A Novel Index for Online Voltage Stability Assessment Based on Correlation Characteristic of Voltage Profiles

Voltage instability is a major threat for security of power systems. preserving voltage stability margin at a certain limit is a vital requirement for today’s power systems. assessment of voltage stability margin is a challenging task demanding sophisticated indices. in this paper, for the purpose of on line voltage stability assessment a new index based on the correlation characteristic of network voltage profile is proposed. voltage profile comprising all bus voltages contains the effect of network topoloy, load-generation patterns and reactive power compensation on the system behavior and voltage stability margin. therefore, the proposed index is capable to clearly reveal the effect of all system characteristics and events on the voltage stability margin. the most attractive feature for this index is its fast and easy calculation from synchronously measured voltage profile without any need to system modeling and simulation and without any dependency on network size. at any instant of system operation by merely measuring network voltage profile and no further simulation calculation this index could be evaluated with respect to a specific reference profile. the results show that the behavior of this index with respect to the change in system security is independent of the selected reference profile. the simplicity and easy calculation make this index very suitable for on line application. the proposed approach has been demonstrated on ieee 39 bus test system with promising results showing its effectiveness and applicability.