Probability Insecurity Index In Complex Power Injection Space Considering Fault Cleaning Time

The probabilistic method for power system security assessment, which considers the influence of some random factors on power system security, is an important supplement to convectional method. In complex power injection space, an insecurity index model reflecting the probability security of power system after a transmission line fault is proposed in the article. In addition to considering the uncertainties of load forecasting at each node, the fault cleaning time, the fault occurrence location, the fault resistance and the reactive power injection, the uncertainty of the proportion of induction motor is also taken into account.Based on the displacement characteristics of the Dynamic Security Region in complex power injection space, through reasonable assumption, the article presents a simplified calculation of the index. A quick calculation method of the corresponding hyperplanes of Dynamic Security Region of different random fault is presented, which improve the speed of the calculation of probability security index.Through much simulation of transmission system Dynamic Security Region in complex power injection space under different fault cleaning time, we can deduce the following property: 1) the boundary hyperplanes of Dynamic Security Region under different fault cleaning time are approximately parallel; 2) the distance between the hyperplanes under different fault cleaning time are nearly linable.By introducing the concept of extended Dynamic Security Region, which considers the distribution of fault cleaning time, this article gives a simplified arithmetic about probabilistic insecurity index. This arithmetic calculates only two critical power injections under different fault cleaning time and one corresponding Dynamic Security Region.Tests on the New England 4-generator 11-bus test system show that the results of simplified arithmetic are more precise than before, and computation is not notably increased.