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In this paper the indirect-lightning flashover rate of a distribution line is obtained following the procedure described in the IEEE Std. 1410 - 2010, but using other parameters of the first stroke distributions (peak current and front time) adopted by CIGRÉ. These parameters were taken from the measured currents of the Morro do Cachimbo Station in Belo Horizonte - Brazil, which are representative of the tropical zone. As a result, the calculated flashover rate with the data of tropical zone is higher than one obtained with the CIGRÉ curves. Such increments could be in the most extreme case of 70%. [ABSTRACT FROM AUTHOR]

This work deals with two kind of resistive models for grounding in transmission lines portrayed in the IEEE 1243- 1997 Standard: counterpoises and supplemental groundings rods. It is analyzed the effect of varying the internal parameters of each model that affect the resistive value of grounding in the reduction or the increase of the backflashover rate due to lightning strikes to the structure or to the ground wire over terrains with several conductivities. It is used the ATPDraw software to obtain the critical currents and then to obtain the back-flashover rate of the line. It was simulated the effect of the number, longitude, radius and depth of the electrodes in the back-flashover rate of a transmission line for several values of ground conductivity. It was obtained reductions percentages of the backflashover rate between 50 and 95%. [ABSTRACT FROM AUTHOR]