A. Every metallic sheath, armor, or conduit that encloses a power conductor shall be electrically continuous throughout and shall be grounded effectively.
B. Every metallic frame, casing, or other enclosure of stationary electrical equipment that can become electrified through failure of insulation or by contact with energized parts shall be grounded effectively, or equivalent protection shall be provided.
C. Any three-phase alternating current circuit that is used underground shall contain either a direct or derived neutral that shall be grounded through a suitable resistor at the power center. A grounding circuit that originates at the grounded side of the grounding resistor shall extend with the power conductors and serve as the grounding conductor for the frame of every piece of electrical equipment that is supplied with power from that circuit. A grounding resistor that is manufactured to meet the extended time rating as set forth in American National standard IEEE C57.32-2015 is deemed to meet the requirements of this section. High-voltage circuits extending underground shall be supplied with a grounding resistor of a proper Ohmic value located on the surface to limit the voltage drop in the grounding circuit external to the resistor to not more than 100 volts under fault conditions. Such grounding resistor shall be rated for maximum fault current continuously and insulated from ground for a voltage equal to the phase-to-phase voltage of the system. Every resistance-grounded alternating circuit used underground shall include a fail-safe ground check circuit to monitor continuously the grounding circuit to ensure the continuity of the ground conductor.