Development of the dynamic fault tree using Markovian process and supercomponent

Abstract

The existing fault tree technique is static, whereas the proposed technique using the Markovian process can treat the fault tree dynamically. By using the Markovian process, it is possible to model the dynamic features of the existing fault tree and to handle the dependencies on the state of the system. This conbination allows detailed consideration of component maintenance, which is normally not considered in the on/off logic of the fault tree. The Markovian process is based on the probabilistic models. It is also characterized by the state and the time, so the system, which is composed of a number of basic events, can be described at any time by specifying its state at that time. In the Markovian approach for fault tree, the concept of the supercomponent is introduced in order to reduce the number of system states and the size of the transition matrix. Now, a number of basic events are considered to be one component in the Markovian process. Using the proposed dynamic fault tree analysis, a sample calculation is performed. As a result, the unavailability is much less than the value for the static fault tree analysis. Namely, the conservatism of the current analysis is excluded in this paper. The dynamic behavior of each system state and of the overall system is well analyzed. The interactions between the supercomponent tested and the supercomponent not tested are dynamically analyzed, too. In conclusion, by using the Markovian process and the concept of the supercomponent, the size of transition matrix is reduced, and especially, the effect of the tested supercomponent on the system is dynamically analyzed.