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One of the world's longest electric power transmissions is the 1,700 km link that transmits power from Inga Falls on the Congo River to the copper mining district of Katanga in the Democratic Republic of Congo (DRC).

The Inga-Kolwezi link (formerly the Inga-Shaba link) is a ± 500 kV, 560 MW HVDC power transmission system. This HVDC transmission line continues to deliver power despite instability in central Africa. The line's extreme length and difficult logistics resulted in a decision to build two monopolar lines with four switching stations. Converter stations were built so the two converter poles can be operated in parallel with ground return, in case of a monopolar line outage.

ABB signed a contract for the converter stations in 1973, but due to civil unrest in the country (formerly called Zaire), the transmission line was not put into service until 1982. The Inga-Kolwezi link is owned by DRC's national electricity utility, Société nationale d'électricité (SNEL).

Each valve hall is equipped with six air-cooled double valves, which at the time featured the highest valve voltage rating in the world. Each single valve has 258 series-connected thyristors.

ABB won a contract to upgrade the link in 2009, including new thyristor valves, high-voltage apparatus and the MACH control and protection system. Refurbishment will extend the links life span, enhance the reliability of the DRC grid and ensure efficient transmission of hydro electricity across the region.

Main data

Commissioning year: Upgrade: 2014
Power rating: 560 MW
No. of poles: 2
AC voltage: 220 kV (both ends)
DC voltage: ±500 kV
Length of overhead DC line: 1,700 km
Main reason for choosing HVDC: Long distance
Application: Connecting remote loads

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