FDTD Computation of Lightning-Induced Voltages on Multiconductor Lines With Surge Arresters and Pole Transformers (original) (raw)
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FDTD analysis of distribution line voltages induced by non-vertical lightning
Electric Power Systems Research, 2020
This paper investigates lightning induced over-voltages on overhead lines considering “bent” and “computationally-generated” non-vertical lightning channels by using a finite-difference time-domain (FDTD) method. In the former case, combinations of vertical and inclined channels with different connecting heights are modeled to represent “bent” lightning. It is made clear that the peak voltage is significantly influenced by the lightning channel geometry under 100-m altitude when severe conditions of a 1/200-μs current and a lightning distance of 50 m are assumed. Induced voltages on the three-phase line show similar characteristics to those on the single conductor line. In the latter case, a lightning-like (zig-zag) channel is computationally generated by a probabilistic calculation based on an electric potential distribution in a three-dimensional space, and its induced voltage is compared with that by a simply-inclined channel. When average inclined angles under 100-m altitude in ...
2001
LEMP to transmission line coupling equations can be dealt with either in the frequency domain or in the time domain. A time domain approach allows handling in a more straightforward way non-linearities which appear when considering corona effect, and/or when protective devices such as surge arresters are present. This is the approach proposed by Agrawal et al. to solve their transmission line coupling equations. In particular, Agrawal et al. proposed a 1 st order point centered Finite-Difference Time Domain (FDTD) integration scheme. In this paper, we propose a 2 nd order FDTD scheme for solving the Agrawal coupling equations. The algorithm applies to multiconductor lines above a frequency-dependent lossy ground, with multiple grounding of shielding wires. 1 st and 2 nd order FDTD techniques are compared. It is shown that the proposed 2 nd order technique leads to more stable numerical results when considering frequency-dependence and/or non linearities. The developed 2 nd order FDTD algorithm for the analysis of overhead multiconductor lines illuminated by an external electromagnetic field is also interfaced with EMTP96.
IEEE Transactions on Electromagnetic Compatibility, 2000
In this paper, the lightning-generated electromagnetic fields over lossy ground produced by lightning strikes either to flat ground or to a tall tower are calculated using the 2-D finitedifference time-domain (FDTD) method. The resultant horizontal and vertical electric fields are used as forcing functions in the discretized Agrawal electromagnetic coupling equations for the calculation of induced voltages on overhead horizontal conductors without employing the Cooray-Rubinstein formula. Comparison of the results with those obtained using the 3-D FDTD method and with experimental data found in the literature is used to test the validity of the examined method. The approach employed here generally provides sufficient accuracy while allowing significant reduction in computation time and storage requirements as compared to the 3-D FDTD method. From the analysis carried out in this paper, induced voltages appear to be strongly dependent on ground conductivity, somewhat influenced by return-stroke speed, and essentially independent of return-stroke model [transmission-line (TL), modified transmission line with linear current decay with height (MTLL), or modified transmission line with exponential current decay with height (MTLE)]. Index Terms-Electromagnetic coupling model, finite-difference time-domain (FDTD) method, lightning electromagnetic pulse (LEMP), lightning-induced voltage.
Electric Power Systems Research, 2015
In this paper, a simplified model of corona discharge for the finite-difference time-domain (FDTD) computations has been applied to analysis of transient voltages at the tower of a transmission line caused by direct lightning strikes to an upper phase conductor. In the simulations, three 40-m towers, separated by 300 m, with one overhead ground wire and three phase conductors are employed. Corona is assumed to occur only on the upper phase conductor struck by lightning. The progression of corona streamers from the conductor is represented as the radial expansion of cylindrical conducting region around the conductor. The reduction of transient-voltage peak due to corona is not very significant, so that the voltage at the nearest tower exceeds the insulation level of 66/77 kV power line considered in this paper. For a 10-kA peak current, the upper-phase-conductor voltage peaks are reduced by 26% and 21% for a positive stroke with 1-sand 3-s-risetime currents, respectively, and those for negative-stroke case are reduced by 18% and 13%, respectively. For a 20-kA peak current, the corresponding upper-phase-voltage peaks are reduced by 32% and 25% for the positive-stroke case, and those for the negative-stroke case are reduced by 22% and 15%.
One of the main issues that has to be faced when evaluating lightning-induced overvoltages on a realistic network configuration is to implement the algorithm that solves the field-to-line coupling problem into an electromagnetic simulator that is able to represent with a high level of detail all the power system components. On one hand, numerical stability conditions of the finite-difference time-domain schemes have been deeply investigated in the presence of boundary conditions known analytically; on the other hand, there is not so much literature on the situations in which such conditions are provided in a numerical way through an external electromagnetic simulator. The study reveals that the commonly used linear extrapolation of currents at the line extremities might rise to numerical instabilities. An efficient solution using the method of characteristics is presented and validated. Index Terms-Finite-difference time domain (FDTD), lightning electromagnetic pulse, lightning-induced effects and protection, numerical methods and modeling.
IEEE Transactions on Power Delivery, 2006
Simulation of very fast surge phenomena in a three-dimensional (3-D) structure requires a method based on Maxwell's equations, such as the finite-difference time-domain (FDTD) method or the method of moments, because circuitequation-based methods cannot handle the phenomena. This paper uses a method of thin-wire representation of the vertical conductor system for the FDTD method which is suitable for the 3-D surge simulation. The thin-wire representation is indispensable to simulate electromagnetic surges on wires or steel frames in which the radius is smaller than a discretized space step used in the FDTD simulation. In this paper, a general surge analysis program named the virtual surge test lab based on the Maxwell's equations formulated by the FDTD method, is used to simulate the surge phenomena of a vertical conductor, including the effects of horizontal wave incidence and vertical wave incidence. Experimental results on the reduced scale model have been presented in order to compare among the simulation results by the FDTD method and the results using numerical electromagnetic code based on the MoM.
2012 Asia-Pacific Symposium on Electromagnetic Compatibility, 2012
In this paper, a simplified model of corona discharge for finite-difference time-domain (FDTD) computations has been applied to analyzing lightning surges propagating along a 25 or 21 mm radius, 2.2 km long single overhead horizontal wire, which simulates the experiment of Wagner et al. [1954]. The critical electric field on the surface of the 25 mm radius wire for corona initiation is set to E 0 =1.3, 2.1 or 2.5 MV/m, and E 0 =2.2 MV/m for 21 mm radius wire. The critical background electric field for streamer propagation is set to E cp =0.5 MV/m for positive voltage application and E cn =1.5 MV/m for negative voltage application. The FDTD-computed waveforms of surge voltage at three different distances from the energized end of the wire agree reasonably well with the corresponding measured waveforms.
IEEE Transactions on Electromagnetic Compatibility, 2000
A computational environment was developed for simulating transient electromagnetic phenomena involving complex structures. The system is based on the finite-difference timedomain method and includes tools such as a graphical user interface, a 3-D structure visualization module, thin-wire formulation, dielectrics and metallic blocks, perfectly matched layers, voltage and current sources, creation of field distribution images, voltage and current calculations, among others, all of them associated with automatic domain division for parallel (distributed) processing. In this paper, this system is used for obtaining full-wave solutions, for the first time, of lightning surge interactions with the structural part of a power substation. Parameters such as transitory step and touch voltages and potential distribution on ground surface are calculated for 1 kA peak for the injected surge current.
IEEE Transactions on Power Delivery, 2004
In this paper, we investigate the effect of periodically-grounded shielding wires and surge arresters on the attenuation of lightning-induced voltages. We discuss the adequacy of the commonly made simplification of assuming the shielding wire at ground potential, instead of being treated as one of the conductors of the multiconductor system. We also compare then the mitigation effect of shielding wires with that achievable by the insertion of surge arresters along the line. The computation results are first validated by means of calculations obtained by other authors referring to a simple line configuration, and then by means of experimental results obtained using a reduced-scale line model illuminated by a nuclear electromagnetic pulse (NEMP) simulator. One of the main conclusions is that the effectiveness of shielding wires and surge arresters depends mostly on the spacing between two adjacent grounding points or surge arresters.
Applications of Time-Domain Numerical Electromagnetic Code to Lightning Surge Analysis
IEEE Transactions on Electromagnetic Compatibility, 2000
Recently, applications of 3-D numerical electromagnetic analysis have been increasing either for lightning electromagnetic impulse (LEMP) studies or lightning surge analyses on transmission and distribution lines. This paper is mainly concerned with the use of time-and frequency-domain codes for electromagnetic analysis of lightning surges. The thin-wire in time-domain (TWTD) code and numerical electromagnetic code (NEC-2) in the frequency domain based on the method of moments are chosen for comparative studies. The accuracy of TWTD code in the analysis of lightning surge characteristics of a double-circuit transmission tower is first investigated by comparing the computed results with the measured results on a reduced-scale tower model, computed results by NEC-2 on a full-scale tower model, and those computed by electromagnetic transients program. In the latter part of the paper, a switch model is combined with the TWTD code, and its applicability in analyzing the lightning surge characteristics of a transmission tower equipped with a surge arrester or in analyzing lightning-induced voltage on an overhead line is demonstrated. Index Terms-Lightning surge, moment method, numerical electromagnetic code (NEC-2), numerical electromagnetic analysis, nonlinearity, thin-wire in time-domain (TWTD).