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  • 1.
    Cooray, V
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Materials Science. Department of High Voltage Research.
    Fernando, M
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences.
    Sörensen, M
    Götschl, T
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences.
    Pedersen, A
    Propagation of lightning generated transient electromagnetic fields over finitely conducting ground2000In: Journal of Atmospheric and Solar-Terrestrial Physics, Vol. 62, p. 583-600Article in journal (Refereed)
  • 2. Nag, Amitabh
    et al.
    Rakov, Vladimir A.
    Schulz, Wolfgang
    Saba, Marcelo M. F.
    Thottappillil, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Biagi, Christopher J.
    Oliveira Filho, Alcides
    Kafri, Ahmad
    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.
    Götschl, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    First versus subsequent return-stroke current and field peaks in negative cloud-to-ground lightning discharges2008In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 113, no D19, p. D19112-Article in journal (Refereed)
    Abstract [en]

    We examine relative magnitudes of electric field peaks of first and subsequent return strokes in negative cloud-to-ground lightning flashes recorded in Florida, Austria, Brazil, and Sweden. On average, the electric field peak of the first stroke is appreciably, 1.7 to 2.4 times, larger than the field peak of the subsequent stroke ( except for studies in Austria where the ratio varies from 1.0 to 2.3, depending on methodology and instrumentation). Similar results were previously reported from electric field studies in Florida, Sweden, and Sri Lanka. For comparison, directly measured peak currents for first strokes are, on average, a factor of 2.3 to 2.5 larger than those for subsequent strokes. There are some discrepancies between first versus subsequent stroke intensities reported from different studies based on data reported by lightning locating systems (LLS). The ratio of LLS-reported peak currents for first and subsequent strokes confirmed by video records is 1.7 to 2.1 in Brazil, while in the United States ( Arizona, Texas, Oklahoma, and the Great Plains) it varies from 1.1 to 1.6, depending on methodology used. The smaller ratios derived from the LLS studies are likely to be due to poor detection of relatively small subsequent strokes. The smaller values in Austria are possibly related ( at least in part) to the higher percentage ( about 50% versus 24-38% in other studies) of flashes with at least one subsequent stroke greater than the first. The effects of excluding single-stroke flashes or subsequent strokes in newly formed channels appear to be relatively small.

  • 3. Schulz, Wolfgang
    et al.
    Sindelar, S
    Kafri, Ahmad
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Götschl, Thomas
    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.
    Thottappillil, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    The Ratio Between First And Subsequent Lightning Return Stroke Electric Field Peaks In Sweden2008Conference paper (Refereed)
  • 4. Sonnadara, Upul
    et al.
    Cooray, Vernon
    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.
    Characteristics of cloud-to-ground lightning flashes over Sweden2006In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 74, no 5, p. 541-548Article in journal (Refereed)
    Abstract [en]

    A detailed study of the characteristics of cloud-to-ground (CG) lightning flashes over Sweden was carried out for the period 1987-2000 using data obtained from the Swedish lightning-locating network. Results are presented by analysing over half a million lightning ground flashes. The average variation of the annual mean of the total number of flashes was found to be 37%. About 12% of the CG flashes were positive flashes and their average variation about the annual mean was 26%. The average peak currents were fairly constant over the years with variations as little as 4% for negative flashes and 5% for positive flashes. The average peak current values for negative and positive flashes were -29.90 and +63.97 kA respectively. A correlation between the mean monthly flash count and percentage of positive flashes was seen. A similar relationship is seen with the mean monthly flash count and the peak currents for both polarities. In general, high flash density and high peak currents were observed in the southern part of Sweden where most of the major cities are located. Flash densities exceeding 0.4 flashes km(-2) were observed for several large cities. The maximum flash rate of 32 flashes h(-1) within a 10 km radius was seen in Jonkoping (14.18 degrees E, 57.78 degrees N) in the province of Smaland.

  • 5. Sonnadara, Upul
    et al.
    Kathriarachchi, Vindu
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Montano, Raul
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Götschl, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Performance of lightning locating systems in extracting lightning flash characteristics2014In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 112, p. 31-37Article in journal (Refereed)
    Abstract [en]

    A study was carried out to compare the negative cloud to ground lightning discharges recorded using Swedish lightning locating system against time correlated direct field measurements. Only the first 200 ms time window was investigated. A total of 167 flashes were recorded and time matched against the lightning locating system records. The comparison shows that for negative cloud-to-ground lightning flashes, the stroke detection efficiency of lightning locating system is at 93% for detecting the first stroke accurately. The efficiency drops to about 77% in detecting all strokes accurately. Thus, the system tends to give a low value for average multiplicity and a significantly higher value for parameters such as percentage of single stroke flashes. In agreement with the direct field measurements, when the individual strokes are identified correctly, both systems show the expected 2:1 ratio between the first and subsequent stroke peak field. Data also shows that the LLS system has a tendency of identifying isolated cloud pulses as positive return strokes. Hence one must take into account the systematic deficiency in lightning locating systems when reporting characteristics of cloud to ground lightning flashes.

  • 6.
    Strömstedt, Erland
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Savin, Andrej
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Heino, Hanna
    Antbrams, Kasimir
    Haikonen, Kalle
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Götschl, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Project WESA (Wave Energy for a Sustainable Archipelago) - a Single Heaving Buoy Wave Energy Converter Operating and Surviving Ice Interaction in the Baltic Sea2013Conference paper (Refereed)
  • 7.
    Theethayi, Nelson
    et al.
    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.
    Thottappillil, Rajeev
    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.
    Montaño, Raul
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Lindeberg, P. A.
    Hellström, U.
    Measurements of Lightning Transients Entering a Swedish Railway Facility2004In: Proceedings of 27th International Conference on Lightning Protection, 2004Conference paper (Other academic)
  • 8.
    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.

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