Analyzing variable time between N-1-1 contingencies in assessing NERC TPL-001-4 multiple events reliability

There is increasing emphasis on accounting for multiple sequential faults when analyzing for system reliability. This research considers N-1-1 contingency analysis as described in NERC TPL-001-4. Existing guidelines allow for the power system to respond to a first event prior to a second fault occurring. This research develops a method to evaluate the more complex situations where there is a variable amount of time between the first and second contingency. It is generally possible for the cumulative effect of transient interactions to be influenced by the timing of a second disturbance. A probabilistic approach is proposed to identify the most severe transient stability outcomes. The results of a large scale simulation study on a 68-bus IEEE stability benchmark model are presented to confirm the benefits of the proposed probabilistic method.