Monitoring the Voltage Stability Margin Using Norton Current Distribution Relationship

The impedance matching condition has been a fundamental assumption of many existing studies on voltage stability assessment. In this paper, it has been proven that the Norton current distribution law is equivalent to the impedance matching condition. Based on this law, a new voltage stability index is proposed, which can be further divided into bus voltage stability index and line voltage stability index. These indexes of the focused load bus can be calculated by phasor measurement units data. Then, the voltage stability margin can be assessed by computing the difference between the index value and 1. The effectiveness of the proposed on-line voltage stability index are verified from simulation results perform in a 10-bus system and 39-bus system. Moreover, practical operating constraints such as the generator power limits are taken into account for practical assessment of the proposed method.