| 1. |
- 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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| 2. |
- Arevalo, Liliana, et al.
(författare)
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The leader propagation velocity in long air gaps
- 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
- Experimental measurements of long gap discharges and its interpretation are the base of engineering equations and complex models to design clearance distances, lightning protection systems, among others. Parameters like leader propagation velocity, average electric field of the leader channel, stability electric field of the streamer region, etc. are derived from experimental measurements for rod-plane arrangements. However, in high voltage engineering geometries are not only rod-plane arrangements but also rounded electrode geometries. Experimental measurements of sphere - plane arrangements are presented in this paper. Attention is given to the velocity of propagation of the leader. The velocity of propagation of the leader is compared for two different applied voltage conditions, such as overvoltage and non-overvoltage. Experimental observations indicate that the velocity of the leader does not have a linear relationship with the increment of the applied voltage, as described by other authors for rod-plane arrangements. By means of a model based on the physics of the discharge, it is observed that the velocity of propagation of the leader depends on the injected charge to the leader channel. The injected charge depends on the background electric field, the potential at the leader tip, the steepness of the applied voltage waveform, among other parameters.
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| 3. |
- Becerra Garcia, Marley, 1979-, et al.
(författare)
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Using low-level currents measured during lightning events to estimate upward leader properties
- 2018
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Ingår i: 34th International Conference on Lightning Protection, ICLP 2018. - : Institute of Electrical and Electronics Engineers Inc.. - 9781538666357
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Konferensbidrag (refereegranskat)abstract
- Low-level currents measured prior to return strokes can potentially provide information about the properties of upward leaders during lightning flashes. However, these currents need to be properly analysed and interpreted in order to be useful for evaluating upward connecting leaders. In this paper, low-level currents measured before return strokes in two lightning events to two structures in Brazil are analysed and interpreted as case studies. The discharge current estimated from one of these events is used as input to a detailed thermohydrodynamic model with an extensive kinetic scheme for N2/O2 mixtures. The model allows the evaluation of the physical and chemical properties of upward connecting leaders. Estimates of the temperature, mass density, electric field and radius of the channel are presented for an upward connecting leader propagating in a lightning event. In addition, estimates of the axial density of electrons, ions and neutral particles (including NO and NO2) are also reported.
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| 4. |
- Bodhika, J. A. P., et al.
(författare)
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Characteristics of thunder pertinent to tropical lightning
- 2018
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Ingår i: 34th International Conference on Lightning Protection (ICLP) (ICLP 2018). - : IEEE. - 9781538666357
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Konferensbidrag (refereegranskat)abstract
- Acoustic effects of lightning flashes are not well studied. Thunder also destructive as electric fields do. Thunder flashes of tropical lightning occurred in Hambantota (81(0) 0'E, 6(0) 10'N) close to the southern coast of Sri Lanka were studied. About 90 thunder flashes recorded with the sampling rate of 100 kS/s in 45 s windows were analyzed to identify their characteristics and damaging effects. Results of the analysis on duration of thunder flashes, peak sound pressure levels, occurrence of thunder claps and frequency distribution were presented. The shortest and longest duration of thunder recorded were 2.2 sec and 33.7 sec respectively. About 75% of thunder flashes were remained for about 5-20 sec. The frequency spectrum of a thunder signal could spread up to 1500 Hz. The peak sound pressure level of 30% of recorded thunder flashes at least 3 km away from the lightning were higher than 2 Nm(-2) (100 dB). One to five claps were identified in thunder flashes with 62% having 1 or 2 claps. Sound pressure level, frequency range and its duration are required quantities to estimate the harmful effects of thunder.
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| 5. |
- Chandimal, A. P. L., et al.
(författare)
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Impedance Behavior of Earth Enhancing Compound Under Lightning Transient Conditions
- 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
- This study was aimed at finding the performance of commercially available earth enhancing compound (EEC) under lightning conditions. Further to that, this is an extension of a previous study conducted by the same authors referring to the same EEC. The selected material seems to perform impressively under lightning conditions passing considerably large current values. The prepared EEC mixture and the setup was tested under dry conditions and exhibited low dynamic impedance characteristics for lightning impulse voltages. Ten-stage Marx-generator was used for the experiment, and due to high conductive nature of the material, HV supply between the sample was unable to increase more than few kV. Thus the 12 cm gap inside the material was complemented with an external air gap of 90 cm. The study was a comparison between "air-gap breakdown" and "air-gap plus material-gap breakdown". The results confirmed a low impedance characteristic for the selected EEC and suggested a very low electric field inside the material gap. An approximate value for the impedance of the test setup was calculated from the collected data. A time window was selected during the steady current discharge appeared just after the point of current peak and the impedance curves for both experiments were compared at a previously defined point at the time axis. The impedance value for EEC setup was estimated to be in the region of 1 - 2 Omega.
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| 6. |
- Cooray, Vernon, 1952-
(författare)
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Latitude dependence of peak lightning return stroke current : A theoretical explanation
- 2018
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Ingår i: 34th International Conference on Lightning Protection (ICLP 2018). - : IEEE. - 9781538666357
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Konferensbidrag (refereegranskat)abstract
- The experimental data show that the peak currents of first and subsequent lightning return strokes increase with decreasing latitude. In this paper the reason for this dependence of current amplitude is explained using the fact that the height of the charge centers increases with decreasing latitude. The results obtained show that in tropical regions peak first and subsequent return stroke currents are located in the vicinity of 42 kA and 15 kA, respectively. This theoretical prediction is in agreement with available experimental data.
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| 7. |
- Cooray, Vernon, 1952-
(författare)
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The power, energy, momentum and the action of the electromagnetic radiation fields of lightning return strokes
- 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
- The energy, momentum and the action associated with the radiation fields generated by a typical subsequent lightning return stroke is estimated. The action is defined as the product of the total radiation energy emitted and the duration of emission, and the momentum refers to the vertical component. The results obtained show that a typical subsequent return stroke generates 2 x 10(6) J, 2 x 10(6) Kgm/s and 2 x 10(6) Js respectively of energy, momentum and action.
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| 8. |
- Gomes, Ashen, et al.
(författare)
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Development of a portable type i to III lightning surge protective device for compact structures
- 2018
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Ingår i: 34th International Conference on Lightning Protection, ICLP 2018. - : Institute of Electrical and Electronics Engineers Inc.. - 9781538666357
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Konferensbidrag (refereegranskat)abstract
- Lightning Surge protection of large structures is done under zonal concept due to the requirement of a system with high current handling capacity and low voltage protection level. Induction of transient voltage in the wiring system within the building is another reason for such. However, in the case of compact structures such as base transmission stations (BTS) of tower sites, outside broadcast vehicles (OBV), various stages of railway systems etc. there are no sufficient lengths in the wiring network for implementing SPDs in such zonal-segment scenario. Also due to the remoteness of most BTSs and need for regular and/or continuous usage of OBVs and railway systems, the time-consuming replacement of outof-order fixed SPDs is most often not warranted. In this backdrop, it was proposed to develop a portable/pluggable system of coordinated SPDs with high current handling capacity and low voltage protection level. A compact SPD system that is capable of handling high currents (50 kA) with low let through voltage (1 kV) was designed using PSCAD and a thorough market research was conducted to identify products that satisfied the requirements of the system designed in PSCAD. Type I and III SPDs capable of handling 50 kA and 2.5 kA respectively, were identified and used for the hardware implementation of the system. Elimination of the type II SPD made the design more compact and better suited for applications at space-restricted locations.
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| 9. |
- Gomes, Ashen, et al.
(författare)
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Impulse flashover characteristics of oil palm trunk (OPT) veneer plywood
- 2018
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Ingår i: 34th International Conference on Lightning Protection, ICLP 2018. - : Institute of Electrical and Electronics Engineers Inc.. - 9781538666357
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Konferensbidrag (refereegranskat)abstract
- Oil palm is one of the largest crop industries in South East Asia, thus, it is of importance to use all parts of the Oil palm trees. Recently Oil Palm Trunks (OPT) have been used to make veneer, which can be processed to produce plywood. Even though OPT plywood doesn't have the same mechanical properties as timber, with proper treatment and adhesives during the processing of veneer to plywood, it can be made to compete with hardwood. OPT plywood has been used in various applications from wooden appliances to housing and roofing structures. These structures are at risk of surface flashovers through lightning and electrical breakdowns. However, no study has been conducted on the effects or characteristics of OPT plywood. In this paper, the effects of impulse surface flashover under different conditions on three-layered OPT plywood has been analyzed. Experiments were conducted to identify the characteristics of OPT under clean and dry, clean and wet, and contaminated surface conditions for both parallel and perpendicular fiber orientations. The 50% breakdown voltage was determined by the up and down method. Results identified the importance of the fibre orientation and the decrease in breakdown voltage under contaminants.
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| 10. |
- Hettiarachchi, Pasan, et al.
(författare)
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Time Domain Analysis of the Lightning Interaction with Wave Energy Converters
- 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
- In this work, we present a simulated study of lightning interactions with wave power generators submerged in seawater in Lysekil, in the southwest coast of Sweden. A time domain 3D electromagnetic simulation involving a Wave Energy Converter (WEC) and the surrounding seawater, air, and the current injection to the WEC from a typical return stroke of a lightning is conducted. The results show that the injected current to the wave power generator is considerably low even under a direct lightning strike. The study also shows that the wave-shape of the injected current to the WEC is significantly altered from a typical return stroke current impulse. It is concluded that likelihood of damages to the WEC or injection of electrical surges to the electrical grid is low. However, in order fully understand the implications of lightning strikes to a WEC further studies should be conducted.
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