Probabilistic constrained load flow for optimizing generator reactive power resources

The generator reactive capability curve normally used in operation planning overestimates the reactive supply or absorption capabilities of the unit because it does not consider the operating conditions of the generator plant and of the electric power system. These are determined by the tap positions on the generator step-up and on the auxiliary unit transformer. This paper presents the application of probabilistic constrained load flow to optimal selection of these taps. It is shown that the technique proposed provides tap settings satisfying the reactive requirements for a whole range of operating conditions taking into account their probabilities of occurrence.