The ±800 kV North-East Agra UHVDC link will have a record 8,000 MW converter capacity, including a 2,000 MW redundancy, to transmit clean hydroelectric power from the North-Eastern and Eastern region of India to the city of Agra across a distance of 1,728 kilometers.
ABB has been selected by Powergrid Corporation of India Ltd. to deliver the world’s first multi-terminal UHVDC transmission link, worth $ 900 million. The link is called the ±800 kV, 6,000 MW HVDC Multi Terminal NER/ER - NR/WR Interconnector – I Project (NEA800 in short and also known as North East - Agra HVDC). The link comprises four terminals located at three converter stations with a 33% continuous overload rating and the power transmission system will thus have the possibility to convert 8,000 MW – which is the largest HVDC transmission ever built.
ABB will execute the project together with its partner Bharat Heavy Electricals Ltd. (BHEL), who will deliver the remainder of the contract, which is worth more than $1.1 billion in total. The partners have a turnkey responsibility for execution, including system engineering, design, supply and installation of three HVDC converter stations. The first stage of the system is scheduled to be operational in 2014 and the second stage in 2015.
The North Eastern region of India has an abundance of hydro power resources, approximately 65 000 MW. The resources are scattered over a large area, whereas load centers are located several hundreds and even thousands of kilometers away. The power has to pass through the so called "chicken neck area"; a very narrow patch of land (22 km width x 18 km of length) in the state of West Bengal having borders with Nepal on one side and Bangladesh on the other side.
Taj Mahal, Agra | 
Assam stream |
India plans to create power pooling points in the North-Eastern region, to collect power from several hydro power stations and to transport it on 800 kV DC bipolar lines to major load centers. HVDC is a excellent way to use the available right-of-way very efficiently. The current project is the first one.
The first pooling point (= converter station) of the first Indian 800 kV HVDC link will be located at Biswanath Chariali in the state of Assam in North Eastern region, while the second converter station will be located near Alipurduar in the state of West Bengal in Eastern region. The other end of the DC line will terminate at Agra where there will be two bipolar converters connected in parallel. (See diagram below.) The 800 kV equipment yard at Agra will, for the first time, be placed indoors.
Simplified single line diagram
(Click to see a larger illustration!)
As each converter pole has a nominal rating of 1,500 MW with a continuous overload rating of 2,000 MW, it is possible to compensate for loss of any converter pole and still transmit 6,000 MW.
The overall control and coordination of the converter poles in the multi-terminal HVDC link, including balancing of the power order to the converters will be performed by the master control to be located in Agra.
This is the second multi-terminal HVDC link that ABB will build. Already in 1990-1992 a large scale three terminal transmission link was constructed in North America, the
Québec - New England HVDC Transmission - the first of its kind in the world, transmitting 2 000 MW.
| Main data |  |
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| Commissioning year: | 2015 |
| Power rating: | 6 000 MW (multiterminal) |
| No. of poles: | Converter: 4
Line: 2 |
| AC voltage: | 400 kV (all stations) |
| DC voltage: | ±800 kV |
| Length of overhead DC line: | 1 728 km |
| Main reason for choosing HVDC: | Long distance, bulk power |
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