| With the development of social economy,people’s demand for electricity is increasing rapidly,and the scale of the power system is also expanding.With the gradual expansion of the scale of the power system,the huge grid structure and the intricate wiring are likely to cause a blackout in the power grid.Once a blackout accident occurs,it will not only cause huge inconvenience to people’s production,life and work,but also cause huge economic losses.Therefore,how to prevent and reduce the occurrence of blackouts is particularly significant.Power grid blackouts are usually caused by the occurrence of grid cascading failures.The occurrence of grid cascading failures is closely related to cascading trips in the grid.The early stage of cascading failures generally manifests as cascading trips.Therefore,studying the cascading tripping of power grids and related problems is extremely important to prevent the occurrence of cascading failures.From the perspective of power grid cascading trips,this paper analyzes and excavates some key factors that affect cascading trips in the power grid,and then analyzes and studies the specific effects of key factors on cascading trips.This paper firstly starts with the occurrence mechanism of cascading trips,combined with the action behavior of relay protection,and gives the mathematical expressions of the identification indexes of cascading trips in the power grid.At the same time,through the analysis of the general manifestation of cascading tripping and the action equation of relay protection,three key factors that have an impact on cascading tripping in the power grid are unearthed,namely the transmission power of the initial fault branch,the setting value of relay protection devices,and the key nodes in the power grid.Then,the three key factors are modeled and analyzed separately,and the influence mechanism of each key factor on the cascading trip is analyzed in their respective models,combined with the safety level index of the cascading trip of the power grid.In the transmission power modeling of the initial fault branch,the direct current method is mainly used to derive the mathematical expression of the transmission power limit of the initial fault branch,and the impact analysis is carried out on this basis;In the research of key nodes,this paper first screens out the severely disturbed branches in the remaining system of the power grid after the initial failure,and then combines the relationship between the severely disturbed branch currents and the system nodes,and uses the FCM clustering analysis algorithm to divide the system nodes to obtain the key nodes in the power grid.Finally,the impact of the node injection power change of the key nodes on the safe operation level of the power grid is studied;In the research of protection setting value,two research ideas of the protection setting value to the safe operation level of the power grid are firstly given,and then a large number of calculation examples are carried out for the two research ideas.In the analysis results of the calculation example,the influence of the change of the protection setting value on the safe operation level of the power grid is summarized.The study of the influence of each key factor on the cascading tripping of the power grid is finally carried out by taking the IEEE14-bus system and the IEEE39-bus system as examples.The results of the calculation example analysis verify the mechanism of the impact of the above three key factors on the cascading tripping and the validity of the built model,which can provide theoretical basis and help for taking measures to prevent the occurrence of cascading trips before and after the initial failure of the power grid. |
