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Electric and magnetic fields from a semi-infinite antenna above a conducting plane
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
2004 (English)In: Journal of Electrostatics, ISSN 0304-3886, Vol. 61, no 3-4, 209-221 p.Article in journal (Refereed) Published
Abstract [en]

The electric and magnetic field structures around a semi-infinite thin-wire antenna vertically placed above a perfectly conducting ground plane are investigated when the antenna is supporting two different types of sources. It is shown that when the wire is carrying a uniform line charge, the electrostatic potentials are equal on the surfaces of imaginary cones of fixed cone angles with axis along the wire and apex at the conducting plane. The electrostatic field vectors are shown to be perpendicular to the imaginary cones and tangential to the meridian lines of half-spherical shells centered at the base of the line charge. The vertical components of the electrostatic field on the surface of these imaginary half-spherical shells of a given radius are constant, except at the wire itself. The magnetic field structure associated with a constant current in the semi-infinite antenna is that of an infinite wire. The electric and magnetic fields due to a time-varying charge or current pulse propagating with the speed of light along the vertical thin-wire antenna have a spherical transverse electromagnetic (TEM) field structure, identical to that for the case of a uniform line charge and a uniform current. The connection between the static and dynamic solutions is derived mathematically using two different approaches.

Place, publisher, year, edition, pages
2004. Vol. 61, no 3-4, 209-221 p.
Keyword [en]
pulse propagation, lightning return stroke, vertical thin-wire antenna, spherical transverse electromagnetic field
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-93297DOI: 10.1016/j.elstat.2004.02.008OAI: oai:DiVA.org:uu-93297DiVA: diva2:166736
Available from: 2005-09-05 Created: 2005-09-05 Last updated: 2013-09-24Bibliographically approved
In thesis
1. Electromagnetic Interference in Distributed Outdoor Electrical Systems, with an Emphasis on Lightning Interaction with Electrified Railway Network
Open this publication in new window or tab >>Electromagnetic Interference in Distributed Outdoor Electrical Systems, with an Emphasis on Lightning Interaction with Electrified Railway Network
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Elektromagnetisk interferens i distribuerade elektriska system för utomhusbruk, med fokus på växelverkan mellan blixtnedslag och elektrifierad järnväg
Abstract [en]

This thesis deals with the electromagnetic compatibility (EMC) problems of distributed electrical networks, especially that caused by lightning to electrified railway. Lightning transients were found to damage important devices that control train movements, causing traffic stoppage and delays. This thesis attempts to develop computational models for identification of parameters influencing the coupling phenomena between those devices and lightning. Some supporting experimental investigations are also carried out. This thesis forms the groundwork on the subject of lightning interaction with the electrified railway networks.

Lightning induces transient overvoltages in railway conductor systems such as tracks, overhead wires, and underground cables, either due to direct lightning strike to the system or due to the coupling of electromagnetic fields from remote strikes. Models based on multiconductor transmission line theory were developed for calculating the induced voltages and currents. A transmission line return stroke model, that can predict the remote electromagnetic fields comparable to experimental observations, is also developed.

Earlier works on modeling earth return impedances for transient studies in power distribution systems are not readily applicable for railways for lightning transients, in cases of low earth conductivities found in Sweden and for large variation in conductor heights. For the wires above ground, the ground impedance models were modified for wide range of frequencies, soil conductivities and wide spread of conductor heights. Influences of pole insulator flashovers, pole-footing soil ionizations and interconnections between the conductors on the lightning surge propagation are studied. Wave propagation in buried shielded and unshielded cables with ground return is studied. Simplified, valid and computationally efficient ground impedance expressions for buried and on-ground wires are proposed. A model for the coupling phenomena (transfer impedance) through multiple cable shields with multiconductor core is also proposed. Besides, experimental studies on lightning induced transients entering a railway technical house, failure modes of relay and rectifier units used in the train position/signaling applications for lightning transients are performed. A high frequency circuit model for the booster transformer for lightning interaction studies is developed. The simulation models are being converted to user-friendly software for the practicing engineers of the railway industry.

Place, publisher, year, edition, pages
Uppsala: Institutionen för teknikvetenskaper, 2005. xxiv + 206 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 76
Keyword
Electrical engineering, Electromagnetic Compatibility (EMC), Lightning, Lightning Protection, Transmission Lines, Electromagnetic Wave Propagation, Underground Cables, Grounding, Electromagnetic Transients, Electromagnetic Interference, Shielding Effectiveness, Railway Systems, Elektroteknik, elektronik och fotonik
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-5889 (URN)91-554-6301-0 (ISBN)
Public defence
2005-09-30, Siegbahnsalen, Ångström Laboratory, Lägerhyddsvägen 1, Polacksbacken, Uppsala, 13:30
Opponent
Supervisors
Available from: 2005-09-05 Created: 2005-09-05 Last updated: 2013-09-24Bibliographically approved

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