Lightning return stroke models for electromagnetic field calculations

Abstract

Return stroke models are used in the calculation of lightning-induced over-voltages in power lines because the electric and magnetic field as a function of distance and height along the line is difficult, if not impossible, to obtain experimentally. Thus the return stroke models should represent faithfully the electric and magnetic fields generated by lightning first and subsequent return strokes, the events that induce largest over-voltages in power systems. Following an introduction and nomenclature, the reader is introduced in Sections 3.2, 3.3 and 3.4 to the various concepts used by engineers (i.e. current propagation, current generation and current dissipation) to construct engineering return stroke models. In Section 3.5, the way in which any given return stroke model could be represented as a current generation or current dissipation type is described. After showing that current propagation concept is a special case of current dissipation concept in Section 3.6, the way in which the current generation and current dissipation concepts could be combined to obtain return stroke models that are in agreement with current pulse propagation along transmission lines in the presence of corona is presented in Section 3.7. In Section 3.8, a review of the basic features of electromagnetic fields of return strokes that are being used in testing the engineering return stroke models are presented. This section is followed by a description of the evaluation of electromagnetic fields, including the horizontal electric field, from return stroke over finitely conducting ground. The chapter ends with concluding remarks.