Spread Vulnerability Assessment Of Power System Cascading Failure Based On Percolation Theory

With the more comoplex structure of power grid and Its connectivity is also gradually improving, When cascading failure occurs in the power grid, its influence is more and more wide.The problem is difficulty for the incidence and prevention of cascading failures. The vulnerability of the power grid failure mechanism different stages of research contribute to the cascading failure prevention. The paper study cascading failure at different stages of development and evaluate cascading failure to predict the path,which is some theoretical significance.The paper describes the problems of different connectivity percolation model on a grid system with a probability p randomly occupy seepage points on the grid and connectivity, at a certain degree of phase change (formation of large regional connectivity). The method describes the system state mutation phenomenon. Has been successfully applied in the field of graph theory, wireless communications networks. The paper attempts to apply the method to introduce the grid cascading failures of crispness assessment.The crispness assessment method of power system cascading failure is studied. Firstly,the paper get the various branches power flow and the system voltage of each node,when cascading failure occurs, the paper establish power breakdown, voltage breakdown, loss of load breakdown,, percolation probability of a failure is obtained by the trend of transfer factor and the transfer to the adjacent line after line trend based on the point of seepage, seepage get failure.The vulnerability of line is obtained by the sum of the four parts. Analysis of cascading failures in the process of development in the grid topology node degree distribution and cumulative distribution, the average distance, line betweenness, correlation coefficient. Then line the various stages of crispness sort, whichever first several conducted to assess the next stage of crispness line.The stage of vulnerability is the sum of each stage of vulnerability. Each path is predicted when cascading failure occurs.The system is analyzed under normal load,120%,150%of load. Simulation results show that the vulnerable line increase with the power breakdown increasing in the breakdown of N-K breaking.When the system happen the N-K fault,we sequence vulnerable line.we remove the line which the sequence is back because of its protection incorrect action then getting brittle variation system becomes large, protected by mistake move and refused to move, such as hidden failures to cascading failures play role in boosting development.Finally, the paper analyse the influence on the power fluctuation system in the different stages of development cascading failure,and give the power changes when a line break sensitivity index, made the corresponding theoretical analysis and simulation experiments.