You handle power cords of 120 or 240 volts all the time with no worry. There is insulation, so there's no risk of getting shocked, unless there is some failure such as it drying out and cracking.
But just how high a voltage can we go and keep it safe to handle, even if the insulation is thicker?
I see lots of insulation rated 600 volts (presumably RMS so it could probably handle 900 volt peaks or more). I suppose then, it is safe to handle a power cord when the voltage goes as high as 600 volts.
But what about beyond that when you beef up the insulation?
I'm guessing thee is a (fuzzy) point where it is just no longer practical to beef up the insulation. Maybe it gets to thick or too stiff to work with.
But is there a voltage level beyond which you simply cannot make wire safe for humans to handle? Would you handle (with no further protection) wire carrying 12000 volts if the insulation is rated for at least twice that?
How does corona play into this? Can corona ever be blocked by a sufficient amount of insulation?