The voltage stability is the ability of the power system to provide adequate reactive power under all operating conditions and to maintain stable load voltage magnitude within specified operating limits. The voltage instability leading to collapse appears to be due to the inability of networks to meet a demand for reactive power at certain critical or weak buses. It can be recognized by noting excessive fall in voltage for small increase in load and increasing difficulty in controlling system voltage. Therefore voltage collapse prediction must take in consideration in power system planning and operation. In this paper a novel indicator from a parallel algorithm will be presented to predict the voltage instability or the proximity of a collapse. The indicator uses the obtained data of a normal load flow to identify the weak buses in the power system.
This method has carried out over changing the load power factor. Obtained results for the IEEE 5 bus system considering the effects of STATCOM on voltage stability are presented and discussed.