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A new approach to ANN-based real time line outage contingency analysis for voltage security assessment in a power system has been proposed in this paper. In this approach a separate ANN has been trained for each of the vulnerable load buses in the system from the voltage stability point of view. The vulnerable load buses of the system are identified by modal analysis of the system reduced Jacobian (of Q-V coupling) matrix. The output obtained from each of these ANN's is the "distance to voltage collapse" in terms of the MVAR margin available at the specific vulnerable load bus corresponding to the current operating point (loading condition) of the system. The novel inputs proposed for these ANN's consist of the complex power contributions of each of the generators and other controllable reactive power sources provided in the system in meeting the load at the particular load bus at the current loading condition and the electrical distances between these sources and the load bus, in addition to the conventionally used inputs of reactive power margins at the sources and the complex power drawn by and the voltage magnitude at the particular load bus. These special inputs have been proposed essentially to take care of two types of evolving voltage instability processes in a system viz. the reactive power sources gradually exhausting their limits as well as the transmission system approaching its maximum power transfer capabilities.