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About Electric Transmission

What is transmission?

Transmission refers to the high-voltage wires and networks that move electricity through states and regions in large quantities -- from power plants where it is produced, to the distribution networks that deliver it to homes and businesses. Transmission is like our region’s interstate highways, while the distribution system is similar to our local roadways.

In the early years of the 20th century, most power plants were located in the immediate area where the electricity was consumed – generally in urban areas. As the population and economy grew, long-distance transmission led to economies of scale in the production of electricity, reducing costs and improving reliability. Interconnected transmission power grids created alternative power paths and enabled electric utilities to buy and sell power from one another and from other electric suppliers.

Who owns and operates the electric power grid?

Many organizations and entities are involved in owning and operating parts of the grid. Of the approximately 200,000 circuit miles of high power lines in North America, about two thirds are owned and operated by investor-owned utilities. The remaining third are owned and operated by federal marketing agencies; cooperatives; municipal, state and provincial authorities and other entities.

To help provide oversight over power transfers and ensure reliability, the North American Electric Reliability Corporation (NERC) was created in 1968. NERC’s members include electric utilities and market participants from all segments of the industry, operating in 10 Regional Reliability Councils across the continental U.S., Canada and northern Mexico. In parts of the nation there also are regional transmission organizations (RTOs) or independent system operators (ISOs), which coordinate planning, operations and reliability oversight. RTOs are well established in the Northeast – with the 80-year-old PJM Interconnection being a prime example.

How does this affect me?

If you live or work in New Jersey, the power you use in your home or workplaces comes from a local utility that is part of the PJM Interconnection. This system stretches from New Jersey to areas of Illinois to the west and North Carolina to the south. It serves about 51 million consumers.

In the Northeast and Mid-Atlantic area, the PJM Interconnection provides an effective working model of a fully-functioning RTO in operation. From a central dispatch point, PJM coordinates the movement and reliability of the electric power supply system in 13 states and the District of Columbia.

What factors determine reliability?

The reliability of the electric system depends on two basic factors: system adequacy and security. Adequacy is the ability of the system to meet demand of all customers at all times including peak usage, taking into account the need for facility maintenance. Adequacy means having a secure, available fuel supply and a strong, well functioning infrastructure – including generating stations with the ability to meet customer demand (with a sufficient reserve margin), as well as transmission and distribution systems to move power and deliver it to where consumers need it. It entails a long-term view of system needs.

Security involves the various protections that keep the system functioning smoothly – reducing and minimizing its vulnerability and enabling it to respond to emergencies. It entails a minute-by-minute view of system needs.  

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