Three Gorges, China is now the world's largest HVDC user.
China’s Three Gorges Hydroelectric Power Plant will be the largest of its kind in the world, with a generating capacity of over 22 GW by 2009. Power from this plant will be sent to East China by three HVDC lines and to South China by one HVDC line. The East China System and the South China System are asynchronous with the Central China System, so the HVDC links also connect the large AC systems asynchronously.
The total capacity of this HVDC transmission system will be 7,200 MW. It will consist of the 1,200 MW HVDC line Gezhouba – Shanghai commissioned in 1989 by ABB and two 3,000 MW lines. The first of these lines, Three Gorges – Changzhou, was commissioned by ABB in 2003. In 2004 ABB was awarded the contract for converter stations for the second 3,000 MW HVDC transmission to Shanghai, which goes into operation in 2007. The two 3,000 MW HVDC lines were compared with five 500 kV AC lines and the HVDC option was found to be the most advantageous, considering investments and losses as well as land use.
The transmission to the South China System is another 3,000 MW line, Three Gorges – Guangdong, which is 940 km long. This was commissioned in 2004 to support rapid load growth in the south.. HVDC was chosen primarily because of the length of the transmission and also because the two systems are asynchronous.
RAPID CITY TIE
In 2003 ABB installed a back-to-back HVDC transmission system link, interconnecting the eastern and western power grids of the United States. The HVDC system, called the ‘Rapid City Tie’ because it passes close to Rapid City, South Dakota, carries 200 MW of power. ABB completed the contract in only 19 months – six months faster than the industry standard.
The HVDC system provides voltage and frequency support in case of disturbances in either of the grids. ABB designed, manufactured and installed the HVDC system as part of the joint project between Basin Electric Power Cooperative of North Dakota, and Black Hills Power of South Dakota.
CROSS SOUND CABLE INTERCONNECTOR
The Cross Sound Cable Interconnector is a 330 MW, 40 km HVDC Light buried submarine cable system that connects the electric transmission grids of New England and Long Island, New York. The Cross Sound Cable Interconnector provides additional power transfer capability between New Haven, Connecticut and Shoreham, Long Island, in either direction. The purpose of the Cross Sound link is to improve the reliability of power supply in the Connecticut and New England power grids and allow increased sharing of power plant capacity, so reducing the amount of power plant capacity each must have for a particular winter or summer. The connection was also designed to promote competition in the New York and New England electricity markets by enabling electricity to be traded among power generators and customers in both regions. After the huge black-out in August 2003, a federal order allowed the first use of the Cross Sound Cable Interconnector. The cable interconnection played a great part in getting Long Island out of the dark, and restoring power to hundreds of thousands of customers across Long Island.
ESTLINK – MORE POWER TO THE BALTIC
Estlink, based on ABB’s HVDC Light technology, went live at the end of 2006. It is the first interconnection between the Baltic states and the Nordic countries, and is an important step towards greater energy efficiency in Europe. Linking these two key grids will improve grid reliability and help to avoid future black-outs, as well as contribute to industrial competitiveness and improve supply to consumers.
The 100km cable link, two-thirds of which runs beneath the Gulf of Finland, is oil-free and has no magnetic field – important environmental considerations. An estimated 2TWh of electricity will be transmitted through the cable, which is rated at 350MW with a low ambient overload capacity of 365MW. The two HVDC converter stations at each end of the link will be capable of generating/consuming up to 125Mvars of reactive power independently of each other and independently of the active power transfer.
Estlink is just one of a number of existing and planned projects connecting mainland Europe and the Baltic countries with Scandinavia and the Nordic region. On land, a 93mm diameter XLPE cable was installed. The submarine cable is also XLPE, with a 96mm diameter and steel armouring.
TROLL A – THE FIRST LAND-POWERED OFFSHORE PLATFORM
In 2005, ABB successfully commissioned an HVDC Light project on behalf of Statoil that made the Troll A platform the first on the Norwegian continental shelf to be powered by electricity generated on land. The project comprised a double circuit, 2 x 40MW subsea cable installation from Kollsnes on land, to Troll A, 67km offshore, to feed two large compressors.
Statoil’s decision to take power from the mainland rather than install generators on the platform was taken for economic and environmental reasons. Conventional platformbased generation, with gas turbines or diesel generators, usually achieves just 25 per cent efficiency compared with land-based combinedcycle generation of 75–80 per cent.
On-platform power generation produces large amounts of CO2. In the case of Troll A it would result in an estimated 230,000 tons of CO2 and 230 tons of NOX and potentially substantial climate tax liabilities.
MURRAY LINK – AUSTRALIA
The Murraylink 220 MW interconnector between the Riverland in South Australia and Sunraysia in Victoria is a 180 km underground high-voltage power link that is believed to be the world’s longest underground transmission system. ABB provided a complete HVDC Light transmission system, comprising XLPE cables and converter stations. The order was placed by Murraylink Transmission Company Pty (TransÉnergie Australia) a subsidiary of TransÉnergie, the transmission division of Hydro-Québec, Canada.
Murraylink benefits both South Australia and Victoria by enabling electricity trading in Australia’s deregulated power market.From its near tri-state border site, it can deliver power from South Australia, Victoria, New South Wales and the Snowy River generation in either South Australia or Victoria. Murraylink used existing corridors and required no private easements, nor use of private land.