L. Verolino

An Exact Closed-Form Solution for Lightning-Induced Overvoltages Calculations

We present the evaluation of the induced voltages in a lossless single transmission line, located at a given height over an infinite conductivity ground plane, and exited by an external field due to a step current moving along a vertical channel. This is a classic topic of the theory of lightning-induced voltages on power lines. The technical literature related to this topic has performed a significant effort; however, only approximated formulas have been obtained so far. In this paper, we derive the exact closed-form solution. We also will discuss, evaluate, and compare the approximated formulas with reference to the proposed exact one, thus contributing to clarifying a matter that still is debated and sometimes misleading, as we will show in the paper. We furthermore recall that the examined lightning-induced voltages model is fundamental for the IEEE standard 1410, a guide for improving the lightning performance of power distribution line.

An improved procedure for the return stroke current identification

We propose an improved procedure to identify the lightning return stroke current characteristics. This procedure follows the inverse approaches, presenting a new expansion basis able to widen the class of function which can be reconstructed.

Lightning electromagnetic fields and induced voltages: Influence of channel tortuosity

Models for calculation of lightning induced overvoltages usually assume a straight and vertical lightning channel. However, it is well known that the lightning path is tortuous on scales ranging from 1 m to 1 km. In this paper the tortuosity effect is analyzed for both lightning-generated electromagnetic fields and induced voltages. For a schematic representation of tortuous lightning channel, it is shown that at close and intermediate ranges the predominant effect is due to the inclination of the lowest channel segment; only for fields at relatively far ranges the overall tortuosity effect becomes appreciable.

A field‐based inverse algorithm for the identification of different height lightning return strokes

An identification procedure for lightning return strokes is proposed. It makes it possible to reconstruct the return stroke height‐dependent attenuation function making use only of the measured vertical component of the electric field radiated by the lightning channel and it can be performed without any information about the channel base current, the measurement of which is generally very difficult and noisy. It is also shown that the method, with suitable modifications, can also be employed for the mathematical evaluation of the lightning channel height, which is a physical quantity a priori unknown. The approach has been validated by means of the numerical simulation of classical TL, MTLL and MTLE engineering models for a wide class of return strokes, with height ranging in the interval 15‐30km.

Analytical Formulations for Lightning-Induced Voltage Calculations

Recently, Andreotti (2009) have presented an analytical solution for the evaluation of voltages induced on an infinitely long, lossless, single-conductor located at a given height above an infinite-conductivity ground plane, and excited by an external field due to a step current wave moving without attenuation and at a constant speed along a vertical lightning channel. The solution presented, in contrast to previously published solutions, was derived in an exact way, i.e., no approximations were introduced in its derivation. In this paper, this exact approach is extended to more practical line configurations. Specifically, still for the case of an external field due to a step current and perfectly conducting ground, the cases of terminated single-conductor line and multiconductor line (including grounded conductors) will be studied. Further, single- and multiconductor lines (including grounded conductors) excited by an external field due to a linearly rising current will be examined.

An inverse procedure for the return stroke current identification

We propose a procedure to identify the lightning return stroke current characteristics, in the context of return stroke engineering models. The main effort of the up-to-date literature is to find approximate current shapes, which best fit the experimental data. The method hereafter proposed does not follow these approaches, but proposes an inverse algorithm, which allows us to accurately identify the return stroke current for simulated data.

Calculation of Voltages Induced on Overhead Conductors by Nonvertical Lightning Channels

Effects of lightning channel tortuosity and tilt on lightning electric fields and voltages induced on overhead conductors are examined. Overall inclination of the bottom few hundred meters of the lightning channel can appreciably change both the ground-level vertical electric held at distances less than 1 km or so and induced voltage peak relative to the vertical-channel assumption. Smaller-scale tortuosity is responsible for the fine structure of held and induced voltage waveforms. This fine structure can be pronounced at some hundreds of meters and beyond, but is insignificant at shorter ranges.

An identification procedure for lightning return strokes

Abstract In this paper an inverse procedure for the identification and the reconstruction of the waveform of the lightning return stroke current is presented. It is based on the acquisition of the vertical component of the electric field radiated by the discharge channel at different locations on the ground and it does not require any information about the channel base current. The approach has been validated by means of the numerical simulation of the classical Transmission Line, Modified Transmission Line Linear and Modified Transmission Line Exponential engineering models, showing good accuracy in all cases.

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

The problem of accurate prediction of lightning-induced overvoltages on power lines still attracts considerable attention. A variety of approaches of different levels of sophistication have been proposed. In particular, transmission-line (TL) approximation 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 practical power distribution lines, the TL approximation and the more rigorous full-wave analysis lead to identical results.

Non-linear behaviour of LEMP excited power lines terminated on surge-arresters

The transient analysis of non-linearly loaded power lines is carried out. The line is excited by indirect lightning and the analysis is performed in the time domain, where the line is represented as an equivalent dynamic m-port and the effects of the lightning excitation are taken into account through equivalent independent sources. The analysis has been carried our taking into account the effects of the finite ground conductivity. Furthermore, an accurate model has been used for the non-linear surge-arresters, to take into account dynamic effects.