Evaluation of the Statistical Characteristics of Grounding Impulse Impedance of Transmission Line Towers

This paper evaluates the representativity of median impulse impedance in lightning response of tower-footing electrodes, for impulses characteristic of first strokes. The analysis is based on the implementation of Monte Carlo method using random front time values to determine the associated values of grounding impulse impedance. Statistical distributions for the impulse impedance values are then obtained, considering counterpoise lengths for different soil resistivities. With these distributions and considering the disruptive effect method, it is evaluated the impact of lightning’s randomness on the impulse grounding impedance value and, consequently, on the performance analysis of transmission lines.