Reliability Modeling of All-Digital Protection Systems Including Impact of Repair

This paper explores the impact of including component repair on the reliability modeling of all-digital protection systems. It is shown that repairable and nonrepairable assumptions make a remarkable difference in the computed reliability indices of the mean time to failure (MTTF) and the mean time to first failure (MTTFF). Theoretical analysis of basic system structures consisting of two components is first examined. Then, a typical all-digital protection system architecture is modeled and numerically analyzed. Some interesting results are found by comparing reliability indices of MTTF and MTTFF and explanations of these results are provided.