Estimation of the resistance effect in the short circuit current through a sensitivity analysis

Abstract

The assessment of the current in an electrical power system (EPS) after a fault, is generally termed short-circuit analysis. The magnitude of those currents is used for dimensioning the protection equipment of the EPS. Short-circuit analysis assumes that the electrical resistances of the components can be neglected, since they do not significantly affect the magnitude of the short-circuit currents. This work quantifies the effect of the electrical resistance of the elements of the EPS on the magnitude of the short-circuit current, by means of sensitivity (SA) and uncertainty (UA) analyses. The SA is based on the variance decomposition of an output variable, and can quantify the main effects (importance) and the interactions of the variables considered. On the other hand, The UA allows assessing how the variations in the variables considered affect the output. The proposed approach is illustrated on two networks from the literature, considering three-phase and single-phase faults. The results of such proposed approach numerically show that the effects due to taking into account the electrical resistance are indeed negligible, when compared to the rest of variables considered in the short-circuit analysis. This result coincide with the assumptions reported in the literature for the calculation of the fault currents.