Comparative Analysis of the Reliability of Instrumentation and Control Systems Using the Signature Theory

Abstract

At the present, in the comparative analysis of design decisions from the point of view of system architecture, a qualitative and quantitative analysis of the indicators for each solution is performed followed by a comparison of the results. The classical method of calculating reliability is very laborious due to the need to take into account the properties of all elements of the system. One of the tools to quantify the reliability of systems consisting of components with random failure rates that are independent and equally distributed is signature theory. The signature describes the structure of the system and can be combined with ordinal statistics of the component failure time to form conclusions about the reliability of the system and compare several systems according to this criterion. The article provides a comparative analysis of the safety of instrumentation and control system using the classical method of calculating reliability indicators as well as using signature theory. As an example, the article considers a protection system that includes the initiating and executive parts. The system architecture is presented in several simplified versions. The dependences of the probabilities of failures of the “failure on demand” and “spurious actuations” type for each of the architecture implementation variants are obtained. It is concluded that, with the exponential distribution of MTBF, there is a complete correlation of the results of circuit comparison performed using both the classical method of calculating reliability (based on the failure rates of components) and using signature theory. Moreover, the use of signature theory greatly simplifies comparing the reliability of systems and networks consisting of components of the same type.