Electric power transmission

Power travels on long wires.

These wires move energy from a plant to you. This is called a transmission line.

Sometimes the power is very strong. This helps it travel a long way. High power can move through many wires. These wires make a big web. We call this the grid.

Most wires hang high in the air. Some wires stay under the ground. Ground wires are hard to build. They cost more money to make.

We must make power as people use it. If we use too much, things might stop. This can cause a blackout. A blackout means the lights go out.

Many wires work together. This helps the power keep moving. It is a very smart system.

Electric power transmission is the way we move power.

It moves electricity from a power plant to a substation. A long wire used for this is called a transmission line. Many lines together form a big network. This network is part of the electrical grid.

Moving power over long distances works best with high voltage. Voltage is the pressure of the electricity. High voltage helps reduce the power lost during the trip. We use transformers to change the voltage levels.

These tools can increase voltage for travel. Then, they reduce it for local use.

Most lines hang high in the air. They are often made of aluminum. Aluminum is light and costs less than copper. Some lines are placed underground. Underground lines are harder to build and cost more. However, they are less affected by the weather.

We must make power at the same rate people use it. If we use too much, equipment might shut down. This can cause a blackout. A blackout is when the lights go out. To prevent this, many lines work together. This gives the power more ways to flow.

Electric power transmission is the way we move electricity over long distances.

It carries energy from a generating site, like a power plant, to an electrical substation. The long wires used for this movement are called transmission lines. When many lines connect together, they form a transmission network. This network is a major part of the electrical grid.

Transmission is different from distribution, which is the local wiring used for customers.

To move power efficiently, engineers use very high voltages. High voltage is important because it reduces the energy lost during the trip. This loss happens because of resistance in the wires.

To change the voltage, we use a tool called a transformer. A transformer can increase voltage for the long journey. Later, another transformer reduces the voltage so it is safe for local use.

Most lines use alternating current, or AC, but some use direct current, or DC. DC is very efficient for traveling hundreds of miles.

In the past, electricity was harder to move long distances. In 1882, direct current could not be easily increased for travel. This meant generators had to be placed very close to the people using them. This changed after Lucien Gaulard and John Dixon Gibbs built an early transformer in 1881. The first long distance AC line was built in 1884 in Turin, Italy.

Later, William Stanley, Jr. developed a practical transformer in 1885. He worked with George Westinghouse to show it could power businesses in Massachusetts.

Today, transmission systems are huge and use many different parts. Most North American lines use high-voltage three-phase AC.

North America has four major interconnections: Western, Eastern, Quebec, and Texas. One single grid connects most of continental Europe.

Overhead wires are often made of an aluminum alloy. Aluminum is used because it is lighter and costs less than copper. These wires can range in size from 12 mm2 to 1,092 mm2.

Keeping the lights on requires a very careful balance. Electricity must be generated at the same rate that people use it. If demand is higher than the supply, equipment might shut down to prevent damage. This can lead to a blackout, where the power goes out.

To prevent this, networks are interconnected into large regional grids. These grids provide extra paths for power to flow if one part fails. This helps make the whole system more reliable for everyone.

Electric power transmission is the bulk movement of electrical energy. It moves energy from a generating site, like a power plant, to an electrical substation.

The long conductors used for this movement are called transmission lines. When these lines connect, they form a transmission network. This network is a vital part of the electrical grid. It is distinct from electric power distribution. Distribution is the local wiring between substations and customers.

Efficient long-distance transmission requires very high voltages. High voltage is necessary because it reduces currents. Lower currents reduce energy losses caused by resistance.

To achieve this, the voltage is often increased for transmission. It is then reduced for local distribution. This change in AC voltage level is often done with transformers.

High-voltage direct current (HVDC) technology is also used. HVDC is very efficient over long distances, typically hundreds of miles. It is also used in submarine power cables longer than 30 miles. HVDC links help stabilize networks during sudden new loads or blackouts.

Transmission lines can be overhead or underground. Most power is transmitted through overhead power lines. These conductors are usually an aluminum alloy. Aluminum is lighter than copper and costs much less.

Conductors can range from 12 mm2 to 1,092 mm2 in size. For large conductors, much current flows near the surface. This is known as the skin effect. To increase capacity, engineers use bundle conductors. These are multiple parallel cables used at high voltages. They help reduce energy loss caused by corona discharge.

Underground transmission is another option. It is common in urban or environmentally sensitive areas. Underground cables have lower visibility and are less affected by weather. However, they have higher installation costs. They also have greater operational limitations. For example, long underground AC cables have significant capacitance. This reduces their ability to provide useful power. DC cables are not limited in length by capacitance. If a fault occurs in a buried line, it can be hard to fix. In some cities, cables are in metal pipes with dielectric fluid. If a leak occurs, liquid nitrogen may be used to freeze the pipe for repairs.

Historically, electricity was difficult to move long distances. In 1882, DC voltage could not be easily increased. This meant generators had to be near the users. This was called distributed generation. In 1881, Lucien Gaulard and John Dixon Gibbs built an early transformer. This made AC transmission possible. The first long-distance AC line was built in 1884 in Turin, Italy.

In 1885, William Stanley, Jr. developed a practical series AC transformer. He demonstrated a system in Massachusetts with George Westinghouse. Later, Nikola Tesla and Galileo Ferraris independently invented induction motors. These ran on polyphase current.

Modern grids are massive and interconnected. North America has four major interconnections: Western, Eastern, Quebec, and Texas. One grid connects most of continental Europe.

These interconnections reduce the risk of failure. They provide redundant, alternative routes for power. If one part of the network shuts down, power can flow elsewhere. This helps prevent large-scale failures. Transmission companies also ensure they have spare capacity. They determine the maximum reliable capacity of each line to ensure safety.

Maintaining the grid requires a constant balance. Electrical energy must be generated at the same rate it is consumed. A sophisticated control system manages this balance. If demand exceeds supply, equipment may automatically disconnect. This prevents damage to the plants and lines. In the worst case, this leads to a cascading series of shutdowns. These are called major regional blackouts. The US Northeast faced blackouts in 1965, 1977, and 2003. Other major US blackouts occurred in 1996 and 2011.