Probabilistic assessment of short-circuit currents in large power systems

Short-circuit currents have by nature a multi-variable stochastic character affected by probabilistic conditions, like the fault location in the network, the type of the fault, the fault impedance and the prefault state of the system. The proposed method takes into account the random nature of these conditions using conditional probabilities and provides an analytical expression for the short-circuit current distribution with a minimum of assumptions. Thus, not only the worst case probability but also the probability of each occurrence is obtained. This increased amount of information can be extremely valuable for an objective decision-making. As a result, not only considerable savings in capital investment can be achieved, but more important designs with known risks, reliability and with sufficient margins of safety can be produced.