Probabilistic load flow for assessment of voltage instability

The paper presents the advantages offered by probabilistic load flow when used for the assessment of voltage instability. The probability density functions of voltages and of unit reactive productions readily provide probabilities of threshold violations for a whole planning period, reflecting the random variation of loads, generation uncertainties, dispatching effects and outages. The voltage standard deviations and the voltage/reactive injection sensitivities are proposed as effective probabilistic voltage collapse indices.