[GerryB]

The different lines are at the same AC voltage, but have different phases (almost always three phases), so there's an instantaneous potential difference between them. The lines need to keep the conductors seperated to prevent potential arcing chances to essentially zero even in wet weather. The higher the voltage, the more seperation is needed.

[ben_w]

My mental image for this whole thread is a UK steel pylons with 7 sets of cable — 3 groups of 4 wires on the left, same on the right, and a lone cable on the top.

I assume that's 3 because 3 phase.

But the point is, each is a group of 4: https://en.wikipedia.org/wiki/Overhead_power_line#/media/Fil...

I think the question is: can towers holding single wires for each (phase?), support e.g. four like this?