TenneT, Germany: Phase‑shifting transformers ensure grid stability

These advanced solutions enable efficient power flow control, reduce grid congestion, and help optimize existing infrastructure. With high performance, low losses, and compact design, Siemens Energy’s transformers contribute to a resilient and future-ready transmission network.

Germany’s energy transition is reshaping the power landscape, with increasing volumes of renewable energy and electrification driving dynamic load flows across the grid. Transmission system operators like TenneT face the complex task of maintaining grid stability while maximizing the capacity of existing infrastructure.

Instead of immediate grid expansion, TenneT follows the NOVA principle — prioritizing optimization and reinforcement. This requires advanced technologies that can actively manage power flows, reduce congestion, and adapt to the evolving energy mix. Siemens Energy was challenged to deliver high-performance phase-shifting transformers that meet demanding technical specifications and support reliable, resilient grid operations.

Or as Dr. Florian Martin, Director Asset Management, from TenneT TSO GmbH puts it:  “In line with the German NOVA-principal, grid optimization before expansion and reinforcement, TenneT invests a lot into possibilities to increase the transport capacity of the existing grid. Therefore, we are looking into innovative system operation methodologies as well as equipment which can help us to reduce congestions. Siemens Energy’s phase-shifting transformers comply to the ambitious requirements of our high-voltage grid to secure the power of supply in accordance with the reliability and resilience of out grid.”

To address the challenge of fluctuating load flows and optimize existing grid infrastructure, Siemens Energy provided a tailored solution: high-capacity phase-shifting transformers (PSTs) designed for active power flow control. These transformers enable TenneT to manage grid overloading, stabilize transmission lines, and support the integration of renewable energy sources.

The first eight PSTs — four for the Wuergau substation in southern Germany and four for Krempermarsch in the north — feature a compact design suitable for rail transport, a high rating of 1420 MVA at 410 kV, and a maximum no load phase angle of ±24°. Their low impedance and quiet operation ensure minimal losses and high efficiency. Siemens Energy’s factory network in Weiz and Nuremberg ensures parallel production and timely delivery, backed by engineering expertise and logistical strength.

This solution not only meets but exceeds the technical requirements of TenneT’s high-voltage grid, supporting reliable and resilient system operation. Martin Kalcher, Plant Manager, Large Power Transformers Weiz, sums it up as follows: “The energy transition is a system challenge that goes beyond individual projects. Our role is to provide technologies that make the grid smarter, stronger, and ready for what comes next. This is exactly what our phase shifting transformers deliver for TenneT and Germany’s power systems.”

Siemens Energy’s phase-shifting transformers offer TenneT a powerful tool to actively manage power flows and strengthen grid resilience. By enabling dynamic control of transmission lines, these transformers help reduce congestion, balance fluctuating renewable inputs, and support cross-border energy exchange.

The compact, high-performance design ensures minimal losses and low noise emissions contributes to environmental sustainability. With optimized logistics and parallel production from Siemens Energy’s factory network, tight delivery schedules are met without compromising quality.

Beyond technical performance, the solution supports long-term operational efficiency and cost savings — helping TenneT meet the demands of the energy transition while maintaining a stable and reliable power supply for millions.