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  • 51.
    Theethayi, Nelson
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Thottappillil, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Paolone, Mario
    Department of Electrical Engineering University of Bologna.
    Nucci, Carlo Alberto
    Department of Electrical Engineering University of Bologna.
    Rachidi, Farhad
    Swiss Federal Institute of Technology.
    External Impdeance and Admittance of Buried Horizontal Wires for Transient Studies Using Transmission Line Analysis2007In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 14, no 3, p. 751-761Article in journal (Refereed)
    Abstract [en]

    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.

  • 52.
    Theethayi, Nelson
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Thottappillil, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Yirdaw, Tegegne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Liu, Yaqing
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Götschl, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Montano, Raul
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Experimental Investigation of Lightning Transients Entering a Swedish Railway Facility2007In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 22, no 1, p. 354-363Article in journal (Refereed)
    Abstract [en]

    Transients caused by lightning in railway facilities have not received much attention. In this paper, we describe the measurements of lightning transients entering a Swedish railway facility during the summer of 2003. The measurements of the transients were made in a technical house that provides an uninterrupted power supply for telecommunication systems and the signal systems. An analysis of the data has shown that transients in excess of 7 kV (peak to peak) can appear across the line-to-neutral supply system due to an indirect lightning strike. Some typical characteristics of the line-to-neutral transient voltages in terms of stroke locations and stroke amplitudes are presented. Further, from the experimental data, an empirical relation for predicting the line-to-neutral transient voltage in terms of stroke location and stroke current amplitude is obtained. Simple induced voltage calculations are presented to identify the levels of induced voltages appearing at the input of the technical house. The influence of ground conductivity on those induced voltages is also presented. The information presented in the paper is an important electromagnetic-compatibility issue associated with the lightning protection for railway systems.

  • 53.
    Thottappilli, Rajeev
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. Avdelningen för elektricitetslära och åskforskning.
    Theethayi, Nelson
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. Avdelningen för elektricitetslära och åskforskning.
    Realistic sources for modeling lightning interaction with towers2006In: First International Symposium on Lightning Physics and Effects: EU COST P18, Vienna, April 3-4, 2006, p. 36-Conference paper (Other academic)
  • 54.
    Thottappillil, Rajeev
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Theethayi, Nelson
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lightning Return Stroke Models and Electromagnetic Field Computation2007Conference paper (Refereed)
  • 55.
    Thottappillil, Rajeev
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electricity. Avdelningen för elektricitetslära och åskforskning.
    Månsson, Daniel
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electricity. Avdelningen för elektricitetslära och åskforskning.
    Theethayi, Nelson
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electricity. Avdelningen för elektricitetslära och åskforskning.
    Bäckström, Mats
    Nilssson, Tony
    Undén, Göran
    Nordström, Barbro
    Bohlin, Per
    Lindeberg, Per Anders
    Hellström, Ulf
    Lindeberg, Peter
    Bohlin, Georg
    Zitnik, Mihael
    Ekenberg, Lise
    Response of Civilian Facilities to Intentional Electromagnetic Interference (IEMI), with Emphasis on the Swedish Railway Network2005In: EMC Europe Workshop, Rome, Italy. Sept. 19-21, 2005, p. 66-68Conference paper (Other scientific)
  • 56.
    Thottappillil, Rajeev
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Rakov, Vladimir
    University of Florida.
    Theethayi, Nelson
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Expressions for far electric fields produced at an arbitrary altitude by lightning return strokes2007In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 112, no D16, p. D16102-Article in journal (Refereed)
    Abstract [en]

    Electromagnetic fields produced at high altitudes by return strokes in cloud-to-ground lightning are needed in studies of transient luminous events in the mesosphere. Such calculations require the use of a lightning return stroke model. Two of the widely used return stroke models are (1) the modified transmission line model with exponential decay (MTLE) of current with height and (2) the modified transmission line model with linear decay (MTLL) of current with height. In this paper, simplified expressions based on the MTLE and MTLL models are derived for calculating far (radiation) electric fields produced at an arbitrary elevation angle by lightning return strokes. It is shown that different (for example, containing either spatial or time integral), but equivalent equations can be derived for each of the models. Predictions of simplified expressions are compared with electric fields computed using exact expressions, including all the field components, and the validity of simplified expressions for distances that are much greater than the radiating channel length is confirmed.

  • 57.
    Thottappillil, Rajeev
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Theethayi, Nelson
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Modeling Lightning Attachment to Tall Towers2007In: Piers 2007 Beijing: Progress in Electromagnetics Research Symposium, Pts I and II, Proceedings / [ed] Kong, JA, 2007, p. 1051-1056Conference paper (Refereed)
    Abstract [en]

    Lightning return stroke resulting from the downward leader attachment to tall towers is modeled as a point current source in series with the lightning channel and tower. Assuming a quasi-transverse electromagnetic field structure, expressions for the current at the top of the tower, at the base of the tower and along the tower are presented.

  • 58.
    Thottappillil, Rajeev
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. elektricitetslära och åskforskning.
    Theethayi, Nelson
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. elektricitetslära och åskforskning.
    Realistic sources for modeling lightning attachment to towers2006In: Proceedings of International Conference of Grounding and Earthing Ground 2006 and International Conference on Lightning Physics and Effects 2nd LPE, Nov 26-29, 2006, Maceio, Brazil, paper no 4, 2006Conference paper (Refereed)
  • 59.
    Thottappillil, Rajeev
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. elektricitetslära och åskforskning.
    Theethayi, Nelson
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. elektricitetslära och åskforskning.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. elektricitetslära och åskforskning.
    Lightning Return Stroke Models and Electromagnetic Field Computation, in Tutorial on EMC aspects of Lightning2006Conference paper (Other academic)
  • 60.
    Thottappillil, Rajeev
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Theethayi, Nelson
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Hågård, T
    Sjöberg, K
    Grape, Ulf
    Security Assessment For Ringhals Nuclear Power Plant, Unit 1, With Respect To Lightning Strikes2008Conference paper (Refereed)
  • 61.
    Thottappillil, Rajeev
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Uman, M. A.
    Theethayi, Nelson
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    TEM field structure of electric and magnetic fields from a semi-infinite vertical thin-wire antenna above a conducting plane2007In: Ultra-Wideband, Short-Pulse Electromagnetics 7 / [ed] Sabath F, Mokole EL, Schenk U, Nitsch D, 2007, p. 33-40Conference paper (Refereed)
    Abstract [en]

    Investigation is carried out on the electric and magnetic field structures around a semi-infinite thin-wire antenna vertically placed above a perfectly conducting ground plane. It is shown that the electric and magnetic fields due to a time-varying point source at the bottom of the antenna have a field structure identical to that for the case of a uniform line charge and a uniform current, and have a spherical transverse electromagnetic (TEM) field structure. Simple, but exact, expressions for the electric and magnetic fields are derived, and it is shown that the general expressions for the electric and magnetic fields from time-varying sources on a thin wire semi-infinite antenna reduce to the same simple expressions if the source is assumed to be a current or charge pulse traveling at the speed of light and without attenuation. In that case, the Poynting vector indicates energy flow in the radial direction from the source at the bottom of the antenna. That is, in this ideal case the only source of radiation is the point source at the bottom of the antenna and the vertical antenna itself does not radiate. The wave impedance at all distances from this antenna is the free space impedance. Further, a general discussion on the TEM type solutions in different structures containing two perfect conductors is provided.

12 51 - 61 of 61
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  • nn-NO
  • nn-NB
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  • asciidoc
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