The work examines the problem of the aging of transmission network units and the impact of it on the reliability of the electric power system (EPS). The criteria and methodology are defined for compiling a priority list for the revitalization of lines and transformers in transmission networks. The criteria are based on the real condition of a unit and the role and relevancy of the unit within the EPS. Through a probabilistic simulation and a multi-scenario analysis the expected annual operating

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... costs of the system are calculated. Based on the difference of these costs at different unavailability levels of the observed units, the individual criteria, which are dependent on the role and relevance of the observed unit, are quantified and the significance index of the revitalization candidates is calculated. Based on that index, and the condition index of individual revitalization candidates, a single priority list of lines and transformers for revitalization is compiled.