Identification of the vulnerable transmission segment and cluster of critical machines using line transient potential energy

When a power system is subjected to a large disturbance, effective identification of vulnerable transmission segment and generator groupings in the electric network contribute to the effective analysis of power system dynamic behaviour and the determination of optimal locations of FACTS devices. Also, computational simple and reliable identification of critical machines is of primary importance in the successful application of direct or hybrid transient stability assessment methods such as TEF, EEAC and hybrid methods. In the paper, a new approach is proposed for identifying the transmission vulnerable segment (the weakest cutset), and then classifying machines into critical cluster and remaining cluster, using a quantitative transmission line vulnerability assessment index derived from the post-fault line transient potential energy and bus voltage changes. The calculation of the index is simple and fast, as only the line flow and bus voltage along the post-fault trajectory are required. Case studies using the IEEE 10-generator and 50-generator test systems are given to illustrate the validity of the proposed method.