Power Cables and Conductors

DOE-HDBK-1092-98

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.

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