The three-position system of the combined electrical apparatus is taken as the research object. The failure forms of main elements are obtained by way of setting up FTA model. The reliability of three-position moving contact subsystem and gearbox system is predicted by the use of such two methods as quantitative FTA and Markov chain. The results show that the former method

in case of dealing with the two-level subsystem fault

can cause the analysis results to be conservative. However

the use of the latter method can describe more comprehensively the type of fault and the severity of the hazard

but its analysis and calculation process are relatively complex. Therefore

the use of the quantitative FTA and Markov chain for comparison analysis can not only predict the reliability of two-stage subsystem more accurately

but also provide theoretical support for the reliability analysis technology of three station system in accordance the system characteristics.