Re: working clearance
It would appear that 110.34(A) would apply, even though it reads like the equipment is inside. Note that the exposed live parts are energized at the higher voltages. Also, 110.31 talks about clearances from fences to equipment.
I am curious what kind of equipment are you refering to? Most breakers, regulators, LTC,s, that I am used to don't have exposed high voltage parts unless they are elevated.
Jim T