Toward a practical performance index for predicting voltagecollapse in electric power systems

Voltage collapse is generally caused by either of two types of power system disturbances: load variations; and contingencies. A number of performance indices intended to measure the severity of the voltage collapse problem have been proposed in the literature. However, few of these performance indices can answer questions such as: “can the system withstand another 100 MVar increase on bus 11?” This paper presents a new performance index that provides a direct relationship between its value and the amount of load demand that the system can withstand before collapse. One of the features that distinguishes the proposed performance is its development in the load-demand space and its ability to answer questions such as: “can the system withstand a simultaneous increase of 70 MW on bus 2 and 50 MVAr on bus 6?” This feature makes the performance index readily interpretable to operators. Moreover, the computation involved in the proposed performance index is relatively inexpensive in comparison with those required in existing solutions. Simulation results on the IEEE 39-bus system and a 234-bus power system are presented with promising results