TOWARD A PRACTICAL PERFORMANCE INDEX FOR PREDICTING VOLTAGE COLLAPSE IN ELECTRIC-POWER SYSTEMS

Voltage collapse is generally caused by either of two types of system disturbances: load variations and contingencies. A number of performan ce indices intended to measure the severity of the voltage collapse pr oblem have been proposed in the literature. However, few of these perf ormance indices can answer questions such as: ''Can the system withsta nd another 100 MVar increase on bus 11?'' This paper presents a new pe rformance index that provides a direct relationship between its value and the amount of load demand that the system can withstand before col lapse. One of the features that distinguishes the proposed performance is its develop ment in the load-demand space and its ability to answe r questions such as: ''Can the system withstand a simultaneous increas e of 70 MW on bus 2 and 50 Mvars on bus 6?''. This feature makes the p erformance index readily interpretable to operators. Moreover, the com putation involved in the proposed performance index is relatively inex pensive in comparison with those required in the existing ones. Simula tion results on the IEEE 39-bus system and a 234-bus power system are presented with promising results.