N-1-1 AC contingency analysis as a part of NERC compliance studies at midwest ISO

This paper addresses the development, testing and implementation of a fast automated process for assessing power system performance following loss of two bulk transmission elements consecutively (N-1-1 contingency analysis) and simultaneously (N-2 contingency analysis). The approach described in this paper offers a flexibility to utilize various sets of system adjustments depending on types and values of post-contingency limit violations. It also incorporates sequential contingency simulation in order to identify potential cascading modes due to thermal overloads. Massive AC contingency analysis, automatically identifying various sets of system adjustments and prediction of cascades are performed within one computational run. The proposed process is utilized as a part of Midwest ISO´s NERC-compliance studies. Flexible reporting ensures that the obtained results are seamlessly integrated into the Midwest ISO´s existing reliability results database. This approach may be used by ISOs and utilities as a part of their compliance studies to assess and improve the reliability of a transmission grid and reduce its vulnerability to cascading outages.