Phase-shifting transformers (PSTs) change the phase angle between two grid points, thereby providing targeted control of power flow. They are playing an increasingly important role in European transmission grids, where renewable energy leads to constantly changing load situations. As the European power landscape shifts toward more renewable generation and volatile power flows, phase-shifting transformers are gaining significant importance.
How does a phase-shifting transformer work?
A special winding arrangement shifts the output voltage relative to the input voltage by a defined angle. Since power flow in an AC line also depends on the phase difference, this allows targeted control of how much energy flows over a particular line. This makes it possible to avoid bottlenecks and make optimal use of transmission capacity.
Key Characteristics at a Glance
- Phase shift typically ±20° to ±30°
- Control of power flows between subnetworks
- Avoidance of bottlenecks during peak-load periods
- Ratings typically 200 to 1,500 MVA
- Frequently used at interconnection points in meshed grids
- Elaborate mechanical on-load tap changer
- Very high demands on design and manufacturing
Frequently Asked Questions
When does it make sense to use a phase-shifting transformer?
Whenever parallel line routes are loaded unevenly and natural power flows lead to overloads. A PST can redirect power flows onto less-loaded paths – without the need to build new lines.
What advantages does a phase-shifting transformer offer over grid reinforcement?
A PST can be implemented faster, requires fewer permits, and avoids physical interventions in the landscape. It thus complements classic grid expansion and can significantly increase the transmission capacity of existing grids.
What are the biggest technical challenges with PSTs?
The biggest challenges lie in precise phase shifting, a reliable on-load tap changer, and managing very high active and reactive power levels. Transport and installation are also demanding due to their size – often exceeding 500 tonnes in weight.
How long does a typical PST project take?
From order to commissioning, 24 to 36 months is typical. Design and manufacturing alone usually take around 18 months due to the complexity, with transport, installation, extensive testing, and connection to the control system added on top. Early planning and close coordination are essential.
For high-performance phase-shifting transformers and custom specifications, our experts are your point of contact. Contact us for a technical discussion.