What type of wire does transmission tower use?
Usually, uninsulated wire. We're talking about these 30–100m high towers, right?

License: CC-by-SA 4.0, photograph &quot;-wuppertaler&quot;
They are high for a reason, and every bit of insulation (and you'd need a lot of isolation for 380 kV) adds weight that makes the whole system mechanically harder to build.

If we're talking about the 3m high poles with which individual houses are connected: yes, these are more commonly isolated cable instead of three uninsulated wires.
Formerly: Uninsulated low-voltage distribution to houses:

License: CC-by-SA 2.5, photograph &quot;Joddel&quot;
Now, much more common: Insulated cabling.

License: CC-by 3.0, photograph &quot;wdwd&quot;

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