About the Power System
New England's Bulk Electric Power Grid Operating Procedures and Guidelines

The Electric Power Grid

New England's bulk electric power system is designed and operated to reliably meet the electricity needs of the region in accordance with established industry criteria. The system is comprised of more than 8,000 miles of high voltage transmission lines and several hundred generating facilities, of which more than 300 units are under the direct control of ISO New England.

There are also several interconnecting transmission lines to bulk power transmission systems in New York State and the provinces of Quebec and New Brunswick in Canada. The interconnections with neighboring systems allow for both the import and export of electricity between regional power systems. These interconnections are used for reliability purposes as well as for the sale and purchase of electricity between regions.

The bulk power systems operating in the northeastern United States were designed and built to standards developed in response to the Northeast Blackout of 1965 and have evolved over time. The fundamental goal of the system's design and operations is to absolutely minimize the likelihood of experiencing a similar event in the future.

North American Reliability Requirements

To provide uniform design and operating standards for electricity generation and delivery systems, the industry created the North American Electric Reliability Corporation (NERC), which was given the responsibility to establish electric system reliability and operating performance standards. In turn, NERC coordinates its activities with ten regional reliability councils who provide oversight at the regional level. The New England bulk power system, or grid, is a part of the Northeast Power Coordinating Council (NPCC) region.

The New England Power Pool has established a bulk power supply resource adequacy standard commonly known as the "one day in ten years" criterion. This standard is widely used by the electric industry and requires that the bulk power system be designed in a manner that the likelihood of having to disconnect non-interruptible customers, resulting from a lack of generating resources, occurs no more than one day in ten years, on average.

A Summer Peaking System

The New England power grid is a summer peaking system. This means that the highest demand for power during the year typically occurs during the summer season. Peak demand on a normal summer day has typically ranged from 19,000 megawatts (MW) to 24,000 MW. In winter, peak demand has typically ranged from approximately 18,000 MW to 20,000 MW. Typical spring and fall peak demand ranges from 15,000 MW to 18,000 MW. On August 2, 2006, the region reached an all-time record demand of 28,130 MW. Summer peak demand is rising at about 400 MW per year, which is equivalent to the output of a medium-sized power plant.

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