With the purpose of designing and constructing industrial facilities. During its early years, it establishes its innovative and pioneering spirit, specializing in the development and implementation of the national energy transmission network, which included high-voltage power lines and substations.

SEMI presents the “Project for the Construction of a National Electric Network in Spain,” which leads to the creation of an entity that would become the precursor to the current Red Eléctrica de España (REE).

SEMI‘s presence in the railway sector has been continuous since 1929. The company began its journey with the electrification of the Madrid-Ávila-Segovia line, the first to be carried out by a Spanish company in the country.

This project was initiated for the Northern Railway Company of Spain, which was later integrated into RENFE.

However, the work was interrupted by the Spanish Civil War, delaying the electrification’s completion until 1946, now under RENFE (established in 1941).

SEMI designs and constructs the Ponferrada-Valladolid line for Endesa, the first line in Spain operating at 220 kV.

Driven by a desire to innovate and explore new fields, the company entered the telecommunications sector. Since then, SEMI has maintained extensive activity in all operations related to the design and construction of communication infrastructures: TV and radio repeaters, mobile telephony, GSM-R; radar and maritime rescue stations; fiber optic networks, real-time data meteorological station networks, and more.

SEMI constructs the antenna field for the Noblejas Shortwave Broadcasting Center, which transmits Radio Nacional de España (RNE) broadcasts to Eastern Europe, the Middle East, Australia, North Africa, Equatorial Africa, and the Americas.

In the 1970s, SEMI designs and constructs Spain’s first conversion of a 220 kV duplex line to a 400 kV triplex line, on the Madrid-La Mudarra route.

Held in Spain with “Naranjito” as the mascot, the event necessitated the modernization of TV and RNE broadcasting center infrastructures to cover the information. SEMI was awarded the construction, reinforcement, and expansion of numerous broadcasting centers, such as Pozo de las Nieves (Las Palmas), Arguis (Huesca), El Viso (Zamora), Torrente (Valencia), Jaizquíbel (Guipúzcoa), as well as the installation of a 46-meter metal tower atop the Torrespaña “Pirulí” in Madrid.

In a challenging economic environment, SEMI experienced a turning point by joining the ACS Group. The history of ACS began in 1983 when a group of engineers acquired the financially troubled Catalan construction company Construcciones Padrós. In 1988, ACS acquired GRESA and SEMI, both previously owned by the Marín family. This marked the beginning of the industrial division of the ACS Group.

Subsequently, GRESA and SEMI merged through absorption, with SEMI remaining as the sole commercial brand. This move allowed ACS to establish itself not only as a construction group but also as an industrial powerhouse.

In the 1990s, numerous telephony licenses were granted to various telecommunications operators in Spain. These concessions allowed SEMI to actively participate in the deployment of new mobile and fixed networks on both national and international scales.

The company was awarded the construction of Base Stations by the four mobile telephony operators in Spain, as well as in Portugal, Morocco, Mexico, Central America, and Venezuela. Additionally, fiber optic networks were deployed for both cable operators and utility companies, utilizing energy transmission networks.

Key milestones for SEMI during this decade were its contributions to the EXPO ’92 and the Olympic Games, which significantly enhanced Spain’s international image, showcasing the technical capabilities of the companies involved in the major transport and communications infrastructures undertaken for these events.

For these occasions, SEMI built the Tower of the Telephone Exchange on La Cartuja Island and completed numerous communication center projects in the Olympic Village to ensure coverage for both events.

Furthermore, SEMI participated in the electrical infrastructure of the NAFA project (New Railway Access to Andalusia) and the mobile telephony coverage for the new railway route, which is used by the AVE Madrid-Sevilla high-speed train. Additionally, in collaboration with the Japanese company NEC Corporation, SEMI installed the antennas for Telefónica’s satellite communication centers in Armuña de Tajuña (Guadalajara) and Agüimes (Canary Islands).

Anticipating the current challenges of renewable energies, SEMI has been carrying out “turnkey” projects for years related to wind, photovoltaic, and solar thermal energy. This reflects the company’s commitment to renewable energy sources and its dedication to environmental sustainability.

SEMI took a significant step forward with the design of the EAC-350 catenary, a project funded by MINER and CDTI, in collaboration with the Universidad Pontificia de Comillas and the Higher School of Mining Engineers at UPM.
The result of this research materialized in the prototype of an alternating current catenary for speeds of 350 km/h, known as C-350. This prototype was accepted and installed on three kilometers of the Madrid-Sevilla AVE high-speed line for real-world testing.
On December 15, 1998, tests were conducted with AVE trains, which successfully reached and exceeded the speeds for which the new catenary was designed.
That same year, the design and construction of the railway catenary for 350 km/h was completed.

The company began construction and reconstruction work in France for EDF following the storms that hit the neighboring country in December 1999.
Responding to EDF’s call for international collaboration, SEMI contributed by sending specialized personnel for high and extra-high voltage works, ensuring the rapid restoration of service and the reconstruction of the French electrical network.
Over time, SEMI obtained certification with EDF and established a permanent presence in France through the creation of its subsidiary, SEMI France.

In 2002, the company began implementing its international expansion plan. After executing several projects in different countries, SEMI decided to establish a permanent presence in Morocco, Mexico, and Costa Rica.

In 2003, the Railway Infrastructure Manager (GIF) awarded SEMI the “Design, installation, and maintenance of the Catenary (GIF Multipurpose Catenary, known as CPG Bicurrent) on the test section of the three-rail track between Olmedo and Medina del Campo.”
This was the first project to apply hybrid technologies to address the need for corridors handling mixed traffic—passenger and freight trains—capable of operating at both 3 kV DC and 25 kV AC. The goal was to certify these corridors for all types of European operators.
SEMI’s engineering development to solve this challenge became the design of choice for implementation on mixed-traffic lines within the Spanish network.

In 2004, SEMI France became a reality, established as an independent company with great potential, serving as a cornerstone for European expansion.

The high-speed system developed by SEMI, which has held the European interoperability certificate since 2008, became a cutting-edge technology and engineering solution, suitable for implementation and international export in any projects of this nature.

Colloquially known as “SEMI Venezuela,” the network of SEMI activities expanded in 2009 through SEDMIVE.

As part of its strategic international expansion plan, SEMI established two new companies in 2010: SEMI Italia and SEMI Panamá.

In 2011, SEMI made a significant push towards internationalization by establishing operations in Germany, Bulgaria, Poland, and the Dominican Republic.

In December 2012, SEMI was selected by NASA to construct an office building at the Goddard Space Flight Center in Maryland as part of a project funded by the U.S. Federal Government. Founded in 1959 and named after physicist Robert H. Goddard, this center is pivotal for NASA’s space and scientific missions. It is where spacecraft are built and communications with the International Space Station are managed.
SEMI developed a four-story, 12,000 m² building with technological innovations to enhance energy efficiency, designed to support future missions to Mars.

Vinci, a global construction and concessions company founded in 1899 with a presence in over 100 countries, became part of SEMI in 2021. Vinci’s core values include responsibility, innovation, sustainable development, ethics and transparency, employee empowerment, and collaborative relationships with stakeholders.
Vinci is committed to safety, sustainability, and excellence in all its operations.

Construction of the first submarine electricity interconnection between Spain and France, connecting Gatika in Spain with Cubnezais in France. This interconnection will increase the electricity exchange capacity, aiming to enhance the security, stability, and quality of the power supply between both countries and the rest of Europe.