Plant maintenance


Plant maintenance is essential for ensuring service quality and continuity.

EU6To ensure that plants can be immediately identified, especially in the event of malfunctions, as well as reached as quickly as possible, Terna’s staff uses a handheld device integrated with a navigation system that shows all the plants superimposed on a geo-referred map.

The main activities performed in 2011 with regard to power stations and lines were the following:

Plant monitoring and inspection: in addition to mandatory checks established by the law, Terna:

  • performed 21,900 periodical technical and surveillance checks on stations at the different voltage levels;
  • inspected 144,000 km of three-phase circuits with on-site checks, including 4,500 km by helicopter, with nearly 2 inspections a year on average;
  • carried out 16,900 instrumental checks of lines, using thermal cameras to identify hot points, DayCor UV cameras to pinpoint the corona effect on insulators and conductors, also climbing the supports using the “works on live wires” technique (LST).

Ordinary maintenance: Terna identifies the work to be done on the basis of deterioration signaled by the integrated remote-management system, online sensors, and plant monitoring. For this purpose, since 2005, it has also been using an expert system to assist line and station maintenance called MBI (Maintenance and Business Intelligence), which enables the Company to optimize its maintenance work.

EN12Controlling vegetation: the proper operation of lines also requires ongoing monitoring to assess the growth of vegetation in order to prevent the latter from getting too close to the conductors and the consequent risk of short circuits and line interruption.

Vegetation control normally consists in cutting it down to the ground or – if there are particular environmental restrictions – in branch removal aimed at keeping trees at a safe distance. Herbicides are never used.

During 2011, vegetation was cut along 16,300 km of power lines.

Work on live wires (LST): maintenance work on live wires was performed nearly 3,300 times.

Performed with the line in operation, such work increases system availability and contributes to the improvement of service quality and continuity.

Special maintenance: during, 2011 Terna reconstructed 54 km of overhead lines and 19 km of buried cable lines.

Line Inspection by Helicopter: the LIDAR project


In the second half of 2009, Terna started the LIDAR (Laser Imaging Detection and Ranging) project, with the objective of creating a geo-referred platform of the National Transmission Grid thanks to the use of laser imaging by helicopter.

The project was implemented to respond to the Ministerial Decree of May 29, 2008, which establishes the criteria for calculating the areas of limited safety along power lines and obliges Terna, as the owner and operator of power lines, to provide municipalities, regions, and other institutions entrusted with the inspections with a series of data such as, for example, the geographical coordinates and heights of pylons, the spatial position of conductors, approximate distances, and the limited-safety areas. For its latest-generation power lines, Terna already had this information, while for its lines with inadequate or obsolete mapping, it had to develop a project to obtain the data quickly. Therefore, the Company decided to use the laser technology, developed by the military, to “photograph” the lines quickly and in detail by installing the required devices on a helicopter.

The laser technology made it possible not only to create an up-to-date database for the HV grid, but also to thoroughly survey the position of the main elements, such as buildings, vegetation, and roads, interfering with electricity lines. In particular, on the entire HV grid, it was possible to measure the distance of each element from the conductors, which had been previously possible only with targeted surveys.

Since 2012 the goal has been to define and test a new method of inspection of HV lines using helicopters to optimize resources, express results and comply with the best practices of the main Transmission System Operators in Europe.


A new method of working on high voltage power line conductors: the three-dimensional isolated platform

Controllo rete

In 2011, a new methodology was implemented to facilitate work on overhead power line conductors, which up to now was only possible by climbing a pylon and walking directly to the conductors or by lowering them to the ground: the use of a truck equipped with an insulating bucket for accessing the workplace on the line, while the power line is in operation, thereby increasing the availability of the systems and improving service quality and continuity.

The vehicle has been in use since early 2011; it is located at the territorial area of Milan but it is also available for other areas.

This type of work has already been carried out at all voltage levels for repairs in case of malfunction, replacement of spacers and resolution of hot spots, for a total of 70 components that were either repaired or replaced.