A Systematic Approach to ${n}$ -1-1 Analysis for Power System Security Assessment

Cascading outages can have a catastrophic impact on power systems. One such recent incident was the September 8, 2011 blackout that affected San Diego and large parts of the southwestern United States. To prepare for such events, the NERC transmission planning standards require utilities to plan for ${n}$ -1-1 outages. However, such analyses can be computationally burdensome for any realistic power system owing to the staggering number of possible ${n}$ -1-1 contingencies. This paper proposes a systematic approach to analyze ${n}$ -1-1 contingencies in a computationally tractable manner for power system security assessment. The proposed approach addresses both static and dynamic security assessment. The proposed methods have been tested on the Western Electricity Coordinating Council (WECC) system. The test results show that a substantial reduction in computational effort is achieved by implementing these methods for an ${n}$ -1-1 contingency analysis. In addition, the reliability of the proposed methods is evaluated by an exhaustive contingency analysis.