77.701 Grounding Metallic Frames, Casings, and Other Enclosures of Electric Equipment
Certain moveable electric equipment, e.g., rail-mounted and pivoting coal stackers, traveling shop cranes on track rails, small traveling hoists on I beams, etc., cannot be strictly classified as portable, mobile or stationary equipment. For the purposes of frame grounding, such equipment shall be considered stationary. Consequently, the grounding requirements of Subpart H apply to such equipment.

This Section requires that metallic frames of electric equipment be grounded by methods approved by an authorized representative of the Secretary. Therefore, rail-mounted and pivoting coal stackers, traveling shop cranes on track rails, small traveling hoists on I beams, and similar equipment shall be grounded in accordance with the following:

All tracks shall be bonded or welded at each joint, and each individual track rail or I beam shall be solidly grounded through a grounding conductor which meets the requirements of Section 77.701-3 to an acceptable grounding medium. In instances where the conveyor, hoisting and/or tramming motors receive power through a trailing cable, the moving frame shall be grounded to an acceptable grounding medium through a proper size grounding conductor inside the cable. In instances where the conveyor, hoisting and/or tramming motors receive power through a trolley system, the moving frame shall be grounded to an acceptable grounding medium through an additional grounding trolley contact.

77.701-1 Approved Methods of Grounding of Equipment
Receiving Power From Ungrounded Alternating-Current Power Systems The metallic enclosures of all equipment supplied power from the same system must be solidly connected to the same grounding medium.

77.701-2 Approved Methods of Grounding Metallic Frames, Casings and
Other Enclosures of Electric Equipment Receiving Power from
a Direct-Current Power System
Paragraph (b) requires that metal battery trays be solidly connected to the grounded frame of the battery charger while the batteries are being charged.

77.702 Protection Other Than Grounding
Portable tools and appliances that are protected by an approved system of double insulation, or its equivalent, need not be grounded. Where such an approved system is employed, the equipment will be distinctly marked.

77.703 Grounding Frames of Stationary High-Voltage
Equipment Receiving Power From Ungrounded Delta Systems The term "ungrounded," as used in Sections 77.701-1, 77.703, 77.704-1(a) and 77.704-11, refers to the type of system grounding. The term does not refer to the grounding of metallic enclosures of electric equipment and circuits.

77.703-1 Approved Methods of Grounding
The grounding methods approved for grounding metallic enclosures of equipment receiving power from ungrounded alternating-current power systems (Section 77.701-1) are acceptable for grounding the metallic enclosures of stationary high-voltage equipment receiving power from ungrounded delta systems, provided the requirements of Sections 77.802 and 77.810 are also met.

77.704 Work on High-Voltage Lines; Deenergizing and Grounding
High-voltage lines shall be deenergized with a disconnecting device so that it can be determined by visual observation that the circuit is deenergized before the lines are grounded (refer to Section 77.704-9 when operating disconnecting devices), except that repairs may be permitted on energized high-voltage lines as specified in the regulations.

77.704-1 Work on High-Voltage Lines
There may be instances where one qualified electrician will go back some distance from the work site and deenergize and ground the high-voltage system to be repaired. This qualified electrician must be in either direct telephone or radio communication with the qualified electrician performing the actual work, and when he/she has deenergized and grounded the system, he/she can inform the qualified electrician to make the repairs.

77.704-8 Protective Equipment; Testing and Storage
Tested gloves that are not in use and kept in a storeroom or warehouse shall be given the same consideration as new gloves.

77.705 Guy Wires; Grounding
Guy wires attached to poles supporting high-voltage transmission lines must either be securely connected to the system ground or provided with insulators installed near the pole end as required by 30 CFR 77.705. One of the safety purposes of this requirement is to ensure that guy wires do not become energized so that a shock hazard is presented to persons on the ground. Therefore, when insulators are installed, they must be located below or extend below all high-voltage lines supported by the pole.

The in-line insulator, if used, should be at least 8 feet from the ground, according to the National Electrical Safety Code, 1973.

A guy wire connected to a pole butt ground which is not connected to the system ground would be an example of noncompliance with this Section.

Subpart I .... Surface High-Voltage Distribution

77.800 High-Voltage Circuits; Circuit Breakers
High-voltage circuits supplying power to portable or mobile alternating-current equipment shall be protected against the harmful effects of a grounded phase in any circuit connected to the same transformer secondary. Consequently, if one bank of transformers supplies power to both stationary and portable or mobile loads, the circuit(s) extending to the stationary loads, as well as the circuit(s) extending to the portable or mobile loads, shall be provided with grounded phase protection.

Grounded phase protection for resistance-grounded circuits should be adjusted to operate on as low a value of fault current as practical; preferably not more than 40 percent of the current rating of the neutral grounding resistor.

77.800-1 Testing, Examination, and Maintenance of Circuit Breakers; Procedures
Paragraph (c) does not require the tank surrounding the oil circuit breakers to be dropped during this examination unless there is doubt of the qualified person making this examination as to conditions inside the tank.

77.802 Protection of High-Voltage Circuits; Neutral Grounding Resistors;
Disconnecting Devices
The exception in this Section applies to high-voltage systems which supply power to stationary surface equipment only. Consequently, if a high-voltage system supplies power to equipment located underground in a mine, as well as equipment located on the surface, the frames of all equipment supplied power from the system shall be grounded in accordance with Section 75.802. Likewise, if a high-voltage system supplies power to portable or mobile equipment located on the surface, as well as stationary equipment located on the surface, the frames of all equipment supplied power from the system shall be grounded in accordance with the resistance grounding requirements of this Section.

77.803 Fail Safe Ground Check Circuits on High-Voltage Resistance-Grounded Systems
The ground check circuit required by this Section shall cause the circuit breaker to trip when any of the following occur:

1. The ground check wire is broken; and

2. Either the ground wire is broken at any point, or the impedance of the grounding circuit increases beyond the amount necessary to cause a 100-volt drop in the grounding circuit external to the grounding resistor under ground fault conditions.

This Section permits the approval of a no less effective device in lieu of a fail safe ground check circuit. The following alternate method shall be considered no less effective than a fail safe ground check circuit for assuring the continuity of the grounding circuit extending to permanently installed stationary equipment which is supplied power from a high-voltage resistance-grounded system:

1. An equipment grounding conductor, sized in accordance with Section 77.701-3, shall originate at the grounded side of the grounding resistor and shall extend along with the power conductors and shall serve as a grounding conductor for the frames of all equipment receiving power from the resistance-grounded system.

2. A grounding electrode conductor shall connect the frames of the stationary equipment to a low resistance ground field located near the utilization location.

3. The ohmic value of the grounding resistor and the impedance of the low resistance ground field shall be maintained in such a manner that not more than 100 volts will appear between the equipment frame and earth under fault conditions in the event that the equipment grounding conductor should be severed.

4. The ohmic value of the grounding resistor and the impedance of the ground field to which the grounding resistor is grounded shall be maintained in such manner that not more than 100 volts will appear between the grounded side of the grounding resistor and earth under fault conditions in the event that the equipment grounding conductor should be severed.

5. This method for assuring the continuity of grounding circuits shall not be approved for high-voltage circuits which supply power to high-voltage equipment underground in a mine or to portable or mobile high-voltage equipment on the surface. The continuity of such grounding circuits shall be continuously monitored by fail safe ground check circuits as required by Sections 75.803 and this Section.

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 groundcheck 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 load-break 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.

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 current-interrupting 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.

1. Such frames, structures and enclosures are solidly connected to a neutral conductor which originates at the neutral point of the power source, 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 neutral conductor is solidly connected to a ground field at the power source and at each utilization location.

77.900 Low- and Medium-Voltage Circuits Serving Portable or Mobile Three-Phase Alternating-Current Equipment; Circuit Breakers
Low- and medium-voltage circuits supplying power to portable or mobile three-phase alternating-current equipment shall be protected against the harmful effects of a grounded phase in any circuit connected to the same transformer secondary.Consequently, if one bank of transformers supplies power to both stationary and portable or mobile loads, the circuits, extending to the stationary loads, as well as the circuits extending to the portable or mobile loads, shall be provided with grounded phase protection.

Grounded phase protection for resistance-grounded circuits should be adjusted to operate on as low a value of fault current as practical; preferably not more than 40 percent of the current rating of the neutral grounding resistor.

77.902 Low- and Medium-Voltage Ground Check Monitor Circuits
The ground check circuit required by this Section shall cause the circuit breaker to trip when any of the following occur:

1. The ground check wire is broken. Existing low- and medium-voltage cable couplers that are not provided 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.

2. Either the ground wire is broken at any point, or the impedance of the grounding circuit increases beyond the amount necessary to cause a 40-volt drop in the grounding circuit external to the grounding resistor under ground fault conditions.

77.904 Identification of Circuit Breakers
Either metal or plastic tags may be used to identify circuit breakers if they are attached securely to the circuit breaker enclosure and are large enough and placed so that they can be readily seen. The trailing cable should also be identified with the circuit breaker.

77.906 Trailing Cables Supplying Power to Low-voltage Mobile Equipment; Ground Wires and Ground Check Wires
Low-voltage trailing cables used with ground check systems not employing ground check wires, as provided in Section 77.902-2,are not required to be equipped with insulated ground checkconductors.

Subpart K .... Ground Control

77.1004 Ground Control; Inspection and Maintenance; General
If an area is posted in accordance with paragraph (b), such posting shall be done in a manner to ensure that any worker in the area would be immediately aware of the hazard.

77.1005 Scaling Highwalls; General
The phrase, "The material removed from a safe location," as used in paragraph (b), means that the person who is removing the material must be in a safe location.

77.1006 Highwalls; Men Working
"Special safety precautions," as used in paragraph (c), shall include a thorough examination of the highwall or spoil bank for dangerous conditions and, if dangerous conditions are found, they shall be corrected before miners are permitted to work in such areas.

77.1008 Relocation of Drills; Safeguards
This Section does not apply when moving from hole to hole in a series, but the requirements apply when moving from one general area to another.

77.1009 Drills; Operation
Should an inspector observe a drill in operation with the controls unattended, enforcement action under this Section should be taken.

Subpart L .... Fire Protection

77.1100 Fire Protection; Training and Organization
The fire fighting organizational plan should include a list of the persons trained and a written plan for extinguishing a fire if one should occur. The written plan should include a list and location of fire fighting equipment. The scope of the training shall be commensurate with the size of the buildings and machinery involved and related to the number of employees.Further information can be obtained from the Fire Protection Handbook published by the National Fire Protection Association,Section II.

77.1101 Escape and Evacuation; Plan
The escape and evacuation plan should be written and posted in a proper location.

The requirements of paragraph (a) refer primarily to surface structures such as preparation plants, drawoff tunnels, shops,and other buildings where persons work. When applying this Section at surface mines, the inspector shall be cognizant of the potential fire hazard at surface mines and require only those means of escape commensurate with the hazard.

Paragraph (b) requires that all employees, including office and clerical personnel, shall be instructed on the current escape and evacuation plan, fire alarm signals, and applicable procedures.

Judgment should be used in enforcing paragraph (c) regarding the maintaining of exits from areas where persons are required to work or travel. For example, small washrooms and certain offices may be equipped with one exit as is common practice in surface buildings. However, large offices, generally those housing three or more people, wash and change houses, plants, shops, lunch-rooms, etc., shall have at least two exits. "Means for exit from all areas" means a continuous and unobstructed way of exit from any point in the building to a public way. The exits should be marked by readily visible signs, and every exit should be suitably illuminated. Should questions arise relative to the number, location, and design of exits, the National Fire Protection Code No. 101 and the Fire Protection Handbook shall be used for references.