Protection Survivability Importance for Evaluating System Survivability in Multi-state Protection Systems

Importance measures are being widely used in risk-informed applications to characterize the importance of component failures, human errors, common cause failures, etc. In order to decrease the impact of external factors and increase the system survivability, a multilevel protection is applied to its components or subsystems. Each level of protection can have multiple states from perfect protection to complete destruction. When the protection of components or subsystems is completely destroyed, the protected components or subsystems can be destroyed. In such protection, different protection states play different roles in providing the system survivability and the sojourn time at different states of one protection has an effect on the system survivability. In this paper, based on the transitions of protection states, the multi-state protection survivability importance is introduced in order to determine which level of protection has the greatest influence on the entire system survivability.