(1) “Approved” means in strict compliance with this act or, in the absence of specific mention, approved by the secretary.

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

(3) “Borehold cable” is a cable designed for vertical suspension in a borehole or shaft and is used for power circuits in the mines.

(4) “Branch circuit” shall be any tap taken off a main circuit.

(5) “Cable sheath (non-metallic)” is a covering consisting of composition tapes, compound jackets of natural or synthetic rubber, thermoplastic or fiber braids applied over the conductor assembly and insulation of multiple conductor cables.

(6) “Cable shield” is a metallic shield consisting of nonmagnetic material applied over the insulation of the individual conductors.

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

(8) “Delta-connected” a delta-connected power system is one in which the unlike ends of windings of three phase A.C. generators, motors or transformers are connected to form a triangular phase relationship, and with external conductors connected to each point at the triangle.

(9) “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 such a system and the earth, as determined by a voltmeter or other suitable instrument. The terms “potential” and “voltage” are synonymous and mean electrical pressure.

(10) “Disconnecting switch” is a form of air switch used for opening the circuit. It has no interrupting rating and is to be operated only after the circuit has been opened by some other means.

(11) “Effectively grounded” is an expression which means 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.

(12) “Electric system” means all electric equipment and circuits that pertain to the operation of the mine and are under control of the mine management.

(13) “Electrical face equipment” is mobile or portable mining machinery having electric motors or accessory equipment normally installed or operated in by the last open crosscut.

(14) “Explosion or flameproof equipment” explosion or flameproof casings or enclosures are those which, when completely filled with a mixture of methane and air, and the same exploded, are capable of either entirely confining the products of such explosion within the casing or of so discharging them from the casing 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 therewith.

(15) “Flame-resistant cable, portable” is a portable cable that has met the department requirement for flame resistance and has been assigned an approval number (P-number).

(16) “Ground (earth)” is 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.

(17) “Ground or grounding conductor (mining)” a grounding conductor (also referred to as a safety ground conductor, safety ground and frame ground) is a metallic conductor used to connect the metal frame or enclosure of an equipment, device, or wiring system, with an effective grounding medium.

(18) “Lightning arrestor” is a protective device for limiting surge voltages on equipment by discharging or bypassing surge current; it prevents continued flow of follow current to ground and is capable of repeating these functions as specified.

(19) “Machine operator” a qualified person who is placed in charge of operating a portable or mobile face machine of any sort.

(20) “Mine power center” is a combined transformer and distribution unit complete within a metal enclosure, from which one or more low voltage or medium voltage power circuits are taken.

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

(22) “Neutral point” in a wye-connected A.C. power system means 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.

(23) “Nonmetallic armor” means 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.

(24) “Portable (trailing) cable” is 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 is impractical.

(25) “Portable electrical equipment” consists of motors and their control equipment and other electrical devices, so constructed or mounted as to facilitate moving them from place to place.

(26) “Potential of a circuit” the potential or voltage of a circuit, machine, or any piece of electrical apparatus, is the electrical pressure normally existing between the conductors of such circuit or the terminals of such machine or apparatus.

(27) “Primary ground” is 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 and/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.

(28) “Protection (electrical)” is provided by fuses or other suitable automatic circuit interrupting devices for preventing damage to circuits, equipment and personnel by abnormal conditions, such as overcurrent, high or low voltage and single-phasing.

(29) “Rectifiers” as referred to in this law mean alternating current to direct current power conversion devices of the mercury are or semiconductor (silicon, selenium or other) type.

(30) “Sectionalizing switch” is a switch used for connecting or disconnecting low or medium voltage supply lines in sections of a mine.

(31) “Wye-connected (Y connected)” a wye-connected power system is a system in which the like ends of each phase winding of the three phase A.C. generators, motors or transformers are connected together to form a neutral point and other ends connected to external conductors.

(32) “Zig-zag transformer (grounding transformer)” is 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.