Numerical estimation of drained lightning currents on MV lines

The study of lightning discharges on electric lines involves a number of variables, which for different reasons, are not exactly defined. One solution to allow the use of these variables in analytical calculations is considering only their mean values or only their maximum values. The problem in this case is that the final results could be far from the real behavior because all the magnitudes are considered with their maximum values at the same time, and this situation rarely happens under real conditions. The use of statistical simulation could solve all this problems, attaching to every possible value of each variable a probability of occurrence. The results obtained are not unique numbers but probabilistic distributions. So, from these distributions, the medium, maximum, or other values may be obtained for lines´ design. In the particular case of lightning over electric lines, medium values of the variables are normally used, but several authors include a numerical simulation for the place of stroke (using Monte Carlo method). In this paper, we propose to simulate all the variables according to their statistical distribution, obtaining a general method for numerical simulation of lightning discharges on distribution lines. This method could be applied with different final objectives as the evaluation of overvoltages, personal risks, number of trip outs, or design parameters. We applied here the method to obtain the currents drained in grounding electrodes due to the lightning strokes on the ground wire, or on the structures. Some results related with the number of expected strokes per year are obtained