G. Ratta

National University of San Juan, Ciudad de San Juan, San Juan, Argentina

Are you G. Ratta?

Claim your profile

Publications (23)18.28 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents the second part of a research work dealing with the performance assessment of commercially available magnetometers. The aim of the article is to continue a comparative study of a magnetometer set, but now using non-sinusoidal signals. Nineteen magnetometers were tested using signals with two and more frequency components; some features of the meters were investigated: fft, rms value, peak value and wave capture functions.
    Measurement. 01/2013; 46(1):747–763.
  • [Show abstract] [Hide abstract]
    ABSTRACT: This article presents and develops main aspects to be considered when harmonics have to be modeled in a power system including wind farms in its generator fleet. In particular, uncertainty involved in the analysis, because the wind speed variations, is considered and included in a more complete methodology, that is capable to compute the possibility distributions of the harmonic voltage distortion at all buses of the power system. Such a methodology, developed by the authors, is the possibilistic harmonic load-flow. Simulations to test the proposal are developed in the IEEE 14-bus standard test system for harmonic analysis, but replacing the generator at bus two, with a wind farm.
    Alternative Energies and Energy Quality (SIFAE), 2012 IEEE International Symposium on; 01/2012
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, a MATLAB model of a Digital Fourier Transform (DFT)-based digital distance relay was developed and then its behavior was analyzed when it is applied on distance protection of a real series compensated transmission system, belonging to the Chilean generation and transmission utility Colbún S.A. The complete signal processing and the impedance calculation of real relays are simulated by the model. The transmission system was modeled with ATP and various fault types at buses and diverse line locations were simulated. The DFT-model response was evaluated in each fault case from the obtained current and voltage signals. The results show how series capacitors impact negatively on the impedance calculation using DFT.
    IEEE Latin America Transactions 01/2012; 10(5):2080-2087. · 0.22 Impact Factor
  • A.A. Romero, H.C. Zini, G. Rattá
    [Show abstract] [Hide abstract]
    ABSTRACT: In a previous study by the authors, a possibilistic harmonic load flow (PHLF) approach was presented. The PHLF was capable of modelling, through possibility distributions, uncertainties regarding magnitude and composition in both linear (LL) and non-linear loads (NLL) connected at the linear (LL) and non-linear loads(PS). However, in that approach, possibility non-interaction between parameters for modelling LL and NLL was assumed. Such assumption is quite conservative and conduces to uncertainty overestimation. In fact, there are well-defined physical relationships among model parameters that constrain the variability of these. This study presents an improved approach which overcomes the aforementioned drawback by including both linear and non-linear equality constraints into the non-linear programming problem used to compute the PHLF. These linear and non-linear equality constraints are specifically used to model the balance of active and reactive power, respectively, at each bus of the PS. The equality constrains inclusion is supported from a possibility theory point of view by means of the `information fusion concept`. Influence of the possibility interaction consideration is evaluated in the IEEE 14-bus PS for harmonic analysis. Then, the complete PHLF is tested in a real 88-bus PS, and comparisons with Monte Carlo simulation results are performed and discussed.
    IET Generation Transmission & Distribution 01/2012; 6(6):528-538. · 1.41 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A computationally efficient multirate scheme was proposed to model a linear and time invariant part of an electric network for electromagnetic transient calculation. The main contribution is expected in the field of real-time calculation, where very efficient models are required to fulfil stringent time performance requirements. Two models of the equivalent sub-network based on different time steps are implemented in the low- and high-frequency channels of a basic Laplacian Pyramid unit. A detailed model based on the longest time step reproduces the low-frequency response, while a simplified (lower order) model, based on the shortest time step, reproduces the high-frequency behaviour. In this way, an accurate response of the equivalent over a wider frequency range can be achieved as compared with previous proposals based on a single low-frequency channel. Also, the proposed scheme make a much greater flexibility in choosing the decimation factor possible as compared with a previous proposal of two co-authors based on a 2-fold decimated filter banks.
    IET Generation Transmission & Distribution 01/2012; 6(8):738-750. · 1.41 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A Power Transformer is an efficient and reliable machine that is designed and built to ensure a long useful life under normal operation. However, among the total number of operative power transformers installed in networks around the world, there are many aged units, which are approaching to the state of final failure. This situation of simultaneous aging becomes a major problem, and its proper solution is critical for the electric utilities because their financial performance and economic viability are unavoidably dependent on the reliability of this equipment. In this regard, this paper presents an overview on the optimal management of a power transformer fleet. The review is focused on a methodological scheme oriented to the assessment of the transformer risk index and its two main components: the probability of failure index and the post-failure consequence index.
    Transmission and Distribution: Latin America Conference and Exposition (T&D-LA), 2012 Sixth IEEE/PES; 01/2012
  • [Show abstract] [Hide abstract]
    ABSTRACT: Harmonics in power systems are responsible for several technical problems that justify the development of models to study them. Well-established models exist to analyse the harmonic load-flow (HLF) from a deterministic point of view. Moreover, models based on the probability theory have been developed to deal with the inherent variability and random nature of loads, network configuration etc. In the last few years, possibility theory has arisen as an alternative tool that in many cases could be better suited to describe and quantify the real nature of the uncertainty involved in harmonic studies. In this study a methodology for HLF calculation based on the possibility theory is presented. Possibility distributions instead of probabilities are the input used to describe the uncertainty in the magnitude and composition of the loads. Tests presented shows that the results of the proposed model are consistent with those obtained with a probabilistic method, and that both models lead to the same ranking of the risk that the bus harmonic voltages exceed a given level. Independent possibility distributions are assumed at the development stage reported here; research is being carried out in order to overcome this constraint.
    IET Generation Transmission & Distribution 05/2011; · 1.41 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: An efficient expert system for the power transformer condition assessment is presented in this paper. Through the application of Duval’s triangle and the method of the gas ratios a first assessment of the transformer condition is obtained in the form of a dissolved gas analysis (DGA) diagnosis according IEC 60599. As a second step, a knowledge mining procedure is performed, by conducting surveys whose results are fed into a first Type-2 Fuzzy Logic System (T2-FLS), in order to initially evaluate the condition of the equipment taking only the results of dissolved gas analysis into account. The output of this first T2-FLS is used as the input of a second T2-FLS, which additionally weighs up the condition of the paper-oil system. The output of this last T2-FLS is given in terms of words easily understandable by the maintenance personnel. The proposed assessing methodology has been validated for several cases of transformers in service.
    Expert Systems with Applications 01/2011; · 1.85 Impact Factor
  • Source
    Expert Syst. Appl. 01/2011; 38:8119-8127.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This work illustrates a network equivalent multirate model based in a Laplacian Pyramid Filter bank of two channels: a low-frequency decimated channel and a high-frequency non-decimated channel. The first one is a detailed model whereas the second one is a simplified network model. The use of a Laplacian Pyramid scheme allows greater flexibility to select the decimation factors and the non-decimated channel model properly reproduces the response in the high-frequency band. Both features, contribute to overcome some limitations that former proposals, based on multirate processing, have experienced. The accuracy and the advantages of the herein proposed model are validated through simulations in a real case.
    Transmission and Distribution Conference and Exposition: Latin America (T&D-LA), 2010 IEEE/PES; 12/2010
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A novel methodology to assess the risk of power transformer failures caused by external faults, such as short-circuit, taking the paper insulation condition into account, is presented. The risk index is obtained by contrasting the insulation paper condition with the probability that the transformer withstands the short-circuit current flowing along the winding during an external fault. In order to assess the risk, this probability and the value of the degree of polymerization of the insulating paper are regarded as inputs of a type-2 fuzzy logic system (T2-FLS), which computes the fuzzy risk level. A Monte Carlo simulation has been used to find the survival function of the currents flowing through the transformer winding during a single-phase or a three-phase short-circuit. The Roy Billinton Test System and a real power system have been used to test the results.
    Electric Power Systems Research 01/2009; 79(4):539–549. · 1.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Harmonic distortion is a growing problem in power systems due to the increasing use of power electronic devices and loads. A possibilistic methodology for harmonic load-flow calculations based on fuzzy numbers has recently been proposed by the authors as an alternative to probabilistic approaches for modeling uncertainties in linear and nonlinear loads. This paper presents a methodology to aggregate uncertainly known bus loads, whose magnitudes and composition are described through fuzzy parameters, into a fuzzy admittance and injected harmonic currents of a possibilistic harmonic load-flow calculation. Interaction between fuzzy parameters (the possibilistic counterpart of probabilistic dependence) is properly modeled. A numerical example is given in the last section.
    Transmission and Distribution Conference and Exposition: Latin America, 2008 IEEE/PES; 09/2008
  • Latin American applied research Pesquisa aplicada latino americana = Investigación aplicada latinoamericana 07/2008; 38(3):205-212. · 0.32 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this work a novel algorithm to evaluate the condition of power transformers is presented. The algorithm evaluates the condition of the equipment via dissolved gas analysis. Firstly, the condition is evaluated using the gas ratio of IEC and the Triangle of Duval. Then, the vector of possible disorders is used as input of a Type-2 Fuzzy Logic System. In this way, the condition is obtained and expressed in words easy to understand by the maintenance personnel. The efficiency of the algorithm has been tested with field data obtained in the bibliography. The validity of the algorithm is shown by means of an example.
    Transmission and Distribution Conference and Exposition, 2008. T&D. IEEE/PES; 05/2008
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The present document is the continuation of part I of the state-of-the-art of the life of power transformers immersed in oil. A revision, of the correlation that exits between the degree of polymerization and the content of furans, is done. The advantages and disadvantages of the methods used to know the life of insulation from power transformer are shown and a classification of the tools used in the analysis of the life of power transformers is done.
    IEEE Latin America Transactions 01/2008; · 0.22 Impact Factor
  • C. Aguilera, E. Orduna, G. Ratta
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents a new approach that deduces the fault direction based on the traveling-wave directional principle. The algorithm by means of wavelet transforms decomposes the voltage signals and calculates the spectral energy at selected detail which allows detecting the fault and to choose the phase to make the slope change analysis. This analysis provides a clear indication of fault direction from the comparison of the slope change polarities of the voltage and current at selected phase during quite a short time. The algorithm, which belongs to the ultra-high-speed protecting relaying, is able to discriminate the direction for all kinds of faults and is not affected by the change of the fault angle inception.
    IEEE Transactions on Power Delivery 11/2007; · 1.52 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The present document is a revision of the state-of-the-art of the problem of the life of the power transformer immersed in oil. The problem of the difference between life of the isolation and life of the power transformer is reviewed, the loading guides of IEEE and IEC are analyzed and, the difference that exists between both loading guides to different values of temperature is shown.
    IEEE Latin America Transactions 04/2007; · 0.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Efficient signal processing techniques are necessary for assessing the exposure to broadband magnetic fields. The use of flat-top windows along with the DFT is a simple and fast method that reduces the characteristic leakage errors and picket fence effects when using the classical DFT for the exposure assessment. This paper proposes a new class of flat-top windows, making a trade-off between the sidelobe fall-off and the maximum sidelobe height, called fast-decaying minimum-sidelobe (FDMS) flat-top windows. Moreover, the procedure used to find the coefficients of the optimal flat-top windows is reviewed, and a new procedure is proposed in order to find the flat-top window coefficients that uses multi-objective optimization and an appropriate selection of constraints. Using this procedure, a new minimum sidelobe (MS) flat-top window with four terms is also found, having better characteristics than a previously proposed 4-term MS flat-top window. In addition, a new MS flat-top window with five terms is proposed having a maximum sidelobe level of . These windows are used to propose a method for assessing the exposure to broadband magnetic fields using flat-top windows and the DFT.
    Signal Processing 01/2007; · 1.85 Impact Factor
  • C. Aguilera, E. Orduna, G. Ratta
    [Show abstract] [Hide abstract]
    ABSTRACT: An approach to line protection that is based on fault characteristics extracted by means of wavelet transforms is presented. Analysis of the spectral energy of the phase voltage signals for different frequency bands enables faults to be detected, classified and faulted phases selected. The proposed approach points to the development of ultra-high-speed protective relaying and has been applied to a series-compensated line. The system has been simulated with MICROTRAN and the protection with MATLAB. The results show the feasibility of implementing this algorithm.
    IET Proceedings - Generation Transmission and Distribution 08/2006; · 1.41 Impact Factor
  • Source
    C. Aguilera, E. Orduna, G. Ratta
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents an adaptive noncommunication approach for line protections that are able to classify the fault as internal or external with respect to the relay protection zone for most of the faults in radial lines and for all faults in meshed networks. Basically, with a combination of the current traveling waves detected at the relay location due to fault and open switching operations with apparent impedance seen by relay, the remote breaker operation is detected and the faulted line is identified. The protection developed is selective and is not affected by power system oscillations. The system was simulated with the MICROTRAN, the results showing the feasibility of implementing this algorithm.
    IEEE Transactions on Power Delivery 08/2006; · 1.52 Impact Factor

Publication Stats

34 Citations
18.28 Total Impact Points

Institutions

  • 2001–2013
    • National University of San Juan
      • • Instituto de Energía Eléctrica (IEE)
      • • Institute of Electrical Engineering
      Ciudad de San Juan, San Juan, Argentina
  • 2007
    • Universidad de La Salle
      Μπογκοτά, Bogota D.C., Colombia