Project overview

The project comprises the construction of a 58-km long, 320-kV underground direct-current (DC) line between Hertel substation in La Prairie and the Canada-United States border.
The project also includes the installation of a converter at Hertel substation, which will convert alternating current to direct current to supply the new interconnection.

The new line will connect to the Champlain Hudson Power Express (CHPE) project, which is currently under study in the United States. The project proponent is Transmission Developers Inc. and the aim of CHPE is to supply power to New York City. The project includes plans to build an underground and underwater DC line between the Canada–United States border and New York City, spanning over 530 km (330 miles).

What is electricity conversion?

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Why a direct-current line?

Direct current is unidirectional, which means the electrons always move in the same direction. A good example is a battery, where a chemical reaction triggers a movement of electrons in one direction inside the conductor: from the negative to the positive terminal of the battery. Alternating current is when electrons move back and forth.

The technology used to transmit direct current is not the most common. However, in projects such as this one, it can be advantageous for transmitting electricity over long distances or connecting systems that aren’t synchronized.

Understanding electricity: direct current

Why an underground line?

Hydro-Québec carries out studies for all its generation (generating stations) and transmission (lines and substations) projects. These studies simultaneously examine environmental, social, technical and economic criteria. With all these aspects considered, transmission projects usually call for the construction of overhead lines.

The technology used to transmit direct current is not the most common. However, in projects such as this one, it can be advantageous for transmitting electricity over long distances or connecting systems that aren’t synchronized. The New York City market is located some 600 km from Québec’s transmission network.

Line operation

Equipment to be installed at the ends of the line, in each of the converters, will allow us to detect and quickly correct any electrical faults. Should the line fail, it is de-energized within less than a second, making it very safe to operate.

Study area

Hydro-Québec has defined a study area, which was surveyed and analyzed to determine different potential line routes.

With a surface area of 793 km2, the study area stretches north to Hertel substation, west to just past Highway 15, south to the border with the United States and east to the Rivière Richelieu (which is excluded). It crosses the territories of three regional county municipalities (MRCs) : Roussillon, Le Haut-Richelieu and Les Jardins-de-Napierville.

Download the study area map [pdf]