General Renovation of the Ernsthofen Substation: Phase-Shifting Transformer Reaches Final Position

Milestone reached: delivery of a two-part phase-shifting transformer

A two-part phase-shifting transformer was successfully transported to the site and positioned onto its foundation, marking an important step in the ongoing modernization project.

Comprehensive renewal of the Ernsthofen substation

Located in the district of Amstetten, the Ernsthofen substation is one of APG’s largest and most critical grid nodes. It connects major national and regional transmission lines and plays a central role in ensuring Austria’s security of supply, transporting renewable electricity along the east–west axis, and providing sustainable energy to some of the country’s strongest industrial and economic regions.

The modernization project, which began in 2017, includes a complete renewal of the 110 kV system (successfully completed at the end of 2022) and a general overhaul of the 220 kV switchgear. This work is being carried out while maintaining system operations through extensive temporary 220 kV facilities.

In addition to the newly delivered phase-shifting transformer from Tauern, two new 220/110 kV power transformers were commissioned in 2022 and 2023. Once the project is finished, ten high-capacity transformers—including the seven already in place—will ensure a secure electricity supply both regionally and throughout Austria. Completion is scheduled for 2029.

APG is invests 150 million euros in Ernsthofen refurbishment

APG is investing around 150 million euros in the renovation of the Ernsthofen substation through 2029. The project is part of APG’s broader investment program, which totals approximately 9 billion euros for Austria’s electricity infrastructure by 2034.

A Logistical Masterpiece: Transporting the Transformers

Two transformers from Tauern (Salzburg) were transported to Ernsthofen: a 242-tonne unit on 19 October and a 253-tonne unit on 26 October. On the day following each transport, the steel giants were moved onto their foundations with millimeter precision in a multi-hour procedure. Each transformer has a rated power of 600 megavolt-amperes (MVA). The next project steps include technical assembly and connection to the switchgear.

The heavy-load transport and foundation placement were remarkable logistical achievements. Both transformers were transported by rail on a through-loading carrier directly to the substation, which is connected to the Austrian Federal Railways (ÖBB) network. There, each unit was transferred onto cross rails and pulled into its final position using transverse traction. From loading to final placement, each transport required a total of six days.

Strengthening Supply Security and facilitating a better integration of Renewables

Transformers serve as the heart of every substation. They connect APG’s nationwide extra-high-voltage grid with regional distribution networks, which supply electricity directly to households and businesses. This ensures that the region can be supplied from the APG grid when needed, and that excess renewable electricity generated locally —such as wind and solar power—can be fed into and distributed throughout Austria.This significantly strengthens Lower Austria as a business and living location and at the same time reduces dependence on imports. 

“Phase-shifting transformers differ from conventional transformers in one key respect: they do not convert electricity between voltage levels. Instead, they can redirect power flows from one line to another, relieving overloaded lines and preventing potential grid bottlenecks. This enables significantly better integration of renewable energy and increases the feed-in capacity for green electricity,” explains Jürgen Pilgerstorfer, APG’s project manager.

Given these capabilities, transformers — and especially phase-shifting transformers — are indispensable components for a secure and affordable energy transition in Austria.
 

About Austrian Power Grid (APG)

As independent transmission system operator Austrian Power Grid (APG) is in charge of ensuring the security of the electricity supply in Austria. With our high-performance and digital electricity infrastructure and the use of state-of-the-art technologies we integrate renewable energies and reduce the dependency on electricity imports, we are the platform for the electricity market, and we provide access to reasonably priced electricity and thus create the basis for Austria as supply-secure and future-oriented industrial and business location and place to live. The APG grid totals a length of about 3,500 km and is operated, maintained, and continuously adapted to the increasing challenges of the electrification of businesses, industry, and society by a team of approximately 1,000 specialists. 67 substations are distributed all over Austria and the majority is operated remotely. Thanks to our committed employees Austria had a security of supply of 99.99 percent also in 2024 and thus ranks among the top countries worldwide. Our investments of 630 million euros in 2025 (2024: 440 million euros, 2023: 490 million euros) are a motor for the Austrian economy and a crucial factor in reaching Austria’s climate and energy targets. Until 2034 APG will invest a total of approximately 9 billion euros in grid expansion and renovation projects.