Leveling reliability in systems with large hydro resources

Reliability analysis of a generating system is established in terms of the reliability characteristics of the different units in the system and in ter ms of the demand of energy to be satisfied. When the analysis is performed for the longterm (one year Or more duration periods), the maintenance needs of thermal units as well as the time distribution of resources for units w ith energy restrictions, must also be taken into account. This paper descri bes a method for determining the optimal strategy for allocating the yearly energy resulting from random water inflows to the different subperiods of a year so that the reliability for all the subperiods is leveled. A charact eristic feature of the method is that the uncertainty inherent in forecasti ng future available hydroenergy is transferred to the reliability index. Th e procedure is illustrated by an example prepared using the Spanish generat ing system.