Plant maintenance


Plant maintenance is essential for ensuring service quality and continuity.

To ensure that plants can be identified immediately and reached as quickly as possible, especially in the event of malfunctions, Terna's workers use a hand-held device that incorporates a navigation system that shows all the plants superimposed on a geo-referred map.

The main actions performed in 2012 with regard to electricity stations and lines were the following:

Plant monitoring and inspection: In addition to the checks prescribed by law, Terna:

  • performed about 20,900 periodical technical and surveillance checks on stations at the different voltage levels;
  • carried out inspections with visual checks on around 142,800 km of lines, 10,000 km of which by helicopter, amounting to an average of about 2 inspections per year;
  • made around 19,800 instrumental checks, using thermal cameras to identify hot spots, and DayCor UV cameras to pinpoint the corona effect on insulators and conductors, also climbing pylons with LLW (live-line working) techniques.

Ordinary Maintenance: Terna identifies the work to be done on the basis of signs of deterioration signalled by the integrated remote-management system, online sensors,and the results of the plant monitoring process. Since 2005, it has made use of an special system to support line and station maintenance work called MBI (Maintenance and Business Intelligence) which enables optimisation of maintenance work.


Controlling Vegetation: for correct operation of the lines, continual monitoring is necessary to assess the growth of vegetation and prevent it from getting too close to energy conductors and causing possible short circuits and line interruption.

Vegetation control normally consists of 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 2012, vegetation was cut along 15,300 km of electric lines.

Live-line working (LLW): Approximately 3,400 monitoring and maintenance jobs were performed on live wires.

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

Special Maintenance: during 2012, Terna reconstructed 62 km of overhead lines and 8 km of underground cables, and replaced approximately 3,100 km of energy and guard wires.

Line inspection by helicopter

Terna started and completed 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 technology adopted made it possible to create a database for the HV grid, and to survey the elements interfering with the overhead power lines, such as buildings, vegetation, and roads.

In 2012, Terna began testing a new method for visual and instrumental monitoring of High Voltage overhead lines with its own personnel in helicopters, in order to improve diagnostics, and to make line controls objective, through the registration of the results of the instrument surveys, in line with the best practices of the leading European Transmission System Operators.

In addition this method reduces survey times and makes the process independent of environmental conditions on the ground.

In view of the positive outcome of the testing, from 2013 the new monitoring method will become operational on a significant portion (approximately one third) of the National Transmission Grid.

The “BE.S.T. P.A.T.H.S.” research project co-financed by the 7th EU Framework Program


The European Union finances research through its 7th Framework Program, operative for years 2007-2013.

The funds are assigned by tenders for the best projects that have results that will help to define strategies for the 20-20-20 targets - the goal of the next EU "Horizon 2020" Program" - and which will translate into recommendations for the member states.

With an eye to a synergistic strategy, aimed at focusing research on national/Mediterranean topics of interest, Terna has joined the Working Group ENTSO-E R&D, from which the EU takes the themes for the tenders it intends to launch.

For Terna, qualified participation in the most important and prestigious international research projects is not just beneficial in terms of access to financing (which covers over 50% of the total budget) and the technological implications for a project already in the Development Plan, but also an opportunity to bring back into the company and the national economy a substantial portion of know-how and economic resources which in any case come out of public expenditure.

Specifically, Terna took part in the: “Large-scale demonstration of innovative transmission system integration and operation solutions for (inter)connecting renewable electricity production”, the most recent tender for sustaining research projects, at the demonstration and prototype phases, on the technological challenges deriving from the large-scale penetration of renewable production and the integration of the European electricity market.

This is research into the development of:

  • smart electricity grids with demanding requisites in terms of “governance” and reliability and consequent reduction of system costs, and with a high rate of integration with the increasing production from renewable sources;
  • new technologies and components for HVDC direct-current: innovative VSC converters, D switches, very high voltage, extruded insulation cables, high performance conductors and insulators;
  • systems with marked interoperability features between the components and sub-systems of different manufacturers and relative technological standards.

These topics have a strong sustainability connotation since they coincide with the guiding principles of the evolution demanded of the transmission grid to comply with a de-carbonised electricity system with de-localised and distributed renewable generation and integrated horizontal and vertical management.

This research further reinforces the networks of collaboration at a European and international level, between utilities, manufacturers and research institutes, as well as public and private parties.

The research project proposal, finally approved by EC in April 2013, provides for a consortium, chaired by Terna, of 40 partners among which TSO ( as well Terna, RTE, REE, 50Herts, Eia, Mavir, Stattnett, REN, EnergieNet), utilities (E-On, Iberdrola), manufacturers (ABB, Toshiba, Alstom, General Cable, Nexans, Silec, ECN, De Angelis), universities and research institutes (RSE, CERN, STRI, Columbus and many others).

The general co-ordinator of the project, which is structured into 5 complementary categories, is the Spanish TSO. Terna has assumed the role of leader of the main category (over 30 million euro out of a total of 75), relative to technological investigations of the components and systems aimed at restoring the SACOI connection (HVDC between Sardinia, Corsica and mainland Italy). Terna also suggested the name/acronym for the entire project: “BEST PATHS” (Beyond State-of-the-art Technologies for re-Powering AC corridors & multi-Terminal HVDC Systems).