In this paper, a new analytical method is presented for calculation of the “N-1″ transmission line outage post contingency states of the power system, without any needs to iterate the calculation process, which makes the method fast enough for online vulnerability assessment under N-1 Transmission line outages for large-scale transmission networks with wind power resources. The proposed method is based on the proposed pretending line outage principle and a pre-contingency Taylor Series Approximation. Moreover, an adaptive technique is proposed for selection of the number of critical lines. First, various test systems including IEEE 9-, 39-, 57-, 118-, 300-, and 2746-bus are used for investigation of the performance of the proposed method in terms of accuracy and computational time. Moreover, the ability of the proposed method in solving the Online Vulnerability Assessment under the uncertainty of the operating condition, caused by wind power resources and load demand forecast error, is investigated in IEEE 118-bus and IEEE 300-bus test systems. Finally, the simulation results are presented to verify that the proposed approach has sufficient speed and accuracy to be used in online operational vulnerability assessments.
