Household Electricity

The power grid

Most appliances in your home are powered by electricity, but have you ever thought about how the electricity actually reaches your home?

1. Electricity is generated in a power plant.

2. The electricity is moved around the country on high voltage transmission lines called pylons. The Department of Energy reports there are more than 157,000 miles of high voltage transmission lines in the U.S. This system of power lines is sometimes referred to as "The Grid."

3. The electricity is then transmitted to sub-stations located all over the country. There, it's transformed down to a lower voltage before it's distributed to various points around a city.

4. The sub-station transports the electricity on wooden distribution poles, which are the traditional power line poles that run through neighborhoods and towns. However, before the electricity can enter a home, its voltage must be lowered once again by a second transformer because it is still at a dangerous level.

5. From the transformer, service lines carry the electricity into the home.

Powering your home

Your home's electrical system includes the electricity that comes in from the power lines, the circuit breaker, electric meter and the outlets and appliances in your home.

Electricity first enters the home via the utility lines supplied by the electric company.

You will notice three wires coming to your home, especially in modern installations. Two of the wires are "hot," meaning they are bringing voltage into the home. The third wire is the grounding wire. This configuration brings two 120-volt lines to your meter and main breaker.

Think of it as voltage part A and part B. Each conductor has 120 volts, but when used together in a circuit, they deliver 240 volts for use in larger appliances such as electric dryers. Voltages may vary from 110 to 120 on a single line conductor and from 220 to 240 volts on a conductor pair. Single breakers in your electrical box are 110/120 volts; double breakers are for the 220/240-volt pairs.

House wiring is installed using cables. 120-volt cables will have three wires: one black, one white and one bare conductor. The black is the hot wire, the white is called the neutral and the bare wire is the ground. A 220-volt cable will have an additional hot wire, red in color.

Each wire serves an important function. The hot wire sends voltage to the receptacle and appliance. The white wire brings the voltage back to the circuit box. Unlike water or gas, electricity must have a complete path from and back to the box.

The grounding wire is attached to the cabinet of the appliance and is not part of the circuit. However, if there is an electrical short to ground, this wire trips the breaker, shutting off the power. That's why you should never break off the round grounding connector on a plug.

The electric meter

An electric meter measures the amount of electricity used by a home or business and is used by the electric company for billing purposes.

Typically found on the outside of a home, the meter measures the amount of electricity consumed in units called kilowatt hours. Each month, the electric company sends out a meter reader who records the reading on your electric meter.

You can check how much electricity you are using by looking at the five dials on your electricity meter. Each dial has an arrow that corresponds to a number. Newer models may have a digital readout. If you write down the number on each dial from left to right, you will get a 5-digit number that equals you electrical usage in kilowatt hours.

To measure how much electricity you use in a month, you need to record the five-digit reading from your meter on the first of the month. After waiting 30 days, again record the reading on your meter. If you subtract the first month's reading from the second, you will get an accurate reading in kilowatt hours.

What is grounding?

Grounding adds a safety factor for your family and your electronics.

Here's how it works.
Electricity travels the path of least resistance. If an appliance like a toaster breaks, electricity can flow to the metal outside of the toaster. Touching it could result in a serious shock, causing injury or even death.But if the electrical system is grounded and the toaster is plugged in with three prongs, the electricity won't flow to the outside of the toaster. Instead it will flow through the third prong back into the wires and harmlessly into the ground.

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