Power system probabilistic fault calculation based on multi-operating conditions

From the known statistical attributes of variations of system parameters, such as the load or generator powers, probability distributions of post-fault voltages and currents are obtained by probabilistic fault analysis. Expectations and variances of the post-fault voltages and currents can be determined by probabilistic analytical methods. Expectations and variances, the two most frequently used numerical characteristics, can describe the probability distribution characteristics of these variables in some degree. Based on the multi-operating conditions formed by the operating curves of nodal injections and PV voltages, from the basic property of numerical characteristics of the random variables, the expectation expressions and linear covariance expressions of the post-fault voltages and currents are deduced in this paper. By the results of the linearized model and the complete second-order model of probabilistic power flow, the calculations and analyses are carried out in the case of three-phase short-circuit fault on an eight-machine system.