30 CFR § 75.825 - Power centers.
(a) Main disconnecting switch. The power center supplying high voltage power to the continuous mining machine must be equipped with a main disconnecting switch that, when in the open position, de-energizes input to all power transformers.
(b) Trailing cable disconnecting device. In addition to the main disconnecting switch required in paragraph (a) of this section, the power center must be equipped with a disconnecting device for each circuit that supplies power to a high-voltage continuous mining machine. A disconnecting device is defined as a disconnecting switch or a cable coupler.
(c) Disconnecting switches. Each disconnecting switch must be labeled to clearly identify the circuit it disconnects, and be designed and installed as follows:
(1) Rated for the maximum phase-to-phase voltage of the circuit;
(2) Rated for the full-load current of the circuit that is supplied power through the device.
(3) Allow for visual observation, without removing any covers, to verify that the contacts are open;
(4) Ground all power conductors on the load side when the switch is in the “open and grounded” position;
(5) Can only be locked out in the “open and grounded” position; and
(6) Safely interrupts the full-load current of the circuit or causes the current to be interrupted automatically before the disconnecting switch opens.
(d) Barriers and covers. All compartments that provide access to high-voltage circuits must have barriers and/or covers to prevent miners from contacting energized high-voltage circuits.
(e) Main disconnecting switch and control circuit interlocking. The control circuit must be interlocked with the main disconnecting switch in the power center so that:
(1) When the main disconnecting switch is in the “open” position, the control circuit can only be powered through an auxiliary switch in the “test” position; and
(2) When the main disconnecting switch is in the “closed” position, the control circuit can only be powered through an auxiliary switch in the “normal” position.
(f) Interlocks. Each cover or removable barrier providing access to high-voltage circuits must be equipped with at least two interlock switches. Except when the auxiliary switch is on the “test” position, removal of any cover or barrier that exposes energized high-voltage circuits must cause the interlock switches to automatically de-energize the incoming circuit to the power center.
(g) Emergency stop switch. The power center must be equipped with an externally accessible emergency stop switch hard-wired into the incoming ground-wire monitor circuit that de-energizes the incoming high-voltage in the event of an emergency.
(h) Grounding stick. The power center must be equipped with a grounding stick to be used prior to performing electrical work to assure that high-voltage capacitors are discharged and circuits are de-energized. The power center must have a label readily identifying the location of the grounding stick. The grounding stick must be stored in a dry location.
(i) Caution label. All compartments providing access to energized high-voltage conductors and parts must display a caution label to warn miners against entering the compartments before de-energizing incoming high-voltage circuits.