Invited speaker:  Prof. Farhad Rachidi,
                           Swiss Federal Institute of Technology, Switzerland

Lightning-Induced Voltages on Overhead Electrical Networks

Abstract: Overvoltages induced by indirect lightning on overhead lines can cause damage to either power systems, or communication network and electronic control/management systems. Moreover, due to its more frequent occurrence, indirect lightning constitutes a more important cause of short-interruptions and voltage sags than direct strikes, especially for distribution networks. Their estimation is therefore crucial for the correct protection and insulation coordination of overhead lines and, as a consequence, has been the subject of various studies during the past decades. The problem has been seriously reconsidered in recent years due to the increasing demand by customers for good quality in the power supply, and new models have been consequently developed to obtain a more accurate estimation of lightning-induced voltages.
In this talk, the theory describing the interaction of lightning electromagnetic fields with overhead lines will be presented, with particular reference to power systems. The LIOV (Lightning-Induced OverVoltage) code developed within the framework of an international collaboration involving the University of Bologna and the Swiss Federal Institute of Technology will be described. The experimental test and validation of coupling models using data from either natural or artificially triggered lightning, EMP simulators, or reduced scale modelling will also be presented. Finally, examples of simulations illustrating the effect of ground finite conductivity, shield wires and surge arresters will be presented.

Biography: Farhad Rachidi received the M.S. degree in electrical engineering and the Ph.D. degree from the Swiss Federal Institute of Technology, Lausanne, in 1986 and 1991 respectively. He worked at the Power Systems Laboratory of the same institute until 1996. In 1997, he joined the Lightning Research Laboratory of the University of Toronto in Canada and from April 1998 until September 1999, he was with Montena EMC in Switzerland. He is currently the head of the EMC Group at the Swiss Federal Institute of Technology, Lausanne, Switzerland. His research interests concern electromagnetic compatibility, lightning electromagnetics and electromagnetic field interactions with transmission lines. He is the convener of the joint CIGRE-CIRED Working Group “Protection of MV and LV networks against Lightning”, Vice-Chair of the European COST Action P18 'The Physics of Lightning Flash and its Effects', Chairman of the Subcommittee “Lightning” of the Technical Committee TC5 of IEEE EMC Society. He is member of the Editorial Board of the Journal of Lightning Research, Associate Editor of the IEEE Transactions on Electromagnetic Compatibility, and member of the scientific committees of various International Symposia in the field of EMC and lightning protection. Farhad Rachidi is author or coauthor of over 200 scientific papers published in reviewed journals and presented at international conferences. He was the recipient of the 2005 IEEE EMC Society Technical Achievement Award and of the 2005 CIGRE Technical Committee Award. In 2006, Farhad Rachidi received the Blondel Medal from the French Association of Electrical Engineering, Electronics, Information Technology and Communication (SEE).