REN operates the RNT which connects generators to extra high voltage consumption centres. It is the only electricity transmission entity in Portugal, covering the whole mainland and having interconnections with REE - Red Eléctrica de España, the Spanish network.
Pursuant to current legislation, REN must conduct planning studies of the transmission grid in order to coordinate grid development plans with national generation and demand forecasts.
These studies must be sent to the competent authorities for prior approval, without which it is not possible to go on to the investment phase. It is also REN's legal obligation to collaborate in official studies of medium and long-term security of the country's electricity supply.
Investment in the transmission grid has kept up with growth in consumption in Portugal. In recent years, as a result of the integration of high levels of new, renewable generation (basically wind power), mostly in inland areas, the RNT has been reinforced for these areas so that it can transmit more renewable energy to consumption centres.
Under agreements between Portugal and Spain on the development of the Iberian electricity market, there has been a substantial increase in interconnection capacity between the two countries, which was only possible after the completion of transmission grid reinforcements on both sides of the border.
REN has 8,733 km of lines all over the country. The 400 kV grid lines mainly run north to south near the coast from the Alto Lindoso power station in the north to the Algarve, and west to east, where they interconnect with the Spanish grid.
The 220 kV lines basically run between Lisbon and Oporto, diagonally between Miranda do Douro and Coimbra, along the River Douro and in Beira Interior.
The extra high voltage grid is complemented by 150 kV lines, the first ever voltage in the RNT (since 1951). Operation is responsible for keeping all equipment and systems up and running efficiently.