Grounding of a Three-Phase Wye Connection question

[Picclo]

I am currently going to college for electrical trades. We're learning about three-phase connections and transformers. I know that in a wye connection we derive a neutral from the center tap in the transformer. And the transformer is grounded so we have a reference point to ground. But do electrons ever flow through this ground down into the earth (other then when there are spikes or surges) or does the current just stay out of it because it wants to take the lowest resistance path back through the circuit. I'm probably just confusing myself and the answer is probably very simple but I seem to make things way more complicated than they actually are. If anyone could help out answering this thanks in advance.

P.S.

Not sure if I posted this in the right section of the forum

 

[augie47]

welcome to the Forum.
I hope I give you the correct answer in telling you that the current will take all paths available, but, as you state, any path involving earth will be of such resistance the current flow would be low.
One of the forum memebers did a "field test" lately on current flow to ground rods.
You might find this thread interesting:
http://forums.mikeholt.com/showthread.php?t=115917

 

[winnie]

First consider the 'ideal' installation. You have a wye transformer secondary supplying a set of loads, and from the center tap of the transformer you have a conductor that goes to a grounding electrode buried in the Earth. All other conductors and circuit elements are properly insulated and there are no 'ground faults'. In this case, there is no closed circuit path that includes the grounding electrode. There might be a very slight current flow due to capacitive coupling of the alternating current, but in a balanced system even that goes away.

Remember that for current to flow, there must be a closed circuit path.

Now consider the common situation where several different users share a single transformer. In North America, the standard is that _each_ user has their own grounding electrode, and each user connects the grounded conductor to their grounding electrode. In this case, there are multiple connections to Earth, and there are closed circuit pathways through the Earth. In this case, some neutral current will flow through the Earth, entering at one grounding electrode and exiting at another, in parallel with any current flowing on the neutral conductor.

-Jon

 

[Picclo]

Thanks

Thanks

thanks guys...that really did help me out. But in the case of electrons flowing from grounding electrode to grounding electrode. Would the current be high enough to be dangerous?

 

[hurk27]

Also remember that transformers isolate current flow, so each transformer is a newly created source for current to flow and return to.

as was said current will flow proportionally across each parallel path back to this source proportionally to the impedance of each pathway.

 

[SG-1]

Picclo, the only thing I would like to add to the great posts so far is that the electrons that came from the transformer secondary are trying to return to that same transformer secondary, not the earth. They may use the earth to accomplish this and/or all other paths that may exist.

Steve