Four years after its inauguration, in October 2015, the electricity interconnection that connects Spain with France through the Pyrenees, between Santa LLogaia (Girona) and Baixas (Roussillon), has led to an overall saving of €528 million for the Spanish electricity system, of which €422 million correspond to savings in the day-ahead market and €106 million to additional income for the electricity system derived from congestion rents.

In addition, during this period, the interconnection has allowed the mean absolute deviation in prices between Spain and France to be reduced by 30% in the day-ahead market (from €16.72/MWh in 2014 to €11.58/MWh in the first half of 2019), and has contributed to increasing congestion rents by 55% (from €72 million in 2015 to €112 million in 2018).

After its commissioning, Spain was able to double the energy exchange capacity ratio increasing it from 1.4% to 2.8%, however exchange capacity is still far from the European Union target, which is set at 10% of a country’s total installed power capacity by 2020 and 15% by 2030.

The financial figures of the project to date exceed its overall amortisation on the Spanish side. The project involved a €700 million joint investment between the two countries, which was financed equally by Red Eléctrica de España and its French counterpart Reseau de Transport d’Électricité. The interconnection also received a €250 million grant from the European Union.

Electricity interconnections are vital for energy security and competitiveness in Europe, as well as for helping better fulfil the decarbonisation and climate change targets to which the EU has committed itself. The European Union believes that an interconnected grid will help achieve the objective of ensuring affordable, safe and sustainable energy that is compatible with growth and employment.

Thus, for the first time, the European Council meeting held in Barcelona in March 2002 approved the goal for Member States to reach a level of electricity interconnection capacity of at least 10% of their installed generation capacity by 2020. Subsequently, the Madrid Declaration signed at the France-Portugal-Spain Summit on 4 March 2015, ratified the importance of setting in motion all necessary efforts to achieve the minimum electricity interconnection target of 10% by 2020 and increase it in subsequent years.

 A world-wide reference

The electricity interconnection with France remains at the forefront at a worldwide level in terms of technology. With a length of 64.5 kilometres, at the time it was commissioned, the link between the two countries was the world’s longest interconnection line in direct current. It links the towns of Baixas, in the French region of Roussillon, and Santa Llogaia, in the region of Alto Ampurdán. Over half the route (33.5 kilometres) runs throughout French territory and the rest (31 kilometres) on Spanish soil, crossing the Pyrenees through a tunnel which is 8.5 kilometres in length and 3.5 metres in diameter, mostly excavated on the French side. In order to minimise the environmental impact, the line, which is buried throughout its route, runs parallel to the high-speed rail network and the AP-7 motorway.

The decision to bury the line was a technological challenge of the utmost difficulty. The length of the route and the fact that it runs underground meant that the electricity running through the line had to be in direct current and not in alternating current, which is what circulates in most of the standard electricity lines. Direct current limits electricity transmission losses but given the voltage level (320kV) and the power capacity of the interconnection (2 x 1000 MW), a special cable was also needed. Therefore, the cables were made of copper coated with cross-linked polyethylene (XLPE), the first time this material had been used at such a high power capacity and voltage level in direct current.

In addition, a milestone was reached as a result of using VSC (Voltage Source Converter) technology in a line of these characteristics; a technology which makes it possible to speed up the conversion of direct current to alternating current and vice versa, while allowing the electricity supply to be quickly restored after a cut in said supply.

All the aforementioned turned this infrastructure into a pioneering installation for future projects. In addition, the project continues to be an example of stakeholder consensus given that both Red Eléctrica and RTE managed to reach agreements with the 26 municipalities affected by the infrastructure. The involvement with the local governments and the social environment has led to the fulfilment of about 200 environmental commitments along the entire route of the line.