Connecting an Indian powerhouse

2014-12-05 - The North-East Agra power connection will be the world’s first multi-terminal ultra-high-voltage direct current link, capable of supplying enough electricity to serve 90 million people at full converter capacity.

India’s Northeast region is a place of verdant forests and tea plantations, rolling hills and plains that extend from the latitude of the Bay of Bengal to the snowy ridges of the towering Himalayas. This extraordinary region’s seven states are collectively called the country’s future “powerhouse” because of their enormous hydroelectric potential.

India’s Central Electricity Authority has identified more than 150 sites for large hydropower projects in the Brahmaputra Basin alone, and more than 80 in the state of Arunachal Pradesh, which promises to add more than 50,000 megawatts (MW) of energy to India’s capacity in the coming years.

The big challenge is delivering some of this huge potential to electrical load centers in the rest of India, thousands of kilometers away. Apart from the distances involved, the delivery issue is complicated by the “Chicken’s Neck”, or Siliguri Corridor, a narrow strip of land some 22 kilometers wide and 18 kilometers long that borders Nepal in the north and Bangladesh in the south, and connects the Northeast region with the rest of India.

Power from the Northeast must be delivered to Indian consumers in the west and north through this corridor, and if ever a geography existed to display the benefits of high-voltage direct current (HVDC) transmission technology, this is it.

The world’s largest HVDC transmission system

ABB together with its partner Bharat Heavy Electricals Limited (BHEL) will demonstrate how it’s done with the North-East Agra power connection, the world’s first multi-terminal ultra-high-voltage direct current (UHVDC) link. At full operating capacity, the North-East Agra UHVDC link will be able to supply enough electricity to serve 90 million people, based on average national consumption. The use of ultra-high voltage minimizes transmission losses and improves efficiency.

The link will use four terminals in three converter stations with a 33 percent continuous overload rating, enabling up to 8,000 MW conversion at ±800 kilovolt (kV) – in other words, the largest HVDC transmission system ever built. The two “sending” converter stations will convert clean Northeast hydropower, collected from local generation sites, from alternating current (AC) to DC, then transmit this power over a single power line passing through the Chicken’s Neck to a third “receiving” station in Agra (home of the Taj Mahal), a distance of 1,728 kilometers. In Agra, the DC power will be converted back into AC for distribution to end users.

The link’s record 8,000 MW converter capacity includes a 2,000 MW redundancy. The multi-terminal configuration provides very high and reliable transmission efficiency, minimal (about one third) use of land through a vital and narrow land corridor, and considerable cost reductions compared with the alternative of installing separate 765 kV AC power links from multiple hydropower plants in the Northeast region to Agra.

ABB continues an impressive heritage with this project. The group was first with commercial HVDC, building the world’s first multi-terminal HVDC link in 1990-1992, a large-scale three terminal transmission link constructed in North America called the Québec-New England HVDC Transmission.

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