In article ,
says...

... at least not fiscally prudent anyway.
Since they do bury high voltage lines some places it can obviously be
done. The added bulk and weight is not necessary on overhead lines tho
and most medium to high voltage conductors are not insulated.
Without insulation, they can use smaller wire. (conductors in free
air).
This is the label off a spool of medium voltage cable that they used
for a buried 13.2kv run underground and then across the bay here.
http://gfretwell.com/electrical/DIRE...le%20label.jpg




Yes, there is insulation that will stand the veryigh voltages. I worked
with a large company that converted the main power to 13,200 volts and
fed it around the plant to about 20 of what we called substations . This
was usually ran in open wire trays. The wire is insulated,but just
layed in the trays. Some inside and some outside. There it was
converted to mostly 480 volt 3 phase and often 600 amps.

Most cars have around 10 to 20 thousand volts on the spark plugs and the
wire is insulated.

One of my ham radio ampifiers has a seperate power supply that sends
around 2600 volts DC down the wire. The wire is less than 18 guage, but
the insulation is about 1/2 inch in diameter with the wire in the
center. It is special insulation compaired to the other wires.

It is the common things around that are not very effective much above
1000 volts. So if any of the power wires that are not on the 240 volt
side of the common pole transformer are laying around, do not try to
move them unless you know what you are doing.