Technical solution

The LitPol Link power interconnection between Poland and Lithuania includes an overhead double-circuit 400kV transmission line extended between the Polish town of Ełk and the Lithuanian town of Alytus, a new 500 MW HVDC “back-to-back” converter station next to 400kV switch yard in Alytus, 330/110 kV substation in Alytus, and 400/110kV Ełk Bis substation combined with the existing 220/110 kV substation in Ełk.

1.  400/110 kV Ełk Bis substation in Poland

The new 400/110kV Ełk Bis substation in Poland will cover the area of 12 ha. The 400 kV substation will be connected to a double-circuit 400 kV line running from Łomża, Poland, and a double-circuit line from Alytus. It will be connected to the existing 220/110kV substation in Ełk operating at 110 kV level by means of a new 110 kv double-circuit line. More 400 kV lines are planned to be connected to the Ełk Bis substation in the future. The plans are to build back-up facilities for passive power compensation.

Contractor for the construction of Ełk Bis substation: Elfeko S.A.

2. Overhead 400 kV transmission line in Poland and Lithuania

The 163 km long transmission line will run across the regions of Alytus and Lazdijai in Lithuania (51 km). In Poland, the line will run across 10 municipal districts in Podlaskie and Warmińsko-Mazurskie provinces (112 km). In sections of the power transmission line crossing areas covered by forest, over-forest high towers are designed to be erected to avoid tree cutting along the line path.  297 and 150 towers are planned to be erected in Poland and Lithuania, respectively.  Average line height is around 60 meters, including 100 m high over-forest towers. The towers will be spaced 300-450 m apart. Phase conductors will be made of a triple bundle with aluminium clad steel wires in the core (AFL-8 350 mm2). A 70-meter wide protection zone is designed for 400 kV transmission lines. Construction and land development limitations will be introduced along this strip of land and air space on the both sides of the line in order to secure free access during maintenance and repair works.

LitPol Link line route

Contractor for the power transmission line in Poland: IDS-BUD S.A., Enprom Sp. z o.o.
Contractor for the power transmission line in Lithuania: A.Žilinskio ir ko UAB

3.  400 kV switch yard in Alytus, Lithuania

The overhead 400 kV switch yard will cover the area of 1.5 ha directly adjacent to the HVDC (high voltage direct current) back-to-back converter station. It will connect the 400 kV double-circuit line from Ełk Bis substation with the BtB station. The switch yard will include 400/58.4kV single-phase transformers.

Contractor for the construction of the switch yard: ABB AB Sweden

4. 500 MW HVDC “back-to-back“ converter station in Alytus, Lithuania

The 500 MW HVDC “back-to-back“ converter station will be located within the existing transformer station in Alytus. This is a technically advanced thyristor controlled HVDC converter which interconnects power grids that would be otherwise impossible to combine. This “power clutch” is an essential tool with which two large, independently operated electricity systems can be interconnected.  It consists of two basic elements: a converter station converting alternating current of the electrical grid into direct current, and the second station where direct current is made into the alternating current. Both converter stations are “back-to-back” stations as they are directly adjacent. This power bridge will combine two asynchronous power transmission systems. The Polish transmission system works synchronously with the synchronous grid of Continental Europe, while the Lithuanian transmission system operates synchronously with the IPS/UPS system.

The 500 MW HVDC converter station is a unique custom-made solution, 100 m wide and 350 m long. It can support energy transfer both ways, from Lithuania to Poland and the other way round. The station will have 8 transformers, 2 of which will be backup transformers.

Contractor for the construction of the switch yard: ABB AB Sweden

5. 330/110 kV substation retrofitting and development in Alytus

The 330/110/10 kV substation next to Alytus is one of the key electricity distribution hubs in southern Lithuania, in the regions of Alytus and Lazdijai. The station was expanded and retrofitted to support power energy transfer between Poland and Lithuania. A new overhead 330 kV power transmission line will connect it to the back-to-back converter station. The 330/110/10 kV station in Alytus is connected with the Lithuanian 330 kV power grid by means of two lines:  Alytus – the Elektrėnai Power Plant, and Alytus – Grodno (Belarus), and with 8 overhead lines at 110 kV voltage. In the future, a new 330 kV overhead double-circuit line will be connected to the station, leading up to the pumped-storage power station in Kruonis (Lithuania).

Contractor: A.Žilinskio ir ko UAB