Program Policy Manual - VOLUME V - Mine Safety and Health ...

MSHA PROGRAM POLICY MANUAL VOLUME V
Portable tools and appliances that are protected by an approved
system of double insulation, or its equivalent, need not be
grounded. Where such an approved system is employed, the
equipment will be distinctly marked.
77.703 Grounding Frames of Stationary High-Voltage Equipment
Receiving Power From Ungrounded Delta Systems
The term "ungrounded," as used in Sections 77.701-1, 77.703,
77.704-1(a) and 77.704-11, refers to the type of system grounding.
The term does not refer to the grounding of metallic enclosures of
electric equipment and circuits.
77.703-1 Approved Methods of Grounding
The grounding methods approved for grounding metallic enclosures
of equipment receiving power from ungrounded alternating-current
power systems (Section 77.701-1) are acceptable for grounding the
metallic enclosures of stationary high-voltage equipment receiving
power from ungrounded delta systems, provided the requirements of
Sections 77.802 and 77.810 are also met.
77.704 Work on High-Voltage Lines; Deenergizing and
Grounding
High-voltage lines shall be deenergized with a disconnecting device
so that it can be determined by visual observation that the circuit
is deenergized before the lines are grounded (refer to Section
77.704-9 when operating disconnecting devices), except that repairs
may be permitted on energized high-voltage lines as specified in the
regulations.
77.704-1 Work on High-Voltage Lines
There may be instances where one qualified electrician will go
back some distance from the work site and deenergize and ground
the high-voltage system to be repaired. This qualified
electrician must be in either direct telephone or radio
communication with the qualified electrician performing the actual
work, and when he/she has deenergized and grounded the system,
he/she can inform the qualified electrician to make the repairs.
77.704-8 Protective Equipment; Testing and Storage
Tested gloves that are not in use and kept in a storeroom or
warehouse shall be given the same consideration as new gloves.
77.705 Guy Wires; Grounding
Guy wires attached to poles supporting high-voltage
transmission lines must either be securely connected to the
system ground or provided with insulators installed near the
pole end as required by 30 CFR 77.705. One of the safety
purposes of this requirement is to ensure that guy wires do not
become energized so that a shock hazard is presented to persons
February 2003 (Release V-33) 187