Vyborg HVDC Scheme - Technical Description

Technical Description

The Vyborg substation is located 9 kilometres (5.6 mi) east of Vyborg at 60°40′49″N 28°55′07″E / 60.68028°N 28.91861°E / 60.68028; 28.91861Coordinates: 60°40′49″N 28°55′07″E / 60.68028°N 28.91861°E / 60.68028; 28.91861. It is connected with the Russian and Finnish high-voltage power systems. The substation is connected to the Russian power system with two 330 kV lines to Vostochnaya substation and with one line to Kamenogorskaya substation. It is connected with Finland with three 400 kV cross-border connections to Yllikkälä (two lines) and Kymi (one line) substations.

The substation consist of four independent, parallel symmmetrical monopole (centre-grounded) back-to-back units, each rated 355 MW and operating with a voltage of ± 85 kV. In contrast to most other HVDC plants, its converters do not allow bidirectional energy to transfer, but only from Russia to the power grid of Finland. Each pole consists of a single Twelve-pulse bridge at each end and was built using thyristors from the outset. The first three poles were originally built using small (60mm) diameter thyristors with three in parallel at each level, but these were later replaced by larger 80mm thyristors which did not require parallel connection.

The converter transformers are of the relatively unusual single-phase, four-winding arrangement, with a 38.5kV filter winding on which the tuned filters are connected. Other high-pass filters are connected directly to the 330 kV or 400 kV AC busbars. With a total transmission rating of 1420 MW, Vyborg was the world's largest HVDC-back-to-back facility until the 1800 MW Al-Fadhili facility was completed in Saudi Arabia in 2009. It is also the only back-to-back HVDC system in Russia and the only fully operational HVDC system in Russia, the others having either been shut down ( Moscow–Kashira), never completed (Ekibastuz–Tambov) or are operated only at reduced capacity (Volgograd–Donbass).