The paper presents a general computational method together with the relevant computer program which can be easily used to perform reliability analysis on electric power installation configurations. The mathematical reliability model of the program is based on the concept of frequency of failures during the useful life period. In other words, it starts from basic configuration component failure-rate data and uses the tie-set approach to carry out the reliability analysis of the system under study. For purposes of illustration the computer program has been applied to a practical h.v./m.v. substation configuration. The program is very conducive to analysis work of reliability sensitivity as a function of the failure rates of the configuration components.