A Basic Understanding Of Electric Distribution

A basic understanding of electric distribution

How electric power gets to your home:

The electric power is produced at a power plant and feed through a step up transformer which steps the voltage up to 400,000 volts for transmission. By stepping the voltage up so high it allows for very low current and cuts down on transmission losses.

Once the high voltage meets a substation it is stepped down the 13,000 volts for transmission to local service areas. These are the lines you see on the power poles along a road.

On the pole near your house is another step down transformer . This transformer steps the voltage down to 240 volts. In the U.S., by center tapping the output windings, it divides the 240 volts into two 120 volt outputs. The center tap, often called neutral, is tied to ground for a reference point only but is still a current carrying leg.

In the home the three legs of transformer output, Hot1, Hot2, and Neutral are fed through the meter into the breaker box or fuse panel.

In the home, you generally have four types of receptacles, or commonly called outlets. One is the standard 120 volt receptacle which has Hot1 and Neutral or Hot2 and Neutral plus ground. The second type is a 240 volt only receptacles that are feed by Hot1 and Hot2 plus ground few modern U.S. appliances use this type but they are common in many other countries. The Fourth is a receptacle for appliances that use both 240 volts and 120 volts for operation. These receptacles have Hot1, Hot2, and Neutral plus ground. Stoves usually use this type receptacle to supply 240 volts for the elements, burners and oven, and 120 volts for lights, timers, and controls.

So... what do you think? Please leave me a comment.


  • Vale: Great post, you explained it very well :D
    Just one question - "By stepping the voltage up so high it allows for very low current and cuts down on transmission losses." How does that work?
  • JLMCDANIEL: Higher current causes a greater heat loss and a stronger magnetic field building and veining that creates a counter induced current that also creates losses. Plus the benefit of using much smaller conductors.
  • Vale: Thanks for explaining :)
  • Ccorvair: My house has knob and tube wiring, with two pronged outlets. And I can’t find a grounding rod in my yard. Am I going super nova or ted Bundy or just a Tesla experiment one morning when I am making toast?
  • JLMCDANIEL: Not to worry Ccorvair, grounding does not provide personal protection. You could replace the outlets with GFCI units to provide actual personal protection for the short term. For the long term you should have the wiring replaced. Many insurance companies are refusing to cover K&T wired houses, it is dangerous if insulation is added to walls or ceilings with K&T wiring in them, and wiring that old has the potential of degraded failing insulation.

Add Your Own Comment:

By clicking 'Submit' you agree to the Site Terms
By entering this site you declare you read and agreed to its Terms, Rules & Privacy and you understand that your use of the site's content is made at your own risk and responsibility. Copyright © 2006 - 2018 DIY Forums