Why multi conductor circuits.?

Question

Why do they always run a hot, common and ground for an electrical circuit when you can get a complete circuit just using the hot and a good grounding rod driven into the ground. This seams redundant and wasteful. Running three copper wires instead sure uses a lot more copper than just one wire with a ground. I take it there are things going on here that I do not understand.
Thanks in advance.

Answer 1

In addition to what the previous posters have told you:
You seem to forget that the circuit to which you refer
is part of a multiphase centrally grounded system.
(I would have to draw diagrams to clearly explain this.
Sorry, but the forum is unsuitable for a clear
explanation.)
Your scheme would not only be unsafe, but would involve
considerable inefficiency.
(You might google or wiki "Three Phase Power Distribution")

Answer 2

As Sporadic mentioned, safety is the main issue. They used to use a single wire earth return (SWER) system in which a single power wire was brought into the house and the AC return was routed through the ground. In some rural areas, they may even still use it.

Another way to look at it, imagine that you are using the single wire system with one return to ground. If lightning strikes, the surge would travel down the hot wire, through your appliances to get back to ground. And if you are touching the appliance when this happens? Ouch.

With the multi wire system entering the house, you now have an additional ground source which is then fed from your breaker box, through an earth ground, for safety.

Answer 3

For safety. Under normal operation no or little current goes through ground. The ground is attached to the metal case of appliances. So if it happens that a live wire of the appliance came into contact with its metal case, and you touched the metal case , the current would go through the grounding rod instead of you. You wouldn't want to run a circuit using just the hot and ground rod. Anytime you grounded yourself by touching the kitchen sink for example, you might get a shock. You don't want to be part of the circuit. That's why they use hot and common for normal operation, so the current is carried back to the power company.

Answer 4

actually everyone is partially correct and note every country uses a three wire system . Example in Korea where it is common to refer ground to neutral. As the asker states this saves money by eliminating copper and reducing wire costs.
Its believed that a 3 wire system to "hard ground" offers the best solution for failure scenarios.

1. shorted appliance
2.Insulation failure in Live Neutral
3 Natural factors (lightning external power source etc)


In addition top the above a three wire system lends itself to the use of ELCB (earth leakage circuit breakers) (also refered to as ELCD)these can be found in most modern consumer units (fuse boxes)


hope this helps

Answer 5

FYI, even your alternative circuit is a multi conductor circuit inside your house.

I really don't know why the circuit pathway
leads back to your electrical utility, but I do know that the alternative pathway to ground is there to protect the circuit user. It's considered an alternative pathway to ground to prevent/mitigate injury to the circuit user. Actually there is a great deal of protection built into electrical installations built according to approved standards, you just aren't aware of it.