The outer material 'insulation' must resemble the techniques used in space *re-entry; the Teflon™ features its ability to adhere at (the expected temp-gradient of a brief encounter with passing greenery/or a falling [right-sized if you're lucky] branch.
* the ablative mixes used on descending space capsules seems to be ~square-one; it's still cheaper than ..2017 to now. Looking..

Nothing can protect against an inferno right under the cable, of course. Undergrounding is a mare's nest. Unacceptable is:
the present flailing about on a 'net' whose switching/routing-inflexibility is the most visible culprit.