This paper introduces a simple method to monitorpower system voltage stability conditions in real-time. Themethod is based on the concept of Voltage Instability Predictor(VIP). The essence of the method is a simple computation of avoltage stability boundary based on VIP derived quantities. Thestability boundary is assumed as a parabolic equation in the P-Qplane identified using measurements collected at a specificsubstation, transmission path, or load center. The computedstability boundary is further visualized in a P-Q plane, togetherwith a point representing the current operating conditions, andgenerally re-computed as soon as the new set of measurements iscollected (preferably at high rates using phasor measurementunits). Simplicity and easy interpretation of the results bringsthis method as a useful tool to increase system operatorsituational awareness. Supporting results are provided usingrelatively big test system (52 bus Nordic test system) and a real-lifesystem (a portion of the North-West USA system).
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