Chapter 7: Electricity Transmission System
After electricity is produced at power plants it has to get to the customers that use the electricity. Our cities, towns, states and the entire country are criss-crossed with power lines that "carry" the electricity.
As large generators spin, they produce electricity with a voltage of about 25,000 volts. A volt is a measurement of electromotive force in electricity. This is the electric force that "pushes" electrons around a circuit. "Volt" is named after Alessandro Volta, an Italian physicist who invented the first battery.
The electricity first goes to a transformer at the power plant that boosts the voltage up to 400,000 volts. When electricity travels long distances it is better to have it at higher voltages. Another way of saying this is that electricity can be transferred more efficiently at high voltages.
The long thick cables of transmission lines are made of copper or aluminum because they have a low resistance. You'll remember from Chapter 3 that the higher the resistance of a wire, the warmer it gets. So, some of the electrical energy is lost because it is changed into heat energy. High voltage transmission lines carry electricity long distances to a substation.
The power lines go into substations near businesses, factories and homes. Here transformers change the very high voltage electricity back into lower voltage electricity.
From these substations (like in the photo to the right), electricity in different power levels is used to run factories, streetcars and mass transit, light street lights and stop lights, and is sent to your neighborhood.
In your neighborhood, another small transformer mounted on pole (see picture) or in a utility box converts the power to even lower levels to be used in your house. The voltage is eventually reduced to 220 volts for larger appliances, like stoves and clothes dryers, and 110 volts for lights, TVs and other smaller appliances.
Rather than over-head lines, some new distribution lines are underground. The power lines are protected from
the weather, which can cause line to break. Have you ever seen what happens after an ice storm?
The picture on the right shows high voltage towers that crumpled from the weight of ice during a 1998 ice storm that hit Canada and parts of the United States. More than 1,000 high voltage towers and 30,000 wooden utility poles were destroyed in Canada by the storm.
Close to 1.4 million people in Quebec and 230,000 in Ontario were without electricity. In many places, power not fully restored for up to a week. Weather people called it the most destructive storm in Canadian history.
When electricity enters your home, it must pass through a meter. A utility company worker reads the meter so the company will know how much electricity you used and can bill you for the cost.
After being metered, the electricity goes through a fuse box into your home. The fuse box protects the house in case of problems. When a fuse (or a circuit breaker) "blows" or "trips" something is wrong with an appliance or something was short- circuited.
Energy Safety Note!
Never play around a transformer. If a ball or toy lands in or near a transformer, go and tell your parents to call the electric company. The electricity from a transformer could kill you.
Never fly a kite around electrical lines. The kite string could link across the wires, completing a circuit. The electricity could be transferred back to you holding the string.
Never let a balloon - especially a mylar foil balloon - escape into the sky. When the helium of the balloon escapes, the balloon can come down a long way aways. The wire or the mylar surface could stretch across high voltage electrical wires causing problems or even a fire.
You should never touch wires inside or outside your house. You should only let an electrician who knows electricity safety work on the wires.
In the next chapter read about Fossil Fuels - Coal, Oil and Natural Gas