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I saw a video where power lines touched due to high speed air and created huge arcs. In another video, a person throws a wire in air, it touches a wire and he gets shocked. Also it is said that birds are not electrocuted because they do not short +ve and -ve wires. Why shouldn't the answer be power lines are insulated by rubber?

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    \$\begingroup\$ You'd need twice as many poles. Expensive. Everything is money. \$\endgroup\$
    – Jeroen3
    Commented Oct 2, 2020 at 7:16
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    \$\begingroup\$ @Jeroen3 you mean wires are not insulated? \$\endgroup\$ Commented Oct 2, 2020 at 7:17
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    \$\begingroup\$ Powerlines in the air are not insulated. If hung properly they shouldn't be able to touch. In really heavy rain and wind you might be able to see some arcs and sparks between the wires, but that is not supposed to happen. \$\endgroup\$ Commented Oct 2, 2020 at 7:20
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    \$\begingroup\$ to stay exact the air is the insulator. Without it the electrons could jump between the wires. Vacuum tubes are based on that phenomena. \$\endgroup\$
    – user136077
    Commented Oct 2, 2020 at 7:28
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    \$\begingroup\$ Power lines are meant to be up for decades. No coating material (invented decades ago) could stand up to weathering for nearly that long. So the logical conclusion would be to design the grid such that wires don't need insulation. And of course $$$ which really drives most decisions \$\endgroup\$
    – Kyle B
    Commented Oct 2, 2020 at 7:40

2 Answers 2

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Powerlines in the air are not insulated.

If hung properly they shouldn't be able to touch.

In really heavy rain and wind you might be able to see some arcs and sparks between the wires, but that is not supposed to happen.

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High voltage (>1KV) overhead lines are nearly always bare wire. Instead insulation is achieved through spacing of the wires and mounting them on insulated supports. This works fine most of the time, but sometimes either support structures break or high winds cause problems by either blowing wires into each other or blowing other stuff onto the wires.

Insulating a HV line is more complicated than just slapping a bit of plastic or rubber on, at high voltages controlling field strengths becomes very important. Insulated HV wires used underground often have multiple layers including a layer of earthed metal and then inside that a "semi-conductive layer" to control field strength. However having earthed metal close to a HV conductor means more capacitive losses.

Low voltage (<1KV) overhead lines were also historically often bare wire. At least in the UK this has fallen out of favor in recent years with new installations tending to use insulated conductors. There is still a lot of legacy bare wire LV overhead around though (and yes this does include service drops to peoples houses).

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  • \$\begingroup\$ Are low-voltage overhead lines insulated because they're low-voltage? That sounds backwards: you'd think that lower voltage would mean less need for insulation. \$\endgroup\$ Commented Oct 2, 2020 at 18:45
  • \$\begingroup\$ Low voltage lines are usually more closely spaced, closer to the ground, closer to foliage and closer to peoples houses. As I understand it there are also less technical difficulties in insulating them. \$\endgroup\$ Commented Oct 2, 2020 at 18:54
  • \$\begingroup\$ low voltagew means less than 1000V it does not mean safe to touch. Once while building a metal atructure I found a low voltage wire with my back, I was most glad for the insulation. \$\endgroup\$ Commented Oct 3, 2020 at 6:11

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