ASSESSING ITALIAN MV NETWORK PERFORMANCE: A DETAILED ANALYSIS OF SHORT CIRCUIT POWER LEVELS

The Italian Regulator (Autorita per l’Energia Elettrica e Gas, hereinafter AEEG) promoted an analysis of the structure and the performances of distribution networks, both on HV (132/150 kV) and on MV levels. This paper is focused on the analysis of MV network structures: for the characterization of these networks, a large sample has been investigated by AEEG. About 400 MV primary busbars (i.e., MV busbars directly fed by a HV/MV transformer) out of about 4,000 MV primary busbars of the overall MV Italian system were selected. The data were requested by AEEG to Distributors: a huge sample of about 60,000 records (each of them representing a bus of a MV feeder, with the relevant information in terms of rated voltage, load connected, short circuit power etc) has been collected. These data allowed for the calculation of shortcircuit power at all busses of the sample; the values obtained have been compared to minimum short-circuit power levels needed to guarantee a suitable performance of the MV network in case of transients (i.e. fast variations due to motor starting) in the customers’ load.