The Phase II line between Radisson and Sandy Pond: A New England–Hydro-Québec success story

The Phase II multiterminal direct-current system (MTDCS) is a very important interconnection for New England, with regular power flows of 1,200–1,400 MW and higher. Construction of this 1,500-km (932-mile) line, which connects Radisson substation in Québec’s Baie-James region with Sandy Pond substation just outside Boston, began in the 1980s through a partnership between Hydro-Québec and New England’s utilities. Two long-term contracts, which solidified commitments to buy and sell energy, were key to the construction of this transmission infrastructure.

Many of the same issues that are creating challenges for New England today were evident in the early 1980s and drove the development of this transmission line: the need to break the region’s reliance on oil, environmental improvement goals and the search for a reliable, competitively priced supply of electricity.

The New England power system faces various challenges: reliability issues, increasing costs, price volatility and a carbon footprint that the region wishes to improve. In recent winters, price peaks for natural gas have made it difficult for New England’s gas generators to secure fuel, sometimes prompting the region to turn to oil-fired generation, which has a much larger carbon footprint. The situation is expected to worsen as nuclear and other non-gas capacity exits the market and several aging facilities are retired, increasing reliance on natural gas.

History of the multiterminal direct-current system


Phase I of a partnership between Hydro-Québec and the New England Power Pool (NEPOOL) for the construction of transmission facilities from southern Québec to northern New Hampshire (Phase I interconnection), to enable NEPOOL to import large quantities of surplus energy from Hydro-Québec.


Beginning of an 11-year contract under which NEPOOL would purchase up to 33 TWh from Hydro-Québec.


Commissioning of Phase II of the multiterminal direct current system (MTDCS), which extends the Phase I interconnection north in Québec to the Baie-James region, and south in New England to Ayer, Massachusetts.


Beginning of a 10-year contract between Hydro-Québec and several New England utilities for a total supply of 70 TWh of clean, reliable electricity.

A new interconnection between Québec and New England

Further to a clean energy request for proposals issued by Massachusetts, Hydro-Québec’s bid was selected to supply 9.45 TWh per year to the state over a 20-year period. The power purchase agreements signed with the three local electricity distributors were approved by the state’s regulatory authorities in 2019. A new transmission line must be built to interconnect the Québec and New England grids before deliveries can begin. The New England Clean Energy Connect transmission project designed for this purpose is currently in the permitting phase.

In collaboration with Central Maine Power, a subsidiary of Avangrid, Inc. (NYSE:AGR), Hydro-Quebec has developed a project for a new 1,200-MW direct current transmission interconnection with Maine: the New England Clean Energy Connect (NECEC). The goal is to increase transmission capacity between the grids and to serve a long-term energy contract with Massachusetts.

New England Clean Energy Connect project

Long-term contracts with Vermont

Hydro-Québec is connected to the Vermont grid via an approximately 24-km (15-mile), 120-kV transmission line that runs from Bedford substation in Québec’s Montérégie region to Highgate substation in the northwest corner of Vermont. The interconnection also includes a back-to-back converter station to synchronize Hydro-Québec’s energy deliveries with the New England grid. With a maximum capacity of 225 MW, the interconnection was commissioned in 1985, enabling Hydro-Québec to supply Vermont utilities under long-term agreements.

The first long-term contract between Hydro-Québec and Vermont was signed in 1987. In 2010, the parties signed a second contract for up to 225 MW, under which Hydro-Québec committed to deliver approximately 1.3 TWh of energy each year through 2038—a volume equivalent to about 25% of Vermont’s annual electricity needs.

Designed to stabilize prices, these long-term contracts are part of the reason why Vermont consumers have not experienced the sharp rate increases that have occurred in other parts of New England in recent years.