APG advances Ernsthofen substation modernisation

Austrian Power Grid is advancing the €140m modernisation of its Ernsthofen substation, one of the most important transmission nodes in the Austrian power system.

Located in the Amstetten district of Lower Austria, the site links supra-regional and regional supply lines and supports supply across parts of Lower Austria and Upper Austria, including Amstetten, Steyr, Wels, the Upper Austrian central region, and Linz. The substation also supports the transport of renewable electricity across Austria’s east-west axis.

The project includes the general renewal of the site’s 220kV switchgear while operations continue. The switchgear area covers around 71,000 sq m, with temporary 220kV arrangements being used to maintain system operation during construction. The first construction phase was completed in 2025, the second phase is scheduled to run until 2027, and the third phase is planned for 2027 to 2029.

Three new 220/110kV large transformers form a central part of the upgrade. The transformers link APG’s national extra-high-voltage network with the regional distribution network and are designed to help control power flows and reduce network bottlenecks. Once the project is complete, the site will have ten major transformers in operation, including seven existing units.

Project information is available through APG’s Ernsthofen modernisation update.

The newly commissioned regional control room is a significant part of the upgrade. APG manages Austria’s electricity system centrally from its Power Grid Control centre in Vienna, where transmission network information is monitored, processed, and used for system operation. Regional control rooms add a further operational layer, giving APG local control capability, redundancy, and faster response options for defined network areas.

At Ernsthofen, the fully digitised regional control room is connected directly to local substations. Operators can monitor voltages, currents, frequencies, switching states, transformer positions, and network conditions, while also supporting switching, maintenance coordination, and faster intervention during faults or operating changes.

The project forms part of a much larger Austrian grid investment requirement. Austria faces a €68bn grid investment requirement, with renewable integration, electrification, regional constraints, and ageing infrastructure all driving the need for reinforcement. Ernsthofen shows how that requirement is translating into high-voltage assets, transformer capacity, and digital control systems.

Delivering major substation renewal while the plant remains part of the operating transmission system requires detailed staging. Temporary switchgear arrangements, planned outages, protection changes, transformer delivery, civil works, and control system migration must be coordinated without compromising supply security.

Digitalisation is also changing the role of substations. Traditional primary assets remain central — busbars, transformers, switchgear, protection relays, disconnectors, and earthing systems — but the operational value of a site increasingly depends on the control and data layer around them. More dynamic renewable flows, flexible loads, storage, and cross-border exchanges require closer monitoring and faster operational decisions.

Across European grid infrastructure, project delivery is increasingly combining high-voltage equipment, digital control, and system integration. The expanded AC grid alliance between Hitachi Energy and Samsung C&T points to the same pressure at project level. Ernsthofen shows it at asset level, where switchgear renewal, transformer upgrades, and digital control are being delivered as one integrated programme.

Completion is planned for 2029. By then, Ernsthofen will have a modernised 220kV switchgear system, expanded transformer capacity, and a digital control environment suited to a more complex Austrian grid.