(a) Underground.--High-voltage cables leading underground and extending underground shall be of the multiple conductor flame-resistant type with a rubber, plastic or armor sheath meeting the requirements of the department for flame resistance. They shall be equipped with metallic shields around each power conductor. One or more ground conductors shall be provided of a total size either:

There shall also be provided an insulated conductor not smaller than No. 10 AWG for the ground-continuity check circuit. Cables shall be adequate for the intended current and voltage. Splices made in the cable shall provide continuity of all components and shall be made in accordance with the cable manufacturers' recommendations. A competent individual designated by the mine electrician shall supervise the making of splices.

(b) Subject to flexing.--High-voltage cables subject to repeated flexing shall be similar in construction to type SH-D in accordance with Insulated Power Cable Engineers Association standard S-19-81.

(c) Couplers.--If couplers are used, they shall be of the three-phase type with a full metallic shell and shall be adequate for the voltage and current expected. All exposed metal on the couplers shall be grounded to the ground conductor in the cable. The coupler shall be constructed so that the ground continuity conductor shall be broken first and the ground conductor shall be broken last when the coupler is being uncoupled.

(d) Equipment passing over or under cable.--At locations where cables cross haulageways or travelways or where equipment must pass over or under the cable, the cables shall be either installed in a trench in the roof, protected by some mechanical means or buried at least 12 inches below combustible material and adequately protected from crushing by the weight of equipment passing over it.

(e) Location of installation.--High-voltage cables shall be installed only in intake airways. They may be installed on intake haulageways only with the approval of the department. The cable may be installed by hanging on suitable hooks or clamps, supported by a suitable messenger cable, burying or installing in metal conduit. When suspended, the distance between supports shall not exceed 20 feet, and they shall be so placed that they do not damage the cable jacket. When hung in a haulage entry containing a trolley wire, the cable shall be installed at least 12 inches from the trolley wire or feeder wires and away from the track.

(f) Excess cable.--Any excess cable which is connected and supplying a load shall be coiled, stored on a reel or otherwise stored at a place near the load where it can be protected by dangering off the storage area. The cable shall not exceed 1,000 feet in length.

(g) Frames and enclosures.--Frames and enclosures of high-voltage switch units, transformers, metallic cable couplers and splice boxes shall be grounded to the common or primary ground for the system in the high-voltage cable.

(h) Taps or branch circuits.--Taps or branch circuits from the high-voltage feeder shall be made through circuit breakers or suitable load break switches.

(i) Non-load-breaking disconnect switches.--When non-load-breaking disconnect switches are used for sectionalizing high-voltage circuits, they shall be fully metal clad, equipped with a door interlock to break the ground-continuity check circuit, thus tripping the feeding breaker when the door is open, and a voltmeter or indicating lights to verify that the circuit is de-energized before the disconnected switches are opened.

(j) Applicability.--For the purpose of interpretation and compliance with subsection (h) and section 313(h),¹ the following apply: