Thanks for the pics guys. wink

Originally Posted by CTwireman

Here is an American open delta setup with a 3-wire (no MGN) primary. Grounding is done by local rod at the pole. This particular setup is in the high desert area in Sothern California Edison territory where I noticed that most, if not all of the local distribution, was done with no MGN and the transformers connected L-L. This would be considered unusual by US standards which is mostly MGN distribution.


I would agree. 95% of the lines around me are 4 wire wye primary with grounded neutral. Do you know what primary voltage they use? In my area, I have noticed that some medium to small towns that are not served by the local electric co-op(s) are served by either their own municipal utility, or by the larger utility and have a small substation are more likely to be supplied with the 3 wire delta. (usually 2.4 kv) I think for several reasons: first, most of these towns have a steady population and the system is adequate. There aren't a lot of businesses that demand more than what a system like this handle. (many of these systems are quite old) There really is no need to replace it. Most of the distribution transformers that they use can be ran from many different voltages and systems. For example: take a two bushing transformer that can run on 2400 Delta, 4160Y2400 wye, 7200 delta or 12470Y7200 volt wye, plus some of the transformers have another tap for a 7.9 KV, the phase to ground voltage for a 13.8 kv wye system like in my town. 3 voltage taps, 5 different systems, one transformer.

A couple pics I shot in towns that have a 3 wire delta:
one older:
[Linked Image from electricalphotos.com]

One newer installation:
[Linked Image from electricalphotos.com]