A 5-phase future

In the Pescara countryside, among the hills that separate Alanno from Popoli, true Italian innovation in electricity transmission can be found in the form of the new “5-Phase pylons”. In fact, Terna — the company that manages the Italian electricity grid — has installed a new generation of high-voltage pylons for energy transport along the 150 kV “Alanno-Popoli” overhead line: a first in Italy, springing from the ingenuity of its technicians. The technology, which has been awarded an Industrial Invention Patent by the Italian Patents and Trademarks Office, represents a crucial step in the evolution of the Italian electricity grid.

More compact, more efficient and more sustainable, “5-Phase” pylons have been created in response to a specific challenge: transporting more energy while reducing electric and magnetic field values and simultaneously improving the environmental and visual effect on the surrounding landscape. This revolution in engineering is destined to change how electricity makes its way across Italy.

The new energy architecture. So, what is the main feature of these new “5-Phase” pylons? Traditional high-voltage power lines typically feature three conductors, i.e. phases, in the standard configuration for three-phase alternating-current transmission. But the energy transition calls for grids capable of transporting large quantities of electrical power over long distances, including for the purpose of integrating the new needs of producers and users, while still guaranteeing the electrical stability of the system. These new scenarios gave rise to the idea for a “5-Phase” pylon: distinguished by the doubling of two of the existing phases with the remaining one placed at the centre of the pole-head, as well as by an arrangement which follows a particular geometry characterised by two almost equilateral triangles.

Despite its seeming simplicity, this geometry is the fruit of years of study and research, which have also incorporated the operating experience of running and maintaining electricity grids into the solution. The results are undeniable: over the same transmission distance, a power line with “5-Phase” pylons can transport over twice as much electrical power compared to a conventional line. For example, a so-called “Terna Single” 220 kV overhead line allows a maximum power of around 370 MW to be transported up to 150 kilometres; over the same transmission distance, a “Terna Double” line enables the transport of up to 740 MW. With “5-Phase” pylons, the power can reach values of up to 1,000 MW. This significant increase in transport capacity does not require greater land use, nor does it intensify the social impact of the infrastructure. In fact, the new pylon configuration developed by Terna means, for example, that an existing electrical backbone can be modernised without altering the land usage needed for the original infrastructure and easement zones. At the same time, thanks to the geometry of the electrical phases described above, it allows a reduction in electric and magnetic fields and in the extent of plant cutting, while also improving mechanical land-working.

The first test: Pescara innovation laboratory. The 150 kV “Alanno/Popoli - Pescara/Salto branch” overhead power line, to give it its full name, has been the nation’s first trial run of this pilot project. Terna has introduced 10 new “5-Phase” pylons along the route of the existing power line, replacing an equal number of traditional pylons. This first installation represents a new approach to grid planning: innovative, sustainable infrastructure with a high transport capacity. The compact configuration of the pylons allows for optimum relative distances between the conductors and an increased useful height from the ground, while leaving the total height of the infrastructure and, as a result, its visual impact on the surrounding landscape unchanged.

This innovative approach will also have repercussions for the future renewal of existing overhead lines: obsolete power lines can be completely reconstructed with the new “5-Phase” pylons, boosting the electrical power transmitted with no increase in land use along the existing infrastructural corridors. This will be a key solution in the plan pursued by Terna to renew and boost the efficiency of the electricity grid, supported by a total investment of 3.6 billion euros as set out in the update to the 2024-2028 Industrial Plan.

A patent that speaks Italian. The “5-Phase” pylon has been awarded an Industrial Invention Patent by the Italian Patents and Trademarks Office for the project's pioneering significance, combining innovation, operating experience and a focus on sustainability. In addition, it is an industrially sustainable technology due to its use of materials, equipment and working methods which are already available to Italian businesses in the electricity sector. This is proof of Terna’s innovative strength, with over 70 registered patents to its credit, half of which have already been granted. This wealth of know-how is testament to the company’s ability to transform technical research into concrete solutions for the national electricity system.

Design and sustainability: energy that works in sync with the landscape. When you look at a “5-Phase” pylon, you’re seeing a piece of engineering that’s also a design project. Symmetry, roundness and structural simplicity were highly prioritised in designing the geometries of the pylons, to achieve the best visual impact with the infrastructure while making its forms more pleasing. A single package combining aesthetics and functionality, in the sense of efficiency and respect for the landscape, it has received appropriate recognition as IP (intellectual property) for innovation, compliance and individuality, with no fewer than 13 design models registered.

But care for the landscape hasn’t stopped there: Terna has experimented with the use of light-dark, two-tone painting for its overhead power lines, which can be adjusted based on the predominant tones in the area, in terms of physical-topographical characteristics and seasonality, to allow the pylons to blend in harmoniously with the surrounding landscapes and against the backdrop of the sky. In addition to this, a form of what its inventors describe as “Pixel Camouflage” can also be used, particularly for single-stem pylons. This attracts observers’ attention to a specific point of the pole, thereby distracting from the pole-head, which is the bulkiest part of the pylon. Again in the spirit of Terna’s pursuit of possible solutions for the visual interaction between electrical infrastructure and the land, the same “Pixel Camouflage” has recently been granted an Industrial Invention Patent by the Italian and European Offices. The latter arrived very rapidly, practically alongside the Italian one, a sign of how the originality of the idea of a single-stem pylon paired with light-dark colouration and a “pixelated” alternation blending this colour scheme has also been appreciated outside of Italy, distinguishing itself both functionally and aesthetically.

An important stepping stone in the energy transition. Infrastructural innovations only make sense if they are helping to achieve a larger goal. In the case of the “5-Phase” pylon, the goal is to work towards the targets of the energy transition. To enable the integration of renewables, we need electricity grids capable of managing ever-increasing and more variable energy flows, given the intermittent and unpredictable nature of these sources. The new pylons patented by Terna represent a concrete tool to enable this transformation, optimising the use of the existing corridors and guaranteeing grid stability without sacrificing the landscape. At a time when decarbonisation is also a reflection of the quality of infrastructure, the “5-Phase” pylons show how innovation can originate and flourish at home, with a sustainable industrial approach.

Italy and the energy of the future. Terna has conducted a variety of studies and technological investigations, particularly in terms of the supports to be used to build new overhead power lines or modernise existing ones. The overhead power line in Abruzzo, where the first “5-Phase” pylons have been installed, has an electrical voltage of 150 kV. However, the “5-Phase” project as a whole has included the development of a series of pylons for voltage levels of up to 220 kV, for both lattice and single-stem types. A solution for 380 kV lines is also undergoing study and engineering, in order to make a set of supports available for every voltage level and fulfil the varied needs of the grid.

Its next applications are already becoming reality: in fact, in the 2025-2034 Development Plan, Terna has made provision for the installation of “5-Phase” supports for the Central Link and the Sardinian Link, strategic works of national importance. Authorisation procedures for both infrastructures were launched in October 2025. The Central Link consists of a reconstruction of the current 220 kV electricity backbone between Umbria and Tuscany, with a total investment of approximately 280 million euros. The Sardinian Link, on the other hand, involves the reconstruction and modernisation of Sardinia’s electrical infrastructure along a route that crosses the island, worth 300 million euros in investments. A distinguishing element of both projects will be the use of “5-Phase” pylons, one piece of the puzzle in terms of the company’s planning and technological development towards the Hypergrid. The Central Link, the Sardinian Link and future projects involving “5-Phase” pylons will further consolidate the high technological standard for the national electricity transmission grid, representing a clear step towards an increasingly efficient and sustainable system.