Fault trees and imperfect coverage: a combinatorial approach

A novel technique for combining a coverage model with a fault tree is presented. For a class of systems, this technique is simpler and faster than those currently used. Given a fault tree model of the system structure, the minimum cutsets are generated using standard techniques. This set of cutsets represents the effects of covered faults and can be used to determine whether the system contains sufficient redundancy to achieve the desired reliability. This set of minimum cutsets is augmented by a set of cutsets that represent uncovered faults. This set of additional cutsets is disjoint from the original cutsets, but they are not independent since covered and uncovered faults are mutually exclusive. The resulting set of cutsets is solved by combination of standard multistate and sum-of-disjoint products solution techniques