Substations in the grid architecture

„Substations are far more than mere infrastructural structures – they are complex systems that form the foundation for secure and future-proof grid operation, without which the energy transition would not be possible. Each substation is unique, shaped by topographical, geological, hydrological and grid-specific conditions. Our task is to reliably feed electricity from a wide variety of sources into the interconnected grid and distribute it, while also continuously renewing and expanding the existing infrastructure to connect wind farms and solar power plants with homes and large consumers such as data centres and industrial facilities. The challenge lies in uniting all aspects, including permits, environmental regulations, logistical requirements and safety considerations, in a comprehensive planning and design concept.

One particular challenge is interface management. Planning and implementation rarely proceed in a strictly linear fashion, with phases often overlapping or needing to be adapted or refined. The electrical design, which forms the basis for the steel construction and structural engineering, is not always complete from the outset and may evolve throughout the project. This requires foresightful planning, including making sound initial assumptions and subsequently verifying them. But this approach also presents opportunities: We have learned to deal flexibly with changing conditions and to proactively coordinate parallel processes.“

Henrik Stender, Project Manager – Major Projects

Without substations, new high-voltage direct current (HVDC) transmission lines could not be integrated into the existing alternating current (AC) grid. Each voltage level has a clear function: The 110 kV level is used for regional distribution and for connections to industrial plants and supply areas. The 380 kV level forms the backbone of the European power grid, facilitating low-loss transmission over long distances. HVDC lines at a level of ±525 kV transmit large amounts of electricity hundreds of kilometres from offshore wind farms or solar power plants. In converter stations, the direct current is then transformed into alternating current and fed into the grid.

Planning and constructing a new substation involves far more than electrical engineering. Many other factors must also be considered, including permitting procedures; environmental and nature conservation regulations; oil-spill containment and fire-suppression measures (particularly aimed at protecting nature from contamination); varying soil conditions and construction processes; and coordination with local authorities, grid operators and, where applicable, residents. Logistical challenges also play a crucial role – for example, the transport and installation of heavy transformers weighing several hundred tonnes. In urban areas, space requirements are becoming increasingly important, with gas-insulated switchgear (GIS) now used more widely because it requires significantly less space than conventional open-air substations and can be integrated into enclosed halls. This opens up new possibilities for grid expansion in densely populated regions without the need for additional land. Sustainability and digitalisation are also increasingly shaping the next generation of substations. Resource-efficient concrete construction, alternative foundation solutions, the use of environmentally friendly insulating gases, and BIM-supported planning and design of complex projects are all responses to the growing demands of today’s rapidly evolving energy infrastructure. Digital operations-management systems, sensors and monitoring technologies facilitate condition-based operation and maintenance, increasing the reliability of the power supply system.