1,721,383 research outputs found
Indirect-lightning performance of distribution lines: Influence of protection devices
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 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. ©2006 IEEE.SCI-STI-FRDESLDepartment of Electrical Engineering, University of Bologna, 40136 Bologna, Italy EMC Group, Power Systems Laboratory, Swiss Federal Institute of Technology (EPFL), Lausanne, 1015, Switzerland, Conference code: 69732, Export Date: 25 April 2012, Source: Scopus, Art. No.: 1668536, doi: 10.1109/TDC.2006.1668536, Language of Original Document: English, Correspondence Address: Borghetti, A.; Department of Electrical Engineering, University of Bologna, 40136 Bologna, Italy, References: Rusck, S., (1977) Protection of distribution systems, Lightning, 2. , Ed. R.H. Golde, New York: Academic Press, Chapter 23; Pettersson, P., A unified probabilistic theory of the incidence of direct and indirect lightning strikes (1991) IEEE Trans. on PWRD, 6 (3), pp. 1301-1310. , July; Chowdhuri, P., Estimation of flashover rates of overhead power distribution lines by lighting strokes to nearby ground (1989) IEEE Trans. on PWRD, 4 (3), pp. 1982-1988. , July; Jankov, V., Grzybowski, S., Flashover rates of overhead distribution lines caused by nearby lightning strokes (1997) Proc. of the 10th International Symposium on high Voltage Engineering (ISH'97), , Montréal, Canada, August 25-29; Hermosillo, V.F., Cooray, V., Calculation of fault rates of overhead power distribution lines due to lightning-induced voltages including the effect of ground conductivity (1995) IEEE Trans. on EMC, 37 (3), pp. 392-399. , August; Nucci, C.A., Rachidi, F., Ianoz, M.V., Mazzetti, C., Lightning-induced voltages on overhead lines (1993) IEEE Trans. on EMC, 35 (1), pp. 75-86. , Feb; Rachidi, F., Nucci, C.A., Ianoz, M.V., Mazzetti, C., Influence of a lossy ground on lightning-induced voltages on overhead lines (1996) IEEE Trans. on EMC, 38 (3), pp. 250-263. , August; Rachidi, F., Nucci, C.A., Ianoz, M., Mazzetti, C., Response of multiconductor power lines to nearby lightning return stroke electromagnetic fields (1997) IEEE Trans. on Power Delivery, 12 -3, pp. 1404-1411; Borghetti, A., Nucci, C.A., Estimation of the frequency distribution of lightning-induced voltages on an overhead line above a lossy ground: A sensitivity analysis (1998) Proc. International Conference on Lightning Protection, , Birmingham, UK, September; Borghetti, A., Nucci, C.A., Paolone, M., Bernardi, M., Effect of the lateral distance expression and of the presence of shielding wires on the evaluation of the number of lightning-induced voltages (2000) Proc. of the 25th International Conference on Lightning Protection, A, pp. 340-345. , 18-22 Sept, Rhodes Greece; Borghetti, A., Nucci, C.A., Paolone, M., Lightning performances of distribution lines: Sensitivity to computational methods and to data (2001) Power Engineering Society Winter Meeting, 2, pp. 796-798. , IEEE; Borghetti, A., Celli, G., Paolone, M., Pilo, F., Effects of Line Grounding Electrodes Modeling on the Evaluation of Lightning-Induced Overvoltages in Overhead Power Distribution Lines (2003) Proc. of the 2003 IEEE Bologna Power Tech Conference, , Bologna, Italy, 24-26 June; Paolone, M., Nucci, C.A., Petrache, E., Rachidi, F., Mitigation of Lightning-Induced Overvoltages in Medium Voltage Distribution Lines by Means of Periodical Grounding of Shielding Wires and of Surge Arresters: Modelling and Experimental Validation (2004) IEEE Trans. on PWRD, 19 -1, pp. 423-431. , Jan, pp; M. Paolone, Modeling of lightning-induced voltages on distribution networks for the solution of power quality problems, and relevant implementation in a transient program, Ph.D. dissert., University of Bologna, Department of Electrical Engineering, March 2002Agrawal, A.K., Price, H.J., Gurbaxani, S.H., Transient response of a multiconductor transmission line excited by a nonuniform electromagnetic field (1980) IEEE Trans. on EMC, 22 (2), pp. 119-129. , May; Paolone, M., Nucci, C.A., Rachidi, F., A New Finite Difference Time Domain Scheme for the Evaluation of Lightning Induced Overvoltage on Multiconductor Overhead Lines (2001) Proc. of the International Conference, on Power System Transient, 2, pp. 596-602. , 24-28 June, Rio de Janeiro, Brasil; Rusck, S., Induced lightning overvoltages on power transmission lines with special reference to the overvoltage protection of low voltage networks (1958) Transactions of the Royal Institute of Technology, (120). , Stockholm; Borghetti, A., Nucci, C.A., Paolone, M., Bernardi, M., Malgarotti, S., Mastandrea, I., Influence of surge arresters on the statistical evaluation of lightning performance of distribution lines (2004) 2004 International Conference on Probabilistic Methods Applied to Power Systems, pp. 776-781. , 12-16 Sept; Nucci, C.A., Bardazzi, V., Iorio, R., Mansoldo, A., Porrino, A., A code for the calculation of lightning-induced overvoltages and its interface with the Electromagnetic Transient program (1994) Proc. 22nd International Conference on Lightning Protection, Budapest, 19-23, , September; Borghetti, A., Gutierrez, J.A., Nucci, C.A., Paolone, M., Petrache, E., Rachidi, F., Lightning-induced voltages on complex distribution systems: Models, advanced software tools and experimental validation (2004) Journal of Electrostatics, 60 (2-4), pp. 163-174. , March; IEEE guide for improving the lightning performance of electric power overhead distribution lines, IEEE Std 1410-2004 (Revision of IEEE Std 1410-1997), 2004Anderson, R.B., Eriksson, A.J., Lightning parameters for engineering application (1980) Electra, (69); Borghetti, A., Nucci, C.A., Paolone, M., Effect of tall instrumented towers on the statistical distributions of lightning current parameters and its influence on the power system lightning performance assessment (2003) European Transactions on Electrical Power, 13 (6), pp. 365-372. , November/December; Modeling guidelines for fast front transients (1996) IEEE Trans. on PWRD, 11 (1), pp. 493-506. , IEEE Fast Front Transients Task Force, Ja
Mitigation of Lightning-Induced Overvoltages in Medium Voltage Distribution Lines by Means of Periodical Grounding of Shielding Wires and of Surge Arresters: Modeling and Experimental Validation
In this paper, we investigate the effect of periodically-grounded shielding wires and surge arresters on the attenuation of lightning-induced voltages. We discuss the adequacy of the commonly made simplification of assuming the shielding wire at ground potential, instead of being treated as one of the conductors of the multiconductor system. We also compare then the mitigation effect of shielding wires with that achievable by the insertion of surge arresters along the line. The computation results are first validated by means of calculations obtained by other authors referring to a simple line configuration, and then by means of experimental results obtained using a reduced-scale line model illuminated by a nuclear electromagnetic pulse (NEMP) simulator. One of the main conclusions is that the effectiveness of shielding wires and surge arresters depends mostly on the spacing between two adjacent grounding points or surge arresters
Interaction between grounding systems and nearby lightning for the calculation of overvoltages in overhead distribution lines
The aim of the paper is to analyze overvoltages in overhead distribution lines induced by nearby lightning return stroke currents taking into account also the conductive coupling between the lightning current injected into the soil and the line's grounding system. Experimental results obtained in 2003 at the International Center for Lightning Research and Testing (ICLRT) in Florida have shown that significant currents were coupled with an overhead experimental line through its grounding system by nearby rocket-triggered lightning. The paper first proposes a conductive coupling model between the lightning current injected into the soil and the nearby line grounding system, then presents the incorporation of such a model into the LIOV-EMTP computer code. The paper finally presents an experimental validation of the proposed models by making reference to results obtained during the above-mentioned triggered-lightning campaign. © 2011 IEEE.DESLDepartment of Electrical Engineering, University of Bologna, Bologna, Italy Swiss Federal Institute of Technology of Lausanne, Switzerland University of Florida, Gainesville, FL, United States EnerNex Corporation, Knoxville, TN 37922, United StatesConference code: 86744Export Date: 25 April 2012Source: ScopusArt. No.: 6019438doi: 10.1109/PTC.2011.6019438Language of Original Document: EnglishCorrespondence Address: Napolitano, F.; Department of Electrical Engineering, University of Bologna, Bologna, Italy; email: [email protected]: Brown, R.E., (2009) Electric Power Distribution Reliability, , CRC Press, Boca Raton, FL; (2010) Guide for Improving the Lightning Performance of Electric Power Overhead Distribution Lines, , IEEE Working Group on the lightning performance of distribution lines, IEEE Std. 1410; (2006) Protection of MV and LV Networks Against Lightning. Part I: Common Topics, , Joint Cigré-Cired WG C4.4.02, Cigré technical brochure, Nr. 287, February; Agrawal, A.K., Price, H.J., Gurbaxani, S.H., Transient response of a multiconductor transmission line excited by a nonuniform electromagnetic field (1980) IEEE Trans. on EMC, 22 (2), pp. 119-129. , May; Yokoyama, S., Yamamoto, K., Kinoshita, H., Analogue simulation of lightning induced voltages and its application for analysis of overhead-ground-wire effects (1985) IEE Proceedings C: Generation Transmission and Distribution, 132 (4), pp. 208-216; Yokoyama, S., DISTRIBUTION SURGE ARRESTER BEHAVIOR DUE TO LIGHTNING INDUCED VOLTAGES (1986) IEEE Transactions on Power Delivery, PWRD-1 (1), pp. 171-178; Short, T.A., Ammon, R.H., Monitoring results of the effectiveness of surge arrester spacings on distribution line protection (1999) IEEE Trans. PWRD, 14 (3), pp. 1142-1150. , Jul; Nucci, C., Rachidi, F., Interaction of electromagnetic fields generated by lightning with overhead electrical networks (2003) The Lightning Flash, pp. 425-478. , V. Cooray, IEE Press, London, UK; Paolone, M., Nucci, C.A., Petrache, E., Rachidi, F., Mitigation of lightning-induced overvoltages in medium voltage distribution lines by means of periodical grounding of shielding wires and of surge arresters: Modelling and experimental validation (2004) IEEE Trans. PWRD, 19 (1), pp. 423-431. , Jan; Borghetti, A., Morched, A.S., Napolitano, F., Nucci, C.A., Paolone, M., Lightning-induced overvoltages transferred through distribution power transformers (2005) IEEE Trans. PWRD, 24 (1), pp. 360-372. , Jan; Schoene, J., Uman, M.A., Rakov, V.A., Jerauld, J., Rambo, K.J., Jordan, D.M., Schnetzer, G.H., Rachidi, F., Lightning Currents Flowing in the Soil and Entering a Test Power Distribution Line Via Its Grounding (2009) IEEE Trans. on PWRD, 24 (3), pp. 1095-2009; Rakov, V.A., Uman, M.A., Rambo, K.J., Fernandez, M.I., Fisher, R.J., Schnetzer, G.H., Thottappillil, R., Clergeries, A.B., New insights into lightning processes gained from triggered-lightning experiments in Florida and Alabama (1998) J. Geophys. Res., 103, pp. 14117-14130; Rakov, V.A., Lightning discharges triggered using rocket-and-wire techniques (1999) Recent Res. Devel. Geophys., 2, pp. 141-171; Rakov, V.A., Uman, M.A., Wang, D., Rambo, K.J., Crawford, D.E., Schnetzer, G.H., Lightning properties from triggered-lightning experiments at Camp Blanding, Florida (1997-1999) Proc. 25 th Int. Conf. Lightning Prot. (ICLP), Rhodes, Greece, 2000, pp. 54-59; Borghetti, A., Gutierrez, J.A., Nucci, C.A., Paolone, M., Petrache, E., Rachidi, F., Lightning-induced voltages on complex distribution systems: Models, advanced software tools and experimental validation (2004) Journal of Electrostatics, 60 (2-4), pp. 163-174. , Elsevier; Napolitano, F., Borghetti, A., Nucci, C.A., Paolone, M., Rachidi, F., Mahseredjian, J., An Advanced Interface between the LIOV Code and the EMTP-RV Proc. 29 th Int. Conf. on Lightning Protection, Uppsala, Sweden, June 23-26, 2008; Shoory, A., Rachidi, F., Rubinstein, M., Thottappillil, R., On the Measurement and Calculation of Horizontal Electric Fields from Lightning (2011) IEEE Trans. EMC, , in press; Tagg, G.F., (1964) Earth Resistances, , GeorgeNewns, London; Sunde, E.D., (1968) Earth Conduction Effects in Transmission Systems, , New York, Dover Publications Inc; Rudenberg, R., (1968) Electrical Shock Waves in Power System, , Cambridge, MA: Harvard University Press; Bourg, S., Sacepe, B., Debu, T., Deep earth electrodes in highly resistive ground: Frequency behavior IEEE Int. Symp. Electromagnetic Compatibility, 1995, pp. 584-589; Grcev, L., Popov, M., On high-frequency circuit equivalents of a vertical ground rod (2005) IEEE Transactions on Power Delivery, 20 (2 II), pp. 1598-1603. , DOI 10.1109/TPWRD.2004.838460; Mata, C., (2003) Interaction of Lightning with Power Distribution Lines, , (Ph.D. Thesis), University of Florida, Gainesville, FL, USA; Nucci, C.A., Rachidi, F., Ianoz, M., Mazzetti, C., Lightning-induced voltages on overhead lines (1993) IEEE Trans. on EMC, 35 (1), pp. 75-86. , Feb; Rachidi, F., Nucci, C.A., Ianoz, M., Mazzetti, C., Influence of a lossy ground on lightning-induced voltages on overhead lines (1996) IEEE Transactions on Electromagnetic Compatibility, 38 (3), pp. 250-264. , PII S0018937596062953; Mahseredjian, J., Lefebvre, S., Do, X.-D., A new method for timedomain modelling of nonlinear circuits in large linear networks Proc. of the 11 th Power Systems Computation Conference (PSCC), Avignon, France, Aug. 1993; Mahseredjian, J., Dennetière, S., Dubé, L., Khodabakhchian, B., Gérin-Lajoie, L., On a new approach for the simulation of transients in power systems (2007) Electric Power Systems Research, 77 (11), pp. 1514-1520. , Sept; Mahseredjian, J., Simulation des Transitoires Électromagnétiques Dans Les Réseaux Électriques, , Édition 'Les Techniques de l'Ingénieur', Dossier n° D4130, Réseaux électriques et applications; Paolone, M., Rachidi, F., Borghetti, A., Nucci, C.A., Rubinstein, M., Rakov, V.A., Uman, M.A., Lightning electromagnetic field coupling to overhead lines: Theory, numerical simulations, and experimental validation (2009) IEEE Trans. EMC, 51 (3), pp. 532-547. , Aug; Paolone, M., Petrache, E., Rachidi, F., Nucci, C.A., Rakov, V., Uman, M., Jordan, D., Schoene, J., Lightning- Induced Disturbances in Buried Cables Part II: Experiment and Model Validation (2005) IEEE Tr. on EMC, 47 (3), pp. 509-520. , Aug; Heidler, F., Analytische blitzstromfunktion zur LEMP-berechnung Proc. 18 th Int. Conf. on Lightning Protection, Munich (ICLP), Germany, Sep. 1985, pp. 63-66Sponsors: IEEE; IEEE Power and Energy Society (PES
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Using Electromagnetic Time Reversal Similarity Metric to Locate Lightning-Originated Flashovers on Overhead Transmission Lines
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