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Four major electric system networks serve the United States and Canada. Two major networks, the Western Interconnection and Eastern Interconnection, are divided roughly where the Rocky Mountains meet the Great Plains. Texas and Quebec are served by their own interconnections.

The BPS consists of the generating resources and high-voltage transmission equipment that comprise these networks. Together these components generate and deliver electricity to customers across North America. The BPS does not include local distribution systems, which generally operate at lower voltages.

Many entities interface to ensure BPS reliability:

  • The North American Electric Reliability Corporation (NERC) is a not-for-profit international regulatory authority whose mission is to assure the reliability and security of the BPS in North America.
  • Regional Entities have responsibility delegated by NERC for assuring BPS reliability in their respective footprints. WECC is the Regional Entity responsible for the Western Interconnection.
  • Reliability Coordinators (RC) monitor the grid in real-time and interact with individual operators and other RCs to maintain reliable operations.
  • Balancing Authorities (BA) are responsible for maintaining load-generation balance within their footprint.
  • Independent System Operators (ISO) and Regional Transmission Operators (RTO) coordinate, control and monitor portions of the electric grid. ISOs and RTOs may also operate wholesale electricity markets. The Western Energy Imbalance Market (EIM) is a real-time market operated by the California ISO (CISO).


Credit: NASA Earth Observatory/NOAA NGDC   

The Western Interconnection serves a population of over 80 million, and spans more than 1.8 million square miles in all or part of 14 states, the Canadian provinces of British Columbia and Alberta, and the northern portion of Baja California in Mexico.

The Interconnection is made up of approximately 136,000 circuit-miles of transmission lines that carry power long distances, from remote areas where generating resources are located to populated areas where load is located, primarily along the West Coast. Electricity generally flows south and west in a "doughnut" pattern, contrasting with a spiderweb configuration in the East.