The minimum clearance requirements for overhead conductors depend on their voltage class and what they are hanging over. Note that engineering considerations and intended use might make higher minimums legally obligatory. If in doubt, make more space.
If the conductors are not over buildings, they must meet one of five enumerated clearances and voltage limits. For example, over residential property and driveways the clearance is 12 ft if the voltage is 300V or less (higher voltage means greater clearance).
If the conductors are over buildings, Sec. 225.19 applies. This is fairly complex; the rules for roofs [225.19] have four Exceptions. You must provide 3 ft of clearance from nonbuilding and nonbridge structures such as signs, chimneys, and TV antennas. You must also provide 3 ft of horizontal clearance.
Final spans must be at least 3 ft from windows that are designed to be opened. And they can’t be installed beneath openings through which material may move or such that they obstruct building openings.
If buildings exceed three stories, you must arrange the overhead conductors (where practicable) to facilitate the raising of fire ladders [per spacing denoted in 225.19(E)].
