AN IMPROVED BACKFLASHOVER MODEL FOR ESTIMATING THE LIGHTNING PERFORMANCE OF TRANSMISSION LINES

An improved backflashover model, which estimates the lightning performance of high voltage overhead transmission lines using Monte Carlo statistical technique, is presented based upon a previous study. In contrast to the earlier approach in which only mean values of design characteristics and meteorological data were considered, this method takes into consideration the characteristics of each one individual tower of the transmission line and the exact meteorological conditions for the particular geographic region where each one tower is located. Furthermore it gives the opportunity to use in the calculations, either the measured footing resistance of each tower, or to estimate the tower footing resistance by providing the resistivity of soil and the geometric characteristics of the grounding system. The improved method coded as a Visual Basic computer program, has been applied, on several operating Hellenic transmission lines, with different geometrical and geographical characteristics, showing much greater accuracy than this which has been shown using the earlier approach and results almost identical to the field observation data. The proposed method can be used as a useful tool in the design of electric power systems, aiding in a more effective protection of them against lightning strokes.