Restoration of the system after black-out by exploiting black start-up capabilities of repowered thermal stations

The role that can be played by thermo electrical power plants in the restoration procedure after blackout events, is discussed in the paper, with particular reference to steam thermoelectric plants repowered by gas turbines (GT) that are provided with bypass valve of the GT exhaust flow. The reassessment of restoration plans, which is taking place in several countries as a consequence of the liberalization of the electrical energy market, renders the above issue of utmost interest. Some results of an investigation carried out in cooperation between University of Bologna and ENEL-CESI are reported. The black start up capability of gas turbines can be exploited by implementing adequate procedures and automatic control devices that would render it possible also for the combined cycle power plant to autonomously start up and contribute to the restoration process after black out.