All electric circuits shall have a grounding system. The system shall protect people from injuries or fatal shock on inadvertent contact. The system shall limit the voltage on all electrical equipment with noncurrent-carrying metallic parts. Grounding of ac and do equipment shall be in accordance with 29 CFR 1910.304(f).

Equipment grounding conductors shall comply with the standards expressed in 29 CFR 1910.304(f)(6)(i).

All installations, modifications, or repairs pertaining to grounding systems shall be followed by a continuity test to ensure the integrity of the systems. The frequency and requirements of he review shall conform to 30 CFR 57.12028.

5.10.3 POWER CABLES AND CONDUCTORS

Cables and insulated conductors shall be protected against physical damage, adverse environmental conditions, and failure of adjacent mechanical equipment.

Cables and insulated conductors shall not be supported from or be in contact with pipelines. Sufficient clearance between pipelines and cables is required to prevent shock hazards when maintenance activities are being performed. A minimum clearance of 10 ft above floor level shall be maintained for all overhead cables/conductors overhead not protected against physical damage as set forth in 29 CFR 1910.304(c)(2)(i).

Electric conductors shall be of a size and current carrying capacity to ensure that a rise in ambient temperature does not exceed the rating of the insulation and conductors. The capacities of electric conductors supplying electrical equipment shall be in accordance with the tables set forth in the NEC (NFPA 70), Article 310. In the case of medium- or high-voltage cable, the manufacturer's ratings shall not be exceeded.

Splices, terminations, and repairs of electric conductors and power cables shall be permitted and shall conform to the requirements expressed in 29 CFR 1910.303(c).

Surge arresters and lightning protection are required for underground facilities and shall conform to the requirements found in 30 CFR 57.12069 and 75.521. Lightning arresters shall be inspected for damage at least annually or after each electrical storm.

Power cables and insulated conductors in shafts and bore holes shall be supported. Support structures and guy wires and supports for cables and conductors shall conform with the requirements expressed in 30 CFR 57.12083.

5.10.4 TRAILING CABLES

Trailing cables used in electrical systems of mines shall meet requirements expressed in 30 CFR 57.12038, 75, and 77, Subparts G.

Each trailing cable of portable and mobile equipment shall have short-circuit and ground-fault protection for each ungrounded conductor. Protective devices shall safely interrupt all ungrounded conductors under fault conditions. Requirements for over current protection of each ungrounded conductor shall be those expressed in 30 CFR 57.12003, 75, and 77, Subparts G.

Trailing cables shall be attached to equipment so that strain on electrical connections does not occur and damage to cable jacket and internal conductor insulation is prevented. Portable distribution boxes can be used and shall meet the requirements in 30 CFR 57.12006 and 57.12007. Trailing cables and power conductors shall be protected against physical damage from mobile equipment by using bridges, trenches, or suspension from the mine roof.

Disconnecting devices for trailing cables shall be equipped with means for attaching a padlock for LO/TO purposes per 30 CFR 57.12016, 57.12017, 75.511, and 77.501.

5.10.5 TROLLEY CIRCUITS FOR TRACK HAULAGE

Trolley wires and exposed trolley-feeder wires shall be installed and maintained in accordance to the requirements in 30 CFR 57.12050, 57.12086, and 30 CFR 75, Subpart K.

Trolley wires and trolley-feeder wires shall be protected against over current in accordance to the requirements of 30 CFR 57.12001 and 75.1001.

Track serving as the trolley circuit return shall be bonded or welded according to the requirements of 30 CFR 57.12042 and 75, Subpart K. Energized trolley wires and exposed trolley-feeder wires shall be guarded in places where accidental contact with them is possible. This includes areas where supplies are stored, loaded, or unloaded.