I think that maybe you are not seeing that the primary is usually fed with a cable, not individual conductors. The secondary lines on the pole 240V/120V are of course individual conductors.
It appears to me, from looking around the web at various sites, that there is ONE primary lead coming into the transformer at "high" voltage (7200?) and none leaving.
The three phase supply entering the neighborhood is typically split three ways. So you may have a 4160Y/2400V or 12400Y/7200V 3-phase supply that will be used to power single phase transformers at 2400V or 7200V.
If you look closely at the fuse holder on the pole in your neighborhood you will notice that the feeder has two conductors, not one. The second conductor is a concentric braid. The center conductor is fused while the neutral (braid) is not. You may then see a piece of this cable connecting to the transformer (appearing like a single wire). Since the voltage is high (current low) the gauge of wire needed is small.
Last edited by Homer; July 3rd, 2005 at 02:27 PM.
Depending on your skills, doing your own electrical work may risk the health and safety of the community. Always find out how to do things safely before beginning.