Quantitative transient voltage dip assessment of contingencies using trajectory sensitivities

A new index, voltage critical clearing time (V-CCT), is presented for quantitative assessment of transient voltage dips subject to various contingencies. Calculation of V-CCT needs estimation using trajectory sensitivities of voltages with respect to fault clearing time. The V-CCT indices indicate the severity of fault-initiated contingencies by comprehensively evaluating transient voltage dips according to dynamic performance criteria. Using trajectory sensitivities to obtain V-CCT minimizes the computational effort by avoiding repetitive trial-and-error time-domain simulations. Performance of the proposed transient voltage dips assessment method has been tested on a 9-bus system, the New England 39-bus system and a 13,000-bus system. For the small test systems, some selected contingencies are compared to verify the consistency of ranking using V-CCT with time-domain simulation analysis. The computational efficiency of the proposed assessment method is analyzed. Then the case studies on the large system build up the relation between analysis results and system operating condition. The results show that the assessment using V-CCT reflects the contingency severity in scope of transient voltage dips.