30 CFR § 75.705
Work on high-voltage lines; deenergizing and grounding.
High-voltage lines, both on the surface and underground, shall be deenergized
and grounded before work is performed on them, except that repairs may be
permitted, in the case of energized surface high-voltage lines, if such
repairs are made by a qualified person in accordance with procedures and
safeguards, including, but not limited to, a requirement that the operator of
such mine provide, test, and maintain protective devices in making such
repairs, to be prescribed by the Secretary prior to March 30, 1970.