Power system planning: evaluation of a transmission network flexibility index

In a free-market scenario, power system planning is affected by significant degree of uncertainty about time and location of generating assets expansion. The paper deals with a methodology for the direct evaluation of the flexibility of the transmission system (defined as the attitude of the system to keep up a desired standard of availability under such uncertainty), by means of an index, based on structural as well as operational network parameters. The proposed index has been applied to a real network and several networks derived from it which can be regarded as planning alternatives: the system chosen for this application is the portion of Italian national transmission system in the region of Sicily. Results, extensively checked by means of Monte Carlo availability simulations, are found to be good.