Vyborg HVDC scheme
|Vyborg HVDC scheme|
|Owner||Ministry for Electrotechnical Industry, Soviet Union|
|Installer of substations||Ministry for Electrotechnical Industry, Soviet Union|
|Type||Back to Back|
|Type of current||HVDC|
|Total length||0 km (0 mi)|
|Power rating||4 x 355 MW|
|DC Voltage||±85 kV|
|Number of poles||4 (symmetrical monopoles)|
The Vyborg HVDC scheme is a system of electricity transmission from the Russian power system to Finland, using high-voltage direct current. It consists of four, 355 MW back-to-back converter blocks, the first three of which were completed in the early 1980s and the last in January 2001.  Much of the original converter equipment has been refurbished or modernised.
Electricity transmission from the 330 kV Russian (then the Soviet Union) system to the 400 kV Finnish system started in 1981. As the Russian and Finnish power systems are asynchronous, a direct AC connection was not possible and a HVDC-back-to-back station was needed. It was decided to build the substation near Vyborg in the Karelian ASSR. The first unit of the substation was commissioned in December 1981 followed by the second unit in the autumn 1982 and the third unit in the summer 1984. The system was manufactured by the Ministry for Electrotechnical Industry of the USSR. A fourth unit was added in 2001  and the control and protection equipment of the three original poles has subsequently been modernised.
The Vyborg substation is located 9 kilometres (5.6 mi) east of Vyborg at Coordinates: . 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 symmetrical 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).
- High-voltage direct current
- HVDC converter
- Moscow–Kashira HVDC transmission system
- HVDC Volgograd–Donbass
- HVDC Ekibastuz–Centre
- Compendium of HVDC schemes, CIGRÉ Technical Brochure No. 003, 1987, pp129-134.
- Ivakin,V.N., Kovalev, V.D., Lazarev,N.S., Lytaev,R.A., Mazurenko, A.K., Balyberdin, L.L., Kraichik, Y.S., Smirnov, A.A., Experience of reconstruction and expansion of Vyborg back-to-back HVDC link, CIGRÉ session, Paris, 2002, paper reference 14-103.
- "Intersystem agreement on 400 kV cross-border connections Russia–Finland" (PDF). Fingrid. 28 December 2007. Retrieved 24 April 2010.
- Tsfasman,G., Mazurenko,A., Mordcovich,A., Tarasov,A., Zmaznov,E., Bastunsky,A., Lubarsky,D., Prochan,G., Popov,A., Rossovsky, E., New integrated control and protection system for VYBORG back-to-back HVDC link, CIGRÉ session, Paris, 2008, paper reference B4-102.
- "Vyborg HVDC scheme". Bonneville Power Administration. Archived from the original on 30 August 2006. Retrieved 24 April 2010.
- Kovalev,V.D, Khoudiakov,V.V., Mazurenko,A.K., Taratuta,I.P., Balyberdin,L.L., Kazarov, S.S., Operation experience of Vyborg back-to-back HVDC link, CIGRÉ session, Paris, 1998, paper reference 14-108.
- Barrett,B.T., MacLeod,N.M, Sud,S., Al-Mohiasen, A.I., Al-Nasser,R.S., Planning and design of the AL FADHILI 1800 MW HVDC inter-connector in Saudi Arabia, CIGRÉ session, Paris, 2008, paper reference B4-113.