Program Policy Manual - VOLUME V - Mine Safety and Health ...

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MSHA PROGRAM POLICY MANUAL VOLUME V circuits as required by Sections 75.803 and this Section. 77.803-2 Ground Check Systems Not Employing Pilot Check Wires; Approval by the Secretary High-voltage trailing cables used with ground check systems not employing ground check wires, as provided in this Section, are not required to be equipped with installed ground check conductors. 77.805 Cable Couplers and Connection Boxes; Minimum Design Requirements Existing medium- and high-voltage cable couplers that are not equipped with a terminal contact for the ground check conductor may be used if suitable means are provided for breaking the ground check conductor first when the coupler is being uncoupled. Suitable means include the installation of a locking switch on the coupler so that the coupler cannot be uncoupled until the ground check conductor is broken, or the installation of an external ground check connector on the coupler so that the ground check conductor is broken first when the coupler is being uncoupled. Except for connections made inside cable connection boxes, totally enclosed metal switchhouses, etc., this Section expressly prohibits the use of single-pole couplers (Miller plugs) in medium- or high-voltage power circuits. 77.808 Disconnecting Devices A "branch line" means a circuit that is formed by connection to an existing high-voltage circuit for the purpose of feeding branch loads. "Visual observation," as referred to in this Section, means that a physical separation in the current-carrying parts of the disconnecting device can actually be seen. Enclosed circuit breakers, oil-filled cutout switches, and other devices which do not have a visual means of determining that the circuit is deenergized do not meet the requirements of this Section. A cable coupler or other device that is not designed for loadbreak purposes is not acceptable as a disconnecting device unless it is used in conjunction with a current-interrupting device such as a circuit breaker or oil-filled cutout which can be used to deenergize the circuit before the cable coupler or other device is opened. If a remote switch in the ground check circuit is used to trip a circuit breaker prior to uncoupling the coupler, visual or audible evidence must be provided to indicate that the circuit breaker has opened when the control switch is operated. February 2003 (Release V-33) 191
MSHA PROGRAM POLICY MANUAL VOLUME V 77.809 Identification of Circuit Breakers and Disconnecting Switches The identifying markers for circuit breakers and disconnecting switches shall be large enough and located where they can be readily seen in the event that the circuit must be deenergized quickly. Either metallic or plastic material may be used for the marker which should adequately identify the circuit (e.g., No. 1 Loader, Dragline, No. 1 Transformer Skid, etc.). Where cable couplers are used in conjunction with currentinterrupting devices to meet the requirements of Section 77.808, both the cable coupler and the current-interrupting device shall be labeled. 77.810 High-Voltage Equipment; Grounding "Effectively grounded," as used in this Section, means that the frames, supporting structures and enclosures of high-voltage equipment are grounded in a manner that will prevent lethal voltages from appearing on such equipment during ground fault conditions. The frames, supporting structures and enclosures of high-voltage equipment receiving power from a system, required by Section 75.802 or Section 77.802 to be resistance grounded, shall be considered effectively grounded only when they are grounded in accordance with the resistance grounding requirements contained in Section 75.802. The frames, supporting structures and enclosures of stationary high-voltage equipment receiving power from a resistance-grounded power system other than a system which is required to be resistance grounded by Section 75.802 or Section 77.802 shall be considered effectively grounded provided: 1. Such frames, structures and enclosures are solidly connected to a grounding conductor which originates at the grounded side of the grounding resistor, extends along with the power conductors and serves as the grounding conductor for the frames, supporting structures and enclosures of all high-voltage equipment supplied power from the system; and 2. The grounding conductor is solidly connected to a ground field at the power source and at each utilization location. February 2003 (Release V-33) 192
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Program Policy Manual - VOLUME V - Mine Safety and Health ...

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