Transmission activities and processes

The Italian electricity system consists of four components: the production, transmission, distribution, and sale of electricity.

Terna’s business regards the transmission of electricity on the high-voltage grid; in particular, the Company manages the electricity system, operating the grid and striving for the utmost efficiency of the infrastructures and excellence in their maintenance through plant engineering and management and grid development.



The main stages of the transmission service are the following. 


Operation of the grid requires at all times a balance between injections and withdrawals, i.e. between the supply of domestic and imported power and the power consumed by end users. This function is called dispatching.

Preparation for real-time operation includes unavailability planning (of the grid and of production plants) with different time horizons, forecasting the national electricity demand, verifying its compliance with the production plan determined as the outcome of the free electricity market (Electricity Exchange and off-Exchange contracts), acquiring resources for dispatching, and verifying power transits for all the lines of the transmission grid.

In the real-time control phase, the National Control Center coordinates other centers throughout Italy, monitors the electricity system and performs the task of dispatching, taking action in case of deviations from the expected operation due to malfunctioning of production plants or grid segments or to a different demand trend compared to forecasts; instructions are thus given to producers and to Remote-control Centers to adjust the supply and the grid setup. In case of an emergency, the National Control Center may also take action to reduce the demand in order to avoid the risk of grid degeneration and extensive outages.

Grid development planning

The analysis of electricity flows on the grid and the development of projections of demand enable Terna to identify the critical aspects of the grid and the new works that need to be constructed in order to ensure the system’s adequacy with respect to meeting the demand, the security of operation, congestion reduction, and the improvement of service quality and continuity.

The new works to be constructed are included in the National Transmission Grid Development Plan, which is submitted for approval to the Ministry for Economic Development every year. Terna then follows the authorization process, from advance consultation with the local bodies to the authorization to construct the work.

Lastly, by analyzing the situation of the grid, Terna identifies the best ways of connecting to the grid the plants of all the operators that so request.


Terna establishes the engineering standards of the plants connected to the grid, in particular construction standards and the performances required for equipment, machinery and components of stations and power lines.

As far as plant construction is concerned, Terna prepares projects for the works authorized. In particular, it establishes the requirements of external resources and the budget for the projects, as well as the work methods and the technical specifications of the components and materials that will be used in constructing the new lines or stations, including the adoption of innovative methods. The construction of new plants is generally outsourced.


Terna carries out the maintenance of its power lines and stations through eight Transmission Operating Areas, which employ most of the Company’s human resources (slightly less than 70%).