| 1. |
- Ahmad, M R, et al.
(författare)
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Measurement of bit error rate at 2,4 GHz due to lightning interference
- 2012
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Ingår i: Proceeding of the 31st International Conference on Lightning Protection ICLP 2012. - 9781467318976
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Konferensbidrag (refereegranskat)abstract
- This paper analyzes the interference of lightning flashes with wireless communication systems operating in the microwave band at 2.4 GHz. A bit error rate (BER) measurement method was used to evaluate BER during 3 heavy thunderstorms on January 25, March 17 and March 20, all in year 2011. In addition, BER measurements also were done on January 21 and March 30, 2011 under fair weather (FW) conditions providing a baseline for comparison. The Transmitter-Receiver separation was fixed at 10 meter with line-of-sight (LOS) consideration. We infer that lightning interfered with the transmitted digital pulses which resulted in a higher recorded BER. The maximum recorded BER was 9.9·101 and the average recorded BER was 9.95·10 -3 during the thunderstorms with the average fair weather BER values under the influence of adjacent channel interference (ACI) and co-channel interference (CCI) being 1.75·10-5 and 7.35·10 -6 respectively. We conclude that wireless communication systems operating at 2.4 GHz microwave frequency can be significantly interfered by lightning.
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| 2. |
- Arevalo, L., et al.
(författare)
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Corona charge produced by thundercloud fields in grounded rods
- 2012
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Ingår i: 31st International Conference on Lightning Protection ICLP 2012. - 9781467318976 ; , s. 6344365-
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Konferensbidrag (refereegranskat)abstract
- Electrostatic fields below the thundercloud lead to the formation of glow charge from grounded objects. The charge accumulated after certain time can initiate or inhibit the called streamer formation and consequently the inception and development of upward leaders. By means of a two dimensional numerical model that takes into account the particles behavior is observed that glow charge can smooth the electric field on top of the grounded rod and consequently hinder the inception of streamers and upward leaders from the grounded rod. It is concluded that to be able to initiate unstable upward leaders from the shielded grounded rod a sudden change of electric field is necessary. A two dimensional numerical model that solves the continuity equations for positive and negative ions and electrons coupled with Poisson equation was implemented. Comparison for different magnitudes of electric field and characteristics of rod are included as well.
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| 3. |
- Cooray, Vernon, et al.
(författare)
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Electric field of a relativistic electron avalanche
- 2012
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Ingår i: 2012 31st International Conference on Lightning Protection, ICLP 2012. - 9781467318976 ; , s. 6344240-
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Konferensbidrag (refereegranskat)abstract
- In the present study, electromagnetic fields of accelerating charges were utilized to evaluate the electromagnetic fields generated by a relativistic electron avalanche. In the analysis it is assumed that all the electrons in the avalanche are moving with the same speed. In other words, the growth or the decay of the number of electrons takes place only at the head of the avalanche. It is shown that the radiation is emanating only from the head of the avalanche where electrons are being accelerated. It is also shown that an analytical expression for the radiation field of the avalanche at any distance can be written directly in terms of the e-folding length of the avalanche. This makes it possible to extract directly the spatial variation of the e-folding length of the avalanche from the measured radiation fields.
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| 4. |
- Cooray, Vernon
(författare)
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Electric field of the return stroke channel
- 2012
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Ingår i: 31st International Conference on Lightning Protection ICLP 2012. - 9781467318976 ; , s. 6344241-
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Konferensbidrag (refereegranskat)abstract
- Return stroke models specify the temporal and spatial variation of the return stroke current along the channel. This information is sufficient to evaluate the temporal development of the electric field along the channel of the return stroke. In this paper the mathematical procedure necessary to do this is introduced. The derived equations can be combined with any return stroke model to calculate the power and energy dissipation during the return stroke.
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| 5. |
- Cooray, Vernon, et al.
(författare)
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Lightning attachment to power transmission lines
- 2012
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Ingår i: Lightning Protection (ICLP). - Vienna. - 9781467318976
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Konferensbidrag (refereegranskat)abstract
- The effect of lightning channel inclination on the attachment of lightning flashes to UHV transmission lines is investigated using a lightning strike model that takes into account the competing connecting leaders issued from different conductors. The results show that the probability of screening failures increases with increasing inclination of the lightning channel.
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| 6. |
- Cooray, Vernon, et al.
(författare)
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On the electric and magnetic fields below a single conductor overhead power line
- 2012
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Ingår i: 2012 31st International Conference on Lightning Protection, ICLP 2012. - 9781467318976 ; , s. 6344307-
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Konferensbidrag (refereegranskat)abstract
- Electromagnetic fields associated with the electric current flowing along a overhead power line with a single conductor located over perfectly conducting ground are estimated using electromagnetic fields pertinent to acceleration of electric charges. It is shown that the electric and magnetic fields that exist below a long overhead power line are nothing but the radiation fields generated by the acceleration of charge at the point of injection of current into the power line.
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| 7. |
- Edirisinghe, M., et al.
(författare)
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Critical electric field needed for the propagation of surface discharges on water
- 2012
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Ingår i: 2012 31st International Conference on Lightning Protection, ICLP 2012. - 9781467318976 ; , s. 6344350-
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Konferensbidrag (refereegranskat)abstract
- The core objective of this study was to investigate the behavior of electric discharge exited in air over water and to study the way in which the lightning impulse is conducted into a water body. During the experiments, standard lightning impulses from -550 kV to 350 kV have been directed on water surfaces and surface discharges has been photographed using two cameras. The conductivity of the water has been varied from 41.5 μS/cm to 51.5 mS/cm. Analysis carried out in the study revealed that the current rather travels along the water surface than into the water when the conductivity of the water is low. A logarithmic variation was observed between the calculated electric field and the conductivity. For this variation a saturating trend could be observed and it appeared as if there is a critical value for the electric field below which no penetration will occur at any level of conductivity. Based on the experimental results of this study it can be estimated that to be less than 1.5×105 V/m for the positive breakdown and -5.0×10 5 V/m for the negative breakdown.
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| 8. |
- Izadi, M., et al.
(författare)
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Analytical fields expressions due to lightning channel considering variation of return stroke velocities along the lightning channel
- 2012
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Ingår i: Lightning Protection, (ICLP) 2012. - 9781467318976 ; , s. 6344252-
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Konferensbidrag (refereegranskat)abstract
- The return stroke velocity is an important factor for evaluation of lightning electromagnetic fields. Measurements showed that the return stroke velocity is varied at different heights along lightning channel while it is usually entered into field calculations with a constant value in previous studies. This paper presents the analytical electromagnetic fields expressions due to vertical lightning channel where velocity profile along channel is considered. The proposed fields expressions can be used to estimate electromagnetic fields directly in the time domain (without needing to apply any extra conversion to Frequency domain) whereas they are based on Heidler current function and can support widely used engineering current models. Likewise, the proposed field expressions are applied on a typical measured profile of velocity and also a function of velocity profile and the evaluated fields are compared to the corresponding simulated fields based on constant value of velocity and the results are discussed accordingly.
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| 9. |
- Izadi, M, et al.
(författare)
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Improved algorithm for evaluation of lightning current using measured field at far distances from lightning channel
- 2012
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Ingår i: 31st International Conference on Lightning Protection ICLP 2012. - 9781467318976 ; , s. 6344251-
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Konferensbidrag (refereegranskat)abstract
- In this paper, the effect of radiation component of electric field on the total electric field at different distances with respect to lightning channel is considered. Results showed by approximating the total electric field with the radiation component at far and intermediate distances, some percentages of electric fields at different time periods will be neglected and this percentage will be higher when decreasing the distance from lightning channel. Whilst the most common inverse procedure algorithms are based on field's radiation component and the total field as input data, this paper proposed the same procedure that based on measured field with the consideration on the effect of radiation component on the total field in the calculations. The results on the prediction of channel base current illustrated that the proposed method is in very good agreement with real lightning channel base current compared to the corresponding predicted current based on existing methods.
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| 10. |
- Nikjoo, Roya, et al.
(författare)
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Effect of transformer winding on the transient response of power transformer bushings
- 2012
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Ingår i: Lightning Protection (ICLP), 2012 International Conference on. - : IEEE. - 9781467318976 ; , s. 6344346-
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Konferensbidrag (refereegranskat)abstract
- This paper deals with the response of power transformer bushings under the effect of transformer windings during electromagnetic transients such as lightning. In transient domain, investigating the characteristic of each power component separately in the network wouldn't be adequate. Each component can make an influence on the transient current and voltage that may be measured from another one. This paper proposes to find the effect of transformer windings on the transient response of the bushing, which contains valuable information on bushing's condition. It may result helpful in diagnostics of such an important power component to avoid catastrophic failure. Natural transients would be helpful in monitoring of the bushing by utilizing them as stimuli for online dielectric response measurement. Transient response of the lumped model of the bushing in EMTP is compared with its finite element model (FEM) in COMSOL Multiphysics to validate the robustness of modeling approach. According to the frequency component of the lightning, transient electromagnetic wave module of COMSOL is applied. Then, the effect of the transformer winding on the transient response of the bushing is investigated in EMTP.
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