As of January 1, 2019, the number of constrained zones in the Italian bidding zone configuration used for reporting actual historical data has been altered. Constrained zones or “points of limited production” are zones that have an insufficient transmission capacity to cover their maximum possible realized generation within the zone. For more information, see GMEs definition here. The alteration is a result of reducing the number of constrained zones by including zones IT-Foggia and IT-Brindisi in the bidding zone IT-SUD. The constrained zone IT-Rossano remains as is. IT-Priolo is now included in IT-SICI.
In order to accurately report thermal production data, we have chosen to report production in IT-SUD including the production in the constrained zones within this geographical region (See bidding zone overview above). This means that historical data for IT-SUD are the aggregate of IT-Rossano, IT-Brindisi and IT-Foggia and IT-SUD. IT-Sicily is the aggregate of IT-Sicily and IT-Priolo.
When comparing the hourly values reported by Entso-e to the monthly values reported by UCTE, we see discrepancies for numerous production types, for example fossil gas. We see that, on average, monthly fossil gas production levels are about 1.7 times the monthly aggregate of hourly levels. Since Entso-e Transparency only requires units larger than 100 MW to report production, we assume monthly UCTE values to be more reliable and therefore scale all hourly data to match them. See more information about thermal production data updates here.