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A 200 MW HVDC link between two radial distribution grids in Vermont and Quebec.

In April 1984, ABB received a contract to supply a 200 MW back-to-back HVDC converter station to the Vermont Electric Power Company (VELCO). An extremely short delivery time of 17 months was required, and the station went into service in September 1985.

This was the result of an agreement that had been reached between the State of Vermont and Hydro Quebec about the import of electric power after the planned shutdown of the Vermont Yankee Nuclear Power Station for maintenance from mid-September 1985 for a period of at least 8 months. These circumstances led to the shortest delivery time for any HVDC project in the world.

ABB is modernizing the Highgate back-to-back converter station, which links the electrical systems of the state of Vermont in the US and the province of Quebec in Canada, and facilitates the transfer of clean hydropower from Canada. A contract to import hydropower to Vermont from Quebec has recently been extended for another 25 years.

The project’s scope includes installation of ABB’s state-of-the-art control and protection system MACH, and replacement of the valves and valve cooling system. The refurbishment will enable the station to run with full overload capacity at 40 degrees ambient temperature.

Planned outage time of just 21 days was an important factor, in order to minimize the impact of Highgate HVDC station being out of service. The 2012 upgrade improves transmission efficiency and stability, and provides greater security of the power supply.

Main data

Commissioning year: 1985; upgrade 2012
Power rating: 200 MW
No. of poles: 1
AC voltage: 120 kV (north side); 115 kV (south side)
DC voltage: 57 kV
Type of link: back-to-back station
Main reason for choosing HVDC: connecting asynchronous networks
Application: interconnecting grids

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