A simulation model for electromagnetic transients in lightning protection systems (original) (raw)
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Transient electromagnetic hazard inside a lightning protection system
This paper deals with the evaluation of electromagnetic (EM) hazard in a lightning protection system (LPS), by taking into account coupling effects among aerial parts and earthed electrodes in order to improve the computation of the quantities which can determine hazard inside the LPS. Field-approach is used; the computer code, entirely developed by the authors, is based on the numerical solution of the well-known thin-wire electric field integral equation in frequency domain. Time profiles of electromagnetic quantities are evaluated via fast Fourier transform. A suitable model to consider the lossy soil in a simplified way is proposed.
Numerical electromagnetic analysis of lightning-induced voltage over ground of finite conductivity
IEEE Transactions on Electromagnetic Compatibility, 2003
The electromagnetic transients of lightning protection system(LPS) under direct lightning strike is studied using NEC2. By employing antenna return-stroke model, lightning channel's inducing effect and finite conductivity of ground are all taken into account. Results show that the lightning channel's inducing effect tends to decrease the current flowing through horizontal conductors, and increases the current flowing through vertical conductors near the striking point. The results obtained under perfect ground assumption have a good agreement with the published experimental results. The simulation also predicts that the finite conductivity of the ground affects the branch current significantly, it increase the LPS's current dissipating efficiency, the higher the soil resistivity, the more uniform the current flowing in vertical conductors.
This paper deals with the evaluation of human body effects on dangerous transient ground voltages in a lightning protection system (LPS). The numerical model set up, based on the field-approach in frequency domain, enables to evaluate the touch and step voltages when a LPS operates, also taking into account the human body presence on the soil surface. To this purpose, a cruciai point is the right evaluation of the currents distributed among the earthed branches of a LPS and this needs to correctly consider mutuai electromagnetic interference among aerial parts and the earth-termination system of a same LPS. After a brief description of the basic concepts related to the employed method, the simulation results obtained by running different LPS are compared and discussed. The capability of the numerical scheme to evaluate realistic dangerous transient touch and step voltages is underlined.
A Mathematical Model for the Transient Lightning Response from Grounding Systems
Progress In Electromagnetics Research B, 2014
With the Fast Fourier Transform (FFT), a mathematical model for accurately computing distribution of a lightning currents flowing along a high voltage a.c. substation's grounding system buried in half infinite homogenous earth has been developed in this paper. It is a hybrid of Galerkin's method of moment (MoM) and a conventional nodal analysis method. The model can directly calculate the distribution of both branch and leakage currents along the grounding system. A dynamic state complex image method and a closed form of Green's function of a dipole or monopole in the half infinite homogenous earth model are introduced into this model to accelerate calculations of mutual impedance and induction coefficients. Analytical formulae for the mutual induction and impedance coefficients have been developed to accelerate the calculation for near field case by using Maclaurin expansion. With the inverse FFT, the model can be used to study the transient lightning response of a grounding system.
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
This paper presents results of the electromagnetic field generated by different configurations of protection structures, when lightning strikes such structures. The transitory of current in the structure, and the return current is taken into account in the calculation of the field. This paper also presents an elegant expression for calculating the resultant electromagnetic field produced by a transient on cable currents or transmission lines. By taking into consideration a line disposed arbitrarily in the Cartesian coordinate system, using the Maxwell equations and applying the magnetic potential vector, we come to the generalized expressions for the electric and magnetic fields as a function of current and position in the time domain. This expression is a generalization of the expression proposed by Christopoulos in [l]. The method has been shown to be very useful in applications where lines are disposed in arbitrary manners and especially in systems in which various lines are interconnected, such as lightning protection systems (LPS) or a grounding system. The results obtained with such expressions are compared to other numerical methods. The results are obtained applying TLM (Transmission Line Modeling) method to obtain the current transient.
Journal of Electrostatics, 2004
In the present paper, transient-induced voltages on a distribution line over finitely conducting ground, which are associated with lightning to a 200-m high stack, have been analyzed by Numerical Electromagnetics Code (NEC-2). An electromagnetic model (EM) of a lightning channel, which contains additional distributed inductance to simulate the reduced propagation velocity of lightning current, has been employed. Validity of the employed model which incorporates a tall structure and a lightning channel has been discussed by comparing calculation with measurements. r
Electromagnetic Field in the Vicinity of Lightning Protection Rods at a Lossy Ground
IEEE Transactions on Electromagnetic Compatibility, 2000
In this paper, the lightning discharge channel in the vicinity of vertical lightning protection rods is modeled in the frequency domain by a vertical mast antenna coupled with vertical parasitic elements. The ground is treated as linear, isotropic, and homogeneous lossy half-space. The vertical mast antenna and the rods are treated as a unique system as for boundary conditions that results in the electric field integral equation (EFIE) for the unknown current distributions along their axes. EFIE is numerically solved by using the method of moments and a polynomial approximation of the current distributions. The influence of the ground is taken into account through a Sommerfeld integral kernel modeled in a simple and very efficient way using one new approximation that can be classified as a two-image approximation. This approximation gives good results in the frequency domain for modeling in both near and far electromagnetic fields.
Journal of Electrostatics, 2009
An in-depth knowledge about the characteristics of lightning generated currents will facilitate evaluation of the interception efficacy of lightning protection systems. In addition, it would aid in extraction of valuable statistics (from measured current data) on local lightning parameters. Incidentally, present day knowledge on characteristics of lightning induced current in typical lightning protection systems is rather limited. This is particularly true with closely interconnected protection systems, like the one employed in Indian Satellite Launch Pad-II. This system is taken as a specific example in the present study. Various aspects suggest that theoretical modelling would be the best possible approach for the intended work. From the survey of pertinent literature, it is concluded that electromagnetic modelling of lightning return-stroke with current source at the channel base is best suited for this study. Numerical electromagnetic code was used for the required electromagnetic field solution and Fourier transform techniques were employed for computing time-domain results. A validation for the numerical modelling is provided by laboratory experiments on a reduced scale model of the system. Apart from ascertaining the influence of various parameters, salient characteristics of tower base currents for different kinds of events are deduced. This knowledge can be used in identifying the type of event, as well as its approximate location. A method for estimation of injected stroke current has also been proposed.