Effect of uncertainties on the precision of lightning studies

The specification of the withstand voltage of apparatuses as well as the location and characteristics of overvoltage limiting devices to be installed to protect them, requires a careful estimation of the fast front over-voltages, which might potentially exist on the system. This is usually done using an EMTP-like software program. The components of the electrical system located in the vicinity of the apparatuses under consideration are modeled to represent their high-frequency behavior. The precision on the results provided by this approach is limited by the uncertainty in the knowledge we have of key-parameters like, for instance, the value of the grounding resistance of towers or the value of the stray capacitance of some elements. We propose in this paper to examine the consequence of these uncertainties upon the precision of the final results provided by EMTP-like software program’s simulations, using stochastic collocation on a practical case of lightning study.