Tapping natural supplies of clean, reliable power

2012-10-22 - Thanks to ABB’s high-voltage direct current (HVDC) technology and systems, the world`s largest multiterminal direct current (MTDC) power link has enabled transmission of clean, renewable electricity between Québec and New England for more than 20 years.

An MTDC system can connect several generating sites to several load points, ensuring power flow even in the event of a terminal going out of service due to maintenance or accident.

Hydro Québec`s ground-breaking, 1,500 kilometer (km) long MTDC system was commissioned from 1986 to 1992. Designed and built by ABB, it is marking two decades of uninterrupted service, delivering hydro-generated electricity from James Bay in northern Québec to load centers in southern Québec and New England.

It is a significant anniversary, because now more than ever the world is searching for reliable, large-scale supplies of renewable energy, and hydropower generation is still the cleanest renewable energy supply available in large quantities.

The province of Québec is blessed with an abundance of this resource, and the province`s electrical utility, Hydro Québec, has made hydropower a cornerstone of its electricity generation strategy. The utility is one of the world’s largest hydroelectric producers with a combined installed capacity of 36,971 megawatts (MW), with only around 6.6 percent (or about 2,440 MW) coming from non-renewable sources.

During the early 1980s, in order to develop market opportunities for its power resources, the utility began to install electrical interconnections with neighboring markets (the provinces of Ontario and New Brunswick in Canada; New York and New England in the United States). These included some DC (back-to-back) interconnections, such as the 450 kilovolt (kV) HVDC link connecting the Québec and New England AC networks. The utility partnered with the New England Electric System (now National Grid USA) to build a 170 km-long commercial DC transmission line with a rated capacity of 690 MW between Des Cantons substation near Windsor, Québec, and Comerford substation in New Hampshire. However, Hydro Québec needed to isolate Des Canton from the rest of its network in order to minimize the loss of power supplied to New England in the event of a major outage in Québec`s power network. So the DC link was extended northward from Des Cantons to the area around James Bay, where the 2,000 MW Radisson rectifier station delivers power from generators that can be isolated, if necessary.

To make use of power generated at Radisson, but not sold to New England, Hydro Québec installed a third converter station – the 2,000 MW Nicolet substation – between Montréal and Québec City. Nicolet is about 1,000 km from Radisson, and was commissioned in September, 1992.

In the United States, New England Power Service Co. built the 2,000 MW Sandy Pond load station between the towns of Ayer and Groton, Massachusetts. Since Sandy Pond is 500 km from Nicolet, the MTDC system can either transmit up to 2,000 MW of electricity down the 1,500 km DC line to Sandy Pond directly, or share it between Hydro-Quebec and its neighboring utilities.

The advantage of the New England MTDC system is that it guarantees alternative sources of electricity to New England population centers like Boston. If Radisson went off line due to maintenance or equipment failure, Boston could continue to receive power from Nicolet.

Such interconnectors are becoming increasingly important as more intermittent renewables are coupled to the grid. Interconnectors stabilize the grid and provide greater opportunities for power trading, but can also allow excess wind power to pump water into storage lakes, which can be brought back online faster than coal or nuclear generation in the event of a service disruption or peak demand. By using an HVDC system for interconnectors two asynchronous AC networks can be connected and in addition, power can be delivered over thousands of kilometers with very low losses.

ABB built the first commercial HVDC system in the 1950s. Of the more than 120 HVDC systems in operation in the world, half have been built by ABB.

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