Electromagnetic Coupling of Lightning to Power Lines: Transmission-Line Approximation versus Full-Wave Solution

Abstract—The problem of accurate prediction of lightning-induced overvoltages on power lines still attracts considerable at-tention. A variety of approaches of different levels of sophistication have been proposed. In particular, transmission-line (TL) approx-imation is widely used for describing electromagnetic coupling of lightning with power lines. In this paper, validity of this approach for lossless lines is demonstrated by analytically demonstrating that, under the assumptions that are typically justified for practi-cal power distribution lines, the TL approximation and the more rigorous full-wave analysis lead to identical results. Index Terms—Full-wave solution, induced overvoltages, light-ning, overhead power lines, transmission-line (TL) approximation. NOMENCLATURE b0y y-component of the incident magnetic field. c Speed of light in free space

On the estimation of lightning peak currents from measured fields using lightning location systems

Although, due to the high variability of key parameters such as the return-stroke speed, it is impossible to determine the lightning current accurately from the remotely measured electric or magnetic field for a given event, we show in this paper that, for an assumed return-stroke model, the statistical estimation (e.g. in terms of mean values and standard deviations) is possible. We show additionally that for the transmission line (TL) model, the equation permitting to infer the mean value of the return-stroke current from the mean value of electric or magnetic field and the mean value of speed has the same functional form as the well-known TL current—far field relationship. This result gives to some extent a theoretical justification to the use of lightning location systems to infer parameters of lightning current statistical distributions from measured fields alone

On the Relationship Between the Signature of Close Electric Field and the Equivalent Corona Current in Lightning Return Stroke Models

Abstract\u2014Engineering return stroke models can be categorized either as current generation (traveling current source type) models or current propagation (transmission line type) models. The current generation models are described among other parameters by a corona current distributed along the channel. Recent studies show that there is equivalence between the models of current generation and current propagation types. Due to this equivalence, any engineering return stroke model of current propagation type can be described in terms of an equivalent corona current per unit channel length. The measurements conducted within 10\u2013500 m from triggered lightning flashes show that the electric field of subsequent return strokes at these distances flattens within 15 μs or so. In this paper, the constraints imposed by this feature on the temporal and spatial variation of the equivalent corona current are investigated. The results showthat in order for the close fields to flatten within 15 μs or so, the equivalent corona current, should be bipolar and the corona current wave shape at late times should be identical to that of the longitudinal current time derivative. This is in contrast to most of the engineering models of current generation type, in which the corona current is assumed to be unipolar

Pulses in Upward Negative Lightning at the Säntis Tower in Northeastern Switzerland

Upward lightning happens predominantly from tall objects. The channel-base currents associated with upward negative lightning initiated from towers exhibit pulses that can be classified, based on their waveform features and on the concurrence with other processes in the flash, into four categories. Three of them (M-component-type pulses, M-component pulses, and Mixed-mode pulses) are always superimposed either on the continuous or on the continuing current, and the remaining type (Return Stroke pulses) is initiated during a zero-current interval. Simultaneous measurements of the channel-base current and electric fields 15 km from the tower were analyzed. Good agreement was found between measured and calculated electric field waveforms when simulations were carried out using the MTLE model for the return stroke and for the mixed mode pulses, and when the model of Rakov at al. was used for M-components and M- component-type pulses. The analysis validates the similarity between M-component-type pulses superimposed on the Initial Continuous Current during the initial stage of upward negative lightning and M-components pulses superimposed on the continuing current that follows some return strokes. In addition, the results indicate that mixed-mode pulses are similar to return strokes. In the two studied flashes, the initial stage was associated with a larger charge transferred to ground than the ensuing return strokes and their associated continuing currents and M components, the factor being almost four-to-one

Effect of traveling-waves of current on the electromagnetic response of a tall Franklin rod considering various lightning return stroke models

none7Free-standing Franklin rods are commonly used to protect ordinary structures from lightning damage. In view of the importance of the sub-microsecond response of such strike object generated by lightning-current impulses, the paper is analyzing i) the development of the voltage at the top of the rod, and ii) the initial electromagnetic fields radiated by the rod and the lightning channel as predicted by different lightning return stroke models.mixedE.P. Krider; S. Guerrieri; F. Napolitano; C.A. Nucci; M. Paolone; F. Rachidi; V.A. RakovE.P. Krider; S. Guerrieri; F. Napolitano; C.A. Nucci; M. Paolone; F. Rachidi; V.A. Rako