Transmission Questions & Answers

How does the electrical system work?
Today’s electric generation and delivery system is a marvel of modern engineering and ingenuity. And while the system’s complexity can be overwhelming when viewed as a whole, it’s easy to understand when broken into its primary elements. This simple illustration helps explain how electricity is transmitted to your home or business.

Electricity is generated at power plants (Fig. 1) then carried over great distances across high-voltage transmission lines (Fig. 2). The electricity is carried to intermediate stations (Fig. 3) where the voltage of the electricity is reduced to lower distribution levels. The power then travels through cities and neighborhoods on distribution lines (Fig. 4) before the voltage is finally reduced to the 120 or 240 volts we use in homes (Fig. 5).

Unlike any other product, electricity must be delivered the instant it is being used. The electricity that lights a light bulb is instantly being generated at a power plant perhaps many miles away.

Undersized or overloaded components between the power plant and the distribution system can pose a threat to reliable service.

Just because you may not have a power plant, transmission line or electrical station in your neighborhood, don't assume these facilities aren't at work for you. Electricity must be generated the instant it is used. Therefore, to maintain reliable electrical service, all components of your electric company's system - generation (or power plants), transmission, and distribution - must be in balance and working together. If one element fails without adequate backup, the entire system is affected.

What is an EHV Line?
Electrical transmission lines are much like water pipes. In the case of transmission lines, the higher the voltage, the more electricity that can be transmitted, just like a wider water pipe can carry a larger volume of water. Electrical transmission lines operate at high voltages and carry large amounts of electricity over long distances. These power lines generally range in voltage from 46 kV to 765 kV; those in the upper levels of that range (230 kV and above) are called extra high-voltage (EHV) lines.

The average 345 kV circuit is typically capable of carrying five times the amount of electricity of a 138 kV circuit, and a 765 kV circuit is typically capable of carrying six times the amount of electricity of a 345 kV circuit.

AEP's power grid is capable of carrying more electric energy over longer distances at a lower cost per kilowatt-hour than any other system. The grid is tied in with the power systems of neighboring utilities at 143 interconnection points to the north, south, east and west.

These interconnections result in even greater reliability of electric service -- not only for AEP's customers, but for the tens of millions of customers served by the electric companies over much of the eastern half of the United States.

The backbone of AEP's transmission network is its 2,100 miles of 765 kV lines, stretching over six states. In 1969, AEP was the first electric company in the country to research, develop, build and operate such lines, and today the company has more miles of 765 kV lines transmission in service than all other U.S. electric utilities combined.

What Does A 765KV Line Look Like?

The Jacksons Ferry-Axton 765 kV transmission line crosses the Blue Ridge Parkway in Floyd County, Va. AEP used the topography of the land, and selective right-of-way clearing practices to obscure the view of the power line for Parkway travelers. By not cutting the right of way near the road, and by crossing the Parkway in a bend, it is difficult for travelers to notice the line.

What are AEP’s Power Line Routing Philosophies?
AEP strives to build power lines that are acceptable solutions to meeting the region’s growing need for reliable electricity. The first step in reducing the disturbance caused from power lines happens at a global level. The company tries to find the best power line corridors with the least impact on people and the environment. AEP reviews publicly recorded data on environmental, cultural and historic resources at this level. Once broad corridors are identified, company officials refine their information and incorporate valuable public input. AEP files applications to construct facilities with the appropriate state agencies responsible for transmission line projects. During the regulatory process, AEP continues to gather additional public input from the state process and work with property owners to refine the proposed corridors. If the state agency determines that a project is indeed necessary for the public good and identifies a project corridor, AEP works with individual property owners to locate the power line right-of-way on individual properties.

What Is AEP’s Right Of Way Compensation Philosophy?
AEP believes that property owners should be treated fairly and made whole for property encumbered by a transmission line project. This simple premise has helped AEP to successfully negotiate more than 95 percent of the transmission line rights of way that it obtains. AEP’s eminent domain authority is the exception, rather than the rule when it comes to acquiring rights of way.

How does AEP build an EHV line?
Once AEP obtains approval to construct a facility it begins acquiring rights of way. Initial clearing starts, followed by constructing tower foundations, erecting transmission towers,

Older versions of power lines utilized aluminum towers.

Newer transmission lines AEP builds utilize darkened steel structures like this tower in Wyoming County, W.Va.

stringing conductors and installing substation equipment to incorporate the new facility into the electric power grid. View photographs of the construction of the Wyoming-Jacksons Ferry 765 kV project.

What new transmission line technologies are being used by AEP?
AEP is a pioneer in electric transmission. A history of cutting edge advances in technology, including development and installation of 765 kV transmission lines, the highest voltage, most-efficient transmission lines in the country, continues today. The latest 765 kV technologies use a new six-bundle configuration that cuts audible noise from the project to half that of earlier generations of 765 kV lines.

Why 765 kV power lines?
There are numerous advantages to 765 kV technology. In most instances, the size of the structures and the right of way needed to build 765 kV are comparable to smaller voltage lines. However, 765 kV transmission lines are much more efficient than lower voltage lines. For example one 765 kV line on a 200 foot wide right of way can carry the same electricity as 15, double circuit 138 kV lines that would require 1,500 feet of right of way. AEP has more than 2,100 miles of 765 kV transmission lines.