Lightning induced voltages on an distribution network over an inclined terrain (original) (raw)
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Electric Power Systems Research, 2014
This paper presents the effect of the terrain geometry in lightning induced voltages calculation on power distribution networks. We have calculated the electromagnetic fields over three different non-flat terrains configurations, by means of the Finite Difference Time Domain (FDTD) method in a two dimensional (2D) cylindrical coordinate system. We have simulated a typical distribution network placed over those terrains, and we have calculated the lightning induced voltages over these lines by means of the Agrawal coupling model. The simulated terrains are for finite and infinite conductivity. It can be seen important differences between the lightning induced voltages over non-flat terrain compared with traditional calculation considering flat terrain, specially when the finite conductivity is considered.
FDTD analysis of distribution line voltages induced by inclined lightning channel
Electric Power Systems Research
This paper investigates lightning induced voltages on a distribution line, when the lightning channel is not vertical but angled to the line and the earth representation is based on the finite-difference time-domain (FDTD) method. The effect of the current flowing into the earth, after the lightning channel touches the earth, is also investigated. The induced voltages are quite dependent on the angle of the channel to the line as can be easily estimated. It is found that the lightning angle with the line causes significant increase of the voltage and the effect of the earth resistivity on the induced voltage has been made clear when considering the inclined channel. Since the induced voltage is, in theory, proportional to the frequency of the inducing current, i.e. inversely proportional to rise time Tf when the inducing and induced circuits are parallel. When the lightning channel is angled, the proportional relation is less clear than that in the vertical channel. This fact has to be taken into account when discussing the effect of Tf. The current flowing in the earth is also affected by the lightning inclination and the voltage drop along the earth surface due to the current becomes larger than that in the vertical lightning case.
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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 ...
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
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.
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2014 International Conference on Lightning Protection (ICLP), 2014
We use a full-wave finite-element-based solution of Maxwell's equations for the evaluation of lightning electromagnetic fields inside a vertically stratified, two-layer ground (oceanland mixed propagation path) and their induced currents on the shield of buried cables. For "normal" incidence (with respect to the ocean-land interface), it is shown that the vertical electric field is the component most affected by the ocean-land mixed path when the observation point is close to the ocean-land interface (i.e., 5 m or so). For "oblique" incidence, however, depending on the angle of incidence and the distance between the observation point and the ocean, all the field components are reduced by the ocean-land interface. For the calculation of induced currents, and for the case of a parallel layout (cable laying in parallel to the ocean-land interface); 1) for a strike to the land, when the cable is buried in the soil and the distance to the ocean is greater than about 100 m, the effect of the ocean is negligible. 2) For a strike to the ocean, the induced current magnitudes are appreciable only when the cable is entirely within the land. For the case of a perpendicular layout (cable perpendicular to the ocean-land interface); 1) for a strike to the ocean, when the cable is totally buried in the ocean, the effect of ocean-land mixed propagation is negligible. However, when the cable extends into the land through one end, the induced currents increase at both ends with increasing length of underland portion. 2) For a strike to the land, when the cable is located entirely inside the land, the effect of ocean-land mixed path on the induced currents at both ends is negligible. However, as the cable extends into the ocean, a remarkable enhancement in the induced currents is observed for the termination located inside the land. This enhancement can be as high as a factor of 2 with respect to the case of a cable in homogeneous soil characterized by the properties of the land.
Jurnal Teknologi, 2013
This paper investigates the effect of design parameters on the induced voltages on a distribution power line. This investigation is based on perfect ground conductivity, single stroke lightning and lightning without branches. The design of the parameters includes, d, the striking distance of the lightning, h, the height of the conductor, and r, the diameter of the conductor, all of which are elements that produce the variations in the induced voltage on a distribution power line with respect to a vertical or an inclined lightning channel. Thus, the outcome of this investigation can act as a guide for utility companies or other power engineers in order to plan an appropriate protection scheme for a distribution power line.
Lightning-induced voltages at both ends of a 448-m power-distribution line
1992
Lightning-induced voltages due to return strokes in ground flashes beyond about 5 km are measured simultaneously at both ends of an unenergized 448-m power-distribution line. The measurements represent an extension of an earlier experiment on the same line in which voltages were obtained at only one end of the line. In addition to the induced voltage measurements, the causative lightning electric and magnetic fields are recorded. The voltage and field measurements are made as a function of the lightning direction and of the power-line termination. For both measured and idealized electric fields as inputs to a time-domain transmission-line coupling model, we calculate line voltages as a function of the incident angle of the lightning electromagnetic radiation and of the line termination. Measured and predicted voltages calculated from the coupling model with measured fields as inputs show, overall, good agreement in waveshape, but the predicted voltages are about a factor of three larger in amplitude. To the extent that the results can be compared, there is reasonable agreement with the earlier experiment on the same line. I. INTRODUCTION EMBERS of the Lightning Research Laboratory of the M University of Florida (UF), working in the Tampa Bay area of Florida during the summer of 1979, made the first simultaneous measurements of lightning return-stroke electric and magnetic fields and the power-line voltages induced by those fields [l]. Voltage measurements were made at one end of a 500-m unenergized overhead distribution line. The Tampa experiment provided evidence of the importance of the lightning horizontal electric field component [2].' Previously, the importance of the horizontal electric field was known theoretically (e.g., [3]), but was not shown experimentally for the case of lightning until 1980 [4]. Further, the vertical component of the electric field was generally viewed in the previous power literature as the only important inducing field (e.g., [5] and [6a]-[6dJ). Comparison of measured line voltages from Tampa with calculated voltages derived from measured vertical electric fields and calculated horizontal Manuscript
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.