Why are high voltage power lines not insulated?
High voltage power lines are not insulated because the thickness of the insulation layer of ordinary wires is far from enough for such high voltage lines¹.
The transmission voltage of high-voltage transmission lines is mostly above 10,000 volts, and the voltage of some lines is as high as 100,000 volts and 500,000 volts¹.
If the insulation layer is to be provided for such a line, the thickness of the insulating layer of the 500,000-volt line is at least about 17 cm¹.
Such a thick insulation layer is bound to greatly increase the weight of the transmission line, so for a transmission line of thousands of kilometers, the cost of investment will certainly increase exponentially¹.
In fact, it’s easier to prevent high-voltage lines from harming people by separating the line from people. If people can’t get close to the line, they will not cause an electric shock.