The liberalization of the electricity market in transition countries will force electricity companies to view their power plants, transmission networks and distribution systems in a new light. Currently in Croatia there is only one Croatian Electricity Company (HEP), which is forced to change and survive in open European electricity market through reduced costs, maximized returns on investments and improved reliability and security of the existing power system. Power system reliability can be evaluated using analytical and simulation methods. This presentation uses Markov three-state models for generators (operational state, derated state and outage state) and two-state models for all other components of the power system. Historical data from HEP TSO Company were analyzed as input data for component reliability. A set of system and load point related reliability indices were calculated using state enumeration model simulation. The analysis was performed on a Croatian National Grid Company transmission system.

Key Words: Reliability Assessment, Reliability Indices, Transmission System, State Enumeration Method, Power Flow