Plenary Lecture

Lightning Performance of Power Distributions Lines: Models and Critical Aspects

Prof. Amedeo Andreotti
Department of Electrical Engineering
University of Naples “Federico II”
Naples – 80123 – ITALY
Tel. +39-081-7683215
Fax +39-081-2396897
e-mail andreot@unina.it

Abstract: The lecture deals with the procedures for the assessment of the overhead line indirect lightning performances. Distribution line outages due to indirect lightning strokes is one important cause of disturbances in distribution systems. The trouble caused to customers, because of the susceptibility of some loads, may be very severe even in the case of transient faults, i.e. those which disappear after the opening and high-speed reclosure of protective breakers. Hence, it is useful and important to reduce the frequency of the occurrence of faults caused by such indirect strokes. From this point of view first of all it is necessary to evaluate the expected frequency of occurrence of faults due to lightning as a measure of the lightning performances of a distribution line. To estimate the expected frequency of occurrence of faults due to indirect lightning any procedure is divided into two parts:
a) evaluation of the overvoltages induced on an overhead line by an indirect lightning;
b) statistical evaluation of the lightning performances of an overhead distribution line.
As far as point a), the procedure involves two main aspects: the evaluation of the electromagnetic field generated by the lightning stroke and the analysis of the field to line coupling in order to calculate the induced voltage.
As far as point b), the estimation of the occurrence of the lightning faults presents many uncertainties due to the random nature of the lightning phenomenon. Hence, to obtain an accurate estimation of the line lightning performances, a statistical treatment of the data is needed. To perform that, the flashover rate of the line is usually calculated. In this circumstance, the results are presented in the form of a graph of flashover rate versus the insulation level of the line. In literature, different methods have been proposed regarding the statistical calculations, and more general Monte Carlo technique has also been used.
Aims of the lecture are to present a review of the models and methods adopted for the estimation of lightning performances of the distribution lines and also the recent developments in literature in this field. Some considerations will also be made about some critical points of some methods adopted in literature.

Brief Biography of the Speaker:
Prof. Amedeo Andreotti is with Department of Electrical Engineering of the University of Naples Federico II in Italy. He teaches Electrical Power Systems. He is author or co-author of more than 20 books (in Italian) in the field of electrical power systems and electrical machines. He is author or co-author of more than 70 scientific papers published on important international reviewed journals in the field of power systems transients, power lines modelling, electromagnetic compatibility. He is member of IEEE, CIGRE, AEIT (Italy).