Eastern Interconnection

The Eastern Interconnection is one of the two major alternating-current (AC) electrical grids in the continental U.S. power transmission grid. The other major interconnection is the Western Interconnection. The three minor interconnections are the Quebec, Alaska, and Texas interconnections.

All of the electric utilities in the Eastern Interconnection are electrically tied together during normal system conditions and operate at a synchronized frequency at an average of 60 Hz. The Eastern Interconnection reaches from Central Canada eastward to the Atlantic coast (excluding Quebec), south to Florida, and back west to the foot of the Rockies (excluding most of Texas).

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 Eastern Interconnection is tied to the Western Interconnection with six DC ties, to the Texas Interconnection with two DC ties, and to the Quebec Interconnection with four DC ties and a VFT.

On October 17, 2009, the Tres Amigas SuperStation was announced to connect the Eastern, Western and Texas Interconnections via three 5 GW superconductor links. As of 2016^[update], it has not started construction.

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