M. Paolone

École Polytechnique Fédérale de Lausanne, Lausanne, Vaud, Switzerland

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Publications (142)57.08 Total impact

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    ABSTRACT: The paper deals with the correlation between lightning and distribution networks faults and/or voltage dips. In particular, the paper presents an application of a method proposed by the authors to correlate lightning events and relays operations based on the integrated use of: (i) data obtained from the Italian lightning location system (CESI-SIRF), (ii) data relevant to the Italian monitoring system of relay operation (CESI-SAM) and (Hi) calculation results obtained by means of an advanced simulation tool for the accurate estimation of lightning- induced voltages on complex power networks (LIOV-EMTP). The correlation algorithm is able to take into account the uncertainty levels associated with the stroke location and peak current estimates provided by lightning location systems. The results obtained by means of LIOV-EMTP are shown to be of fundamental importance to achieve the appropriate estimation of the correlation of interest. A plus of the proposed algorithm is that it can make use, mostly during its validation/tuning phase, also of measured lightning-induced overvoltage waveforms recorded by means of a distributed monitoring system of voltage transients, which has been installed in a portion of the Italian distribution network.
    Power Tech, 2007 IEEE Lausanne; 08/2007
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    ABSTRACT: The aim of this paper is to present the results of the performance study of medium voltage overhead distribution lines against lightning discharges, in the way to define methodologies to reduce the system failures. The results are obtained within the partnership among the High Voltage Laboratory of the Federal University of Itajuba, AES Sul Utility Company and the University of Bologna. The resultant performance is presented in terms of expected faults for 100 km of line for a density of discharges to the ground (GDF) of 1 discharge/km<sup>2</sup>/year. Commentaries on the relative performance and comparisons of different construction configurations of overhead lines are presented.
    Power Tech, 2007 IEEE Lausanne; 08/2007
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    ABSTRACT: The paper investigates the applicability of some closed form expressions for the ground impedance and ground admittance of buried horizontal wires (bare and insulated) for lightning or switching transient analyses based on transmission line (TL) theory. In view of the frequency contents that typically characterize such transients, the behavior of the ground impedance and admittance is studied for a wide frequency range up to 10 MHz. Low frequency approximation of the ground impedance is not always appropriate for transient analysis. Sensitivity analyses show that, unlike overhead wires, the ground impedance for buried wires is little sensitive to the ground conductivity. On the other hand, the ground admittance varies strongly with the ground conductivity. The paper also discusses the results of transient analysis of buried cables performed by means of electromagnetic transient programs (EMTP) that neglect the ground admittance. The limits of such an approximation are discussed in order to evaluate the applicability of EMTP-like programs to the transient analysis of buried conductors. Transient pulse propagation in time domain based on finite difference time domain (FDTD) method of solution of TL equations is also discussed for a future inclusion of non-linear phenomena, like soil ionization and arcing/breakdown mechanisms, in the soil. The analysis presented could be useful in estimating surge propagation characteristics of buried wires for appropriate insulation coordination and transient protection.
    IEEE Transactions on Dielectrics and Electrical Insulation 07/2007; · 1.36 Impact Factor
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    ABSTRACT: The paper describes a test set-up, based on the use of a digital signal processor (DSP), developed for the evaluation of the operational characteristics of an autonomous auxiliary power unit (APU). The considered APU includes a 4.8 kW commercial proton exchange membrane (PEM) fuel cell and a set of electrochemical batteries. Both power sources are connected to a common AC bus through power electronic converters. The DSP-based test set-up is also conceived so to incorporate the basic functions of the APU energy management system. The paper also presents some experimental results, with particular reference to the assessment of the PEM fuel cell performances.
    Clean Electrical Power, 2007. ICCEP '07. International Conference on; 06/2007
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    ABSTRACT: The paper deals with a microgrid test facility, settled at the CESI RICERCA laboratories, equipped with various distributed energy resources (DERs) and connected to a LV network. The operation of such a microgrid is supervised by a central automatic microgrid management system (MMS). The paper first reports and discusses some experimental results carried out for the assessment of DERs performance and for the implementation of specific MMS functions. Then, it describes the functions of the energy resources scheduler (ERS) implemented in the MMS. The scheduler periodically updates the set points of DERs regulators in order to achieve economic, reliability and power quality objectives, starting form the load and renewable production forecasts and from the results of the system state estimation. The ERS is composed by two main parts, namely: a day-ahead economic scheduler of active power set points during the following day for the minimization of the overall costs, and an intra-day scheduler that every 15 minutes settles the set points of the DERs regulators to optimize the voltage profile at the grid buses, taking into account both technical constraints and the day-ahead economic schedules.
    Clean Electrical Power, 2007. ICCEP '07. International Conference on; 06/2007
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    ABSTRACT: The aim of this paper is to present the results of the performance study of medium voltage overhead distribution lines against lightning discharges, in the way to define methodologies to reduce the system failures. The results are obtained within the partnership among the High Voltage Laboratory of the Federal University of Itajubá, AES Sul Utility Company and the University of Bologna. Direct discharges and induced surges were simulated into real networks to identify the major factor of influence for network failures. Then commentaries on the relative performance and comparisons of different construction configurations of overhead lines are presented.
    04/2007;
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    ABSTRACT: This paper deals with scale models of power distribution systems for the study of lightning induced voltages on overhead lines. The scale model technique is useful for the investigation of situations which are prohibitively complex to be treated theoretically. For instance, urban distribution networks are usually characterized not only by complex topologies but also by the presence of nearby buildings, whose influence on the lightning induced effects can be successfully evaluated by means of reduced models. The paper first describes the scale model implemented for such a purpose at the University of Sao Paulo, Sao Paulo, Brazil. It then presents a comparison between the experimental data obtained with the scale model and the computer simulations obtained by using the LIOV-EMTP code, a software tool able of calculating lightning-induced electromagnetic transients in distribution systems having complex configurations. Finally, the paper shows an application of the scale model in the evaluation of lightning induced voltages on distribution networks considering the presence of nearby buildings
    IEEE Transactions on Power Delivery 02/2007; · 1.52 Impact Factor
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    ABSTRACT: This paper deals with the assessment of the lightning performance of distribution lines, namely the estimation of the annual number of lightning-induced flashovers versus the critical flashover voltage of the line insulators. The procedure proposed by the authors is compared with the one described in IEEE Std. 1410-2004 Guide for improving the lightning performance of electric power overhead distribution lines. The two methods differ: 1) for the models adopted to evaluate the induced voltages and 2) for the adopted statistical approach. The reasons for differences in the results predicted by the two methods are discussed and the parameters playing the major role in the achievement of the results are identified. The proposed method represents an improvement compared to IEEE Std. 1410 because it takes into account more realistic line configurations and the effect of the finite ground conductivity
    IEEE Transactions on Power Delivery 02/2007; · 1.52 Impact Factor
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    ABSTRACT: We discuss in this paper the influence of the presence of an elevated strike object on the peak of the lightning return stroke current determined from remote field measurements. We develop analytical expressions relating the lightning return stroke channel-base current and the far electromagnetic field for different specific cases, namely, (1) ground-initiated return strokes (classical transmission line (TL) model), (2) ground-initiated return strokes including possible reflections at ground level, (3) tall strike objects for which the current's zero-to-peak time is smaller than the travel time along the object, and (4) electrically short strike objects. It is shown that for tall structures, the field enhancement relative to a return stroke initiated at ground level is expressed through a factor equal to ktall=[1+c/v(1-2ρt)]/(1-ρt), where v and c are the return stroke front speed and the speed of light in vacuum, respectively, and ρt is the top reflection coefficient. For very short towers and/or very slow return stroke current wavefronts, when the condition tf⪢h/c applies, expressions relating the far electromagnetic field and the return stroke current were also derived. For case (2), return strokes initiated at ground level, the field enhancement relative to a return stroke initiated at ground level, case (1), is expressed through a factor equal to kshort=(1+(c/v)ρch–g)/(1+ρch–g), where ρch–g represents the reflection coefficient between the lightning channel and the grounding impedance.
    Journal of Electrostatics. 01/2007;
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    ABSTRACT: The aim of this paper is to present an experimental validation of a frequency-domain approach to the solution of the lightning electromagnetic field-to-buried cable coupling equations. The coupling to the inner conductor is evaluated using the concept of cable transfer impedance. The theoretical model and relevant computer code are tested using experimental data on lightning-induced currents in buried cables carried out in 2002 and 2003 at the International Center for Lightning Research & Testing (ICLRT) at Camp Blanding, Florida where currents induced by triggered lightning events were measured at the ends of a buried coaxial cable, both in the shield and in the inner cable conductors. Reasonably good agreement has been found between numerical simulations and recorded waveforms. In particular, the early-time response of the cable and the peak value of the induced currents were generally well reproduced by the simulations.
    Journal of Electrostatics. 01/2007;
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    ABSTRACT: Methods aimed at locating the position where a fault is occurred can be seen as part of a complex measurement system oriented at more general power quality purposes. This paper faces the comparison between two methods recently proposed in literature for fault-location in distribution networks, based on a distributed and on a single-ended measurement system, respectively. By assuming a common distribution system topology, the two methods are applied in order to compare their performances as well as the obtained results. On the basis of the different drawbacks and advantages shown by the two methods, potential improvements are eventually taken into account, and a possible integration of the two approaches is investigated and discussed.
    01/2007; XIII.
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    ABSTRACT: The paper deals with the subject of the source-identification of transient voltage disturbances in distribution system buses. In particular, a statistical procedure is proposed for the evaluation of the probability that a lightning flash detected by a lightning location system (LLS) could cause a fault and, therefore, relay interventions, generally associated with voltage dips. The proposed procedure is based on the coordinated use of the information provided by the LLS and the availability of an advanced simulation tool for the accurate simulation of lightning-induced voltages on complex power systems, namely the LIOV-EMTP code. The uncertainty levels of the stroke location and of the peak current estimations provided by the LLS are discussed and their influence on the lightning-fault correlation is analyzed
    Probabilistic Methods Applied to Power Systems, 2006. PMAPS 2006. International Conference on; 07/2006
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    ABSTRACT: For an improved assessment of the indirect-lightning performances of distribution systems, the real configuration of the system, which means the topology, the presence of protection devices such as surge arresters and shielding wire/neutral groundings, must be taken into account. In this paper, the indirect lightning performance of a distribution line with realistic configuration is evaluated by means of a statistical procedure based on the Monte Carlo method. Accurate models are used to evaluate the lightning induced overvoltages, in order to estimate the effects of arresters spacing and characteristics. Results relevant to a line length of 100 km, as it is often presented in the power/lightning literature, appear to be not as useful as those relevant to the real system of interest
    Transmission and Distribution Conference and Exhibition, 2005/2006 IEEE PES; 06/2006
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    Journal of Fuel Cell Science and Technology - J FUEL CELL SCI TECHNOL. 01/2006; 3(4).
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    ABSTRACT: The paper illustrates a procedure based on the continuous-wavelet transform (CWT) for the analysis of voltage transients due to line faults, and discusses its application to fault location in power distribution systems. The analysis carried out shows that correlation exists between typical frequencies of the CWT-transformed signals and specific paths in the network covered by the traveling waves originated by the fault. The paper presents a procedure for determining fault location in MV distribution systems, which exploits the above-mentioned correlation. The MV distribution system analysed in the paper is accurately represented by means of an EMTP model; various fault types and network characteristics are examined. The paper presents also the basic concepts of a measurement and fault location prototype system with distributed architecture.
    International Journal of Electrical Power & Energy Systems. 01/2006;
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    ABSTRACT: In this paper, we present a review of theoretical methods to compute lightning induced currents and voltages on buried cables. The evaluation of such induced disturbances requires the calculation of the electric field produced by lightning along the cable path. We show that the Cooray's simplified formula is capable of predicting accurately the horizontal electric field penetrating the ground, at distances as close as 100 m. Regarding the parameters of the buried cable, a comparison of several approximations of the ground impedance is presented. We show that the Pollaczek expression corresponds to the Sunde general expression, when the displacement current is neglected. The analysis shows also that all the proposed approximations provide very similar results for the considered range of frequencies (up to 30 MHz). Most of the approximate formulas neglect the contribution of the displacement current and, therefore, predict values for the ground impedance which tend to infinity at higher frequencies. This corresponds in the time domain to a singularity of the ground transient resistance at t=0. By analogy to the Sunde approximation for the ground impedance of overhead lines, we propose a logarithmic approximation for the ground impedance of a buried cable. In addition, unlike most of the considered approximations, the proposed formula has an asymptotic behavior at high frequencies; therefore, the corresponding transient ground resistance in the time domain has no singularity at t=0. It is also demonstrated that within the frequency range of interest, the wire impedance can be neglected, due to its small contribution to the overall longitudinal impedance of the line. The ground admittance, however, can play an important role at high frequencies (1 MHz or so) especially in the case of poor ground conductivity. The ground admittance needs to be taken into account in the calculation of lightning induced currents and voltages on buried cables. This is in contrast with the case of overhead lines in which its contribution is generally negligible, even in the MHz range. We also investigate the time-domain representation of field-to-transmission line coupling equations. The coupling model includes the effect of ground admittance which appears in terms of an addi- tional convolution integral. An analytical expression for the ground transient resistance in the time domain is also proposed which is shown to be sufficiently accurate and nonsingular. Finally, we present a time domain solution of field-to-buried cable coupling equations using the point-centered finite difference time domain (FDTD) method, and a frequency domain solution using Green's functions. In our companion paper (Part II), we compare both solutions to experimental waveforms obtained using triggered lightning.
    IEEE Transactions on Electromagnetic Compatibility 09/2005; · 1.33 Impact Factor
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    ABSTRACT: This paper presents experimental results obtained at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida during the summers of 2002 and 2003. Currents induced by triggered and natural lightning events were measured at the terminations of a buried power cable, in the cable shield, and in the inner cable conductor. Measurements of the horizontal component of the magnetic field above the ground surface for both natural and triggered lightning are also presented. For distant natural lightning events, locations of ground strike points were determined using the U.S. National Lightning Detection Network (NLDN). Based on the theoretical developments presented in Part I of this paper , the field-to-buried cable coupling equations are solved in both the time domain and in the frequency domain. The obtained experimental results are then used to validate the numerical simulations provided by the relevant developed codes.
    IEEE Transactions on Electromagnetic Compatibility 09/2005; · 1.33 Impact Factor

Publication Stats

710 Citations
57.08 Total Impact Points

Institutions

  • 2005–2014
    • École Polytechnique Fédérale de Lausanne
      Lausanne, Vaud, Switzerland
  • 2009
    • Arak University
      Solţānābād, Markazi, Iran
  • 2000–2009
    • University of Bologna
      • "Guglielmo Marconi" Department of Electrical, Electronic and Information Engineering DEI
      Bologna, Emilia-Romagna, Italy
  • 2007
    • Uppsala University
      • Department of Engineering Sciences
      Uppsala, Uppsala, Sweden
    • University of São Paulo
      San Paulo, São Paulo, Brazil
    • Università degli Studi di Palermo
      Palermo, Sicily, Italy
  • 2005–2007
    • University of Toronto
      • Department of Electrical and Computer Engineering
      Toronto, Ontario, Canada
  • 2006
    • CESI
      Milano, Lombardy, Italy
  • 2004
    • University of Guadalajara
      Guadalajara, Jalisco, Mexico