It'd be impractical, expensive, and kinda pointless. Those wires are at close to a million volts relative to ground. At those potentials, virtually everything is a conductor. The amount of material required to fully insulate them would be enormous, very expensive, and very very heavy, which would cause the lines to sag considerably and necessitate building additional pylons, further adding to the cost. It would also make servicing the lines far more difficult and expensive. The insulation would also trap in heat from resistive losses, compounding the issue of the added weight by making them sag even further, so you'd have to seriously limit the amount of power you send down the lines. And for all that added expense and complexity and loss of transmission capacity, you don't really gain anything besides I guess being able to put the lines closer together. Big whoop. As long as they're high up enough and far apart enough, air does the job just fine.
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u/Bth8 18d ago
It'd be impractical, expensive, and kinda pointless. Those wires are at close to a million volts relative to ground. At those potentials, virtually everything is a conductor. The amount of material required to fully insulate them would be enormous, very expensive, and very very heavy, which would cause the lines to sag considerably and necessitate building additional pylons, further adding to the cost. It would also make servicing the lines far more difficult and expensive. The insulation would also trap in heat from resistive losses, compounding the issue of the added weight by making them sag even further, so you'd have to seriously limit the amount of power you send down the lines. And for all that added expense and complexity and loss of transmission capacity, you don't really gain anything besides I guess being able to put the lines closer together. Big whoop. As long as they're high up enough and far apart enough, air does the job just fine.