Cut Sequence Set Generation for Fault Tree Analysis

For a fault tree, especially for a dynamic fault tree, the occurrence of top event depends on not only the combination of basic events, but also on the occurrence order of basic events. Cut sequence is a set of basic events that fail in a particular order that can induce top event. Cut sequence set (CSS) is the aggregate of all cut sequences in a fault tree. The paper puts forward an algorithm, named CSSA (CSS Algorithm), to generate the CSS of a fault tree. CSSA uses sequential failure symbol (SFS) to describe the sequential failure relationship between two events. And then, cut sequence can be expressed by sequential failure expression (SFE), which is a chain of basic events connected by SFSs. In order to get the CSS, SFS transformation is applied to static gates and dynamic gates, the result of which is reconstructed to the standard form of CSS according to the inference rules of SFE. At length, an example is used to illustrate the detailed processes of the approach. CSSA provides a new qualitative method that extends the existing fault tree analysis models.