Understanding Electric Distribution Pole Anatomy

Can you please take a look at these two overhead distribution pole images (US and Canada) and let me know what are the 1,2,3, and 4 wires in each images? Can you also let me know what is main difference between these two?

Image A - US

• I'm interested in the answers you get, if any. I honestly can't provide anything better than poor guesswork. But one thing stands out to my lay-eye: the US turns their poles on a lathe and Canada uses a two-handed drawknife to make their poles.
– jonk
Apr 3, 2021 at 7:34
• @jonk: I'd have to look at a nearby Canadian pole, but I expect US and Canadian poles are manufactured in the same fashion. Apr 3, 2021 at 16:48
• @PeterBennett I expect so, too. Just these two pictures with a common, central object in the middle -- the pole itself. (That's where my mind went to, lacking anything useful to add.) So I thought about how they were made. (I make stuff: carpentry, TIG, MIG, and stick weld, farm my land, manage my forest, etc. So my mind goes often to how I might make what I see.) That Canadian pole shows tool markings on it and a more natural shape reflecting how trees may grow. It actually makes me curious about the story of that pole, while the US pole does not inspire any questions.
– jonk
Apr 3, 2021 at 20:55

I expect you'll find both arrangements in both countries - they are at different stages in the power distribution system.

In the top photo, wires 1, 2, and 3 are three-phase high voltage (13.2 kV in my area) The single wire running at right angles to 1, 2, 3 is a single HV phase to supply local step-down transformers to deliver 120/240 V to homes. Wire 4 is Ground/Neutral - it should be connected to ground posts frequently.

In the lower photo, wire 1 is High Voltage (like the unlabeled wire in the top photo). Wire 2 is Ground/Neutral and wires 3 and 4 are the two 120 V "hot" wires (240 V between them). If you follow wire 1 to other poles, you'll probably find step-down transformers on every third or fourth pole, with the transformers feeding 120/240 V to wires 3 and 4. Wires 3 and 4 will be broken with insulators between transformers.

On the farther pole, you can see the 3 phase HV lines at the top of the pole. You may be able to see the connection from one of those lines to the HV line running to, and past, the top of the nearer pole.

On the nearer pole, there is a connection through a fuse to the top connection on the transformer (big grey can). The secondary terminals of the transformer connect to the lower group of three wires marked "120/240 V". Cables go from those three wires to the individual homes.

The thick bundle of cables lower on the pole, and the many small wires from them are for telephone and cable TV. The boxes on hte pole just below those wires are a micro cell phone repeater.

• Wouldn't wires 1 2 and 3 be evenly spaced if they were three-phase hots? I would have thought those would be split-phase hot, cold, and neutral. Although I don't see any reason those wouldn't be evenly-spaced, too, I suppose... Apr 3, 2021 at 17:13
• @Hearth: It is may be easier to put the insulator for the center HV wire on the crossbar rather than on top of the pole. I'd have to go out in the rain to see what the power company has done here... Apr 3, 2021 at 17:28
• is this SWER, or is there a return lin from that transformers primary? Apr 4, 2021 at 5:06
• The low side of the transformer primary appears to be internally connected to the secondary center tap, then to the Ground/Neutral wire. Apr 4, 2021 at 5:13

In the US picture, the wire 4 is not related to 1,2,3. As you can also see different spacing, it's not a three phase network.

In Canada picture, the upper 1 is a lightning protection, connected to the earth, While 2,3,4 are L1,L2,L3 three phase network.

• Do you have a source for this? It contradicts @PeterBennett's answer, and I'm not sure which seems more believable. Apr 3, 2021 at 17:14
• @Hearth Frankly I am EU guy, so it's different here. I guess you would not find any source for such a mess of wiring. But the explanation of user Peter seems a little bit off, specially of the top HV wire that goes to the three phase transformer, I mean for sure you don't have a 3 ph transformer combined with a single HV phase, makes no sense. The 1st pic, IMO are two hots+neutral, that can be changed to 3 phase + neutral by placing a 4th wire in between. Apr 3, 2021 at 20:51
• @MarkoBuršič: In my photo, I show a single phase transformer connected to one of the three phases available on the pole in the background. This transformer has a center-tapped secondary to produce the 120/240 V single phase power we use in our homes in North America. Wire 4 in the OP's first photo will be the Neutral/Ground of the Wye-connected high voltage. Apr 3, 2021 at 23:03
• @PeterBennett OK. As said I am not very familiar with US, Canada, we don't have split phase systems, here. I guess you are right, it makes sense now why one HV wire becomes three LV wires. Apr 4, 2021 at 8:42