ECN Forum Forums General Topics of the Trade General Discussion Area Local HV distribution

A quickie for you:

What's the most usual HV system feeding xfmrs. for residential & light commercial services?

In my area, 12.45kv is typical resi hv on the primary, this of course is the urban, in the city of Warren, Ohio they are using 13.8kv.

Distribution in my area is usually 12.47 KV. Branch distribution for housing tracks is usually 6.9KV. (one leg and neutral of the 12.47KV system. They call it that although I know when you do the math it's 7.2KV... Lineman ) Some larger plants are fed with 69 KV and stepped down to whatever the plant needs. 4160V is also a fairly common distribution voltage but not near as common as 12.47KV. I could go on about the multitude of different voltages around here but I guess that is not the question!

4160/7200V Wye on the Xformer primaries, 19.9KV Delta on the top...

Primary voltage here in Houston is 12470Y/7200 and 34500Y/19920. Being in residential, commercial, industrial areas has no bearing on the voltage. Generally most of our inner city is 7200 while new developments in rural areas are 19.9KV. Reasoning behind this is that the 7200 was already in place and there are more substations in town that already exist. In rural areas less substations have to be built since the 34.5KV/19.9 can have longer circuits than 7200.
QOUTED BY NICK...
"Distribution in my area is usually 12.47 KV. Branch distribution for housing tracks is usually 6.9KV. (one leg and neutral of the 12.47KV system. They call it that although I know when you do the math it's 7.2KV... Lineman )"

Nick , I have never heard anyone around here refer to 12470Y/7200 as 6.9KV. I am like you the math simply does not add up. Heck even the trans nameplates are labeled as 12470Y/7200. If they are only running at 6.9KV then their secondary voltage must be awfully low. Given a trans rated for 7200 with a 30:1 turns ratio they would only get 115/230 from the secondary.

Oh boy... Another innocent question of mine that's started something....

I guess you still have quite a few different systems in operation.

I hadn't realized that some residential feeds were off one leg of a Wye system.

The next highest standard voltage above 240/415V in the U.K. is 11kV which feeds most residential area sub-station xfmrs (wired delta-star). We don't have any primaries wired one phase & neutral, but then 90% of LV distribution is 3-phase anyway.

In remote places where a single-phase xfmr. is installed the primary is fe from two phases of the 11kV line.

Not quite with you on this one.

Do you mean that the 4160/7200 is feeding all the 120/240 or 120/208 xfmrs, but the same poles are also used to carry 19.9kV on the uppermost cross arm?

Pauluk,
Exactly!

-Virgil

Gotcha - Thanks.

It's just a little strange to me, because we don't normally have different voltage lines on the same poles (except for where they meet at a transformer, of course!).

Poles around here are multi-purpose. I have seen 12.47KV with 34.5KV on top and others with 66KV on top. There is even a line in my town that combines 12.47KV with 115KV on top.