Complete circuit in power line - Page 1
Forum section: electronics / general

author: nForce
author_rank: Frequent Contributor
timestamp: January 01, 2018, 09:17:46 pm
content: This is maybe an unusual question:If we would connect power line with ground (earth) with something let's say a tree falls on the power line. And the transformer for that power line is far, far away let's say 100 miles. To complete the circuit the electric current must run from that tree to the transformer. Would we measure current if we would connect A-meter to earth? And how does electricity know which transformer is the right one of many?Thanks.

author: tom66
author_rank: Super Contributor
timestamp: January 01, 2018, 09:19:54 pm
content: Earth has very low impedance. It's moist soil. So it would complete the circuit, and you would measure a very large current until a breaker downstream trips or something melts. Possibly the boiling of the earth around the connection point may be sufficient to disconnect the circuit.The low impedance of the earth is the reason it is used as a path for fault currents.

author: Gregg
author_rank: Super Contributor
timestamp: January 01, 2018, 10:16:33 pm
content: Unintentional ground faults on a high voltage grid can cause fatalities for miles from the fault from the potential difference on the surface of the earth. Here is a pretty good explanation:http://www.esgroundingsolutions.com/what-is-step-and-touch-potential/Grounding of electrical systems is very complex and often not intuitive.

author: floobydust
author_rank: Super Contributor
timestamp: January 02, 2018, 12:47:47 am
content: Single-phase distribution also runs the neutral wire, which gets daisy-chain earth-grounded at every house along the way. Every house has neutral and earth-ground bonded at the service.I think OP's disconnection would cause high-earth currents between each side of the break, for the primary-side of the distribution transformer.Earth impedance is not always low, especially places withigneous rock.Lightning protection is also very difficult with high resistance earth.

author: Electro Detective
author_rank: Super Contributor
timestamp: January 03, 2018, 09:33:01 am
content: Rubber shoes and living in the desert sounds about safe enough from earth power blundersand a big isolation transformer in the harem if you need to power a labAssuming that real estate in the desert is still affordable... ?

author: Lord of nothing
author_rank: Super Contributor
timestamp: January 03, 2018, 01:02:47 pm
content: Quote from: nForce on January 01, 2018, 09:17:46 pmeven in Estonia the People use the Metric System.

author: Zero999
author_rank: Super Contributor
timestamp: January 03, 2018, 02:48:10 pm
content: Quote from: Lord of nothing on January 03, 2018, 01:02:47 pmCome on, let's not derail anther thread to metric vs imperial.I wonder what is done for earthing in dry areas? I suppose the earth rod needs to go down to the water table. I wonder if some unscrupulous electricity companies employ magicians to locate water. Oh, let's not derail the thread to dowsing.

author: floobydust
author_rank: Super Contributor
timestamp: January 03, 2018, 08:52:23 pm
content: In high earth-resistivity areas, what I have seen is the use of conductive concrete to make large ground electrodes. A deep long trench with special concrete.It is absolutely worst on mountain sides with radio towers, they get lightning hits and the power grid has a poor ground.