010
Resumen: A grande quantidade de publicações encontradas em revistas especializadas, conferências, dissertações e teses mostram o progresso atingido por trabalhos recentes na área da Proteção Diferencial Digital de Transformadores de Potência. A maioria desses trabalhos propõe diferentes metodologias para a resolução dos problemas encontrados nos esquemas de proteção diferencial tradicionais. Diante disso, este artigo objetiva apresentar uma revisão das diferentes técnicas digitais propostas para a resolução dos problemas encontrados nos esquemas convencionais de proteção diferencial de transformadores de potência. Cabe ressaltar que o objetivo desta revisão é apresentar alguns dos aprimoramentos encontrados no que se refere à proteção digital direcionada aos transformadores de potência. Portanto, visando uma melhor apresentação das pesquisas realizadas, este artigo divide as mesmas em vários grupos, a saber: Proteção de transformadores de potência baseadas na utilização de ferramentas inteligentes; Proteção de transformadores de potência baseadas na aplicação da Transformada Wavelet (TW); Proteção de transformadores de potência baseadas na combinação de diferentes técnicas de análise.
M. O. Oliveira, A. S. Bretas Nova Metodologia para Identificação de Correntes de Inrush em Transformadores de Potência (Resumen) VI Worskpot: International Workshop on Power Transformers 2010
Resumen: Importantes chaveamentos acontecem nos Sistemas Elétricos de Potência (SEP) devido a desequilíbrios entre a geração de energia e a carga atendida. Este fato gera nos transformadores uma corrente de magnetização transitória chamada “corrente de inrush” que se apresentam com valor de pico inicial elevado (até 20 vezes o valor de pico da corrente nominal), duração de vários ciclos e amplo espectro de harmônicos predominando a 2ª harmônica. Ditas correntes transitórias geram uma série de inconvenientes tanto no esquema de proteção do transformador quanto na qualidade da energia fornecida por ele. Assim sendo, este trabalho apresenta uma nova metodologia para identificação e discriminação de correntes de inrush em transformadores de potência, a qual utiliza a Transformada Wavelet Discreta (DWT) para extrair e avaliar os sinais transitórios induzidos durante a energização do transformador. Visando avaliar o desempenho operacional do algoritmo implementado em ambiente MATLAB®, modelou-se um sistema elétrico de transmissão de 138 kV, contendo um transformador de 30 MVA através do software BPA’s ATP/EMTP (Alternative Transient Program).
D. S. Gazzana, A. S. Bretas, G. A. D. Dias, M. Tello Numerical Methodologies for EMC Analysis in High Frequency Grounding Systems (Resumen) 5th IET International Conference on Power Electronics, Machines and Drives 2010
Resumen: This paper presents a revision of the state-of-the-art methodologies currently used for simulation and evaluation of Electromagnetic Compatibility (EMC) transients in high frequency grounding systems. The most applicable numerical techniques as Moments Method, Finite Element Method, Finite Difference Time Domain Method and Transmission Line Modeling Method are discussed with focus in its characteristics, advantages and disadvantages Later, practical aspects of the computational implementation of Transmission Line Modeling Method are presented with emphasis in the grounding impedance study
D. S. Gazzana, A. S. Bretas, G. A. D. Dias, M. Tello Comparative Analysis of EMC Methodologies Applied on Transients Studies of Impulsive Grounding Systems(Resumen) International Conference on Industrial Technology - ICIT 2010 2010
Resumen: This paper presents a review study on state of the art techniques used for electromagnetic transient studies on grounding systems. First, an introduction about the subject is presented, emphasizing the importance of grounding in population safety and equipments protection. Following, the Circuit Approach, Transmission Line Approach, Electromagnetic Field Approach and Hybrid Approach are reported. The most currently used numerical methodologies for electromagnetic compatibility (EMC) problems solution, as Finite Difference Time Domain Method (FDTD), Moments Method (MoM), Finite Element Method (FEM) and Transmission Line Modeling Methods (TLM) are also discussed with focus in its characteristics, advantages and disadvantages. Finally, simulation results using TLM are presented emphasizing the easiness of implementation of this method
M. C. R. Paz, R. G. Ferraz, A. S. Bretas, R. C. Leborgne System Unbalance Effect on Faulted Voltages and Currents(Resumen) 3rd Global Conference on Power Control and Optimization - PCO 2010 2010
Resumen: This paper presents a numerical study of the system unbalance effect on faulted power systems analysis. Two short circuit techniques, the symmetrical components and phase component algorithms are implemented and analyzed based on numerical simulations of faults on IEEE 13 bus test feeder. Test cases include load and system unbalance effect and fault impedance effect on faulted voltage and current. The results show that the fault currents and voltages are greatly affected by the system unbalance.
M. C. R. Paz, R. G. Ferraz, A. S. Bretas, R. C. Leborgne System Unbalance Effect on Faulted Power Systems: A Distribution System Case Study(Resumen) APAP - International Conference on Advanced Power System Automation and Protection 2009
Resumen: This paper presents a numerical study of the system unbalance effect on faulted power systems analysis. Two short circuit techniques, the symmetrical components and phase component algorithms are implemented and analyzed based on numerical simulations of faults on IEEE 13 bus test feeder. Test cases include unbalance effect analysis, fault condition effect analysis and fault location effect analysis. Test results present cases relation to short circuit techniques performance indicating the unbalance system operating condition effect on faulted power systems analysis.
M. O. Oliveira, R. J. Cabral, A. S. Bretas Optimización de un Algoritmo de Protección Diferencial de Transformadores Mediante Análisis de Varianza(Resumen) COINI- Congreso Argentino de Ingeniería Industrial 2009
Resumen: Este artigo apresenta um estudo de otimização de um algoritmo de proteção diferencial de transformadores trifásicos mediante a utilização de um experimento fatorial cruzado. A característica de qualidade especificada pelo cliente é a eficiência do algoritmo de proteção diferencial quantificada neste trabalho através do tempo de operação do relé. Este tempo de operação é medido em milisegundos [ms] e é uma variável de saída do tipo menor-e-melhor. Para a análise dos dados foram utilizados: um projeto fatorial cruzado de 3 fatores controláveis com três repetições, uma tabela ANOVA e os gráficos de interação entre os fatores controláveis. Os resultados obtidos permitiram achar a melhor combinação dos fatores controláveis do algoritmo para atingir o menor tempo de operação do relé de proteção e conseguir otimizar a característica de qualidade estudada.
K. R. C. de Oliveira, R. H. Salim, A. Shuck Jr., A. S. Bretas Faulted Branch Identification on Power Distribution Systems Under Noisy Environment(Resumen) IPST- International Conference on Power Systems Transient 2009
Resumen: Faulted branch identification is extremely important for power distribution systems operation and restoration. Also, noisy environments are common in substations, where the relays are normally installed. In this paper a novel formulation that estimates the faulted section of an unbalanced power distribution system considering a noisy environment is presented. The method uses travelling waves and autocorrelation theory, and was developed using only local voltage data. The encouraging results demonstrate the technique’s high precision in determining faulted branches considering faults without resistance.
D. S. Gazzana, A. S. Bretas, G. A. D. Dias, M. Tello Metodologias Aplicadas para a Modelagem e Análise de Sistemas de Aterramento Impulsivo Revisão do Estado da Arte(Resumen) 11th Spanish-Portuguese Conference on Electrical Engineering 2009
Resumen: This paper presents a review study about the main techniques used to solve transient problems related to impulsive and high frequency grounding systems. Firstly, an introduction about the matter is made, emphasizing the importance of grounding in the protection of people and equipments. Following, circuit approach, transmission line approach, electromagnetic field approach and hybrid approach are reported. The most applicable numerical methodologies for electromagnetic compatibility problems solution, as finite difference time domain method (FDTD), moments method (MoM), finite element method (FEM) and transmission line modeling methods (TLM) are discussed with focus in its characteristics, advantages and disadvantages.
O. H. Ando Junior, R. C. Leborgne, A. S. Bretas Desenvolvimento de uma Metodologia para Cálculo e Gerenciamento de Indicadores de Qualidade da Energia Elétrica(Resumen) VIII Congresso Brasileiro de Qualidade de Energia 2009
Resumen: Este trabajo presenta una nueva metodologia para el análisis y gerenciamiento de la calidad de energia a través de la identificación y cuantificación de los distúrbios electromagnéticos. Esta metodología utiliza técnicas de procesamiento digital de sañales que posibilitan la contrucción de filtros digitales para la detección del evento y para estimar la frecuencia de las señales eléctricas estudiadas. Los principales distúrbios de calidad definidos por las normas de la ANEEL y del ONS son cuantificados a través de un algoritmo robusto. El programa desarrollado fue probado utilizando diferentes formas de onda con distúrbios previamente conocidos. Posteriormente fueron analizadas formas de onda obtenidas mediante mediciones de campo para evaluar la robustez del algoritmo ante disturbios reales.
M. O. Oliveira, A. S. Bretas Application of Discrete Wavelet Transform for Differential Protection of Power Transformers(Resumen) PowerTech Conference 2009
Resumen: This paper presents a novel formulation for differential protection of three-phase transformers. The Discrete Wavelet Transform (DWT) is employed to extract transitory features of transformer three-phase differential currents to detect internal faulty conditions. The performance of the proposed algorithm is evaluated through simulation of faulty and non-faulty test cases on a power transformer using ATP/EMTP software. The optimal mother wavelet selection includes performance analysis of different mother wavelets and resolution number of levels. In order to test the formulations performance, the proposed method was implemented on MatLab® environment. Simulated comparative test results with a percentage differential protection with harmonic restraint formulation shows that the proposed technique improves the discrimination performance. Simulated test cases of magnetizing inrush and close by external faults are also presented in order to test the performance of the proposed method in extreme conditions.
M. O. Oliveira, R. H. Salim, A. S. Bretas Protección Diferencial de Transformadores Trifásicos Mediante Análisis de Transitorios(Resumo) Conferencia Técnica Andina ANDESCON 2008 2008
Resumen: This paper proposes a novel formulation for differential protection of three-phase transformers using Wavelet Transforms (WTs). The new proposed methodology implements the WTs to extract predominant transient signals originated by transformer internal faults and captured from the current transformers. The three phase differential currents are the input signals used on-line to detect internal faults. The performance of this algorithm is demonstrated through simulation of different internal faults and switching conditions on a power transformer using ATP/EMTP software. The analyzed data is obtained from simulation of different normal and faulty operating conditions such as internal faults – phase/phase, phase/ground-, magnetizing inrush and external faults. The case study shows that the new algorithm is highly accurate and effective.
M. O. Oliveira, R. H. Salim, A. S. Bretas Wavelet Transform Approach for Differential Protection of Three-Phase Transformers (Resumen) 43rd International Universities Power Engineering Conference 2008
Resumen: This paper proposes a novel differential protection technique of three-phase transformers using Wavelet Transforms (WTs). The Wavelet Transform is an efficient signal processing tool used in non stationary signals with fast transition studies (high frequency components). The three phase differential currents are the input signals used on-line in the proposed formulation. The performance of the proposed formulation is evaluated through simulation of different internal faults and switching conditions on a 138 kV system containing a 25 MVA transformer (138/13,8kV). Simulations studies are made with ATP/EMTP software. The paper also presents a study of the optional wavelet analysis selection that includes both the optimal mother wavelet and the optimal number of levels of resolution. The proposed formulation was constructed in MATLAB® environment. The case study shows that the proposed algorithm is highly accurate and effective when compared to traditional differential relay protection.
M. O. Oliveira, R. H. Salim, A. S. Bretas Differential Protection of Three-Phase Transformers Using Wavelet Transforms (Resumen) 2008 IEEE PES Transmission and Distribution Conference and Exposition 2008
Resumen: This paper proposes a novel formulation for differential protection of three-phase transformers using Wavelet Transforms (WTs). The new proposed methodology implements the WTs to extract predominant transient signals originated by transformer internal faults and captured from the current transformers. The Wavelet Transform is an efficient signal processing tool used to study non stationary signals with fast transition (high frequency components), mapping the signal in time-frequency representation. The three phase differential currents are the input signals used on-line to detect internal faults. The performance of this algorithm is demonstrated through simulation of different internal faults and switching conditions on a power transformer using ATP/EMTP software. The analyzed data is obtained from simulation of different normal and faulty operating conditions such as internal faults – phase/phase, phase/ground-, magnetizing inrush and external faults. The case study shows that the new algorithm is highly accurate and effective.
M. O. Oliveira, R. H. Salim, A. S. Bretas A New Technique For Differential Protection Of Three-Phase Transformers (Resumo) VIII Conferência Internacional de Aplicações Industriais INDUSCON 2008
Resumen: This paper introduces a novel relaying scheme for power transformer protection using the Wavelet Transform. This paper aims to prove that the Wavelet Transform is a reliable and computationally efficient tool for distinguishing between the inrush currents and the fault current. The three-phase differential currents are the input signals used for transient’s detection and analysis. The performance of this algorithm is demonstrated by the simulation of different operating cases comprising internal faults, magnetizing currents and external faults on a three-phase transformer using ATP/EMTP software. The test results show that the new algorithm is very fast and accurate.
M. Resener, A. D. Filomena, R. H. Salim, A. S. Bretas Localização de Faltas em Sistemas de Distribuição Ramificados e Desequilibrados (Resumen) II Simpósio Brasileiro de Sistemas Elétricos (SBSE) 2008
Resumen: Neste artigo é apresentada uma formulação estendida para localização de faltas em sistemas desbalanceados e ramificados baseada na impedância aparente. Sistemas de distribuição de energia são normalmente caracterizados pela existência de laterais e sublaterais, linhas não simétricas e cargas variáveis ao longo do dia. Tais características comprometem a eficiência dos métodos de localização de faltas tradicionais. A formulação proposta utiliza como dados de entrada medidas locais de tensão e corrente. Resultados obtidos através de simulações numéricas utilizando-se dados reais de um alimentador de distribuição da Companhia Estadual de Distribuição de Energia Elétrica do Rio Grande do Sul (CEEED) comprovam a eficiência da formulação. Os resultados comparativos mostram a robustez da técnica proposta em relação às limitações encontradas nos métodos tradicionais, como distância, resistência e ângulo de incidência de falta, bem como para variação de carga.
M. Resener, A. D. Filomena, R. H. Salim, A. S. Bretas Optimized Fault Location Formulation For Unbalanced Distribution Feeders Considering Load Variation (Resumen) 16th Power Systems Computation Conference 2008
Resumen: In this paper an extended impedance based fault location formulation for unbalanced distribution systems is presented. The majority of distribution feeders are characterized by the existence of several laterals, nonsymmetrical lines, highly unbalanced operation and timevarying loads. These specific characteristics compromise traditional fault location methods performance. The oneterminal proposed formulation uses as input data local voltages and currents, system’s topology and pre-fault loads. Test results are obtained from numerical simulations using real distribution system data from a Brazilian energy company. Comparative results show the technique robustness in respect to traditional fault location limitations, such as fault distance, resistance, inception angle, as well as for load variation.
A. D. Filomena, M. Resener, R. H. Salim, A. S. Bretas Fault Location for Underground Systems with Capacitive Current Compensation (Resumen) 16th Power Systems Computation Conference 2008
Resumen: Underground systems are normally exposed to permanent faults, due to specific construction characteristics. In these systems, visual inspection can only be performed in inspection boxes. To overcome this limitation, accurate fault location techniques must be applied. In this paper, a novel impedance based fault location algorithm for underground distribution systems is described considering three-phase faults. The formulation is developed on the phase frame representation and calculates the apparent impedance using line’s voltage and current data from one-terminal. The technique also proposes an iterative algorithm for capacitive current compensation. Test simulations on a real data underground distribution system demonstrate the proposed method robustness and accuracy. The algorithm performance presents negligible effects from different fault resistances and fault distances.
A. D. Filomena, M. Resener, R. H. Salim, A. S. Bretas Fault Analysis of Unbalanced Systems using Fault Resistance Estimation (Resumen) 16th Power Systems Computation Conference 2008
Resumen: Fault resistance (RF) is a critical parameter of faulted power systems due to its stochastic nature. If not considered, RF may interfere in fault analysis and protection schemes efficiency. To overcome these limitations, a novel fault analysis formulation for unbalanced threephase distribution systems is proposed. The formulation is based on short-circuit analysis through bus impedance matrix (Zbus) and a novel iterative algorithm for fault resistance estimation. The method’s robustness and potential for online applications is demonstrated through numeric simulations.
A. D. Filomena, M. Resener, R. H. Salim, A. S. Bretas Extended Impedance-Based Fault Location Formulation for Unbalanced Underground Distribution Systems (Resumen) IEEE Power Engineering Society General Meeting 2008
Resumen: Underground distribution systems are commonly exposed to permanent faults. Due to specific construction charac-teristics, visual inspection for fault location cannot be performed. To overcome this limitation, accurate fault location techniques must be applied. In this paper, an extended impedance-based fault location formulation for unbalanced underground distribu-tion systems is described considering single line-to-ground faults. The technique uses only local voltages and currents as input data. An iterative algorithm for cable capacitive current compensation in the fault location formulation is proposed. The formulation focuses an easily practical implementation and is based on typical available system’s data, as lines impedance and admittance ma-trices, and also system loads. Test simulations on a real data underground distribution system demonstrate the proposed extensions improvements. The algorithm performance presents negligible fault resistance, distance, and inception angle variation effects.
R. H. Salim, K. R. C. de Oliveira, A. S. Bretas Detecção e Classificação de Faltas Monofásicas em Sistemas Elétricos Utilizando a Transformada Wavelet (Resumen) XIX Seminário Nacional de Produção e Transmissão de Energia Elétrica (SNPTEE) 2007
Resumen: O presente trabalho apresenta uma nova metodologia para a detecção, classificação e determinação do instante de ocorrência de faltas monofásicas em sistemas elétricos. A ferramenta de análise para a tomada de decisão é a transformada wavelet, através da análise multiresolução dos sinais de corrente medidos na subestação. Simulações são utilizadas para a validação da metodologia e para o projeto dos parâmetros necessários. Os resultados mostram que a metodologia proposta é eficiente e robusta na detecção de faltas ocorridas em qualquer das fases do sistema, inclusive para faltas com resistência elevada.
K. R. C. de Oliveira, R. H. Salim, A. S. Bretas Estimação do Ramo Faltoso em Sistemas de Distribuição Desequilibrados (Resumen) VIII Congresso Brasileiro de Redes Neurais (CBRN) 2007
Resumen: A determinação do ramo de ocorrência da falta é de extrema importância para os sistemas de distribuição subterrâneos, visto que os sistemas atualmente estão cada vez mais ramificados. Neste trabalho é apresentado um método que estima o ramo faltoso de um sistema de distribuição subterrâneo desequilibrado(SDSD). Este método é baseado em redes neurais artificiais (RNA). O uso das RNAs é motivado pelo fato que estas são capazes de aprender e generalizar, englobando assim, pequenas alterações no sistema. Assim, visando melhorar os métodos de estimatimação já existentes, este trabalho propõe e discute os resultados obtidos por simulações implementadas através de dados reais. Os resultados obtidos demonstram a potencialidade e a robustez desta técnica.
R. H. Salim, K. R. C. de Oliveira, A. S. Bretas Fault Detection in Primary Distribution Systems using Wavelets (Resumen) 7th Internacional Conference on Power Systems Transients, Lyon 2007
Resumen: This paper presents a new methodology for phase-to-ground fault detection in primary distribution systems. The wavelet transform is the tool used, through the multiresolution analysis of the current signals measured at the relay point. Traditional tools such as the Fourier Transform and the Short-Time Fourier Transform have a frequency resolution inversely dependent of time resolution, providing a lower level of robustness to the fault detection procedure. In this paper, the proposed technique is designed and validated through several computational simulations in the IEEE 37 bus test feeder. The proposed technique is also compared to a Neural Network approach, using the same simulations and protection philosophy. Test results show that the proposed scheme is an efficient methodology for single phase fault detection in unbalanced distribution systems, including faults with high impedance.
A. D. Filomena, R. H. Salim, M. Resener, A. S. Bretas Fault Resistance Influence on Faulted Power Systems with Distributed Generation (Resumen) 7th Internacional Conference on Power Systems Transients, Lyon 2007
Resumen: Fault resistance (RF) is a critical component in power systems protection schemes and fault locations algorithms. It introduces an error that if not taken into account for, may cause misoperation of ground distance relays and fault locators. The presence of distributed generation (DG) is becoming common in power systems, and new fault location methods and power system protection schemes are being developed to consider it. This paper proposes an analysis of the RF influence in power system relaying and fault location algorithms with and without DG, allowing future research for fault resistance compensation.
A. S. Bretas, R. H. Salim Fault Location in Unbalanced DG Systems using the Positive Sequence Apparent Impedance (Resumen) IEEE Power Engineering Society Transmission and Distribution Conference and Exposition: Latin America, Caracas 2006
Resumen: The fault location techniques for power distribution systems (PDS) in use nowadays assume that the system has a radial power flow. Since new technologies in development, such as the distributed generation (DG), change this characteristic, it is necessary to adjust the already existing methods for fault location, since they show to be inefficient. Moreover, the unbalance between phases due to different loading at laterals is another issue that interferes in the fault location methodologies. In this paper, it is presented a new fault location method based on positive sequence apparent impedance. Computational simulations were made and the method was tested in two systems and compared with other existing fault location techniques in order to validate it. The basic characteristics of the method, the new algorithm and a variety of case studies are presented in the paper in order to illustrate its efficiency in unbalanced distribution systems with DG.
A. S. Bretas, M. Moreto, R. H. Salim, L. O. Pires Novel High Impedance Fault Location for Distribution Systems considering Distributed Generation (Resumen) IEEE Power Engineering Society Transmission and Distribution Conference and Exposition: Latin America, Caracas 2006
Resumen: In this paper it is proposed a novel high impedance fault detection and location scheme for power distribution feeders with distributed generation. The proposed scheme is capable to obtain precise fault location estimations for both linear low impedance and non-linear high impedance faults. This last class of faults represents an important subject for the power distribution utilities because they can be difficult to detect an locate by the protection devices commonly used in today's electric distribution systems. The proposed scheme uses real time data which are processed in a way that the fault detection and location can be estimated by a set of characteristics extracted from the voltage and current signals measured at the substation. This characteristic set is classified by an artificial neural network based scheme whose output results in a fault detection and location. The scheme is based on the calculation of the symmetrical components of the current signal harmonics at the relay point. Other traditional fault detection and location methodologies were also implemented, making possible to obtain comparative results. The scheme was applied in two simulated feeders. The results of this work shows that the proposed methodology is worthy of continued research objecting real time applications.
G. C. Tarnowski, R. Reginatto Regulação de Potência Ativa de Parques Eólicos com Aerogeradores de Velocidade Variável (Resumen) XVI Congresso Brasileiro de Automática (CBA), Salvador 2006
Resumen: Uma maior integração da geração eólica no sistema elétrico requer parques eólicos com regulaçãO da potência gerada. Neste trabalho propõe-se um sistema de controle da potência ativa de parques eólicos com aerogeradores de velocidade variável, com o objetivo de injetar na rede uma potência com mínimas variações. O controle proposto atinge o objetivo de regulação da potência ativa do parque sem impor prejuízos signicativos na produção total de energia, aproveitando-se da não-uniformidade dos ventos sobre as Turbinas do parque. Tal desempenho pode ser ainda melhorado usando adequadas ferramentas de previsão da potência eólica. Através desta metodologia, os riscos existentes na geração eólica são diminuídos, ampliando as possibilidades de penetração da energia eólica no sistema elétrico.
A. S. Bretas, M. Moreto, L. O. Pires, R. H. Salim Metodologia Baseada em Redes Neurais Artificiais para Detecção e Localização de Faltas de Alta Impedância em Sistemas de Distribuição com Geração Distribuída (Resumen) XVI Congresso Brasileiro de Automática (CBA), Salvador 2006
Resumen: Faltas de Alta Impedância (FAIs) são falhas de difícil detecção e localização por parte dos relés tradicionais. Neste artigo é apresentado uma nova proposta para a detecção e localização de FAIs em Sistemas de Distribuição de Energia com Geração Distribuída (GD) baseado em Redes Neurais Artificiais (RNAs). A metodologia tem como entrada as componentes de fase de tensão e corrente locais, fornecendo como saída uma detecção, classificação e localização da falta, quando da ocorrência da mesma. As características básicas, o algoritmo e testes comparativos com outras metodologias de detecção e localização de faltas são apresentados no artigo. Os resultados comparativos da técnica com esquemas de detecção e localização de faltas usuais demonstram a alta eficiência e robustez do método.
A. S. Bretas, R. H. Salim, A. D. Filomena Localização de Faltas em Sistemas de Distribuição desequilibrados com Presença de Geração Distribuída (Resumen) XVI Congresso Brasileiro de Automática (CBA), Salvador 2006
Resumen: Os métodos existentes de localização de faltas para sistemas de distribuição de energia elétrica consideram o sistema radial, ou seja, não consideram a presença de outros pontos de geração de energia elétrica na linha de distribuição. Assim, em sistemas com a presença da geração distribuída, estes métodos mostram-se ineficazes, e se faz necessário um estudo e proposição de uma nova metodologia para estimar os locais das faltas nestes sistemas. Como os sistemas de distribuição usualmente são sistemas com desequilíbrio entre as fases, esta característica deve ser considerada na metodologia de localização de falhas utilizada. Neste trabalho é apresentado um novo método de localização de faltas baseado em impedância aparente de seqüência positiva. Para a validação do mesmo, simulações computacionais foram feitas e o método foi testado e comparado com outras técnicas existentes, assim como em sistemas equilibrados e desequilibrados. As características básicas do método, o novo algoritmo e uma variedade de casos de estudo são apresentados no artigo de forma a ilustrar sua eficiência.
G. C. Tarnowski, R. Reginatto Metodologia de Operação de Geradores Eólicos com Geradores de Indução de Dupla Alimentação visando o Despacho de Potência. (Resumen) X Simpósio de Especialistas em Planejamento da Operação e Expansão Elétrica (SEPOPE), Florianópolis 2006
Resumen: O aumento da geração eólica afeta o comportamento e a operação dos sistemas de energia elétrica. Atualmente, os geradores eólicos de velocidade variável são operados de forma a funcionar com a maior eficiência aerodinâmica. Conseqüentemente, devido às flutuações da velocidade do vento, são produzidas grandes variações da potência elétrica gerada. Além disso, em um sistema elétrico com elevado índice de penetração eólica torna-se difícil a programação do despacho de potência. Neste trabalho realiza-se uma análise da operação de Aerogeradores com Geradores de Indução de Dupla Alimentação (DFIG), adotando uma estratégia de controle da potência ativa gerada com o intuito de permitir o despacho de potência. Essa estratégia de controle é focada para uma operação continua sendo a característica mais importante a possibilidade de gerar potência ativa constante dentro de uma ampla faixa de variação da velocidade do vento. Isso é possível através da implementação conjunta do controle vetorial do conversor de potência conectado ao rotor do DFIG e do controle do ângulo de passo das pás da turbina. Para a análise utilizam-se modelos apropriados dos componentes do aerogerador e da rede conectada. Utiliza-se um modelo de vento visando representar um comportamento real da velocidade. São realizadas simulações usando o software Simulink/MATLAB® sobre um sistema eólico de 2MW em condições de funcionamento normal. O método de controle usado é comparado com o método clássico de controle do Cpmax. Resultados mostram que a metodologia utilizada serve para realizar despachos de potência, mesmo com variações na velocidade do vento. Para o despacho seguro, a potência elétrica gerada deve ser menor que a potência media entregue pelo vento, sendo menor o desempenho energético. Contudo, esta estratégia de operação pode ser utilizada para planejar despachos de energia eólica, reduzindo os riscos existentes neste tipo de geração, e ampliar as possibilidades de penetração da energia eólica no sistema elétrico.
A. S. Bretas, R. H. Salim Um Novo Método de Localização de Faltas para Sistemas de Distribuição com Geração Distribuída baseado na Impedância Aparente de Sequência Positiva (Resumen) XVII Seminário Nacional de Distribuição de Energia Elétrica (SENDI), Belo Horizonte. 2006
Resumen: Os métodos existentes de localização de faltas para sistemas de distribuição de energia elétrica consi-deram o sistema radial, ou seja, não consideram a presença de outros pontos de geração de energia elétrica na linha de distribuição. Assim, em sistemas com a presença da geração distribuída, estes mé-todos mostram-se ineficazes, e se faz necessário um estudo e proposição de uma nova metodologia para estimar os locais das faltas nestes sistemas. Neste trabalho é apresentado um novo método de localização de faltas baseado na impedância aparente de seqüência positiva. Para a validação do mesmo, simulações computacionais foram feitas e o método foi testado e comparado com outras téc-nicas existentes. As características básicas do método, o novo algoritmo e uma variedade de casos de estudo são apresentados no artigo de forma a ilustrar sua eficiência.
A. S. Bretas, R. H. Salim High Impedance Fault Detection and Location in Unbalanced Distribution Feeders with Distributed Generation Using Artificial Neural Networks (Resumen) 3rd Conference on Critical Infrastructures (CRIS), Old Town Alexandria 2006
Resumen: High impedance faults (HIF) are failures with difficult detection and location in power systems. The detection and location of these faults in power distribution systems (PDS) are more difficult because of the inherent characteristics of these systems, as imbalance between phases because of different loading in laterals. The insertion of distributed generation (DG) on PDS adds another challenge to these procedures, since it contributes to the fault and changes the characteristics of the PDS. In this way, in this paper it is proposed a new fault detection and location scheme for PDS. The scheme is based in Artificial Neural Networks (ANN). Comparative test results with other standard techniques shows the high precision of the scheme.
A. S. Bretas, R. H. Salim A New Fault Location Algorithm for Distribution Feeders Considering Different Power Injection of Distributed Generators (Resumen) 3rd Conference on Critical Infrastructures (CRIS), Old Town Alexandria 2006
Resumen: Power distribution systems (PDS) are experiencing changes due to the insertion of distribution generation (DG) facilities in its boundaries. This directly affects the protection schemes of distribution feeders, occasioning problems related to the safety and reliability of these systems. Fault location techniques are specially influenced by the DG and a new methodology was studied and developed in this work in order to help distribution companies to precisely locate permanent and temporary faults in these systems.
A. S. Bretas, R. H. Salim Fault Detection and Location on Distribution Feeders with Distributed Generation Using Artificial Neural Networks (Resumen) 3rd International Conference on Cybernetics and Information Technologies, Systems and Applications (CITSA), Orlando, Florida 2006
Resumen: High Impedance Faults (HIF) are faults of difficult detection and location while using traditional digital relaying. In this article it is presented a new proposal for HIF detection and location in distribution systems with distributed generation (DG). The technique is based on artificial neural networks. The methodology inputs are the local measured voltage and current phase components, supplying as output the detection, classification and location of the fault, when it occurs. The basic characteristics, the algorithm and comparative tests with other detection and location methodologies are presented in this article. The proposed scheme was tested in a simulation platform of a distribution system with DG. The comparative results of the technique with usual fault detection and location schemes show the high efficiency and robustness of the method.
A. S. Bretas, R. H. Salim Fault Location in Distribution Feeders with Distributed Generation using Positive Sequence Apparent Impedance (Resumen) WSEAS International Conference on Energy and Environmental Systems, Chalkida, Grécia 2006
Resumen: The existing methods of fault location for distribution systems consider that the system has a radial power flow, in other words, they don't consider the presence of another generator in the distribution line. Thus, in systems with the presence of distributed generation, these methods show to be inefficient. In this paper, it is presented a new fault location method based on positive sequence apparent impedance. Computational simulations were made and the method was tested and compared with other existing fault location techniques in order to validate the method. The basic characteristics of the method, the new algorithm and a variety of case studies are presented in the paper in order to illustrate its efficiency.
A. S. Bazanella, C. L. Conceição Towards sharper Lyapunov functions for power systems 6th NOLCOS - IFAC Symposium on Nonlinear Control Systems, Stuttgart 2004
Resumen: Aqui vai o Resumen
M. Moreto, A. S. Bretas, A. S. Bazanella Diagnóstico De Faltas De Alta Impedância Em Sistemas De Distribuição Utilizando Redes Neurais Artificiais XV Congresso Brasileiro de Automática (CBA), Gramado 2004
Resumen: Aqui Vai o Resumen
L. F. Gonçalves, R. Reginatto, A. S. Bazanella Influência Da Resistência Da Linha No Estudo De Sistemas De Geração Distribuída XV Congresso Brasileiro de Automática (CBA), Gramado 2004
Resumen: Aqui vai o Resumen
L. F. Gonçalves, R. Reginatto, A. S. Bazanella Uma Plataforma Experimental Para Estudo De Sistemas De Geração Distribuída XV Congresso Brasileiro de Automática (CBA), Gramado 2004
Resumen: Aqui vai o Resumen
M. Moreto, A. S. Bretas, A. S. Bazanella Uma Metodologia Baseada em Redes Neurais Artificiais Para Localização de Faltas de Alta Impedância em Sistemas de Distribuição VIII Simpósio Brasileiro de Redes Neurais (SBRN), São Luiz 2004
Resumen: Aqui vai o Resumen
E. Spier, E. Knorr, A. S. Bazanella, F. A. B. Lemos Análise do Comportamento Dinâmico de Geração Distribuída Conectada em Sistemas de Distribuição de Energia Elétrica XVII Seminário Nacional de Produção e Transmissão de Energia Elétrica (SNPTEE), Uberlândia 2003
Resumen: Aqui vai o Resumen
A. S. Bretas, N. G. Bretas Diagnóstico de Faltas de Alta Impedância em Sistemas Elétricos de Potência utilizando Algoritmos Conexionistas XVII Seminário Nacional de Produção e Transmissão de Energia Elétrica (SNPTEE), Uberlândia 2003
Resumen: Aqui vai o Resumen
A. S. Bretas, N. G. Bretas Formação de Ilhas Elétricas Para Restauração de Sistemas Elétricos de Potência XVII Seminário Nacional de Produção e Transmissão de Energia Elétrica (SNPTEE), Uberlândia 2003
Resumen: Aqui vai o Resumen
E. Spier, F. A. B. Lemos, M. A. Rosa, A. S. Bazanella Avaliação da conexão de produtores independentes em alimentadores radiais de sistemas de distribuição VIII Simpósio de Especialistas em Planejamento da Operação e Expansão Elétrica (SEPOPE), Brasília - DF. 2002
Resumen: Aqui vai o Resumen
E. Spier, F. A. B. Lemos, A. S. Bazanella, M. A. Rosa Von Voltage Control of Distributed Generation Connected to The Distribution Grid Power Systems Computation Conference (PSCC), Sevilha 2002
Resumen: Aqui vai o Resumen
A. S. Bretas, N. Hadjsaid Fault Diagnosis in Deregulated Distribution Systems using an Artificial Neural Network (Resumen) IEEE Power Engineering Society Winter Meeting, Columbus 2001
Resumen: With the arrival of deregulation, the traditional vertically integrated power systems are faced with some challenging uncertainties. Many uncertainties concern the control, operation and protection of distribution systems in a competitive electric market especially with the introduction of deregulation. This paper presents the problems in fault diagnosis of high impedance faults (HIF) in a deregulated distribution system and a proposed solution based on artificial neural networks (ANN).