A system is a collection of components arranged to a specific design in order to achieve desired functions with acceptable performance and reliability. Reliability engineers often need to work with systems having elements connected in series and parallel, and to calculate their reliability. To this end, when a system consist of combination of series and parallel segments, engineers often apply very convoluted block reliability formulae and use software calculation packages. As the underlying statistical theory behind the formulae is not always well understood, errors or misapplications may occur. In this paper, exponentially distributed failure rate of the components will be considered for unit or component redundancies and evaluation of basic probability indices for various system configurations like series parallel, series-parallel, parallel-series configurations and complex systems have been dealt with deriving generalized expressions for ‘n’ component repairable systems. A computer program has been developed to apply generalized expressions for various systems. Application of the derived formulae is used to obtain basic probability indices of load point and for the Power System network.
