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Technology, competence and collaboration: this is how a converter substation is made

Stories of Terna/ Francesca Pede, head of Converter System Design.

Terna, as the TSO, operates the electricity transmission grid: almost 75,000 kilometres of high-voltage lines and hundreds of electrical substations. There are switching, converter and transformer substations: it is here that the lines transporting energy converge so that it can be distributed and, when necessary, transformed. In fact, not all energy is the same: that which circulates in the national transmission grid, at high and medium voltage, is different from that at medium and low voltage which arrives in our homes, schools, shops, industries, both for safety reasons and for adjustment to the devices and equipment to be powered.

Francesca Pede, electrical engineer of the "Engineering and Construction" area, has precisely this job. On joining Terna ten years ago, right from the start she was engaged in the construction of direct current plants. Today, in particular, she works on designing HVDC (High Voltage Direct Current) converter substations, with really unique and exceptional characteristics.

These nodes of the grid are fundamental for electricity transmission because they convert High Voltage Direct Current into alternating current or vice versa. For its specific features HVDC is particularly suited to travelling long distances with really minimal dispersion. A quality which Terna, as Transmission System Operator, needs, to guarantee despatching. Thanks therefore to HVDC technology, energy travels along overhead and undersea lines and arrives at the dedicated converter substations in a very efficient way.

The converter substation of Cepagatti (PE), an example of technological excellence from which the Italy-Montenegro HVDC interconnection runs (photo by Terna)

In the Converter System Design area, of which Francesca is the manager, these infrastructures are designed. «Among the last plants on which I worked there was Italy–Montenegro; the connection between Italy and France; the renewal of the Suvereto-Lucciana-Codrongianos connection, between Sardinia, Corsica and Tuscany (SACOI 3); and the very modern Tyrrhenian Link. The HVDC substations are in fact used often precisely for undersea connections and in any case are present, precisely for this very advanced technology, in most of the projects implemented or being implemented, by Terna». Even before a contract is signed awarding work for the construction of a converter substation, Francesca and her colleagues are called upon to define the technical construction standards, before concentrating, later, on support to the contractor, and on overseeing the final design.

«As soon as an HVDC project is begun and the location of the converter substation is decided, the Terna colleagues send to our unit the request to study its feasibility, to help to define the construction area, to prepare the documentation… so our work begins and it will only finish when the substation comes into operation».

The greatest challenge? «To guarantee quality in ever-shorter times. The specific characteristics of every single component are needed in fact to guarantee the success, the operation and the future maintenance of the entire construction. At Terna we have detailed technical specifications for every part of the plant, studied taking into account the regulatory framework but also building upon our experience».

«Our objective? Continual improvements to the system, that can be adopted even in the regulations themselves, in the hope of increasingly ensuring the efficiency and quality of the plants and constructions. What counts most in the choice of plants is the energy transition».

The procedure for defining all these aspects is scrupulous. «Months of technical and technological research, detailed and feasibility studies are done. Above all, consulting the people responsible for Dispatching, we collect the needs and problems to which the new connection must respond. Not immediately final projects, therefore, but a careful check that what we have in mind is feasible».

In this sense there is great team work. Work groups are created with skills and professionalism transversal to the whole company. «We, together, form a large group that dissects the project from various points of view. Only when we have the expected performance clear we move on to the heart of the construction». The need to find increasingly advanced technological solutions to deal each time with new scenarios, that depend on the time and the context of reference, enables the team to be always attentive to the latest innovations tackling every project as if it were the first.

The Terna specialist Francesca Pede together with the President of the Republic Sergio Mattarella, during the inauguration of the Italy-Montenegro interconnection (photo by Terna)

«The specific nature of our projects also explains why after so much time I still have so much enthusiasm and love for my work. Today, after ten years at Terna, I’m still learning very many things. In this way I maintain the high attention and interest for the activities that I perform».

Francesca says that the work group is closely knit and very young. The objective every day is «to make continual improvements to the system, that can be adopted even in the regulations themselves, in the hope of increasingly ensuring the efficiency and quality of the plants and constructions. What counts most however in the choice of plants is the energy transition. The macro-objective, therefore, is to facilitate decarbonisation, through the creation of large infrastructural networks in a logic that integrates development and sustainability».

Sustainability is a subject that Francesca has at heart since she was at university: «I graduated in 2008, the moment of the boom in renewables, and I gained experience in the photovoltaic field, before arriving at Terna in 2011. For an electrical engineer, Terna is one of the greatest ambitions. I did everything I could to get in! I was lucky that they selected me that year; doubly lucky because it is a solid and reliable company, which has become increasingly aware over time of its role as director of the energy transition».