EFFECT OF UNIT SIZE OF STEAM POWER PLANTS ON RELIABILITY INDICES OF IRAN POWER GENERATION SYSTEM

Reliability is one of the main factors in determining the unit size of steam Power Plant during generation expansion planning. In this paper the reliability indices like LOLE and ELL of Iran intereonnected power generation system are determined based on loss of load method and the computer program " PSREP", for existing and also for future system of year 1999 with already planned and under construction power plants. To find the effect of unit sizes of steam power plant on the reliability of Iran Power System up to year 2004, six different unit sizes from 250 to 800 MW are considered. Based on having the same reliabilites, the needed capacity additions are calculated for each six alternatives with the present worth value of their total life costs. The result shows that unit size of 500 MW is the optimum unit size of steam power plant for future power system of Iran up to year 2004, Considering both reliability and economics factors.