In 1975 the AC ties were disconnected, because DC ties were found to work more reliably. However, the AC ties did not have high capacity and were subject to oscillations, and so their connection proved unreliable. In 1934, with the passage of the Public Utility Holding Company Act, electric utilities were recognized as public goods of importance and were given outlined restrictions and regulatory oversight of their operations.įrom 1967, the East and West interconnections were directly connected together. In the United States in the 1920s, utilities formed joint operations to share peak load coverage and backup power. The Eastern and Western grids are connected with 1.32 GW. The regions are not usually directly connected or synchronized to each other, but there exist some HVDC interconnectors. Each region delivers power at a nominal 60 Hz frequency. Three other regions include the Texas Interconnection, the Quebec Interconnection, and the Alaska Interconnection. The Eastern Interconnection and the Western Interconnection are the largest. The electrical power grid that powers Northern America is not a single grid, but is instead divided into multiple wide area synchronous grids. The electric power transmission grid of the contiguous United States consists of 120,000 miles (190,000 km) of lines operated by 500 companies. Series of electrical grids that power the US and Canada The two major and three minor North American Electric Reliability Corporation (NERC) interconnections, and the nine NERC Regional Reliability Councils.

Texas grid map