A transformer is used to raise or lower the voltage of alternating current. Stepping up the voltage facilitates the transmission of massive volumes of electricity, reduces energy losses and lowers the total cost of power transmission—for example, by avoiding the construction of additional power lines. As it approaches the load centres, its voltage is stepped down to the point where homes are supplied with low-voltage power, namely 120/240 volts.

Hydro-Québec’s research institute in Varennes is home to the company’s largest transformer. It weighs 507 tonnes and holds 212,000 litres of mineral oil, an insulating material.