Hierarchical approach to contingency evaluation considering simultaneous double faults

This paper proposes a hierarchical approach to simultaneous contingency evaluation considering simultaneous double faults. The expectation of contingency impact is discussed with consideration of the probability of fault occurrence and the estimated damage of the fault. A hierarchical approach is adopted for contingency analysis; the higher level deals with the online contingency evaluation for single line contingencies and the lower level deals with offline evaluation for numerous double contingencies. To improve the accuracy and the computation speed of the contingency analysis, the Peterson method has been adopted with the Sherman-Morrison formula and a matrix decomposition method. The triangular factor table technique is also adopted, to compute the inverse matrix in the load flow calculation. Based on these methods, simulation considering several cases show that double circuit simultaneous faults analysis suggested in this paper offer fast load flow computation in short time by calculating relative accurate phase angle variation.