The 735-kV transmission line celebrates 50 years

The innovation that transformed Québec’s energy development

On November 29, 1965, Québec revolutionized the world of electricity. Before the dignitaries present for the event, the world’s first 735-kV high-voltage line was commissioned. This innovation, which was closely followed by the international scientific community, would soon transform Québec’s energy development.

The challenge
By the early 1960s, electricity demand in Québec was growing rapidly—at a rate of 7% per year—prompting Hydro-Québec to double its generating capacity every decade. At the time, hydropower generating stations were located relatively close to the major load centres in southern Québec. However, continuing to develop Québec’s hydraulic resources would require going farther and farther away. A number of hydropower projects in the north seemed promising: Manic-Outardes, La Grande... But how to ensure they were profitable? And how to transmit all that electricity to the south?

This represented a huge challenge for the power transmission technology of the time.

To efficiently transmit electricity over longer distances, a higher voltage must be used. This limits the number of lines needed and reduces electricity losses along the way.

In 1958, in Québec, high-voltage transmission lines were operated at a maximum of 315 kV. Twelve 315-kV lines covering a distance of 600 km would have been required to transmit the 7,500 MW eventually generated by the Manic-Outardes complex. The cost of materials, construction, maintenance, and electricity losses incurred would have been enormous. Not to mention the land area required.

Seeing ahead
While other countries were looking into developing 500-kV, and even 600-kV, high-voltage lines, Jean-Jacques Archambault, a young Hydro-Québec engineer, was studying a voltage level never before considered: 735 kV. Based on his calculations and plans, Mr. Archambault was able to convince Hydro-Québec’s management that this voltage level was the optimal long-term solution for Québec’s needs.

Jean-Jacques Archambault, the inventor of the 735-kV line.

In August 1962, the Québec Hydro-Electric Commission gave the project the green light. For the next three years, an army of engineers and technicians was mobilized.

The size of the project, the often hostile weather conditions, the difficult geography, and the crossings of the Saguenay fjord and the Fleuve Saint-Laurent represented tremendous technical and human challenges. Seeing this innovation through was an achievement that required courage, vision and determination.

Impact of the 735-kV line
The 735-kV line transformed the future of Québec’s energy development.

By making large, remote hydroelectric projects cost-effective, this technology allowed Québec to choose hydropower, a clean and renewable source of energy, to drive economic and industrial development, rather than building thermal or nuclear generating stations.
Today, hydropower provides more than 99% of the electricity generated in Québec and Quebecers enjoy the lowest electricity rates in North America.

Each 735-kV line can carry more than 2,000 MW, enough power for 700,000 households.

Transmission system development
Over the years, Hydro-Québec has continued developing its transmission system to meet Quebecers’ evolving electricity needs. Fifty years later, our system includes nine 735-kV lines covering over 11,000 km. These lines are the main arteries of our transmission system, the largest in North America. They transmit the electricity produced by generating facilities located primarily in northern Québec—in the Baie-James region and the Manicouagan-Outardes corridor in the Côte-Nord region—to load centres in southern Québec.

Thanks to this proven, robust and efficient grid, Quebecers can count on a reliable supply of electricity.

The next step
On April 24, 2015, the Québec government announced the next step in the development of the 735-kV system: the Chamouchouane–Bout-de-l’Île project. This project will increase the overall capacity of the transmission system while meeting growing demand in southern Québec.
The new 735-kV line, the first in over 20 years, will ensure the continued reliability and efficiency of the Québec transmission system, as well as the long-term supply of the major load centres.

An internationally recognized trailblazer
A genuine breakthrough in the energy industry, the first 735-kV line made a significant contribution to the international reputation of Hydro-Québec and Québec’s electricity industry.

In 2001, 735-kV transmission was named “Québec’s most important technological innovation of the 20th century” by the Québec order of professional technologists.

Fifty years after its inception, 735-kV transmission is used around the world, highlighting the technological expertise and innovative spirit of Hydro-Québec’s engineers.