30 CFR § 77.807-3
Movement of equipment; minimum distance from high-voltage lines.
When any part of any equipment operated on the surface of any coal mine is
required to pass under or by any energized high-voltage powerline and the
clearance between such equipment and powerline is less than that specified in
for booms and masts, such powerlines shall
be deenergized or other precautions shall be taken.