Preliminary study on the modelling of negative leader discharges (original) (raw)
Related papers
IEEE Transactions on Dielectrics and Electrical Insulation, 2000
This paper presents a predictive dynamic model enabling a description of the whole negative lightning discharge. The proposed model takes into account the different phases of the propagation (i.e., the initiation of the first corona, the pilot leader, the negative and space leaders and their junction up to the final jump). This model is based on an LCR line electrical network parameters derived with electromagnetic field, physical laws and gas discharge theories (L, C and R, being respectively the inductance, the capacitance and the resistance). Criteria for initiation, development, stand-off and some atmospheric conditions are also introduced. From this model the main macroscopic parameters of the negative lightning can be computed.
Numerical modelling of negative discharges in air with experimental validation
Journal of Physics D: Applied Physics, 2011
Axisymmetric finite element models have been developed for the simulation of negative discharges in air without and with the presence of dielectrics. The models are based on the hydrodynamic drift-diffusion approximation. A set of continuity equations accounting for the movement, generation and loss of charge carriers (electrons, positive and negative ions) is coupled with Poisson's equation to take into account the effect of space and surface charges on the electric field. The model of a negative corona discharge (without dielectric barriers) in a needle-plane geometry is analysed first. The results obtained show good agreement with experimental observations for various Trichel pulse characteristics. With dielectric barriers introduced into the discharge system, the surface discharge exhibits some similarities and differences to the corona case. The model studies the dynamics of volume charge generation, electric field variations and charge accumulation over the dielectric surface. The predicted surface charge density is consistent with experimental results obtained from the Pockels experiment in terms of distribution form and magnitude.
Numerical Modeling of Electrical Discharges in Long Air Gaps Tested With Positive Switching Impulses
IEEE Transactions on Plasma Science, 2018
This dissertation deals with research on the numerical modelling of electrical discharges in laboratory long air gaps excited with positive switching impulses. It begins with the preliminary work of several scientists during the last decades, making a detailed analysis of different approaches for modelling all the stages in a full discharge. The relations between these models are identified as well as the effect on the outcome when modifying some important input parameters. The general concept describing the discharge phenomenon usually includes three main elements: the streamer inception, the streamer-to-leader transition and the stable leader propagation. These elements are present in many of the analysed models and the main differences between them are the assumptions and simplifications made by each author at a specific point in their methodologies. The models are usually simplified by assigning experimentally determined values to physical constants pertinent to different stages of the full discharge. These constants are the potential gradient in the leader-corona region to sustain the leader propagation, the charge per unit length along the leader channel which depends on the atmospheric conditions and the voltage impulse wave shape; and the leader propagation velocity, which is closely related to the discharge current. The dissertation includes the results of laboratory work related the study of leaders in long gap discharges, electrical parameters and optical records. By reconstructing the three-dimensional leader propagation for the rod-toplane configuration, it was possible to study the random tortuous path followed by the leader as it propagates. One important element included in the discharge modelling is the representation of the leadercorona region in front of the leader tip as it propagates towards the grounded electrode. For the calculation of the net charge available in the leader-corona region, two new methodologies were proposed based on the electrostatic potential distribution obtained from a finite element method solver. This allowed the inclusion of more elements representing different parts of the discharge in the simulation domain. In the final part, all the analysed elements and the new proposed ones were included in a new methodology for the modelling of electrical discharges in long air laboratory gaps. The results obtained from this methodology were compared to experimental data. A good agreement was found between the simulation results and the experimental data.
Simulation of lightning discharges: Influence of ground objects and positive leaders
Proceedings of the IPSL Technical Sessions, 25 (2009) 13-20
Cloud-to-ground (CG) lightning discharges in 3D domain were simulated using a stochastic dielectric breakdown model. The influence of ground objects on simulated lightning flashes was studied by introducing additional boundary conditions to the ground plane. It was observed that pointed structures on the ground have a higher probability of attracting simulated lightning discharges. An extension was introduced to the dielectric breakdown model to simulate the development of positive leaders that occur during CG lightning flashes. It was found that the height of the stepped leader tip above the ground (at the time when the positive leader initiation occurs) is dependent on the local electric field associated with the discharge step controlled by the parameter E break . The height to the leader tip was found to decrease exponentially as E break is increased.
Atmosphere, 2016
Using an automated data processing algorithm, we examined electric field records of 5498 negative cloud-to-ground flashes reported by the U.S. National Lightning Detection Network (NLDN) within 50 to 500 km of the Lightning Observatory in Gainesville (LOG), Florida. Out of the 5498 flashes, 3496 (64%) had detectable preliminary breakdown (PB) pulse trains. Only 3077 flashes with a single PB pulse train and NLDN-reported first-return-stroke (RS) peak current ≥50 kA were selected for detailed analysis. The arithmetic mean values of PB pulse train duration, PB-RS interval, and PB/RS pulse peak ratio were 2.7 ms, 8.8 ms, and 0.15, respectively. The PB-RS interval was found to decrease with increasing RS peak current (Spearman correlation coefficient was statistically significant and equal to −0.80). The range-normalized PB pulse peak exhibited statistically significant positive correlation with the RS peak current, with Spearman correlation coefficient being 0.48. Thus, it appears that the high-intensity (≥50 kA) negative lightning is characterized by shorter (and, by inference, faster) stepped leaders and more pronounced PB pulse trains.
Sensitivity analysis of leader channel models used in long air gap positive discharge modelling
2014 International Conference on Lightning Protection (ICLP), 2014
Leader models used in electrical discharge simulation have been proposed in theoretical works by different authors. Their application can be found in the study of lightning upward connecting leaders or long air gap laboratory testing, and can be considered engineering or physical according to their detail level. Based on simplifications and assumptions, these models are capable of predicting the 50% breakdown voltage for certain electrode arrangements, time evolution of physical phenomena like particle densities, temperatures, electric fields, leader and streamer progress, among others. An important parameter in a leader model is the potential distribution along the channel as it propagates. In present work, we compare an engineering and a physical leader model against experimental data recorded while testing a rod-to-plane 10 m gap with switching-like voltage impulse. A sensitivity analysis was done with some basic input parameters of two leader models in order to compare the outcome for different cases. The results showed a strong dependence of the leader channel evolution with the assumed constant average potential gradient used in most of the leader models.
Study and Numerical Simulation of Negative and Positive Corona Discharge: A Review
Periodica Polytechnica Electrical Engineering and Computer Science
Two models to describe the phenomenon of corona discharge are presented: the first is known as the plasma model which with plasma chemistry defines the volumetric and surface reactions among charge carriers such as electrons, positive, and negative ions. This model uses Poisson's equation and a formulation of the space-charge density to calculate the electric field necessary to solve the species transport equations. Besides, only the plasma model determines the density of the charge carriers. The second is a simplified model which describes the corona discharge in terms of current conservation coupled with Poisson's equation. This model does not have any connection with the attributes of plasma chemistry. Both models propose solutions for the electric potential and space charge density distribution from the corona electrode to the ground electrode.
Research of the discharge with parameters of lightning channel
Czechoslovak Journal of Physics, 2004
The experiments were taken place in the High Voltage Laboratory at the Institute of Plasma Physics and Laser Microfussion in Warsaw. We investigated the parameters of discharge (200 A, 60 C) at atmospheric pressure. The visible spectroscopy and high-speed cameras as the main diagnostic tools were used. During the discharge current channel transformations and ball-like structures formation were observed. Lifetime of this balls increases with its diameter. In visible spectra a lot of lines belonging copper none ionized atoms were present. We also found several lines that represent CuII and CuIII emission and a few lines of OI, OII and NI, NII. The plasma temperature and density was calculated assuming the local thermal equilibrium. The records of high-speed cameras were used to determinate the diameter and evolution of plasma channel and to calculate the characteristic speed of plasma transformation. Acquired data provided both to make confrontation of pressures in the plasma and to observe the creation of ball structures. From this comparison we may deduce that the atmospheric pressure plays the main role. Magnetic pressure controls the dynamics of the channel in relatively long scales of ms.
Numerical Simulation of Stepping and Branching Processes in Negative Lightning Leaders
Journal of Geophysical Research: Atmospheres, 2020
• Numerical model capable of reproducing the dynamics of negative-leader stepping 10 and branching processes has been developed 11 • Model predictions on leader speed, step length, interstep interval, and charge trans-12 fer are in reasonably good agreement with observations 13 • As an independent model prediction, current pulses generated at the end of step-14 formation process carry positive charge over hundreds of meters upward along the 15 negative leader channel
A New Modelling For The Simulation Of The Positive Spark
2008
This paper presents a new modelling of the positive discharge development, based on new simplifying assumptions. The main hypothesis is that the E-field within the corona region keeps a constant value. The simulations are compared and discussed with experimental results performed in a rod-plane gap.