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#30036 09/30/03 09:44 AM
Joined: Aug 2002
Posts: 1,081
In all of the pictures/discussions of power transmission equipment, I have noticed that there are four conductors:
Three are "phase" conductors, and one is a "neutral" conductor.

Fast-forward from the power generation, "high-tension" lines, etc. to the wooden poles at the curb here.

There is one primary conductor entering the can, and three secondary conductors exiting--two "legs" of a 120/240 service and the neutral.

The other day, I happened upon a POCO employee and was chatting with him.

He explained to me that the line at the top is a 4kv line, and that no neutral is used on the pole because the can is grounded. Each pole has its own ground rod.

My question is, why do some distribution systems use a neutral wire and the ones here do not?

I asked him if the "messenger" cable was the neutral for the 4kv, he said it's not, it's just that, a messenger cable. If that's the case, is the messenger cable energized also? Are 4kv lines even insulated?

Just wondering.

#30037 09/30/03 10:50 AM
Joined: Oct 2001
Posts: 597
We had a discussion about [b]S.W.E.R (single wire earth return)[/b] a while back. It might be helpful.

If your area that you are sussing out is a residential urban or suburban area that incorporates a community water distribution through a metal pipe system, and that has multiple residences connected to single transformer, you will most likely have the 120 / 240 volt single phase secondary neutral acting as the return conductor (as well) for the 4 kV line. This thread discusses this second point, a rather widely used PoCo method.

Al Hildenbrand
#30038 09/30/03 02:23 PM
Joined: Aug 2002
Posts: 1,081

Thanks. I thought I had read something here about that, but wasn't sure if this was the same thing. Looks like it is.

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