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

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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
MSHA PROGRAM POLICY MANUAL VOLUME V on the ground. Therefore, when insulators are installed, they must be located below or extend below all high-voltage lines supported by the pole. The in-line insulator, if used, should be at least 8 feet from the ground, according to the National Electrical Safety Code, 1973. A guy wire connected to a pole butt ground which is not connected to the system ground would be an example of noncompliance with this Section. February 2003 (Release V-33) 188
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