Hertel‑New York interconnection line

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. 

   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. 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. 

   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.

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.

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).