The main advantage is the contribution to the security and continuity of the electricity supply in the interconnected systems; thanks to energy exchanges as and when they are necessary. Interconnections are the most significant instant backup for security of supply.
The second advantage, which is subject to the first, is the increase in efficiency of the interconnected systems. With the capacity that is not being used in lines and that is not destined for security of supply, commercial electricity exchanges are established daily taking advantage of the differences in energy prices between interconnected electricity systems. These exchanges allow the use of more efficient technologies for electricity generation, making it possible for energy to be transported from where it is cheaper to where it is more expensive.
A third advantage is the increased competition between neighbouring systems. Energy imports from other countries require agents in each country to submit more competitive proposals if they want their offers to be accepted, generating a reduction in the price of electricity at the wholesale level.
Finally, they provide greater integration of renewable energies. As interconnection capacity increases, the volume of renewable production that a system is capable of integrating under secure conditions is maximised, due to the fact that the renewable energy that cannot be integrated into the system itself can be sent to other neighbouring systems to optimize the available renewable energy generation. At the same time, when faced with problems in the grid or in the absence of renewable production, a high degree of exchange capacity allows energy from other countries to be imported.
The Spanish electricity system is interconnected with the Portuguese system (thus configuring the Iberian electricity system), with the North African system, through Morocco and with the Central European electricity system, through the French border. In turn, the Central European electricity system is connected to the Nordic countries, to the countries of Eastern Europe and to the British Isles, forming the largest electricity system in the world.
The European Union recommended in 2002 that all Member States should achieve in 2020 a minimum of a 10% interconnection ratio, this being the sum of import capacity versus installed generation capacity, with the aim to eliminate isolated systems, facilitate mutual support and promote the Single Market for electricity. Currently, Spain’s interconnection ratio is under 5%, which is still far below the recommended target. If we consider that the actual support to the Iberian Peninsula can come only from Central Europe through the French border, the interconnection ratio of the Iberian Peninsula is only 2.8% even whit the new interconnection between Spain and France through the Eastern Pyrenees. Therefore, in essence, Spain can still be considered as an electrical island.
In 2020, with the planned interconnections, Spain will be the only country in continental Europe below the target of 10%, so it will be necessary to continue developing new interconnections. These new projects are the northern interconnection with Portugal between Galicia and Portugal's Minho region, a 220 kV phase-shifting transformer in Arkale and a study is underway for a new submarine interconnection with France through the Bay of Biscay in the mid/long-term horizon.
The strengthening of interconnections represents the top priority to be undertaken in the coming years in the development of the transmission grid. Investment in these infrastructures will be a priority; whereby for it to be fully implemented it will require the fulfillment of some basic premises, such as maintaining a stable regulatory framework and adequate returns on investment, as well as an improvement in the social acceptance of the facilities.
Import capacity / net generation capacity in 2011 and 2020. Source: ENTSO-E
The strengthening of interconnections will facilitate the creation of supergrids, understood as supranational grids of high transmission capacity over long distances, and that can help to balance the fluctuations inherent to renewable energies.
The formation of these electricity highways will allow the optimum utilisation of renewable marine and terrestrial resources, and will provide support between interconnected electricity systems depending on the situation of the generation, the transmission grid and the demand existing in each one of them. The targets for 2020 and the European Union’s 2050 roadmap, require the progressive development of electrification and supergrids.