Improved Voltage Collapse Proximity index for prediction of Voltage instability in distribution networks

One of the main criteria for voltage stability limit in modern power systems is load-ability limit (LL) real-time monitoring of system status and voltage collapse prediction based on the basic concept of maximum power transfer through a line; reassess to estimate closeness to the nose point of P-V curve in this paper. This article proposes an improved voltage collapse proximity index (IVCPI ) that considers the relative direction of active and reactive powers at the receiving end for assessment of the voltage stability status of the system. The proposed approach has been applied to 12-bus and 69-bus distribution systems to validate its practicability. The results also present the estimate of the maximum load-ability of the line due to voltage instability and distance to the line loading margin. It is proved that the proposed index gives adequate results in finding load-ability margins in all practical cases.