On the Stability of FDTD-Based Numerical Codes to Evaluate Lightning-Induced Overvoltages in Overhead Transmission Lines (original) (raw)
Related papers
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, 2015
In this paper, lightning-induced voltages on multiconductor lines with surge arresters and pole transformers have been computed using the 3-D finite-difference time-domain 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 experiment of Piantini et al. (2007).
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.
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 ...
IEEE Access
This paper presents a macro-model, which can be used to calculate the lightning-induced overvoltages (LIOVs) on overhead lines on MATLAB/Simulink platform. First, a macro-model according to Agrawal's field-to-line coupling model is derived, in which the distributed equivalent voltage sources due to the horizontal components of the incident electric fields are lumped at the terminals of the transmission lines. In order to interface with MATLAB/Simulink, the propagation function of the transmission line is approximated by a delayed rational function and described by a state-space representation, and Brune's synthesis is adopted to model the equivalent multiport equivalent circuit of the transmission line in order to overcome the passivity violation problem. Combining with the built-in components in MATLAB/Simulink, the proposed modeling approach is applied to evaluate LIOVs of an overhead lines system, and the influence of the arrester and ground wire on the LIOVs is discussed in this paper. Furthermore, considering that the peak values of LIOVs are mainly concerned in the insulation coordination, a simple model for the early time response is proposed, which can further simplify the procedure. The accuracy of the proposed modeling method is validated by some examples.
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.
A SPICE simulation of lightning induced overvoltages on power transmission lines
Advances in Engineering Software, 2000
In this study, overvoltages produced on multiconductor power lines by indirect lightning are analysed. In particular, the case of power lines with ground wires terminated on non-linear loads is studied. The power line is represented by an equivalent time±domain m-port and the effects of the lightning excitation are represented through equivalent independent sources. The time±domain circuit has been implemented in SPICE. Simulations have been carried out in order to evaluate the shielding effect of the ground wires and to analyse the effects of surge arresters. The results have been compared to those available in the literature. q
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%.
The Impact of Transmission Line Modeling on Lightning Overvoltage
Energies
In most of the work that investigates the backflashover phenomenon due to direct lightning strikes, using EMT-type simulators, transmission lines are represented by the J. Marti model and the ground effect is computed employing J. R. Carson’s formulations. Thus, the ground displacement current is neglected, the line voltage definition corresponds to the wire potential formulation, and soil resistivity is considered frequency-independent. These considerations can lead to erroneous measurements of the occurrences of the backflashover phenomenon in the insulator strings of transmission line. In this sense, this paper presents a systematic sensitivity analysis study of lightning overvoltage in insulator strings considering more physically consistent models of the transmission line, which consider the displacement current, ground admittance correction, rigorous voltage definition, and frequency-dependent soil parameters. According to the results, for the case study, transmission line par...
Lightning – Induced Overvoltages on Overhead Lines : Modelling and Experimental Validation
2007
The evaluation of induced overvoltages from indirect lightning has been for more years one of the most important problems in designing and coordinating the protection of overhead power lines. In this paper, we present the frequently coupling model used in the power lightning literature for the calculation of lightning induced overvoltages, the Agrawal approach. The algorithm applies to single conductor line above a perfectly conducting ground. The computation results are first validated by experimental results obtained using a reduced scale line model illuminated by the EMP simulator of the Swiss Federal Institute of Technology in Lausanne (SEMIRAMIS), and then are compared with the computation results obtained by the LIOV code (beta version).