Lightning channel’s EM effects of large earth electrodes by moments method (original) (raw)
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This paper presents the transient behavior of an earthing system under the influence of lightning current injected in to it. Vertical rod and horizontal electrode buried in homogeneous soil are considered in this analysis. State-space representation based transmission line methodology is adopted with non-linear parameters for modelling the earthing electrodes in the time domain. Soil ionization phenomenon is taken up with the presence of residual resistivity. In this method, soil resistivity variation is adopted to evaluate the soil ionization phenomenon that occurs due to changes in the electric field. This study incorporates mutual coupling between the electrode segments for low and high soil resistivity. Earthing electrodes are subjected to a high-magnitude of lightning current impulse with different peaks. Transient voltage and impulse impedance are calculated to analyse the transient behaviour of earthing electrodes with soil ionization. Impulse impedance of vertical earthing r...
Scattering effects of large earth electrodes in the EM lightning fields
Proceedings of 8th Mediterranean Electrotechnical Conference on Industrial Applications in Power Systems, Computer Science and Telecommunications (MELECON 96), 1996
In this paper, starting from a previously developed electromagnetic model of earthing electrodes d ircxtly fed by a lightning stroke, the Authors propose an useful improvement, or ienl t 4: d tow a r d s Mom en t s method application, t o study scattering phenomena due to an incident field propagating into the soil. The cas8e of a transient plane wave is considered and some examples of transient performancies of scattered systems buried in the soil are reported.
Lightning current distributions in a vertical earthing electrode
2016
This paper presents a model for calculating the transient space-time current distributions in vertical electrodes and to the surrounding ground. The model is based on the electromagnetic field theory for calculations of the step function wave-pair response. The method takes into account the parameters of the electrode, such as: the radius and the length of the electrode. Furthermore, the conductivity, permittivity and the propagation velocity of the currents in the ground are also considered. In the analysis, the electrode is divided into finite sections. Thereafter, the "Compensating Currents", ground leakage currents and the current in the electrode in each section are calculated at all times. The model is applied by a MATLAB code for the calculations of the above-mentioned currents' distributions. The results show that for soils of high conductivity values, relative short electrodes are needed for dissipating transient currents such as lightning currents. Furthermore, soil conductivity is a more sensitive parameter compared to the radius of the electrode and the permittivity of the ground.
A Model to investigate lightning performances and coupled effects among buried long electrodes
In this paper a field approach to investigate the transient performance of long grounding electrodes is presented. The method is based on the spectral analysis and, as a great advantage in comparison with circuit approach, it enables us to calculate electrical and magnetic fields in the surrounding soil. As a particular matter, this paper, after having investigated the behaviour of a single electrode, is devoted to study fields transferred from an electrode to a separate one, in any mutuai position. As examples, time behaviour of main electric quantities are reported assuming a lightning stroke injected current.
COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, 2020
Purpose The purpose of this paper is to investigate the simultaneous effects of ionization and dispersion of soil on the impulse behavior of grounding electrodes under first and subsequent stroke currents. Design/methodology/approach A recently introduced technique called improved multi-conductor transmission line (MTL) is simplified for grounding electrodes buried in both-affected soils. Findings The simulation results show that including the two effects simultaneously in highly resistive soils under high-valued subsequent stroke current is recommended. Otherwise, simultaneous effects can be disregard. Originality/value To the best of the authors’ knowledge, there is no research on sensitivity analyses for the simultaneous inclusion of the two effects on the effective length and the induced voltage on the soil surface. To this end, the simplified MTL is applied to the grounding electrodes. The simulation results show that the computational efficiency in comparison with previous met...
Evaluation of Transient Response of Different Earthing Configurations due to Lightning Impulses
International Journal of Recent Technology and Engineering (IJRTE), 2019
Earthing system is very important in order to protect the electrical equipment as well as the human’s safety against over voltages. The main function of the earthling system is to remove unwanted excessive electrical currents caused by unusual conditions such as fault and lightning or switching over voltages by providing a low resistance path to the earth. Researchers had studied the behaviour of the earthling system to improve its performance for the past few years. There are few factors that influence the performance of the earthling system such as soil resistivity and soil ionization which need to be focused in order to improve the earthling. Thus, this paper evaluates on the factors that affect the behaviour of the earthling system based on simulation works using MATLAB and Safe Grid Software. Some analytical calculations are used to obtain the soil resistivity and resistance as well as the touch and step voltages. The simulation results were validated based on comparison with o...
IET Science, Measurement & Technology, 2008
The non linear effects of soil ionisation on the behaviour of earth electrodes are investigated by a finite difference time domain numerical scheme. A time variable soil resistivity is used in order to simulate the soil breakdown; step by step the resistivity value is controlled by the local instantaneous value of the electric field compared with the electrical strength, fixed for the soil. No a priori hypothesis about the geometrical shape of the ionised zone around the electrodes has to be enforced. Simulation results related to complex earth electrodes of limited extension are reported. The model has been validated by comparing the computed results with data available in technical literature. A discussion about dangerous earth voltages is reported, by underlining the role of soil ionisation. Electrodes of larger extension can be straightforwardly simulated by means of larger computational resources.
IEEE Transactions on Electromagnetic Compatibility, 2013
This paper presents a comprehensive study on the effect of the frequency dependence of soil electrical parameters on the lightning radiated electromagnetic fields as well as their associated induced voltages on overhead lines. To this aim, a fullwave approach based upon the finite-element method (FEM) is utilized. In the analyses, frequency dependence of soil conductivity and relative permittivity is introduced, using available analytical formulae that is obtained from experimental data. It is shown that the radial electric field is the only component which is significantly affected by the frequency dependence of soil electrical parameters at observation points as close as some tens of meters from the lightning channel. The vertical component of the electric field and the azimuthal component of the magnetic field are not much influenced by this property of soil at moderate distances (up to several hundred meters) from the lightning channel. For distant observation points and for poorly conducting grounds, however, these components are also affected. It is also shown that for soils characterized by relatively moderate and low resistivity values (less than 1000 Ω.m), lightning-induced voltages are not significantly affected by the frequency dependence of soil electrical parameters. For poorly conducting soils, instead, the frequency dependence of soil electrical parameters results in a decrease of lightning-induced voltages. Index Terms-Electromagnetic fields, FEM, frequency dependence, lightning induced voltages, lightning return stroke channel. I. INTRODUCTION E VALUATION of lightning electromagnetic fields and their associated induced voltages on overhead lines has attracted remarkable attention during the last decades (e.g., [1] and [2]). Studies focused on lightning return stroke modeling Manuscript
The Transient Current Distributions in a Vertical Electrode and the Ground
This paper presents a model for calculating the transient space-time current distributions in vertical electrodes and to the surrounding ground. The model is based on the electromagnetic field theory for calculations of the step function wave-pair response. The method takes into account the parameters of the electrode, such as: the radius and the length of the electrode. Furthermore, the conductivity, permittivity and the propagation velocity of the currents in the ground are also considered. In the analysis, the electrode is divided into finite sections. Thereafter, the "Compensating Currents", ground leakage currents and the current in the electrode in each section are calculated at all times. The model is applied by a MATLAB code for the calculations of the above-mentioned currents' distributions. The results show that for soils of high conductivity values, relative short electrodes are needed for dissipating transient currents such as lightning currents. Furthermore, soil conductivity is a more sensitive parameter compared to the radius of the electrode and the permittivity of the ground.
Analysis of ground potential distribution under lightning current condition
2017
The grounding system of a lightning protection scheme is designed basically to avoid arcing and dangerous step potentials. The grounding impedance of the system varies depending on soil structure and frequency. This paper describes the effect of harmonic impedance (also called frequency dependence of soil) on potential distribution under lightning strike to a metal tower with single grounding path, for different soil types. The results show that the peak value of ground potential rise (GPR) and step voltage (SP) may reach extremely hazardous values even at distances in the order of 90 m from the tower footing, especially when soil resistivity is high. Hence, we emphasise that, in contrast to power grounding, when designing of grounding systems that are meant to handle transient or high frequency currents as well, the frequency dependent soil parameters should be considered to avoid hazardous situations, especially at locations with a high probability of lightning strikes such as met...