Ensuring the stability of the electricity system of an island was extremely complex because of the difficulty of having the support of associated systems. However, after the implementation of the first interconnection between Mallorca and the Iberian Peninsula, there was a notable strengthening of the guarantee of supply in Mallorca and on the islands of Ibiza and Fomentera, also connected to Mallorca by underwater cables. Finally, with the construction of the Mallorca-Minorca interconnection, the integration of all the islands into a single Balearic system was completed.
With the aim of improving its system, REE then established a new protection strategy, defined as "multifunctionality", which reduces the equipment per position, while incorporating advantages for the operation and maintenance of the electrical system.
The project was very complex both because of the laying of the underwater cable (one of the longest and deepest in the world) and because of its technology, given that the link was made with direct current.
The complex control system of the DC and AC substations between the peninsula and Mallorca was successfully carried out by Arteche and since 2012 the system is in service, guaranteeing the stability and quality of the island's electricity supply.
After completing the interconnection between the Peninsula and Mallorca with which the supply of the archipelago is reinforced, the next step was to guarantee the supply between both islands.
The link consists of a three-pole 132 kV, 2,300 tonnes terrestrial-submarine cable. The underwater route is 41.7 km, with a maximum depth of 8 meters, and the land route, which is underground, adds up to more than 13 kilometers between the two islands.
New protection and control system
Traditionally REE had a protection system in each position consisting of three protections: primary, secondary and circuit breaker failure. In addition, each position had a multi-converter equipment to capture the operation measures.
In order to reduce the field wiring, all the protection and measurement equipment communicate with the position control equipment. In this regard, Arteche is a clear model in REE, with more than 2000 equipment installed in more than 270 substations.
The new solution reduces the number of protections from three to two and eliminates the measurement equipment whose function is redundantly integrated in the two protection equipment. The two protections are mirrored so that they have the same protective functions and settings.
This new architecture allows the maintenance of one of the position protections, without the need to request a discharge on the line, which significantly facilitates the maintenance of the system while improving its reliability. This implies that the control system designed by Arteche must manage the capture of the two IEDs with the same information and in a redundant way, both at the level of digital signaling and at the level of measuring the position.
This new system makes it possible to improve the availability of the electricity system while facilitating the operation, maintenance and exploitation of the national electricity system.
Arteche is the first REE supplier to develop and successfully implement the new protection architecture with this multifunctionality.
These works were carried out during country's confinement due to COVID-19, which complicated all the work permits, as well as the travel logistics and commissioning works.