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this paper is a result of ongoing activity carried out by Understanding, Prediction, Mitigation and Restoration of Cascading Failures Task Force under IEEE Computer Analytical Methods Subcommittee (CAMS). The task force's previous papers [1, 2] are focused on general aspects of cascading outages such as understanding, prediction, prevention and restoration from cascading failures. This is the second of two new papers, which extend this previous work to summarize the state of the art in cascading failure risk analysis methodologies and modeling tools. The first paper reviews the state of the art in methodologies for performing risk assessment of potential cascading outages [3]. This paper describes the state of the art in cascading failure modeling tools, documenting the view of experts representing utilities, universities and consulting companies. The paper is intended to constitute a valid source of information and references about presently available tools that deal with prediction of cascading failure events. This effort involves reviewing published literature and other documentation from vendors, universities and research institutions. The assessment of cascading outages risk evaluation is in continuous evolution. Investigations to gain even better understanding and identification of cascading events are the subject of several research programs underway aimed at solving the complexity of these events that electrical utilities face today. Assessing the risk of cascading failure events in planning and operation for power transmission systems require adequate mathematical tools/software.

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Interconnected power grids throughout the world are very reliable but occasionally suffer massive blackouts with multibillion dollar costs to society. Cascading failures present severe threats to power grid reliability, and thus reducing their likelihood, mitigation and prevention is of significant importance. This paper is one in a series presented by Cascading Failures Task Force, under the IEEE PES Computer Analytical Methods Subcommittee (CAMS) with primary focus on mitigation and prevention of cascading outages. The paper presents the basic methodologies for mitigation, summarizes currently deployed special protection schemes, and lists cases of successful and unsuccessful mitigation of cascading outages and lessons learned. Future developments and challenges in the area of mitigating cascading outages are also discussed.

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 postcontingency 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.