As used in this chapter, the following words and terms shall have the meanings given to them in this section unless the context clearly indicates otherwise:

“Armored cable.” A cable provided with a wrapping of metal, usually steel wires or tapes, primarily for the purpose of mechanical protection.

“Borehole cable.” A cable designed for vertical suspension in a borehole or shaft and is used for power circuits in a mine.

“Branch circuit.” A tap taken off a main circuit.

“Cable sheath.” A covering consisting of composition tapes, compound jackets of natural or synthetic rubber or thermoplastic or fiber braids applied over the conductor assembly and insulation of multiple conductor cables.

“Circuit breaker.” A device which may be controlled by relaying or protective equipment for interrupting a circuit between separable contacts under normal or abnormal conditions.

“Delta-connected.” A delta-connected power system is one in which the windings of transformers or AC generators are connected to form a triangular phase relationship with the phase conductors connected to each point of the triangle.

“Difference of potential.” The difference of electrical pressure or electromotive force existing between any two points of an electrical system, or between any point of a system and the earth, as determined by a voltmeter or other suitable instrument.

“Effectively grounded.” Grounded through a grounding connection of sufficiently low impedance, inherent or intentionally added, or both, so that fault grounds which may occur cannot build up voltages in excess of limits established for apparatus, circuits or systems so grounded.

“Electric system.” All electric equipment and circuits that pertain to the operation of the mine and are under control of the mine management.

“Electrical face equipment.” Mobile or portable mining machinery having electric motors or accessory equipment normally installed or operated inby the last open crosscut in any entry or room.

“Explosion-proof or flame-proof.” Casings or enclosures which, when completely filled with a mixture of methane and air and the same exploded, are capable of either entirely confining the products of the explosion within the casing or discharging them from the casing so that they cannot ignite a mixture of methane and air combined in proportions most sensitive to ignition and entirely surrounding the points of discharge and in most intimate proximity with the points of discharge.

“Flame-resistant cable.” A cable that meets the MSHA testing requirements for flame resistance and has been assigned an approval. A cable shall also be considered flame resistant if it meets the criteria for flame resistance by a nationally recognized testing lab that is equivalent to the MSHA testing criteria and that is appropriately identified. All flame-resistant cables used underground shall have the approval number embossed or indented on the jacket at intervals not to exceed 12 feet.

“Ground.” A conducting connection, whether intentional or accidental, between an electric circuit or equipment and earth or to some conducting body which serves in place of the earth.

“Grounding conductor.” A metallic conductor used to connect the metal frame or enclosure of an equipment, device or wiring system with an effective grounding medium.

“High voltage.” Voltage higher than 1,000 volts nominal.

“Lightning arrestor.” A protective device for limiting surge voltages on equipment by discharging or bypassing surge current and for preventing continued flow of current to ground.

“Low voltage.” Voltage up to 660 volts nominal.

“Machine operator.” An individual who possesses a machine runners certification and is placed in charge of a portable or mobile face machine of any sort where a gas examination is required under this act or regulations promulgated under this act.

“Medium voltage.” Voltage from 661 to 1,000 volts nominal.

“Mine power center.” A combined transformer and distribution unit which may include a rectifier, complete within a metal enclosure, from which one or more low-voltage, medium-voltage or high-voltage power circuits are taken.

“Neutral.” A neutral point of connection established through the use of a grounding or zig-zag transformer with a normally ungrounded delta power system.

“Neutral point.” The connection point of transformer or generator windings from which the voltage to ground is nominally zero and is the point generally used for system grounding in a wye-connected AC power system.

“Nonmetallic armor.” A tough outer covering or cable sheath of rubber, rubber compound or thermoplastic designed to protect the cable conductors and insulation from abrasion or other damage from external sources.

“Portable trailing cable.” A flexible cable or cord used for connecting mobile, portable or stationary equipment in mines to a trolley system or other external source of electric energy where permanent mine wiring is prohibited or impracticable.

“Potential of a circuit.” The voltage of a circuit machine or any piece of electrical apparatus is the potential difference normally existing between the conductors of such circuit or the terminals of the machine or apparatus.

“Primary ground.” A low-impedance ground bed or system consisting of several interconnected ground rods or buried conducting mesh, or both, located near an outdoor substation and used as a lightning arrestor or station ground or, separately, as a basic ground for one conductor of a power transmission or distribution system. A single ground rod of any length is not considered a primary ground.

“Protection.” Fuses or other suitable automatic circuit-interrupting devices for preventing damage to circuits, equipment and personnel by abnormal conditions, such as over-current, high- or low-voltage and single phasing.

“Rectifiers.” Alternating current to direct-current power conversion devices of the mercury-arc, silicon, selenium or other type.

“Shielded cable.” A cable in which the insulated conductor is covered with a conductive material for the purpose of clearing ground faults.

“Voltage.” The phase-to-phase or line-to-line root-mean-square value assigned to a circuit or system for designation as its voltage class. Actual voltage at which the circuit or systems operated may vary from the normal voltage with a range, which permits satisfactory operation of the equipment. The difference of electrical pressure or electromotive force existing between any two points of an electrical system, or between any point of a system and earth, as determined by a volt meter or other instrument. The term shall be synonymous with the term potential and shall mean electrical pressure.

“Wye-connected.” A system in which one end of each phase winding of transformers or AC generators are connected together to form a neutral point and the other ends of the windings are connected to the phase conductors.

“Zig-zag transformer.” A three-phase transformer used to provide a neutral point on delta systems and capable of carrying continuously the maximum ground fault current of the system.