Croatia orders phase-shifting transformer to manage transmission power flows

Transmission grid operators across Southeastern Europe face escalating challenges in managing loop flows and unexpected power redistributions. The recent contract between Croatian transmission system operator Hrvatski operator prijenosnog sustava and a domestic transformer manufacturer, valued at 11.5 million euros excluding value-added tax (or approximately 12.8 million US dollars), demonstrates the strategic value of phase-shifting units in resolving localised bottlenecks.

Phase-shifting transformers serve as crucial control elements in high-voltage alternating-current networks. By introducing a phase angle difference between the input and output voltages, these specialised transformers allow system operators to direct active power along preferred transmission paths. Rather than allowing power to flow strictly according to line impedance, utilities can dynamically balance burdens across parallel circuits. At nodes such as the Gracac substation, installing active flow-control technology improves overall operational security, enhances transmission flexibility, and maximises the throughput of existing network assets without requiring lengthy overhead line construction.

For transmission network planners and asset managers, deploying advanced flow-control units represents a cost-effective operational intervention. As renewable energy integration increases regional flux, physical grid constraints frequently cause loop flows across cross-border interconnectors and internal corridors. Phase-shifting units mitigate thermal overloads, eliminate market curtailments, and reduce stress on auxiliary equipment, extending the working life of secondary assets across adjacent substations.

What this means for asset owners in the Balkans and the Black Sea region: Grid operators and substation managers in Croatia and neighbouring power systems must evaluate flow-control assets as part of ongoing grid modernisation schemes. Incorporating phase-shifting units into long-term capital plans helps mitigate unexpected loop flows, reduces the risk of transformer overload outages, and optimises existing asset utilisation, though procurement timelines require planning long maintenance and outage windows well in advance of commissioning.