My inner engineer is saying only a few CM or single digit inches at 60kV, but that is under good conditions. Stuff can always happen (like static discharges) that will jump across a larger gap and once the low current arc is started it will keep going.
Safety margins of 10-15 feet are entirely reasonable, while it doesn't seem that the phases are spaced that far apart up on the poles (I think). The really high voltage major distribution lines probably are. Higher up off the ground too.
Spacing inside gear for 120V primary wiring is like 1/4" and sparks won't jump 1/4" at 120V, but stuff happens so that is the standard.
Who in his right mind will admit publicly to bumping into a power line? Especially somebody who should know better? The press reports I saw said they did not touch. It is an unfortunate accident and hopefully getting burned once is enough.
JR
