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The striking distance of lightning flashes and the early streamer emission (ESE) hypothesis
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära och åskforskning.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära och åskforskning.
2007 (Engelska)Ingår i: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 65, nr 5-6, s. 336-341Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The attachment of a lightning flash to a lightning conductor (or to any other structure) takes place through a connecting leader that rises from the structure towards the descending stepped leader of a lightning flash. The spatial separation between the tip of the stepped leader and the lightning conductor (or the grounded structure) at the initiation of the connecting leader is known as the striking distance. In this paper the striking distance of stepped leaders is derived as a function of conductor height, conductor radii and the prospective return stroke current. Based on these results the validity of the early streamer emission (ESE) hypothesis is discussed. According to the ESE hypothesis, the striking distance of a lightning conductor can be increased by the artificial initiation of streamers from a lightning conductor. The results cast doubt on the validity of the ESE hypothesis. This in turn calls for more experimental data and field validations before using the ESE hypothesis in standard lightning protection practice.

Ort, förlag, år, upplaga, sidor
2007. Vol. 65, nr 5-6, s. 336-341
Nyckelord [en]
Early streamer emission, Lightning, Lightning protection, Stepped leader, Striking distance
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
URN: urn:nbn:se:uu:diva-93305DOI: 10.1016/j.elstat.2006.09.006ISI: 000246039400009OAI: oai:DiVA.org:uu-93305DiVA, id: diva2:166744
Tillgänglig från: 2005-09-05 Skapad: 2005-09-05 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
Ingår i avhandling
1. Electromagnetic Interference in Distributed Outdoor Electrical Systems, with an Emphasis on Lightning Interaction with Electrified Railway Network
Öppna denna publikation i ny flik eller fönster >>Electromagnetic Interference in Distributed Outdoor Electrical Systems, with an Emphasis on Lightning Interaction with Electrified Railway Network
2005 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Alternativ titel[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.

Ort, förlag, år, upplaga, sidor
Uppsala: Institutionen för teknikvetenskaper, 2005. s. xxiv + 206
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 76
Nyckelord
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
Nationell ämneskategori
Elektroteknik och elektronik
Identifikatorer
urn:nbn:se:uu:diva-5889 (URN)91-554-6301-0 (ISBN)
Disputation
2005-09-30, Siegbahnsalen, Ångström Laboratory, Lägerhyddsvägen 1, Polacksbacken, Uppsala, 13:30
Opponent
Handledare
Tillgänglig från: 2005-09-05 Skapad: 2005-09-05 Senast uppdaterad: 2013-09-24Bibliografiskt granskad

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