Reliability analysis of defense plans against slow and fast cascading phenomena

The development of a blackout can be typically divided in two stages: slow cascading and fast cascading events. The role of the human operator and of the fast automatic actions varies depending on the speed of the blackout process. This paper first provides a breakdown of a blackout in different stages based on the speed of the outage propagation. This helps identify the importance of the system operator and automatic actions in each blackout stage. Next, a reliability assessment framework is presented for assessing the impact of operators´ ineffective response during the early stages of an electrical disturbance. In addition, a method based on Markov modeling and fault tree analysis is proposed for evaluating the reliability of System Integrity Protection Schemes (SIPS), which are usually installed to provide protection against fast dynamic events.