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!
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.