Availability analysis of combined cycle power plant layouts which employ generator circuit-breakers and three-winding step-up transformers

During the recent decades, several combined cycle power plants have been installed or planned to be installed in Iran. Since a considerable number of generating units is involved, the question of operating power plants with the highest possible availability at the lowest possible cost is of utmost importance. The present paper is specifically concerned with the availability assessment of different layouts of combined cycle power plants. The analysis provides important insights in the optimization of power plant layouts, evaluating the possible employment of three-winding step-up transformers in conjunction with generator circuit-breakers both for the gas and for the steam portions of the power plant. Simulations of the behaviour of different power plant layouts have been carried out with the help of the Monte Carlo method. In order to make a more thorough comparison between the different power plant layouts, an economic evaluation has also been performed. The economic benefit which results from the reduction of power plant unavailability has been assessed and the results are shown with the aid of a risk index. The optimal solutions, depending on power plant layout and reliability parameters of power plant equipment have been evaluated.