Online Voltage Stability Assessment using Wide Area Measurements

Loads and operating conditions continuously undergo changes in a power system. Changes in load are arbitrary in nature and the load power factor may or may not remain constant. Load change affects the voltage profile of the system. Excessive change in load may lead to voltage instability in the system and a proper indication is required to confirm how far the system is from impending instability through the usage of voltage stability indices. Available voltage instability identification methods, depending on rate of voltage variation with respect to active/reactive load power changes, are valid only for variations in active/reactive load or for load variations with constant power factor. An index for assessing voltage stability has been proposed here. It is valid for any type of load variations with variable power factor. The method, proposed in this paper, is implemented on New England 39 bus system and North Eastern grid of India consisting of 233 buses. Results demonstrate the accuracy of the method.