11kV Overheads and Water Spray.

You do not need much insulation to hold off 6 to 7kV RMS, in dry conditions a few mm of polyethylene will do. (there are cables that put 50kV DC between the inner and outer of URM67 without issue, except at the ends where the connection needs to be re-entrant by 2-3 inches) The problem with anything outdoors  is the tracking over a surface with dust, or mud and a little moisture leading to local heating and a far longer fault path is needed to avoid this.
And given the higher voltage means the current that flows via  boot leather, clothing,  etc is enough to do serious injury, (as well as set fire to the boots with your feet in them).

Hence the shiny and ribbed water shedding shapes on insulators, and even then you sometimes see flashover when there is a cloud of pollen or a dust storm in just the wrong place. (its not unknown for lines to trip near where there has been dust from explosive demolition, especially of chimneys and so on where the dust is sooty and partly conducting.)

Insulating the wires of the 11kV and 33kV  networks has been considered, and is already done in high risk places, but is far from universal, and not without problems of its own, damaged insulation can trap water and the wire rots, and again, current tracking over the insulation surface may cause heating damage.

Mike

You do not need much insulation to hold off 6 to 7kV RMS, in dry conditions a few mm of polyethylene will do. (there are cables that put 50kV DC between the inner and outer of URM67 without issue, except at the ends where the connection needs to be re-entrant by 2-3 inches) The problem with anything outdoors  is the tracking over a surface with dust, or mud and a little moisture leading to local heating and a far longer fault path is needed to avoid this.
And given the higher voltage means the current that flows via  boot leather, clothing,  etc is enough to do serious injury, (as well as set fire to the boots with your feet in them).

Hence the shiny and ribbed water shedding shapes on insulators, and even then you sometimes see flashover when there is a cloud of pollen or a dust storm in just the wrong place. (its not unknown for lines to trip near where there has been dust from explosive demolition, especially of chimneys and so on where the dust is sooty and partly conducting.)

Insulating the wires of the 11kV and 33kV  networks has been considered, and is already done in high risk places, but is far from universal, and not without problems of its own, damaged insulation can trap water and the wire rots, and again, current tracking over the insulation surface may cause heating damage.

Mike