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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... more
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.
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We consider dynamics of the lightning-channel corona sheath that is implicitly specified by lumped-current-source lightning return-stroke models. Two slightly different corona models for prediction of charge motion in the corona sheath... more
We consider dynamics of the lightning-channel corona sheath that is implicitly specified by lumped-current-source lightning return-stroke models. Two slightly different corona models for prediction of charge motion in the corona sheath are proposed. Both models can be viewed as generalizations of the model proposed by Maslowski and Rakov (2006) and are in agreement with measurements of the horizontal (radial) electric
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Expansion of positive (return-stroke) corona sheath inside the negative (leader) corona sheath is examined. It is shown that the positive corona sheath radius is smaller than that of the negative corona sheath. As a result, the overall... more
Expansion of positive (return-stroke) corona sheath inside the negative (leader) corona sheath is examined. It is shown that the positive corona sheath radius is smaller than that of the negative corona sheath. As a result, the overall corona sheath during the return-stroke stage is composed of two concentric zones: inner zone with net positive charge and outer one with negative
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A review of recent lightning corona sheath dynamics research is presented together with a short description of early views of lightning corona sheath. A current state of knowledge about corona sheath conductivity is described and a short... more
A review of recent lightning corona sheath dynamics research is presented together with a short description of early views of lightning corona sheath. A current state of knowledge about corona sheath conductivity is described and a short discussion on a role of radially flowing corona current in longitudinal extension of the channel is given. Consequences of adoption of corona current
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A new formulation for lumped-source-type (transmission-line-type) lightning return-stroke models is proposed. This formulation expresses the longitudinal current at height z’ as the channel-base current minus the overall longitudinal... more
A new formulation for lumped-source-type (transmission-line-type) lightning return-stroke models is proposed. This formulation expresses the longitudinal current at height z’ as the channel-base current minus the overall longitudinal current change from ground surface to z’. In general, the longitudinal current change consists of two components, one of which is associated with the upward propagation delay (transferred charge density component) and
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Research Interests: Power System, Magnetic field, High Frequency, Numerical Simulation, Model validation, and 12 moreIEEE, Electromagnetic, Transmission Line, Power Distribution, Asymptotic Behavior, Time Domain, Electric Field, Electrical And Electronic Engineering, Predictive value of tests, Finite Difference Time Domain, Frequency Domain, and Electromagnetic coupling
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The experimental evidence indicates that the large scale electric field in the cloud at the time of lightning initiation is about 100 kV/m [1], which is an order of magnitude lower than the expected conventional breakdown field. One... more
The experimental evidence indicates that the large scale electric field in the cloud at the time of lightning initiation is about 100 kV/m [1], which is an order of magnitude lower than the expected conventional breakdown field. One important problem in atmospheric physics is to understand how lightning flashes are initiated in such low fields. Some scientists suggest that the
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Positive transferred charge inside the lightning channel core during the return-stroke stage dominates the total charge when the speed of the return stroke current wave is relatively low and negative leader line charge density is less... more
Positive transferred charge inside the lightning channel core during the return-stroke stage dominates the total charge when the speed of the return stroke current wave is relatively low and negative leader line charge density is less than typical values inferred from field measurements. As a result, the positive charge inside the channel during the returnstroke stage can be temporarily greater
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Positive transferred charge inside the lightning channel core during the return-stroke stage dominates the total charge when the speed of the return stroke current wave is relatively low and negative leader line charge density is less... more
Positive transferred charge inside the lightning channel core during the return-stroke stage dominates the total charge when the speed of the return stroke current wave is relatively low and negative leader line charge density is less than typical values inferred from field measurements. As a result, the positive charge inside the channel during the returnstroke stage can be temporarily greater
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Positive transferred charge inside the lightning channel core during the return-stroke stage dominates the total charge when the speed of the return stroke current wave is relatively low and negative leader line charge density is less... more
Positive transferred charge inside the lightning channel core during the return-stroke stage dominates the total charge when the speed of the return stroke current wave is relatively low and negative leader line charge density is less than typical values inferred from field measurements. As a result, the positive charge inside the channel during the returnstroke stage can be temporarily greater
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Research Interests: Power System, Magnetic field, High Frequency, Numerical Simulation, Model validation, and 10 moreElectromagnetic, Transmission Line, Power Distribution, Asymptotic Behavior, Time Domain, Electric Field, Electrical And Electronic Engineering, Finite Difference Time Domain, Frequency Domain, and Electromagnetic coupling
ABSTRACT Full paper available at: http://authors.elsevier.com/a/1P~Oq1M7~0LpvC We examine the effect of channel branching on electric field waveforms produced by first return strokes in negative cloud-to-ground lightning using a modified... more
ABSTRACT Full paper available at: http://authors.elsevier.com/a/1P~Oq1M7~0LpvC We examine the effect of channel branching on electric field waveforms produced by first return strokes in negative cloud-to-ground lightning using a modified transmission line model. From computed return stroke electric field waveforms it is found that the presence of an ungrounded branch results in sharper initial peak and a secondary peak in the falling part of the return stroke waveform. The time interval between the primary and secondary peaks depends upon the height of the branching point above ground and the speed at which the incident current wave moves upward from the ground. The presence of branch serves to slightly decrease the magnitude of the opposite polarity overshoot. The effects of the height of the branching point above ground, fraction of total channel current flowing to the branch, and current reflections from the branch unconnected end are illustrated. http://www.sciencedirect.com/science/article/pii/S0378779614002764
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In this paper, we have computed lightning-induced voltages on distribution lines in the presence of nearby buildings using the 3D finite-difference time-domain (FDTD) method. In the simulations, four-conductor lines with surge arresters... more
In this paper, we have computed lightning-induced voltages on distribution lines in the presence of nearby buildings using the 3D finite-difference time-domain (FDTD) method. In the simulations, four-conductor lines with surge arresters and pole transformers are considered. It appears that the presence of nearby buildings cause reduction of lighting induced voltages, as expected. The observed trend is in general agreement with that reported from the small-scale experiment by Piantini et al. (2007).
—In this paper, lightning-induced voltages on multi-conductor lines with surge arresters and pole transformers have been computed using the 3D finite-difference time-domain (FDTD) method. This method uses a subgrid model, in which spatial... more
—In this paper, lightning-induced voltages on multi-conductor lines with surge arresters and pole transformers have been computed using the 3D finite-difference time-domain (FDTD) method. This method uses a subgrid model, in which spatial discretization is fine (cell side length is 0.5 m) in the vicinity of overhead wires and coarse (cell side length is 5 m) in the rest of the computational domain. In the simulations, four-conductor lines with surge arresters and pole transformers are considered. The 1-cm-radius overhead conductors are represented by placing a wire having an equivalent radius of about 0.12 m (≈ 0.23 × 0.5 m) in the center of an artificial rectangular prism having a cross-sectional area of 1 m × 1 m (2 cells × 2 cells) and the modified (relative to air) constitutive parameters: lower electric permittivity and higher magnetic permeability. The computed lightning-induced voltage waveforms agree reasonably well with the corresponding ones measured in the small-scale exp...
A simplified model of corona discharge for the finite difference time-domain (FDTD) computations has been applied to analysis of lightning-induced voltages at different points along a single overhead wire in the presence of corona space... more
A simplified model of corona discharge for the finite difference time-domain (FDTD) computations has been applied to analysis of lightning-induced voltages at different points along a single overhead wire in the presence of corona space charge around the wire. The magnitudes of FDTD-computed lightning-induced voltages in the presence of corona discharge are slightly larger than those computed without considering corona.
In this study, we characterized the preliminary breakdown (PB) pulse trains in negative cloud-to-ground lightning. The data were acquired at the Lightning Observatory in Gainesville (LOG), Florida, in 2013. Distances to lightning channels... more
In this study, we characterized the preliminary breakdown (PB) pulse trains in negative cloud-to-ground lightning. The data were acquired at the Lightning Observatory in Gainesville (LOG), Florida, in 2013. Distances to lightning channels ranged from 21 to 118 km. For 104 flashes, the geometric mean (GM) PB pulse train duration is 2.1 ms. The GM interval between the beginning of PB pulses train and first return stroke pulse onset (TPB-RS) is 20 ms. The GM ratio of the largest PB pulse peak to the first return stroke pulse peak is 0.2. In our dataset, we found 9 flashes with very short (≤6 ms) T_PB-RS, which appears to be due to very high stepped leader speed. The GM NLDN-reported peak current of the first return stroke in these flashes is as high as 131 kA. We also examined the effect of noise on detectability of PB pulse trains. We found that 29% of 221 flashes had detectable PB pulses, and that after filtering the percentage increased to 47%. The percentage of flashes with detecta...
We have estimated the GLD360 performance characteristics using data for 201 negative return strokes in 42 flashes triggered during 2011–2013 at Camp Blanding, Florida. The flash and stroke detection efficiencies were 67% and 37%,... more
We have estimated the GLD360 performance characteristics using data for 201 negative return strokes in 42 flashes triggered during 2011–2013 at Camp Blanding, Florida. The flash and stroke detection efficiencies were 67% and 37%, respectively. Out of 75 detected-strokes, 1 (1.3%) was reported with incorrect polarity. The median location error was 2.1 km. The median absolute current estimation error was 27%.
We have estimated the ENTLN performance characteristics using data for 62 negative return strokes in 12 flashes triggered during 2013 at Camp Blanding, Florida. The flash and stroke detection efficiencies were 100% and 94%, respectively.... more
We have estimated the ENTLN performance characteristics using data for 62 negative return strokes in 12 flashes triggered during 2013 at Camp Blanding, Florida. The flash and stroke detection efficiencies were 100% and 94%, respectively. The ENTLN misclassified 53% of detected return strokes as cloud discharges. The median location error was 603 m and the median absolute current estimation error was 20%. The 2013 results are compared to those for 2009–2012, both corresponding to the same processor, implemented in November of 2012.