Carlo Alberto Nucci - Profile on Academia.edu (original) (raw)

Papers by Carlo Alberto Nucci

IEEE open access journal of power and energy, 2021

In the usual practice, the evaluation of overvoltages due to direct lightning strikes to overhead... more In the usual practice, the evaluation of overvoltages due to direct lightning strikes to overhead power lines is focused on the representation of the effects of the lightning current injection, whilst the effects of the coupling between the conductors and the lightning electromagnetic pulse (LEMP) is disregarded. Motivated by recent results obtained for the case of a medium voltage line configuration with a shield wire, this paper extends the analysis to assess the contribution of the LEMP on the lightning performance of an overhead distribution line with and without periodically grounded wires and surge arresters. Moreover, the paper deals with the LEMP effect on the occurrence probability of flashovers on different phases, which is an important information on the service continuity of networks with isolated or compensated neutral earthing. A validation of the results is obtained by comparing the overvoltages calculated by the electromagnetic transient program including the model of the line illuminated by the LEMP and those obtained by a three-dimensional finite difference time-domain approach.

Lightning-induced voltages on an overhead line above a lossy ground: a sensitivity analysis

International Conference on Lightning Protection, 1996

IEEE Transactions on Power Delivery, Oct 1, 2018

This paper proposes the application of a recursive stratified sampling technique for improving th... more This paper proposes the application of a recursive stratified sampling technique for improving the assessment of the lightning performance of power distribution lines through the application of the Monte Carlo method. The accuracy of the results is expressed by means of the confidence interval of the estimated annual number of expected overvoltages. The paper shows the results for a single overhead line, with and without surge arresters, and the case of a feeder with laterals. The adoption of the stratified sampling techniques allows for a computational time reduction up to more than 75% with respect to a standard Monte Carlo procedure. The conceived calculation procedure is applicable to any type of network, regardless of the presence of non-linear devices and avoiding the application of any heuristic rule.

Journal of Geophysical Research, 1990

We compare five lightning return stroke current models that exhibit a simple relationship between... more We compare five lightning return stroke current models that exhibit a simple relationship between the current at the return stroke channel-base and the current along the return stroke channel, namely the Bruce-Golde (BG) model, the transmission line (TL) model, the Master, Uman, Lin, and Standler (MULS) model, the Traveling Current Source (TCS) model, and the Modified Transmission Line (MTL) model, by assuming a common current wave shape at the channel base and then calculating the channel currents and charges and the resultant electric and magnetic fields. There are basically two characteristics that distinguish the models, namely, (1) the treatment of the return stroke wave front and (2) the spatial and temporal distribution of charge removed from the leader channel. The simpler BG model can be used as an excellent approximation to the TCS model. The latter reduces to the former when the current injected downward by the traveling current source has an infinite speed. The MULS model is equivalent to the MTL model when the MULS uniform current is assumed to be zero. The BG and TCS models produce sharper initial field peaks than do the TL, MTL, and MULS models. The ratio of the peak field derivative to the peak current derivative is near the ratio of the peak field to the peak current for the MULS and MTL models and is equal for the TL model, whereas for the BG and TCS models the ratio of the peak derivatives is about twice the ratio of the peak field to peak current. The TL model is unrealistic for long-time field calculations due to the fact that no net charge is removed from the channel. The other four models produce overall fields which are reasonable approximations to measured fields from natural lightning even though, for the assumed channel-base current, the BG and TCS models do not reproduce the observed distant-field zero crossing and the MTL and MULS models do not reproduce the magnetic "hump" observed after the initial field peak at close range. None of the models can reproduce the fine structure observed in the measured fields. 1.

Statistical Assessment of Lightning-Induced Overvoltages in Low Voltage Lines

The aim of the paper is to present an efficient procedure for the accurate assessment of the freq... more The aim of the paper is to present an efficient procedure for the accurate assessment of the frequency of lightning-originated faults in low voltage distribution lines. The advantage of the proposed procedure lies in the application of the stratified sampling technique, which allows to reduce the computational effort required by the Monte Carlo method. Indeed, such a sampling technique is particularly effective when the collecting area is very large, as in the lightning performance analysis of low voltage lines. The paper shows the results for the case of an overhead cable line and similar results have been obtained for a line with bare conductors. The procedure is also applied for the selection of surge protective devices through the assessment of the statistical distribution of their absorbed charges.

Analyse du champ électromagnétique dû à une décharge de foudre dans les domaines temporel et fréquentiel

Annales Des Télécommunications, Nov 1, 1988

Résumé L’article présente une analyse dans les domaines temporel et fréquentiel du champ électro... more Résumé L’article présente une analyse dans les domaines temporel et fréquentiel du champ électromagnétique généré par une décharge de foudre négative, calculé au niveau du sol. Cette analyse a été effectuée en se basant sur le modèle de la « ligne de transmission » modifié par les auteurs, qui donne des résultats concordant avec les données expérimentales. L’influence de plusieurs paramètres

Guide for numerical electromagnetic analysis methods: application to surge phenomena and comparison with circuit theory-based approach

CIGRE - Int. Council on Large Electric Systems, 2013

The aim of this document is to provide an extended description and application guide of methods b... more The aim of this document is to provide an extended description and application guide of methods belonging to the so-called Numerical Electromagnetic Analysis (NEA) applied to the calculation of electromagnetic transients in power systems. As known, the accurate computation of electromagnetic transients is a fundamental requirement of several studies in the area of power systems. Lightning and switching studies are, for instance, typical subjects where the accuracy of transient\u2019s computation has a direct influence to the proper sizing of components like insulators and breakers. Traditional approaches adopted since now were based on the combination of circuit and transmission lines theories. These approaches, analytically and numerically validated by numerous contributions to the literature, rely on specific assumptions that are inherently relaxed by NEA methods. Indeed, NEA methods mostly rely on the numerical solution of the full-wave Maxwell\u2019s equations and, in this respect, the assessment of their accuracy, as well as the description of the various numerical methodologies, have motivated the preparation of this Technical Brochure

Using Electromagnetic Time Reversal Similarity Metric to Locate Lightning-Originated Flashovers on Overhead Transmission Lines

2019 International Symposium on Lightning Protection (XV SIPDA), 2019

The paper presents a method to locate flashovers resulting from direct lightning strikes to overh... more The paper presents a method to locate flashovers resulting from direct lightning strikes to overhead transmission lines. The method exploits the electromagnetic time-reversal theory and uses the cross-correlation between the flashover-originated transient current observed in the direct time and the transverse branch currents in the reversed time at the guessed flashover locations as a similarity metric to identify the location of the flashover. The performance of the similarity metric is numerically illustrated using two simulation case studies associated with a shielding failure and a back-flashover.

Este trabalho tem como objetivo analisar e comparar o desempenho de possíveis projetos de redes d... more Este trabalho tem como objetivo analisar e comparar o desempenho de possíveis projetos de redes de distribuição aéreas de média tensão sob descargas atmosféricas. Sendo realizado em uma parceria entre o

Lightning-Induced Voltages on Buried Cables. Part II: Experiment and Model Validation

22nd International Conference and Exhibition on Electricity Distribution (CIRED 2013), 2013

The aim of the paper is to assess the risk of insulation failure of distribution transformers con... more The aim of the paper is to assess the risk of insulation failure of distribution transformers connected to overhead distribution due to indirect lightning induced voltages. The annual frequencies of occurrence of dangerous voltages are evaluated through a Monte Carlo procedure and by using the LIOV-EMTP code for the calculation of the Lightning Electromagnetic Pulse (LEMP) and its effects on the multiconductor line. The probability of distribution transformers insulation to withstand the stresses caused by lightning overvoltages is inferred from the results of experimental test.

Far Field-Current Relationship for Lightning Return Strokes to Elevated Strike Objects

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

An energy resource scheduler implemented in the automatic management system of a microgrid test facility

Abstract The paper deals with a microgrid test facility, settled at the CESI RICERCA laboratories... more Abstract The paper deals with a microgrid test facility, settled at the CESI RICERCA laboratories, equipped with various distributed energy resources (DERs) and connected to a LV network. The operation of such a microgrid is supervised by a central automatic microgrid management system (MMS). The paper first reports and discusses some experimental results carried out for the assessment of DERs performance and for the implementation of specific MMS functions. Then, it describes the functions of the energy resources scheduler ...

Lightning hazard of structures and protection system efficiency

Conference Record of the IEEE Industry Applications Society Annual Meeting

ABSTRACT A probabilistic method for assessing the lightning hazard of structures and a simplifica... more ABSTRACT A probabilistic method for assessing the lightning hazard of structures and a simplification of this method for practical purposes is proposed and discussed. The risk of structural damage is evaluated as a function of the efficiency of the lightning protection system, the probability of damage due to a single flash, and the frequency with which lightning flashes strike the structure. Simplifications of this method are introduced; the damage probabilities are replaced by a weighting coefficient corresponding to different properties of the structure but without respect to economical factors, which should be considered on the background of local particularities. These considerations are illustrated by practical examples.< >

Journal of Electrostatics, 2004

The evaluation and the analysis of the lightning electromagnetic pulse (LEMP) response of distrib... more The evaluation and the analysis of the lightning electromagnetic pulse (LEMP) response of distribution networks require the availability of accurate models of LEMP-illuminated lines and their implementation into software tools able to calculate lightning-induced electromagnetic transients in distribution systems having complex configuration. This paper deals indeed with a computer code, LIOV (lightning induced overvoltage code), and with two interfaces recently realized between it and (a) the DCG/EPRI EMTP96 on the one hand and (b) the SimPowerSystems program in the Matlab-Simulink environment on the other hand. The aim of these interfaces is to extend the simulation capabilities of the LIOV code, which computes lightning-induced voltages on a single multiconductor transmission line above lossy ground, to the case of distribution systems characterized by complex yet realistic configurations. Models/code validation by means of a comparison with experimental results is also presented.

IEEE Transactions on Power Delivery, 2004

This paper presents a new approach to model a transmission tower for lightning performance studie... more This paper presents a new approach to model a transmission tower for lightning performance studies. It consists of representing each part of the tower by equivalent vertical and/or horizontal transmission lines as required. While horizontal line parameters are obtained from standard line formulas, specific expressions are derived for the parameters of vertical lines. Moreover, mutual coupling between any two parallel vertical transmission lines is taken into account. Transient waveforms obtained using the proposed method are compared with experimental data obtained using a reduced-scale model and field experiments. The agreement between simulated results and experimental measurements is satisfactory.

IEEE Transactions on Electromagnetic Compatibility, 2008

Engineering return stroke models can be categorized either as current generation (traveling curre... more Engineering 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 10-500 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 show that 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.

Lightning-induced voltages on an overhead line above a lossy ground: a sensitivity analysis

ENERGIA ELETTRICA-MILAN-, 2001