30 CFR § 77.704
Work on high-voltage lines; deenergizing and grounding.
High-voltage lines shall be deenergized and grounded before work is performed
on them, except that repairs may be permitted on energized high-voltage lines
if (a) such repairs are made by a qualified person in accordance with
procedures and safeguards set forth in §§77.704-1
77.704-11 of this Subpart H as applicable, and (b) the operator has tested
and properly maintained the protective devices necessary in making such