This paper proposes a simple method of determining the distance to voltage collapse using some local information such as bus voltage magnitude and load current magnitude. First the voltage and current information are carefully processed to establish a voltage stability index (VSI) that varies almost linearly with load. The VSI is then used to estimate the distance to voltage collapse using linear extrapolation. The effects of generator reactive power limits, line tripping, non-uniform increase in load and additional shunt reactive power sources on the VSI are also investigated. The effectiveness of the proposed method of determining the distance to voltage collapse is then tested on the IEEE 30-bus system. The results obtained by the proposed method are also compared with the corresponding actual values found through repetitive power flow simulations and are observed to be in very good agreement.
