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  • 251. M.A.R.M, Fernando
    et al.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lightning surges at distribution transformer secondary2010Conference paper (Refereed)
  • 252.
    Mohd Esa, Mona Riza
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Ahmad, Mohd Riduan
    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.
    Occurrence of Narrow Bipolar Pulses between Negative Return Strokes in Tropical Thunderstorms2014Conference paper (Refereed)
  • 253.
    Mohd Esa, Mona Riza
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Ahmad, Mohd Riduan
    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.
    Time-Frequency Profile of Discharge Processes Prior to the First Return Stroke2014In: 2014 INTERNATIONAL CONFERENCE ON LIGHTNING PROTECTION (ICLP), IEEE conference proceedings, 2014, p. 1134-1137Conference paper (Refereed)
    Abstract [en]

    We aim to investigate the time-frequency profile for sets of lightning processes that occurred prior to the first return stroke which include narrow bipolar pulses, preliminary breakdown pulses and stepped leaders. The work is mainly using the wavelet transformation in order to gain the frequency spectrum while not losing the time information of the located pulses. 2 sets of events that include the narrow bipolar pulse (NBP) followed by preliminary breakdown pulses (PBPs), stepped leaders (SLs) and the first return stroke (RS) are used in this paper. All selected data are recorded during northeastern monsoon season at the end of year 2012 in Malaysia. Parameters that used in this works includes the (1) upper and (2) lower frequency spectrum for both spectral and spread regions and (3) power spectrum. In average, the upper and lower frequency spectrum for NBP is at least 10 times higher when compare to the first return stroke. It is also found that the NBP radiates predominantly between 61 kHz and 168 kHz which much higher than the first return stroke with range from 2 kHz to 12 kHz. PBP pulses radiate intensely within 65 kHz to 1 MHz, whereas SL pulses radiate predominantly between 163 kHz and 455 kHz. In terms of power spectrum, PBP pulses tend to produce higher magnitude of power spectrum in the earlier stage and decreased towards the end of its process. In the contrary, SL pulses' power spectrum magnitudes are lower in the beginning and tend to increase when approaching to the first return stroke.

  • 254.
    Mohd Esa, Mona Riza
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Ahmad, Mohd RiduanUppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.Cooray, VernonUppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Wavelet Analysis of the First Pulse of Initial Breakdown Process in Lightning Discharges2013Conference proceedings (editor) (Refereed)
  • 255.
    Mohd Esa, Mona Riza
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Ahmad, Mohd Riduan
    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.
    Wavelet Profile of Initial Breakdown Process Accompanied by Narrow Bipolar Pulses2014In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824Article in journal (Refereed)
  • 256.
    Mohd Esa, Mona Riza
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Ahmad, Mohd Riduan
    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.
    Ahmad, Noor Azlinda
    Universiti Teknologi Malaysia.
    Signatures of Narrow Bipolar Pulses as Part of Cloud-to-Ground Flashes in Tropical Thunderstorms2014In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824Article in journal (Refereed)
  • 257.
    Montano, Raul
    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.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    An Efficient Implementation of the Agrawal et al. Model for Lightning-Induced Voltage Calculations Using Circuit Simulation Software2008In: IEEE Transactions on Circuits and Systems Part I: Regular Papers, ISSN 1549-8328, Vol. 55, no 9, p. 2959-2965Article in journal (Refereed)
    Abstract [en]

    One of the popular, simple, and accurate field-to-wire coupling models for studying transmission-line lightning interaction is the Agrawal et al model [1]. In this model, the coupling mechanisms are represented by distributed sources along the line, wherein each distributed source is due to the horizontal component of the illuminating electric field at that point on the line. These sources give rise to the propagating scattered voltage along the line, while the total voltage at any instant at a given point along the line is the sum of scattered voltage and the voltage at that point due to the illuminating vertical component of the electric field. There is a difficulty in applying the Agrawal et al. model with the built-in transmission-line models of various circuit simulation software such as the Alternate Transients Program-Electromagnetic Transients Program [2]-[5], PSpice [6], Simpow [7], PSS/E [71, etc., as the voltage source due to the horizontal component of the electric field in the Agrawal el al. model is in series with the line impedance [1], [8] and not in between two transmission-line segments. In this paper, a simple circuit approach for efficient implementation of the Agrawal et al. model using any circuit simulation software that has built-in transmission-line models is proposed.

  • 258.
    Montaño, Raul
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Becerra, Marley
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Rahman, Mahbubur
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Liyanage, Prasanna
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Resistance Of Spark Channels2006In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 34, no 5, p. 1610-1619Article in journal (Refereed)
    Abstract [en]

    A study undertaken to measure the resistance of spark channels in air with two different current waveforms is presented. In one experiment, the spark was created by a Marx generator. In this case, the gap length was maintained at 12.8 cm, and the current flowing through the spark had a peak current lying in the range of 0.2-2.2 kA. The decay time of the current was larger than 100 mus. In the other experiment, the spark was created by a current generator. In that experiment, the gap length was maintained at 1 cm, and the current flowing through the spark had peak-current amplitudes in the range of 35-48 kA. The decay time of the current was larger than 500 mus. The results show that the resistance of spark channels initially decreases, reaches a minimum value, and then recovers as the current in the spark gap decreases. The minimum resistance of the spark channel decreases with an increasing peak current. The results are compared with various theories that attempt to predict the temporal variation of the resistance of spark channels. The comparison shows that further developments in the existing theoretical models are needed in order to reproduce with better accuracy the dynamic behavior of the channel resistance

  • 259.
    Montaño, Raul
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Penetration of lightning induced transient from high voltage to low voltage power system across distribution transformers2004In: Proceeding of the 27th International Conference on Lightning Protection, 2004Conference paper (Refereed)
  • 260.
    Montaño, Raul
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Edirisinghe, Mahesh
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Roman, Francisco
    Behavior of low-voltage surge protective devices under high-current derivative impulses2007In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 22, no 4, p. 2185-2190Article in journal (Refereed)
    Abstract [en]

    It has been observed by scientists that maximum rate of change of current with respect to time of subsequent return strokes could be as high as 150 kA/mu s. This fact is not reflected in the present day testing of surge protecting devices (SPDs). Usually, they are tested with 8/20 mu s current impulses the time derivative of which are considerably less than the time derivatives of subsequent-return stroke current pulses. When SPDs are subjected to current impulses with a high-current derivative, the voltage yields on their terminals will be highly influenced by the inductance of the lead connections. Therefore, a high di/dt impulse current can produce a voltage across the SPDs terminals that can exceed the threshold level of the protected equipment, causing partial or permanent damage in their insulation. In this study, the behavior of few selected surge protective components for fast current transients is analyzed and compared with standard 8/20 mu S current impulses. The experiment was performed on disk type varistors and ceramic type gas discharge tubes (GDT). The result show that, the clamping voltages due to fast transients for tested component is considerably greater than the ones observed with standard 8/20 mu S current impulses.

  • 261.
    Montaño, Raul
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Edirisinghe, Mahesh
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Roman, Francisco
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Varistor models: a comparison between theory and practice2004In: Proceeding of the 27th International Conference on Lightning Protection, 2004Conference paper (Refereed)
  • 262.
    Montaño, Raul
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Edirisinghe, Mahesh
    Fernando, Mahendra
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Transient response of DC Converter station subjected to LIOV2005In: Proceeding of the VIII International Symposium on Lightning Protection, 2005Conference paper (Refereed)
  • 263. Mäkelä, J. S.
    et al.
    Edirisinghe, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Fernando, M.
    Montaño, Raul
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    HF radiation emitted by chaotic leader processes2007In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 69, no 6, p. 707-720Article in journal (Refereed)
    Abstract [en]

    This paper presents direct measurements of narrowband 10 MHz HF radiation from so-called "chaotic leaders" associated with subsequent return strokes. Although the term is controversial and poorly defined, we find that more than 30% of subsequent strokes in close lightning flashes contain electric field characteristics that are best described as "chaotic". In earlier studies, return strokes have consistently been observed to be the strongest sources of HF radiation, but the results for leader processes are less consistent. We also observe return strokes to be the main HF emitter, and the leaders before the first return stroke in a flash sequence also emit HF though somewhat less intensely. The leaders preceding subsequent strokes typically emit little or no HF radiation, whether they are dart or dart-stepped leaders. However, it was observed that the presence of a chaotic component increases the leader HF intensity dramatically Defining the HF intensity unequivocally can be problematic for processes like chaotic leaders which have a combination of continuous and impulsive phenomena. Two time-domain methods were used to measure the HF intensity, the peak energy and the RMS energy. In the frequency domain these correspond to the energy spectral density (ESD) and power spectral density (PSD), respectively. It was found that the methods are not necessarily compatible. Thus, it is suggested that to clarify future work, leader processes should be characterized by the PSD rather than the ESD.

  • 264. Mäkelä, J. S
    et al.
    Porjo, N.
    Jantunen, J.
    Tuomi, Tapio
    Mäkelä, A.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Hämäläine, A
    Ahola, T
    Using ratio between breakdown and return stroke intensity for narrowband flash distance estimation2008Conference paper (Refereed)
  • 265. Mäkelä, Jakke S.
    et al.
    Porjo, Niko
    Jantunen, Joni
    Ahola, Tom
    Mäkelä, Antti
    Tuomi, Tapio
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Single-station narrowband ranging of active storm cells without lightning-type discrimination2009In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 71, no 8-9, p. 911-922Article in journal (Refereed)
    Abstract [en]

    We present a statistical technique for ranging the edges of active storms cell using a very simple narrowband receiver tuned to 1 MHz (the MW band in radio, just below HF frequencies). We show that a principle based on the "30-30 rule" can be used to define practical warning levels. From the measurements carried out in Finland, we show that the narrowband source intensities of cloud-to-ground lightning vary log-normally; this results in a ranging uncertainty of about 20%, which can be reduced if a suitable floating average is used. Based on one storm, we suggest that the differences between intra-cloud and ground-to-cloud signals at 1 MHz are small enough to make an IC-CG discrimination. Eliminating such a discrimination allows all lightning impulses to be used in the range and improves the accuracy, since more flashes are then available as inputs into the distance-estimation algorithm. Although the system is only validated against a single storm, we provide definitions by which this and other narrowband detectors could be independently verified; existing narrowband devices have not been verified in this manner, due in part to a lack of such standardized definitions.

  • 266. Mäkelä, Jakke S.
    et al.
    Porjo, Niko
    Mäkelä, Antti
    Tuomi, Tapio
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Properties of preliminary breakdown processes in Scandinavian lightning2008In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 70, no 16, p. 2041-2052Article in journal (Refereed)
    Abstract [en]

    Lightning flashes are usually preceded by preliminary breakdown processes (PBPs) before a stepped leader is initiated. These breakdown processes are not well understood. An early model, the so-called BIL model, has been called into question in later studies. However, we have found that the BIL model is quite successful in describing initial processes at least in high-latitude Scandinavian lightning. We present results from one summer of measurements in Finland, during which the vertical electric field was measured with a standard broadband plate antenna system. Lightning flash locations were provided by a lightning detection network and magnetic fields were measured with an experimental narrowband detection system. The relationship between the preliminary breakdown and the first return stroke (RS) is studied for 193 flashes at distances of 5-70 km. We can identify a preliminary breakdown in at least 90% of the flashes. The peak electric field of the RS is on average four times as intensive as the highest peak of the PBP. However, in 25% of the cases the PBP peak is more intensive. On the other hand, we show that this method of comparing intensities is physically arbitrary, since the PBP is continuous and the RS is impulsive. The narrowband measurement allows a physically consistent definition for intensities as the root-mean-square (RMS) sum of the most intense parts of signals. The PBP and RS are shown to have almost equal intensities at small distances. At larger distances, the PBP weakens more rapidly. This is suggested to be due to different propagation regimes, with the PBP signal changing from space-wave to ground-wave propagation with increasing distance, while the RS is predominantly ground wave at all distances. The result may have practical applications in narrowband detection of lightning. The BIL model suggests a characteristic signal in the narrowband signal, which could be used to identify the start of a lightning flash. The change in the RS-PBP ratio as a function of distance is statistically significant, but is too weak to significantly improve ranging methods.

  • 267. Mäkelä, J.S
    et al.
    Porjo, N
    Mäkelä, A
    Tuomi, Tapio
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Evidence against naturally occurring bipolar lightning flashes2008Conference paper (Refereed)
  • 268.
    Nanayakkara, Sankha
    et al.
    Univ Colombo, Dept Phys, Atmospher Phys & Lightning Res Grp, Colombo, Sri Lanka.
    Fernando, Mahendra
    Univ Colombo, Dept Phys, Atmospher Phys & Lightning Res Grp, Colombo, Sri Lanka.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Features of K-Changes Observed in Sri Lanka in the Tropics2019In: Atmosphere, ISSN 2073-4433, E-ISSN 2073-4433, Vol. 10, no 3, article id 141Article in journal (Refereed)
    Abstract [en]

    General characteristics of K-changes, including their duration and probability of occurrence associated with ground flashes in Sri Lanka in the tropics, together with their fine structure, are presented. In 98 ground flashes where the small step changes associated with K-changes are clearly visible, there were about two K-changes per flash on average. The mean K-change time duration observed in this study is 0.38 ms. In 53 of the ground flashes, there were 120 consecutive K-changes. In these cases, the geometric mean of the time interval between K-changes was 12 ms. Analysis of the fine structure of the K-changes reveals the K-changes are always associated with either a chaotic pulse train or a combination of chaotic and regular pulse trains. The results suggest that the small step-like static electric fields identified in the literature as K-changes are the step-like static fields associated with the processes that generate chaotic or a combination of chaotic and regular pulse trains. Thus, at larger distances where the static fields are negligible, K-changes may appear as a chaotic pulse train or a combination of chaotic and regular pulse trains.

  • 269. Nanayakkara, Sankha
    et al.
    Vayanganie, S. P. A.
    Gunasekera, T. A. L. N.
    Fernando, M.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    K - change: Is it a static field of a chaotic pulse burst?2014In: 2014 INTERNATIONAL CONFERENCE ON LIGHTNING PROTECTION (ICLP), 2014, p. 634-642Conference paper (Refereed)
    Abstract [en]

    Electric field changes associated with K - changes have been studied since 1956. In this study, the electric field variations of K changes observed in the tropics, in Sri Lanka, was analyzed to study the inter K change duration, K change duration, and possible contribution from other activities on K changes. Selected 144 k-changes of 64 lightning flashes, measured with 6.4 ns sampling rate were used for the analysis. The inter K change time interval was found to vary from 0.62 ms to 75.92 ms with an average of 16.92 ms. The duration of K-changes were found to vary from 0.44 ms to 1.65 ms with an average value of 0.48 ms. In this study, it was observed that all K - changes were combined with chaotic pulse trains (CPT). This suggests that the K - changes may be a result of slow electric field changes associated with chaotic pulse activities.

  • 270.
    Ong, J. Y.
    et al.
    Univ Tekn Malaysia Melaka UTeM, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Durian Tunggal 76100, Melaka, Malaysia.
    Ahmad, M. R.
    Univ Tekn Malaysia Melaka UTeM, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Durian Tunggal 76100, Melaka, Malaysia.
    Periannan, D.
    Univ Tekn Malaysia Melaka UTeM, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Durian Tunggal 76100, Melaka, Malaysia.
    Sabri, M. H. M.
    Univ Tekn Malaysia Melaka UTeM, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Durian Tunggal 76100, Melaka, Malaysia.
    Seah, B. Y.
    Univ Tekn Malaysia Melaka UTeM, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Durian Tunggal 76100, Melaka, Malaysia.
    Aziz, M. Z. A. A.
    Univ Tekn Malaysia Melaka UTeM, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Durian Tunggal 76100, Melaka, Malaysia.
    Ismail, M. M.
    Univ Tekn Malaysia Melaka UTeM, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Durian Tunggal 76100, Melaka, Malaysia.
    Esa, M. R. M.
    Univ Teknol Malaysia, FKE, Inst High Voltage & High Current IVAT, Johor Baharu 81310, Johor, Malaysia.
    Mohammad, S. A.
    Univ Teknol Malaysia, FKE, Inst High Voltage & High Current IVAT, Johor Baharu 81310, Johor, Malaysia.
    Abdul-Malek, Z.
    Univ Teknol Malaysia, FKE, Inst High Voltage & High Current IVAT, Johor Baharu 81310, Johor, Malaysia.
    Yusop, N.
    Univ Kebangsaan Malaysia, Inst Climate Change, Space Sci Ctr ANGKASA, Bangi 43600, Selangor Darul, Malaysia.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lu, G.
    Chinese Acad Sci, Inst Atmospher Phys, Key Lab Middle Atmosphere & Global Environm Obser, Beijing, Peoples R China.
    Performance Analysis of Stacked Capacitive Antenna for Lightning Remote Sensing2018In: 2018 INTERNATIONAL CONFERENCE ON ELECTRICAL ENGINEERING AND COMPUTER SCIENCE (ICECOS), IEEE , 2018, p. 305-308Conference paper (Refereed)
    Abstract [en]

    Antennas are the important elements in the lightning detection system. To improve performance of the lightning detection system, it is so necessary to improve the efficiency of the antennas. There are two types of antennas used in the system which are capacitive antenna for electric field sensing and loop antenna for magnetic field sensing Pi. Both of these antennas arc big in size and causing inconvenient during set up. Thus, small and portable antennas are designed. It is so important to remain or improve the sensitivity of the antennas even though it is small in size. Stacking method is used in capacitive antenna by increase copper plate layer in between the parallel plate antenna. After prototype the multi stacked capacitive antenna, performance analysis is carried out. Performances of the antennas are compared using CST simulation and hardware set up. Multi-stacked capacitive antenna is compared with the single plate antenna and found that the performance of the antenna increases as the stacked number increases.

  • 271. Peer, J
    et al.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Gerald
    Kendl, A.
    Erratum and addendum to “Transcranial stimulability of phosphenes by long lightning electromagnetic pulses” [Phys. Lett. A 374 (2010) 2932]2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 374, no 47, p. 4797-4799Article in journal (Refereed)
    Abstract [en]

    The comparison of electric fields transcranially induced by lightning discharges and by TMS brain stimulators via (E) over right arrow = -partial derivative(t)(A) over right arrow is shown to be inappropriate. Corrected results with respect to evaluation of phosphene stimulability are presented. For average lightning parameters the correct induced electric fields appear more than an order of magnitude smaller. For typical ranges of stronger than average lightning currents, electric fields above the threshold for cortical phosphene stimulation can be induced only for short distances (order of meters), or in medium distances (order of 50 m) only for pulses shorter than established axon excitation periods. Stimulation of retinal phosphene perception has much lower threshold and appears most probable for lightning electromagnetic fields.

  • 272. Perera, C.
    et al.
    Fernando,, M.
    Liyanage,, P.
    Rahman,, Mahbubur
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Correlation between current and channel diameter of long laboratory sparks2008In: 29th International Conference on Lightning Protection, ICLP-2008, Uppsala, Sweden, June 23-26, 2008Conference paper (Refereed)
  • 273. Perera, C.
    et al.
    Fernando, M.
    Rahman, Mahbubur
    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.
    Leader propagation speed and the final jump distance of 8 m long laboratory sparks2013In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 71, no 3, p. 568-571Article in journal (Refereed)
    Abstract [en]

    Vertical profile of the leader in long laboratory sparks was analyzed using high speed video photographs. Sparks were generated in an 8 m gap of sphere - plane electrodes with positive impulse voltage of 250/2500 mu s wave form. The spatial resolution of the high speed frame camera was 19.6 mm per pixel with a time resolution of 50 mu s. It was found that the average final jump distance of five sparks was about 4 m and the average electric field in the final jump region is about 5 x 10(5) V/m the leader speed varies from 1.3 x 10(4) m/s to 3.1 x 10(4) m/s as it propagates toward the ground. The average leader speed of the leader was in the order of 1.8 x 10(4) m/s. The observations show that there is a significant increase in the leader speed just before the final jump.

  • 274. Perera, C.
    et al.
    Rahman, Mahbubur
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Fernando, M.
    Liyanage, P.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    The relationship between current and channel diameter of 30 cm long laboratory sparks2012In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 70, no 6, p. 512-516Article in journal (Refereed)
    Abstract [en]

    In this study the dependence of channel diameter of 30 cm long sparks on discharge current is analyzed using a photographic technique. The results show the radial channel intensity variation follows a Gaussian distribution. The channel diameter (D), defined as the width of the intensity profile at 10% level, increases with the increasing peak current (I-p) up to 3 kA. The relationship between the two parameters can be represented by the equation, D = 8.36 ln(I-p) + 1.598, where D is in mm and I-p is in kA. The experimental results agree reasonably well with the available theory.

  • 275. Perera, Chandana
    et al.
    Fernando, Mahendra
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Analysis of Channel Tortuosity using 8 m Long Laboratory Sparks2018Conference paper (Refereed)
  • 276. Perera, Chandana
    et al.
    Fernando, Mahendra
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Liyanage, Prasanna
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Unusual slow development of cloud-to-air discharges observed in Sri Lanka in the tropic2008Conference paper (Refereed)
  • 277. Perera, Chandana
    et al.
    Fernando, Mahendra
    Vayanganie, S. P. A.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Continuing Currents and Luminosity of Cloud Flashes2014In: 2014 INTERNATIONAL CONFERENCE ON LIGHTNING PROTECTION (ICLP), IEEE conference proceedings, 2014, p. 1587-1593Conference paper (Refereed)
    Abstract [en]

    In this study, continuing currents and luminosity of cloud flashes were investigated using time resolve photographic technique. In ground flashes, the flow of current after the end of the return stroke is called the continuing currents. Typical cloud flashes have two stages called early stage (or active stage) and final or late stage. The continuing current and luminosities reported in this paper are observed in late stage of the cloud flashes. In ground flashes the shortest reported duration of continuing current is longer than the 3 ms. For the first time in literature the continuing currents in cloud flashes were studied. No major difference between the time duration of continuing currents of ground flashes and long current variation of cloud flashes were observed.

  • 278. Perera, Chandana
    et al.
    Vayanganie, S.P.A
    Fernando, Mahendra
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Continuing Currents in Cloud Flashes2014Conference paper (Refereed)
  • 279.
    Rahman, M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, V.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    NOx Production in Laser -Induced Plasma as a Function of Dissipated Energy2003In: EOS Trans. AGU, 84(46), Fall Meet. Suppl., Abstract AE32A-0158, 2003, San Francisco, USA, 2003Conference paper (Other academic)
  • 280.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    A study of NOx production in air heated by laser discharges: Effect of energy, wavelength, multiple discharges and pressure2008In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 40, no 1, p. 208-214Article in journal (Refereed)
    Abstract [en]

    An experimental study on the production of NOX in air heated under the action of a concentrated laser beam is presented. In this experiment laser induced plasma was produced in air in a closed Teflon chamber of inner volume 1600 cm3 by focusing a laser beam with either the wavelength of 1064 or 532 nm from a Q-switched Nd:YAG laser. The NOX production was measured by chemiluminescence method and the possible effect of wavelengths, multiple discharges, and pressure on the yield of NOX was studied. The results show that within the studied plasma energy range of 26-253 mJ for 532 nm beam and 16-610 mJ for 1064 nm beam, the NOX production scales linearly with the dissipated plasma energy. For a given energy, 532 nm beam produces more NOX in air at atmospheric pressure than the 1064 nm beam. In an attempt to see the possible influence of multiple discharges on the production of NOX, discharges were created using 2-8 pulses with a repetition rate of 10 pulses per second in stationary air at atmospheric pressure. The results indicate that a certain amount of the NOX created by a given pulse is destroyed by the subsequent pulses. In order to study the pressure dependence of the NOX production, the pressure was varied from 16 to 100 kPa in the chamber and it was found that the NOX production efficiency scales linearly with pressure.

  • 281.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    NOx Generation in Laser-produced Plasma as a Function of Dissipated Energy2002In: 26th International Conference on Lightning Protection, ICLP2002, Cracow, Poland, September 2-6, Vol. 2, p767-770, 2002, Vol. 2, p. 767-770Conference paper (Refereed)
  • 282.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    NOx generation in laser-produced plasma in air as a function of dissipated energy2003In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 35, p. 543-546Article in journal (Refereed)
  • 283.
    Rahman, Mahbubur
    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.
    The propagation speed of low pressure discharge with special attention to blue jets and sprites2012In: 16th Asian Conference on Electrical Discharge, 10-12 December 2012, The Zon, Johor Bahru, Malaysia, 2012Conference paper (Refereed)
  • 284.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Ahmad, Noor Azlinda
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Nyberg, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Nuclear Physics.
    Rakov, V. A.
    Sharma, Sriram
    X rays from 80-cm long sparks in air2008In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 35, no 6, p. L06805-Article in journal (Refereed)
  • 285.
    Rahman, Mahbubur
    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.
    Montano, Raul
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Liyanage, Prasanna
    Atmospheric Physics and Lightning research group, Dept of Physics, University of Colombo, Sri Lanka.
    Becerra, Marley
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    NO(X) production by impulse sparks in air2011In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 69, no 6, p. 494-500Article in journal (Refereed)
    Abstract [en]

    An experimental study on the production of NO(X) by impulse sparks in air is presented. The emphasis is placed on the dependence of the NO(X) yield on the signature of the discharge current waveforms. A voltage and two current impulses were used in the experiments to create a spark and the NO(X) production was measured by the method of chemiluminescence. The results show that, for a given current waveform, the NO(X) production varies linearly with the peak current and the gap length. In addition, it was found that the NO(X) yield increases with the duration of the current for a given peak current.

  • 286.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Montaño, Raùl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Liyanage, Prasanna
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Becerra, Marley
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    NOx production in laboratory discharges2008Conference paper (Refereed)
  • 287.
    Rahman, Mahbubur
    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.
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Tandem Laboratory.
    Efficiencies for production of nitrogen oxides by proton impact in air2013In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 94, p. 1-4Article in journal (Refereed)
    Abstract [en]

    We present present the first laboratory measurements of nitrogen oxides generated by proton impact in air. Experiments were conducted at the Tandem Laboratory of Uppsala University. A proton beam with known current and energy was injected into an air tight ionising chamber for a fixed time duration and the resulting nitrogen oxides were measured by the method of chemiluminescence. The data are presented in terms of number of produced NOX (NO+NO2) molecules for different proton energy, proton beam current and duration. The efficiency for NOX production by proton impact in air can on average be estimated to about 0.2 NOX molecules per ion-pair based on 1 cm diameter proton beam with energies from 2 to 4 MeV and varied currents from 0.1 to 10 nA. 

  • 288.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Ion Physics.
    Nyberg, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Nuclear and Particle Physics.
    An experimental quantification of the NOx production efficiency of energetic alpha particles in air2006In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 68, no 11, p. 1215-1218Article in journal (Refereed)
  • 289.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Rakov, V. A.
    X-ray Production in Laboratory Sparks in air2007Conference paper (Other academic)
  • 290.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Rakov, V.A.
    Uman, M.A.
    Liyanage, P
    deCarlo, B.A.
    Jerauld, J
    Rob III, R.C.
    Direct measurement of NOx produced by lightning2006In: EOS Trans. AGU, 87(52), Fall Meet. Suupl., Abstract AE53A-0289, 2006, San Francisco, USA, 2006Conference paper (Other academic)
  • 291.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Rakov, V.A.
    Uman, M.A.
    Liyanage, Prasanna
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    DeCarlo, B.A.
    Jerauld, J.
    Olsen III, R.C.
    Measurements of NOx produced by rocket-triggered lightning2007In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 34, no 3, p. L03816-Article in journal (Refereed)
    Abstract [en]

    We present the first direct measurements of NOx generated by specific lightning sources. In July 2005, three negative lightning flashes were triggered using the rocket-and-wire technique at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida. The NOx produced by these three rocket-triggered flashes was measured. The NOx production per unit charge was between 2 and 3 · 1020 molecules per meter per coulomb. The data show that the NOx production is primarily from long-duration, steady currents, as opposed to microsecondscale impulsive return stroke currents. This observation implies that cloud discharges, which transfer, via a steady current of the order of 100 A, larger charges than ground discharges, but do not contain return strokes, are as efficient as (or more efficient than) cloud-to-ground discharges in producing NOx.

     

  • 292.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Hettiarachchi, Pasan
    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.
    Dwyer, Joseph
    Rakov, Vladimir
    Rassoul, Hamid
    Observations of X-rays from Laboratory Sparks in Air at Atmospheric Pressure under Negative Switching Impulse Voltages2019In: Atmosphere, ISSN 2073-4433, E-ISSN 2073-4433, Vol. 10, no 4, article id 169Article in journal (Refereed)
    Abstract [en]

    We present observations of X-rays from laboratory sparks created in the air at atmospheric pressure by applying an impulse voltage with long (250 µs) rise-time. X-ray production in 35 and 46 cm gaps for three different electrode configurations was studied. The results demonstrate, for the first time, the production of X-rays in gaps subjected to switching impulses. The low rate of rise of the voltage in switching impulses does not significantly reduce the production of X-rays. Additionally, the timing of the X-ray occurrence suggests the possibility that the mechanism of X-ray production by sparks is related to the collision of streamers of opposite polarity.

  • 293. Rajakaruna, Manoj
    et al.
    Nanayakkara, Sankha
    Sapumange, Nilantha
    Chandimal, Lasantha
    Fernando, Mahendra
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    The behavior of earthing impedance and step-potential for surge currents2018Conference paper (Refereed)
  • 294.
    Raysaha, Rosy Balaram
    et al.
    High Voltage Laboratory, Dept of Electrical Engineering, Indian Institute fo Science, Bengaluru, Indien.
    Kumar, Udaya
    High Voltage Laboratory, Dept of Electrical Engineering, Indian Institute fo Science, Bengaluru, Indien.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Analysis for the Reflected Waves Transmitted on to the Channel by Tall Grounded Objects Using a Special Case2012In: IEEE transactions on electromagnetic compatibility (Print), ISSN 0018-9375, E-ISSN 1558-187X, Vol. 54, no 2, p. 262-271Article in journal (Refereed)
    Abstract [en]

    During lightning strike to a tall grounded object (TGO), reflected current waves from TGO are transmitted on to the channel. With regard to these transmitted waves, there seems to be some uncertainties like: 1) will they get reflected at the main wavefront; and 2) if so, what would be their final status. This study makes an attempt to address these issues considering a special case of strike to a TGO involving equal channel core and TGO radii. A macroscopic physical model for the lightning return stroke is adopted for the intended work. Analysis showed that the waves transmitted on to the channel merges with the main wavefront without any sign of reflection. Investigation revealed that: 1) the nonlinear spatio-temporal resistance profile of the channel at the wavefront is mainly responsible for the same; and 2) the distributed source provides additional support. The earlier findings are not limited to the special case of TGO considered. In spite of considering equal TGO and channel core radii, salient features of the model predicted remote electromagnetic fields agree well with the measured data reported in literature.

  • 295. Raysaha, Rosy
    et al.
    Kumar, Udaya
    Cooray, Vernon
    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.
    Special case of lightning strike to tall objects on ground2010In: 30TH International Conference on Lightning Protection, ICLP, Cagliary, Italy, 2010Conference paper (Refereed)
  • 296. Romero, Fabio
    et al.
    Piantini, Alexandre
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    On the Influence of Stroke Current Propagation Velocity on Lightning Horizontal Electric Fields2014In: IEEE transactions on electromagnetic compatibility (Print), ISSN 0018-9375, E-ISSN 1558-187X, Vol. 56, no 4, p. 940-948Article in journal (Refereed)
    Abstract [en]

    This paper discusses the influence of stroke current propagation velocity on the characteristics of lightning horizontal electric fields, considering different types of soil and distances to the stroke location. The MTLE model is adopted for the determination of the current distribution along the return stroke channel, whereas the effect of the finite-ground conductivity is taken into account by using the modified Cooray-Rubinstein approximation. This paper also discusses the effect of the propagation velocity on each of the horizontal electric field components. The results show that the horizontal electric field is strongly influenced by the stroke current propagation velocity even for the case of good conductive ground and observation points relatively close to the stroke location. Regardless of the ground conductivity, the peak value of the static component decreases and the negative peak of the radiation component increases with the propagation velocity. Therefore, for short distances to the lightning channel, the absolute peak value of the horizontal electric field tends to decrease as the velocity increases, while for distances of few kilometers or larger its behavior is just the opposite, i.e., the amplitude increases with the propagation velocity.

  • 297. Saba, Marcelo
    et al.
    Naccarato, Kleber
    de Paiva, Amanda R
    Schumann, Carina
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Hettiarachchi, Pasan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Diendorfer, Gerhard
    Piantini, Alexandre
    de Oliveira e Silva, José Claudio
    Ferro, Marco A S
    Custodio, Diogo Machado
    The study of lightning strikes to common buildings in Brazil2016Conference paper (Refereed)
    Abstract [en]

    Most of what is known about the electric current of downward flashes and striking distance of lightning protection systems come from information gathered on tall towers. There are no observational data of lightning attachment to common structures or buildings (under 60 m) that are present in almost every city. In order to study lightning strikes to common buildings, several instruments were installed in and around two identical buildings located in São Paulo city, Brazil. This paper describes the setup of electric field sensors, current transformers, X-ray sensors, high-speed video and standard video cameras. Some of the data already obtained in its first two months of operation are also shown.

  • 298.
    Sabri, M. H. M.
    et al.
    Univ Teknikal Malaysia Melaka, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Durian Tunggal 76100, Melaka, Malaysia.
    Ahmad, M. R.
    Univ Teknikal Malaysia Melaka, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Durian Tunggal 76100, Melaka, Malaysia.
    Esa, M. R. M.
    UTM, Inst High Voltage & High Current IVAT, Skudai 81310, Johor Bharu, Malaysia.
    Periannan, D.
    Univ Teknikal Malaysia Melaka, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Durian Tunggal 76100, Melaka, Malaysia.
    Lu, G.
    Chinese Acad Sci, Inst Atmospher Phys, Key Lab Middle Atmosphere & Global Environm Obser, Beijing 100029, Peoples R China.
    Zhang, H.
    Chinese Acad Sci, Inst Atmospher Phys, Key Lab Middle Atmosphere & Global Environm Obser, Beijing 100029, Peoples R China.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    William, E.
    MIT, 77 Massachusetts Ave, Cambridge, MA 02139 USA.
    Aziz, M. Z. A. A.
    Univ Teknikal Malaysia Melaka, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Durian Tunggal 76100, Melaka, Malaysia.
    Abdul-Malek, Z.
    UTM, Inst High Voltage & High Current IVAT, Skudai 81310, Johor Bharu, Malaysia.
    Alkahtani, A. A.
    Univ Tenaga Nas, Jalan IKRAM UNITEN, Kajang 43000, Selangor, Malaysia.
    Kadir, M. Z. A. A. B.
    Univ Tenaga Nas, Jalan IKRAM UNITEN, Kajang 43000, Selangor, Malaysia.
    Initial electric field changes of lightning flashes in tropical thunderstorms and their relationship to the lightning initiation mechanism2019In: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895, Vol. 226, p. 138-151Article in journal (Refereed)
    Abstract [en]

    In this paper, the key finding is that all the examined first classic Initial Breakdown (IB) pulses in tropical flashes within the reversal distance were found to be initiated by a clearly detectable Initial E-field Change or IEC (45 -CG, 32 normal IC, and 3 IC initiated by +NBE). The durations of IECs for both -CG and IC flashes in tropical storms were longer than in Florida storms. On the other hand, for the magnitudes of the E-change, the values were smaller compared to Florida storms with averages of 0.30 V/m compared to 1.65 V/m for -CG flashes, and -0.81 V/m compared to -6.30 V/m for IC flashes. The IEC process of lightning flashes in tropical regions took longer to increase the local electric field in order to produce the first IB pulse because of the smaller magnitude of E-change. On the other hand, in Florida storms, the IEC process took a shorter time to increase the local electric field to produce the first IB pulse because of the larger magnitude of E-change. We found that very high frequency (VHF) pulses for tropical thunderstorms started sometime prior to the onset of the IECs. They started between 12.69 and 251.60 mu s before the initiation of the IEC for two normal IC flashes. The first two VHF pulses were detected alone without narrow IB pulses (fast antenna and slow antenna records) or any pulses from the B-field and dE/dt records. Furthermore, the VHF pulses for three IC flashes initiated by + NBEs were also detected before the onset of the IEC. The IEC started immediately after the detection of the + NBE. It is clear that the IEC is initiated by VHF pulses. It can be suggested that lightning is initiated by Fast Positive Breakdowns or FPBs (which emit strong VHF pulses and large + NBEs) and is followed by several negative breakdowns (weak VHF pulses and/or weak NBE-type pulses) before the IEC started. For the case of normal IC flashes, several weaker VHF pulses (mean values of 41.97 mV and 46.4 mV compared to the amplitudes of the VHF pulses of + NBEs of around 800 mV) were detected before the onset of the IEC. As FPBs can occur with a wide range of VHF strengths and E-change amplitudes, it can be suggested these weak VHF pulses accompanied by narrow IB pulses or weak NBE-type pulses detected before the onset of IEC are actually FPBs followed by negative breakdowns or several attempted FPBs.

  • 299.
    Sabri, M. H. M.
    et al.
    Univ Tekn Malaysia Melaka UTeM, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Durian Tunggal 76100, Melaka, Malaysia.
    Ahmad, M. R.
    Univ Tekn Malaysia Melaka UTeM, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Durian Tunggal 76100, Melaka, Malaysia.
    Periannan, D.
    Univ Tekn Malaysia Melaka UTeM, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Durian Tunggal 76100, Melaka, Malaysia.
    Seah, B. Y.
    Univ Tekn Malaysia Melaka UTeM, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Durian Tunggal 76100, Melaka, Malaysia.
    Aziz, M. Z. A. A.
    Univ Tekn Malaysia Melaka UTeM, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Durian Tunggal 76100, Melaka, Malaysia.
    Ismail, M. M.
    Univ Tekn Malaysia Melaka UTeM, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Durian Tunggal 76100, Melaka, Malaysia.
    Esa, M. R. M.
    Univ Teknol Malaysia, FKE, Inst High Voltage & High Current IVAT, Johor Baharu 81310, Johor, Malaysia.
    Mohammad, S. A.
    Univ Teknol Malaysia, FKE, Inst High Voltage & High Current IVAT, Johor Baharu 81310, Johor, Malaysia.
    Abdul-Malek, Z.
    Univ Teknol Malaysia, FKE, Inst High Voltage & High Current IVAT, Johor Baharu 81310, Johor, Malaysia.
    Yusop, N.
    Univ Kebangsaan Malaysia, Inst Climate Change, Space Sci Ctr ANGKASA, Bangi 43600, Selangor Darul, Malaysia.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lu, G.
    Chinese Acad Sci, Inst Atmospher Phys, Key Lab Middle Atmosphere & Global Environm Obser, Beijing, Peoples R China.
    VHF Emissions Prior to the Onset of Initial Electric Field Changes of Intracloud Flashes2018In: 2018 INTERNATIONAL CONFERENCE ON ELECTRICAL ENGINEERING AND COMPUTER SCIENCE (ICECOS), IEEE , 2018, p. 301-304Conference paper (Refereed)
    Abstract [en]

    We present the observation of VHF impulses electric (E) field emissions found in two normal intracloud (IC) flashes accompanied by initial electric field changes (LECs) in a tropical thunderstorm. The data was collected on November 23rd, 2017 (within reversal distance) to our lightning sensor in Malacca, Malaysia. The durations from the onset of IECs to the first initial breakdown (IB) pulse are range between 0.68 and 0.69 ms and the magnitudes of IECs are range between 0.18 and 0.50 V/m. Besides that, before the onset of LECs there is small pulses was detected for IC flash (Nov_67) same with the VHF impulse for both IC flash. It was detected earlier before the onset of IEC by 12.69 and 251.60 mu s for the VHF impulse.

  • 300.
    Sabri, Muhammad Haziq Mohamad
    et al.
    Univ Tekn Malaysia Melaka, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Durian Tunggal, Melaka, Malaysia.
    Ahmad, Mohd Riduan
    Univ Tekn Malaysia Melaka, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Durian Tunggal, Melaka, Malaysia.
    Esa, Mona Riza Mohd
    UTM, Fac Engn, Sch Elect Engn, Inst High Voltage & High Current IVAT, Skudai, Johor Bharu, Malaysia.
    Periannan, Dinesh
    Univ Tekn Malaysia Melaka, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Durian Tunggal, Melaka, Malaysia.
    York, Seah Boon
    Univ Tekn Malaysia Melaka, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Durian Tunggal, Melaka, Malaysia.
    Mohammad, Sulaiman Ali
    UTM, Fac Engn, Sch Elect Engn, Inst High Voltage & High Current IVAT, Skudai, Johor Bharu, Malaysia.
    Abdul-Malek, Zulkurnain
    UTM, Fac Engn, Sch Elect Engn, Inst High Voltage & High Current IVAT, Skudai, Johor Bharu, Malaysia.
    Lu, Gaopeng
    Chinese Acad Sci, Inst Atmospher Phys, Beijing, Peoples R China.
    Zhang, Hongbo
    Chinese Acad Sci, Inst Atmospher Phys, Beijing, Peoples R China.
    Yusop, Norbayah
    Univ Tekn Malaysia Melaka, Fak Kejuruteraan Elekt & Kejuruteraan Komputer, Ctr Telecommun Res & Innovat CeTRI, Atmospher & Lightning Res Lab, Durian Tunggal, Melaka, Malaysia; Univ Kebangsaan Malaysia, Inst Climate Change, Space Sci Ctr ANGKASA, Bangi, Selangor, Malaysia.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Al-Kahtani, Ammar Ahmed
    Univ Tenaga Nas, Jalan IKRAM UNITEN, Kajang, Selangor, Malaysia.
    Ab Kadir, Mohamad Zainal Abidin
    Univ Tenaga Nas, Jalan IKRAM UNITEN, Kajang, Selangor, Malaysia.
    Hatta, Norhasliza Mohd
    TNB Res Sdn Bhd, Kajang, Malaysia.
    Abdullah, Noradlina
    TNB Res Sdn Bhd, Kajang, Malaysia.
    Yahaya, Mohd Pauzi
    TNB Res Sdn Bhd, Kajang, Malaysia.
    Environmental Analysis of Quasi-Static Electric Field Changes of Tropical Lightning Flashes2019In: Ekoloji, ISSN 1300-1361, Vol. 28, no 107, p. 373-378, article id UNSP e107013Article in journal (Refereed)
    Abstract [en]

    The environmental conditions leading to the bouncing-wave discharge and the subsequent electron beam remain to be investigated in more detailed future studies. The analysis of quasi-static initial electric field changes (IECs) were found at the beginning of all 24 lightning flashes detected within reversal distance (22 Negative Cloud-to-Ground (–CG) and 2 normal Intra-Cloud (IC) flashes) in a tropical storm on June 15th, 2017 close to our station in Malacca, Malaysia (2.314077° N, 102.318282° E). The IECs durations averaged 4.28 ms for –CG flashes (range 1.48 to 9.45 ms) and averaged 11.30 ms for normal ICs flashes (range 7.24 to 15.35 ms). In comparison to Florida storms, the duration of IECs for –CG and IC flashes were 0.18 ms (range 0.08 to 0.33 ms) and 1.53 ms (range 0.18 to 5.70 ms), respectively. Moreover, the magnitudes of E-change for tropical thunderstorm were 0.13 V/m (range 0.03 to 0.44 V/m) for –CG flashes and -0.20 V/m (range -0.13 to -0.27 V/m) for IC flashes. The E-change magnitudes of tropical flashes are significantly larger than Florida flashes.

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