Transmission grid flexibility assessment in electricity market: Bulk system indices for the operational planning

The paper includes a review of the concept of “flexibility”, usually integrated as attribute in analysis of industry processes, for making it applicable in the transmission grid operational planning in electricity market context. Definitions reported in the modern scientific literature, concerning flexibility, are summarized and critically explained. Then a specific definition of transmission system flexibility in respect of the generation changes and some bulk system flexibility indices are proposed. The mathematical models and calculation methodology are presented, and a dedicated tool for indices computation is briefly described. The tool is in test at the Italian Transmission System Operator (TERNA) for the flexibility evaluation of parts of the National Transmission Grid.