| 1. |
- Abegunawardana, Sidath, et al.
(författare)
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Audible Frequency Analysis of Ground Flashes
- 2018
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Konferensbidrag (refereegranskat)abstract
- Thunder signatures categorized into three types based on peak pressure and variation in fundamental frequency, have been studied by using acoustic spectrum of thunder. S-transformation has been used to estimate the dominant frequency variation around the peak pressure. The mean fundamental frequencies of type 3 ground and cloud flashes are 160 Hz and 98 Hz respectively. The mean frequencies of type 2 ground and cloud flashes are 108 Hz and 82 Hz respectively.
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| 2. |
- Abegunawardana, Sidath, et al.
(författare)
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Sound Source Localization of Lightning Discharges
- 2018
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Konferensbidrag (refereegranskat)abstract
- The lightning channel can be retraced by thunder signature recorded with an array of microphones. Four microphones were arranged to capture thunder sound, and acoustic cross-correlation of captured pressure signals estimated the time lag of each pair of microphones. A wave segment with 0.25 s or 0.5 s of duration was compared with the acoustic signal recorded by other microphones to estimate time lapse. The direction of channel propagation has been estimated by the time difference of arrival of each pair of microphones. Thunder source locations estimated by this method can be extended to investigate the channel propagation inside clouds.
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| 3. |
- Abewardhana, Ruwan, et al.
(författare)
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Lightning Localization Based on VHF Broadband Interferometer Developed in Sri Lanka
- 2018
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Ingår i: 2018 34th international conference on lightning protection (ICLP 2018). - New York : IEEE. - 9781538666357
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Konferensbidrag (refereegranskat)abstract
- A basic broadband digital interferometer was developed, which is capable of locating Very High Frequency (VHF) radiation sources in two spatial dimensions and time. Three antennas sensed the time series of broadband electromagnetic (EM) signals and digitized with 4 ns sampling interval for a duration of several milliseconds. A technique based on cross-correlations has been implemented for mapping lightning source locations. A map of the first return stroke (RS) and the preceding stepped leader was mapped successfully, using the system with a time resolution of few milliseconds. The result was compared with the visible events of the ground flash to validate the system.
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| 4. |
- Chandimal, Lasantha, et al.
(författare)
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A field study on the energy dissipation associated with step and touch voltage in earthing systems encased in earth enhancing compounds
- 2024
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Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 231
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Tidskriftsartikel (refereegranskat)abstract
- An extensive field experiment was conducted to investigate the effects of earth -enhancing compounds on earthing systems. Four identical vertical earth rods were installed, each encased in concrete, Bentonite, and two commercial enhancing materials. Lightning impulse signals were injected into all electrode arrangements, and the measured responses were used to analyse the associated risks of step and touch voltages. The peak voltage values and the corresponding energy dissipation for each measurement were calculated and compared to those of a reference electrode. The analysis of step voltage measurements and the corresponding energy dissipation demonstrated that the use of concrete exhibited greater advantages than the use of Bentonite. However, touch voltage measurements and the associated energy dissipation indicated that despite the lower touch voltage exhibited by Bentonite, its energy dissipation exceeded that of the reference electrode. Consequently, the unique findings reveal that specific variations of earth -enhancing compounds can exhibit reduced earth impedance and lower step or touch voltages while also yielding higher energy dissipation, introducing an unforeseen risk of injury.
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| 5. |
- Sapumanage, Nilantha, et al.
(författare)
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How physical attributes of transient voltages limit the efficiency of SPD array
- 2018
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Ingår i: 2018 34th international conference on lightning protection (ICLP 2018). - : IEEE. - 9781538666357
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Konferensbidrag (refereegranskat)abstract
- This study was conducted to understand what inherent limitations are associated with SPD arrays in confronting with real transient over voltages. To devise the study 403 transient voltages were selected with different physical attributes covering a range of peak-to-peak voltages, starting from 175 V up to 2861 V. The sample comprises 218 cloud-to-clouds and 185 clouds to ground generated transient voltages with mean and median values of 676.80 V and 551.00 V respectively. Impulses were segregated into three subclasses based on their physical attributes and assessed the tendency to drift through the protection array once they placed at the +90, zero and -90 phaser angles. The study revealed that 100% of positive impulses in the sample could drift through the selected array once pitched at any phaser angle on 230 V, 50 Hz utility signal. It was observed that out of the negative pulses, 90.35% at +90, 74.39 % at zero and 42.21% at -90 phaser angles, could freely move through the array. In addition to that, almost 100% of the positive portions of bipolar impulses too can reach the sensitive systems through the protection array irrespective of the pitching phaser angle.
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| 6. |
- Sapumanage, Nilantha, et al.
(författare)
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Insight of SPD limitations caused by incident phaser angle and physical attributes of transient voltages
- 2018
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Ingår i: 2018 34th international conference on lightning protection (ICLP 2018). - : IEEE. - 9781538666357
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Konferensbidrag (refereegranskat)abstract
- This study was devised to investigate how the pitching phaser angle and the time domain voltage profile would compel surge protective devices (SPDs) to fall short in providing guaranteed protection. The study showed that the phaser angle at which the transient voltage pitching on the 230 V power frequency signal and its time domain voltage profile play a significant role in deciding the efficiency of the protection array and the amount of incident energy that infiltrates to reach the sensitive loads connected to the low voltage power installation. The analysis managed to prove that the selected SPD array can effectively reduce the harmful energy content of the impulse to around 40% and hence it is always advantageous to have a cascaded array than a single SPD. The study emphasized that it is practically impossible to have a universal protection system that can provide the same degree of protection under all circumstances. Moreover, the study further revealed that it is rational to design a SPD array considering regional and local lightning characteristics.
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| 7. |
- Sapumanage, Nilantha, et al.
(författare)
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Time-Frequency and Energy Correlations of the Transient Voltages Triggered by Cloud to Cloud Discharges
- 2019
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Ingår i: IEEE transactions on electromagnetic compatibility (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9375 .- 1558-187X. ; 61:6, s. 1782-1792
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a study performed on time, frequency, and energy correlations of transient voltages generated by the cloud to cloud discharges. It revealed that the energy embedded in transient voltages have been lumped over few segments of time domain voltage profile than uniquely scattering over the time span. The study further determined that the energy concentration becomes higher in and around the vicinity of the time domain voltage maxima or minima, and such high energy-concentrated segments confined to a minute time span in comparison to the total time span of the transient voltage. The study also established that there is a small time lead or lag between the time domain voltage maxima or minima and the time of energy maximize. Moreover, the analysis deduced that the time lead or time lag phenomenon, is not sensitive to the orientation of the time domain voltage profile, but fuelled by the pulse type. The response time of surge protective devices can become crucial if the stipulated clamping voltages of the protection devices fall close to local peaks of the transient voltages.
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