PSE procurement expands two northern 400kV substations

Polskie Sieci Elektroenergetyczne is procuring expansion work at the Gdańsk Przyjaźń and Żydowo Kierzkowo substations, two 400kV nodes within the reinforcement of northern Poland’s transmission network. The package includes infrastructure associated with reactive-power compensation, 400kV line operation, and modifications within the Żydowo Kierzkowo station.

The works form part of a longer sequence of investment rather than a stand-alone equipment purchase. PSE has developed double-circuit 400kV line sections between Gdańsk Przyjaźń, Żydowo Kierzkowo, and Słupsk, strengthening a part of the network where new generation and changing power flows are increasing the demands placed on voltage control and transmission capacity.

Reactive power is central to the programme. PSE has previously identified additional compensation requirements at both Gdańsk Przyjaźń and Żydowo Kierzkowo, with planning material assigning 150Mvar requirements to each location.

Although reactive power does not deliver usable energy to consumers in the same way as active power, it is essential for maintaining voltage within acceptable limits across an alternating-current network. Long transmission circuits, transformer operation, loading patterns, and the location and type of connected generation can all alter the balance.

A network can consequently encounter voltage constraints even where its lines and transformers still have thermal capacity available. Excess voltage can develop under lightly loaded conditions, while heavier transfers can make voltage support more difficult, requiring equipment capable of absorbing or supplying reactive power according to the operating state of the system.

PSE has linked its wider compensation strategy to the expansion of renewable generation, including offshore wind. Large conventional synchronous generating units have historically supplied reactive-power capability and short-circuit strength as part of their normal operation, but those services cannot be assumed to remain available in the same locations or at the same times as the generation mix changes.

Transmission operators can address the resulting requirement through equipment including shunt reactors, capacitor banks, synchronous compensators, and power-electronic systems such as STATCOMs. The appropriate technology depends on whether the network requires fixed or dynamic compensation, the speed of response needed, the expected operating range, and the characteristics of the surrounding system.

Żydowo Kierzkowo also occupies an important position between voltage levels. Its 400(220)/110kV configuration reflects a transmission site being developed around the 400kV system while continuing to interface with established 220kV and 110kV infrastructure.

Changes of that scale involve substantially more than adding individual circuit bays. Busbar arrangements, protection and control schemes, line terminations, transformer interfaces, telecommunications, auxiliary supplies, and planned outages all have to be coordinated around equipment that remains part of an operating power system.

Gdańsk Przyjaźń sits within the same northern reinforcement programme, helping create transmission capability closer to the Baltic coast. As new generating capacity connects in the region, the engineering problem is not simply one of carrying additional megawatts southwards but of keeping voltages and stability within limits across a much wider range of operating conditions.

Reactive-power equipment can therefore determine whether nominal transmission capacity is usable in practice. A circuit that remains within its current rating can still face operating limits if voltage rises or falls outside permitted ranges, while system stability may impose further constraints before thermal limits are reached.

Additional compensation gives dispatchers more control over those conditions. Reactors can absorb reactive power during periods of high voltage, while other equipment can support voltage when required, allowing the network to operate closer to its intended transfer capability without relying solely on changes to generation dispatch.

The present procurement advances defined parts of work already identified in PSE’s network-development planning. Treating it as a delivery stage rather than a newly conceived programme is important because major transmission reinforcements usually move through studies, design, procurement, outages, construction, and commissioning over several years.

For equipment suppliers and contractors, the resulting scope spans high-voltage primary plant, secondary systems, protection and control, civil works, auxiliary equipment, testing, and integration with live transmission assets. Outage planning can be as important as equipment delivery because existing circuits have to remain available for system operation while sections of the station are modified.

Northern Poland’s transmission build-out will continue to be driven by generation and interconnection requirements, but additional line capacity alone will not settle every constraint. At Gdańsk Przyjaźń and Żydowo Kierzkowo, voltage control is becoming part of the physical grid expansion rather than an operational problem left for later.