The Québec Interconnection is one of the three minor alternating current (AC) power grids in North America. The other two minor interconnections are the Texas Interconnection and the Alaska Interconnection. The two major interconnections are the Eastern Interconnection and the Western Interconnection
The Québec Interconnection covers all of the Province of Québec and operates at an average system frequency of 60 Hz. It is not technically an "interconnection" in the sense of having multiple synchronized systems, because it contains only one electric utility company: Hydro-Québec. Nonetheless it is operated as an independent AC grid for physical reasons.[1] Because of its unique status, it is often functionally considered part of the Eastern Interconnection.
Interconnections can be tied to each other via high-voltage direct current power transmission lines (DC ties), or with variable frequency transformers (VFTs), which permit a controlled flow of energy while also functionally isolating the independent AC frequencies of each side. The Québec Interconnection is tied to the Eastern Interconnection with four DC ties and a VFT.