Risk Assessment in Extreme Events Considering the Reliability of Protection Systems

This paper presents a new risk assessment method that is applicable to extreme cases in power systems. This paper analyzes the interactions among protection system components and the power grid in extreme events pertaining to simultaneous faults and cascading failures. The hidden failures of protection systems could exacerbate power system conditions if cascading events tend to follow a path to a blackout. The proposed risk assessment considers detailed reliability models of protection system components including circuit breakers (CBs) and protective relays. The failure probability of a CB is formulated considering its component degradation rate and operation times. The failure model of a protective relay is constructed using the dynamic fault tree. The evolution of cascading failures of power systems in extreme conditions, which deteriorates due to protection system malfunctions, is modeled based on the actual physical system behavior. The effectiveness of the proposed risk assessment method is demonstrated using a modified 9-bus system and the IEEE 68-bus system.