Hertel‑New York interconnection line

Preliminary activities : December 2023
Beginning of the work : January 2024

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Work from Hydro-Quebec - Caution: Obstacles to navigation on Rivière Richelieu

Work is scheduled to be carried out on the river, near the Canada/US border, on or around July 22, 2024 and is expected to take 2-3 days

The work involves running and protecting an underwater cable in the middle of Rivière Richelieu on the north-south axis.

In Québec, the disruption to access will begin 150 m north of the water border before continuing south on the American side.

It will therefore be impossible for boats to cross the river from one side to the other (east to west) in the area where the work is being carried out.

Patrol boats will ensure the safety of the population at all times. They will also ensure that all access rules are followed near the work.

Project overview

The Hertel‑New York interconnection line project aims to supply clean, renewable energy to New York City. In Québec, the project involves the construction of a line that will span 57.7 km (56.1 km underground and 1.6 km underwater). This 400-kV direct current line will connect Hertel substation in La Prairie to an interconnection point in the Rivière Richelieu at the Canada–United States border.

The project also includes installing a converter at Hertel substation. It will convert alternating current to direct current to supply the new interconnection.

The new line will connect to the line planned under the Champlain Hudson Power Express (CHPE) project, overseen by Transmission Developers Inc. (TDI) in the U.S. The CHPE project involves building an underground and underwater DC line between the Canada–U.S. border and New York City, a distance of roughly 545 km. In addition to receiving all required authorizations in the U.S., this project has been selected by the authorities of New York State to deliver hydropower to the heart of New York City.

Location and status of the project

Lighting New York City with Our Clean and Renewable Energy

Prevents the emission of approximately 3.9 million tonnes of greenhouse gases annually

line about 60-km

Addition of a converter at Hertel substation

Allows for the export of 1,250 MW of power

The project in videos

Project overview

Sébastien Bélanger, project manager, explains the project justification.

Duration: 1 minutes 27 seconds

The environment: At the heart of everything we do!

Valérie Groison, environmental project manager, explains the environmental approach.

Duration: 2 minutes 56 seconds

Understanding the work

Michel Laboissière, transmission line project engineer, explains the underground line work.

Duration: 2 minutes 53 seconds

Understanding electric and magnetic fields and stray voltage

Jean-Pierre Tardif, science communications advisor, explains the electric and magnetic fields and the stray voltage.

Duration: 3 minutes 02 seconds

Answers to your questions

How does an interconnection work?

The alternating current generated in Québec arrives at Hertel substation and passes through transformers to lower the voltage. The current is then sent to a converter (Δ) that converts alternating current into direct current.

When the conversion is complete, the electricity runs through two underground cables in Québec that connect to two underground cables in the U.S. Once it reaches the U.S. power system, at Astoria substation, the direct current is converted back to alternating current.

  1. Synchronous interconnexion

    An interconnection can be synchronous or asynchronous. An interconnection is synchronous when the two power systems operate at the same frequency and phase, and is asynchronous if this is not the case.

  2. Asynchronous interconnexion

    This is the situation for the Québec and US systems, which operate at the same frequency of 60 Hz but do not reach their maximum value at the same time, so they are

  3. How?

    An asynchronous connection is therefore required to link the two grids. In the case of the new interconnection with New York, a converter installed at Hertel substation makes it possible.

    The alternating current generated in Québec arrives at Hertel substation and passes through protection equipment and transformers to lower the voltage. The current is then sent to a converter (Δ) that electronically converts alternating current into direct current. The frequency of the resulting current is zero.

    When the conversion is complete, the electricity runs through two underground cables that connect the grids in Québec and the US. Once it reaches the American power system, the direct current is converted back to alternating current and delivered to load centers.

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. In alternating current, on the other hand, electrons move back and forth.

Usually, electricity is transmitted on the grid as alternating current. However, direct current can be useful for transmitting electricity over long distances or connecting systems that aren’t synchronized, like the Québec and U.S. systems. Because New York City is located some 600 km from Québec’s transmission network, these two conditions are met, and its use is advantageous in this project.

Did you know?

The nature of overhead and underground DC lines static magnetic field is similar to the Earth's own magnetic field.

Discover more on that subject

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 geological conditions and technical context of the Hertel‑New York project, particularly the possibility of using public rights-of-way over most of the proposed route in Québec, allow the line to be undergrounded over a long distance, with no need for additional electrical equipment on the surface.

  • In the U.S., the Champlain Hudson Power Express project calls for the construction of an underground and underwater line stretching some 545 km between New York City and the Canada–U.S. border. It has been approved by U.S. regulatory bodies.
  • The Québec portion of the project (57.7 km) accounts for about 10% of the total length of the lines (605 km).

Other questions?

See our FAQ page

Project schedule

  • Spring 2021 Public consultation
  • Fall 2021 Solution selected
  • Winter 2022 – Summer 2023 Government approvals
  • Fall 2023 Start of construction
  • Spring 2026 Commissioning

Project background

A first version of the project was developed in Québec in 2012–2013, when the draft-design studies and public consultations were carried out. In fall 2020, Hydro‑Québec teams contacted community organizations again and began updating its environmental surveys and collecting field data.

Additional studies and surveys were then carried out to identify the technical and environmental optimizations required to adapt the initially proposed project to current needs and circumstances.

Hydro‑Québec also collected public input to learn more about the project’s environment and minimize impacts during construction. Comments and questions from community organizations, the general public and land users have helped improve the project.