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.
How it works
Video: Overview of the Electricity Grid Watch the VIDEO by PJM.
Bulk electrical power is not stored but rather produced and transmitted according to demand. Transmission lines are high voltage utility wires that carry 138,000, 230,000 or 500,000 volts of electricity. They are strung over long distances and are designed to transmit large amounts of energy over vast areas. Transmission lines are typically constructed on metal towers located within the Rights-of-Way on PSE&G easements and company-owned land.
Transmission lines are composed of:
- Conductors (the system’s power carrying cables and wires that are grouped in threes)
- Overhead transmission structures (poles or towers that support the conductors and separate the wires)
- Insulators (from which the wires are suspended from the structures)
The conductors are electrically insulated from each other as well as from the transmission structures that support them. A primary concern in the design of transmission lines is the need to minimize voltage drop over long distances. The higher the voltage, the greater the insulation needed between conductors and the ground.
Overhead conductors are comprised of highly conducting metals such as copper or aluminum and are engineered to withstand weather, mechanical and electrical loads. Transmission line structures are typically lattice or pole type make of metal, but wood can also be used in certain circumstances. Lattice towers are constructed at a cross-braced metal angle, commonly with four legs at a wide-set base that tapers up to a broad, horizontal cross member or a narrower taller cage with vertical arms.
Insulators, separating the conductors from the structure, typically consist of porcelain, glass or a synthetic material and are attached to the structure. The insulators are used to maintain the necessary distance between the conductors (wires) and the transmission structure.
The electric power is then transformed by lowering the voltage at the substation to supply the lines that distribute power to the customers or end use.
Transmission Contact Information
The Transmission network is overseen by the Transmission Supervisor of Vegetation Management.
Transmission Supervisor - Vegetation Management
Transmission Manager - Vegetation Management
Trees located along PSE&G’s Right of Way and in proximity to electrical lines are a danger to the reliability of the electrical grid, the lives of our employees, and the safety of the general public.
A tree in close proximity to a transmission line has the potential to short-out the line, which will cause a hazardous electrical current to traverse through the ground and into underground wires and cables. This can initiate a serious situation that could inflict significant property damage and create a variety of safety concerns.
An outage on a transmission line could impact hundreds of thousands of customers. PSE&G actively maintains the area around transmission lines.
The New Jersey Board of Public Utilities (“BPU”) has made vegetation maintenance a major priority since the blackout of August 14, 2003. Recent tree maintenance regulations require that an integrated vegetation management approach be utilized on the border zone. This would allow for, in most cases, low-growing compatible species to remain in this area.
The regulations also require that only vegetation under 3 feet in height that is located underneath a transmission wire (also known as the wire zone) is permitted to remain.
Points to remember:
- No buildings, swimming pools, decks, sheds, barns, garages, fences, or any other structures can be located within the Right of Way.
- No lighting fixtures are permitted to be placed under the Right of Way.
- Septic systems and wells cannot be located within the Right of Way.
- No materials of any kind are allowed to be hung or affixed to the Transmission Right of Way Towers or any other Right of Way structures.
- All roads or paths permitting access to transmission Right of Way structures must be clear and unobstructed.
- Excavations near Transmission Structures are not permitted without proper approval from PSE&G.
- Activities such as kite flying and model airplane flying are prohibited on or near the Right of Way.