Beyond the pylons: a map of Italy as it renews its “invisible” highways

In recent years, the energy transition and the modernisation of high-voltage electricity transmission networks have become strategic priorities for the country’s security and resilience. In this context, the undergrounding of cables is one of the solutions most favoured by the public and local authorities because it eliminates the visual impact, can often free up land currently occupied by pylons, and reduces the effect of electromagnetic fields. However, as the technicians and engineers at Terna – the national transmission grid manager– point out, undergrounding power lines is not a technical solution that you can indiscriminately apply to any geographical or topographical context.
The installation and management of underground cabling require a rigorous cost-benefit analysis and a complex geotechnical assessment. In rural areas or in geomorphologically fragile environments such as hillsides prone to landslides or mudslides, or near watercourses, traditional overhead lines ensure higher safety standards. A support structure positioned at a higher level is above any ground instability, whereas an underground cable could be severely impacted by landslides and the like, causing complex faults and potentially very long repair times.
There are also environmental and maintenance-related reasons why cable undergrounding may not be permitted: in protected natural areas, carrying out repairs to an underground fault by using excavators and heavy machinery would cause far greater damage to the ecosystem than having overhead cable supports. On the other hand, underground cabling becomes an essential and priority option in heavily urbanised and metropolitan areas, where building density makes it almost impossible to erect pylons and where demand for energy is constantly growing.

Operational standards and land management. High-voltage cables are typically laid at a depth of between 1.20 and 2.00 metres below road level. The first metre beneath the tarmac falls within the competence of the road owning body; a 20 cm buffer layer beneath this allows for the routing of various underground utilities – fibre-optic cables, telecommunications cables, gas pipes – without impacting on the high-voltage infrastructure.
Horizontal Directional Drilling (HDD) is often used when crossing watercourses, busy highways or sensitive areas; this technique (known in the trade as “No Dig”) does not involve open-cut excavation and significantly reduces the impact on the surface and on traffic flow.
Under normal circumstances, urban work sites are organised as a series of small, progressively moving phases. This system allows traffic to continue to flow via alternating one-way systems or diversions, supported by temporary signage and notices on information boards. Operations are carried out in close coordination with local authorities and the municipal police.

The “Dorsale Romana” and the evolution of cable technology. The plan to modernise the capital’s electricity network – known as the “Dorsale Romana” project – is a driver of the technological transition currently taking place on high-voltage networks. Approved in 2016, the project arose from the need to replace the old liquid oil insulation cables, which were installed and brought into service in the mid-1970s and had reached the end of their useful life. Their successors were latest-generation cables made of extruded cross-linked polyethylene (XLPE). The new XLPE cables ensure greater power-carrying capacity, increased reliability of the electricity system and improved operating and maintenance conditions. Fault management is a particularly significant aspect: with older liquid oil cables, repairing a complex fault could take as long as 2-3 months, but with XLPE technology, repair times can be reduced to around 20 days by replacing the damaged section and making the necessary unions. This reduction in downtime is a strategic benefit for the network operator, as it increases the resilience of the electricity grid and significantly reduces the operational risks associated with prolonged outages.
As well as laying the new underground power lines, Terna is installing an integrated digital monitoring system
that is remotely monitored 24 hours a day, 7 days a week. The system monitors three key parameters. Partial discharges, monitored at unions and terminals; they allow the accurate assessment of the condition of the insulation and the early identification of signs of deterioration. Again, cable temperature, measured along the entire route to identify any thermal anomalies caused by external interference or changes in installation conditions. Finally, vibrations; these are monitored to allow the early detection of any activity or events that could compromise the integrity of the infrastructure.
This approach relies on a predictive maintenance strategy, gradually moving away from the traditional model based solely on periodic maintenance or repairs carried out only after a fault has occurred. As the time between an abnormal event and potential damage to the infrastructure can be very short, remote monitoring is supplemented by on-site surveillance and inspections, which are generally carried out on a weekly basis. The combination of advanced sensor technology, digitalisation and remote control enables more efficient asset management, better service continuity and higher standards of electricity grid safety and sustainability.

An Italy undergoing renewal: a map of work sites from north to south. The transformation currently taking place in the capital is part of a modernisation strategy that enables Terna to rethink the country’s electricity infrastructure.
In Friuli-Venezia Giulia, the upgrade plan for the Trieste area involves over 32 kilometres of underground cables, divided between the Duino Aurisina-CP Roiano and CP Valmartinaga-CP Rozzol branches. The system is designed to withstand the considerable force of the Bora winds and ensure the electrification of the commercial port. A little further west, along the border between Veneto and Emilia-Romagna, works on the Adria Sud-Ariano power line involve the laying of 18 kilometres of underground cables, which will cross two branches of the River Po. The use of “No Dig” technology – in this case Horizontal Directional Drilling – eliminates the need for open-cut excavation. Heading down towards the Romagna coast, the project for the132 kV Rimini-Riccione link addresses the issue of surges in summer demand due to tourism: with 17 kilometres of new underground cables spread across 8 municipalities, the project will enable the removal of over 40 kilometres of overhead power lines and 171 pylons dating back to the 1970s, restoring to the local community an area equivalent to around 170 football pitches.
Moving on to the Alps and the Po Valley, in Lombardy approval has been granted for the redevelopment of the west Brianza area (15 kilometres of underground cables to free up 30 hectares in the Parco delle Groane), while in Trentino-Alto Adige, the new 10-kilometre underground XLPE cable link between Dobbiaco and Sesto will help preserve the Alpine valleys by protecting them from snowfall and storms. Finally, in Piedmont, the works under the Biella Area Resilience Plan (13 kilometres of highly reliable, wind-resistant cables) are complemented by already-completed projects such as the Bricherasio-Luserna San Giovanni line in Turin: a 7.3-kilometre underground cable project that is already operational, allowing the dismantling of 26 old pylons.

Moving down towards Central Italy, the principle of urban integration guides the works in Abruzzo. The undergrounding of the Pettino-Scoppito line in Aquila will transform perceptions of the city’s outskirts: 2 kilometres of underground cable will replace the old overhead line, enabling the removal of 10 pylons, the reclamation of 2 hectares of urban land and the refurbishment of the Pettino substation with new compact switchgear modules.
In Campania, the Montecorvino-Avellino-Benevento backbone project stretches for 90 kilometres, with as much as 70 kilometres of the cable laid underground. This project, designed to carry power from the Tyrrhenian Link, will result in the dismantling of over 100 kilometres of old overhead lines and 300 pylons, thus freeing up around 290 hectares of land in Campania. Elsewhere in the region, modernisation continues with the reorganisation of Salerno Sud (25 kilometres of underground cable, allowing the removal of 254 pylons), infrastructural development in the industrial area with the primary cabin in Nola (15 kilometres of undergrounding), the new 220 kV Napoli Levante-Ercolano cable (10 kilometres), the underground variant of the Piano di Sorrento-Vico Equense line and the Caserta-Maddaloni link, a project involving 7 kilometres of XLPE cable already in operation.
Continuing southwards, Basilicata offers an exemplary model of collaboration between Terna and local authorities for the protection of cultural heritage. In Matera, following on from the work begun in previous years, the undergrounding of the Matera CP-Matera Nord line (8 kilometres of underground cable) will allow 20 pylons to be removed from the city centre, freeing up more than 5 hectares of land.
Looking to the large islands, the strategy remains the same. In Sicily, the modernisation of the Catania metropolitan area involves replacing the old 1977 liquid-oil cable on the Misterbianco-Villa Bellini line with a new 1-kilometre underground XLPE cable outside the city centre. In the province of Syracuse, the new underground cable connections to the stations at Sortino and Lentini (a total of 6 kilometres) will allow 50 kilometres of obsolete overhead lines to be dismantled. Finally, in Sardinia, the ongoing works between Lula and Galtellì will see the final laying of 19 kilometres of underground cable by the first half of 2027, ensuring a more reliable and continuous electricity supply for the entire Nuoro area.

Strategic vision for the cities of the future. The development, modernisation and maintenance of the national electricity grid are a cornerstone of Italy’s energy future. Technological advances in underground cables – which are guaranteed to last at least 25-30 years but are protected by containment structures capable of lasting for centuries – combine an increase in energy transmission capacity, including that of renewable energy, with a reduction in grid losses.
Bringing high-voltage power directly into the heart of cities and industrial districts minimises energy loss, improves safety and restores to public use those areas previously occupied by pylons. An integrated approach that combines cutting-edge engineering, environmental sustainability and ongoing dialogue with local communities.