Thanks for that C-H. I guess that not being a lineman I'd just never noticed one of these systems before.
There are quite a lot of rural networks where a 480, sorry 460, volt supply is taken. I suspect there are still quite a few farms or small rural businesses around with 480 volt motors fitted.
The main reason for this type of supply was cost. Many rural areas weren't electrified until the 50's and 60's. At that time loads were thought to be fairly static with an average admd (after diversity maximum demand) of about 2kva. It was cheaper to run single phase 11kv and three wire lv, rather than a full three phase system.
A 2 wire lv system will have a significantly greater voltage drop for a given load than a three wire system. If the transformer sits right alongside just two or three cottages, no problem, use 2wire, but if the cottages are spread out over a few hundred yards, then volt drop problems have to be taken into consideration.
That does indeed describe the area where this transformer is located. It's not the typical one or two houses standing on their own, but a very rural backroad where there are maybe a couple of dozen houses spread over a few hundred yards, plus a couple of farm buildings as well.
Next time I'm out that way I think I'll take a closer look and see if any of those farms look like they have a 3-wire service to them.
By any chance is it feeding a timed lighting circuit ? or perhaps it was in the past? Or even traffic signals, back-lit signs? or something to do with the telecom's network ?
Sorry to disappoint, but no.......
Nearest street lights are in Stalham, several miles away. As for traffic lights, I had to stop and think about that one. I think the nearest set are in North Walsham, nearly 10 miles distant!
[This message has been edited by pauluk (edited 06-20-2004).]