Chapter 14 - Restoration Processes after Blackouts

This chapter aims at illustrating the power system dynamic behavior during restoration scenarios in transmission networks, with particular reference to the analysis of thermal power plant black-start capabilities. This chapter is structured into three parts. Section 14.2 briefly reviews the requirements and the structure of power system restoration processes. The unbundling and liberalization of electrical power systems justifies the reassessment of power system restoration strategies, also by increasing the number of black-start resources, traditionally only represented by hydro stations and gas turbines (GTs). Hence, Section 14.3 deals with the analysis of the black-start capabilities of thermal stations equipped with both steam turbines (STs) and GTs. Moreover, accurate modeling of the dynamic interaction between the power plant and the restoring electrical power system, throughout the use of modern computer simulation tools, appears to be of considerable help to study the early stage of the restoration plans and to design specific control systems to support the feasibility and reliability of black-start maneuvers. Therefore, Section 14.3 also includes the analysis of the typical transients occurring during load restoration maneuvers and islanding formation for two representative types of power plants, namely a once-through boiler steam group repowered by a gas turbine and a combined combined-cycle unit. The models of the two relevant simulators and their identification by means of experimental data are described in Section 14.4.