CABLES AND CONDUCTORS, AERIAL LINES AND TRAILING CABLES
216. Protection of cables. All conductors and electric lines to control gear which are required to be covered with insulating material except aerial lines and trailing cables shall be enclosed throughout in a metallic covering if the voltage of the circuit exceeds 125 volts alternating current or. 250 volts direct current. This requi-rement is not obligatory in places at the surface of a mine if the voltage of the circuit does not exceed the limits of medium pressure:
Pro~ided that it shall be permissible to use single conductor cables having a continuous sheath of ductile metal, for connections to generating or transforming plant at the surface of the mine, if the said cables are so placed and s.tfeguarded as to prevent danger.
This regulation shall not apply to shot-firing cables.
217. Metallic covering of cables. All metallic coverings shall be constructed, installed and maintained so as to comply with the following requirements:-
(a) The metallic covering shall enclose all the conductors of the Circuit.
(b) The metallic covering shall be electrically continuous throughout.
(c) The metallic covering, including any joints therein, shall have a conductance of not less than half that of the same length of the largest of the live conductors enclosed thereby.
(d) Where the metallic covering ends it shall be securely attached to the metallic structure of the apparatus associated with the conductors which it encloses.
218. Protection of armoured cables, etc. The following requirements shall apply underground to the use, installation and protection of armoured cables and apparatus accessory thereto:-
( a) Cable suspended in shafts, unless adequately protected by position, shall be specially protected against injury by the normal operations of winding or falling material.
Unless the cable is designed to sustain its own weight it shall be secured at such intervals and in such manner as may be necessary to relieve the cable from undue stress.
(b) Cable suspended in roadways shall be placed so as to be reasonably clear of passing traffic, or it shall be specially protected therefrom.
Where cable is suspended it shall ~e supported at sufficiently frequent intervals and in such manner as to avoid undue sag or injury to the cable.
(c) Supporting devices shall not comprise readily ignitable material and they shall be designed to release the cable when subjected to abnormal stress.
Regulations rr. 219-226 89
(d) Where cable is buried, it shall be enclosed in a substantial duct or culvert of concrete or other fireproof construction.
(e) The armouring of cables shall be specially protected against corrosion where necessary.
(f) Where cables are joined or terminated, the insulating material, of whatever description, shall be effectively sealed in a cable sealing and dividing box against access of moisture and the armouring shall be securely attached to the box.
If the cable includes a lead sheath, a gland or clamp shall be used to connect the lead sheath electrically to .the box.
219. Cable joint boxes. Cable joint boxes shall be housed in a recess, 'or otherwise protected effectively against damage by traffic and falls of ground, as may be necessary to prevent danger.
220. Protection of cable joint boxes. Adequate precautions sl).all be taken to protect cables and cable joint boxes from damage while repairs of the roadway are in progress.
221. Joints. All joints in conductors shall be mechanically efficient and electrically continuous. They shall be suitably soldered, except where a mechanical connector is used.
222. Connections to terminals. Conductors shall be connected to terminals only by soldered lugs or approved metal clamps, or terminal block!>.
223. Passing through openings. Where conductors and cables including flexible cables and cords are to be threaded through tubes or channels or passed through openings formed in metalwork, such tubes, channels or openings shall be of ample size, and shall have no sharp edges or projecting edges which would be likely to damage a conductor or the insulating material of a cable. Open ends through which cables pass shall be bushed or so shaped as to prevent abrasion of the insulation of the cables. Where bushes are used, they shall be securely fixed in position.
224. Cable entries to apparatus. All motors, generators and fully enclosed metal clad apparatus shall be provided with suitable glands, screwed apertures or clamps for securing thereto the protective covering of the connected cables or with suitable bushed or shaped apertures for the entry of the cables.
225. Use of insulators. All insulators for the support of cables shall be of ample capacity and of sufficient mechanical strength.
226. Support of unarmoured cables. Unarmoured cables below ground shall-
(a) Not be directly supported on wooden cleats or metallic fastenings;
(b) Be supported on insulators when in damp places;
(c) Be kept clear of roof, floor, and walls and also of any timber or metal supports;
(d) Be suitably bushed where they pass through any stopping or screen.
227. Specifications and regulations applicable to aerial lines. ( 1) All aerial lines and apparatus associated therewith shall be constructed and installed in accordance with the requirements of "The Electric Light and Power·Regulations of 1938" issued under "The Electric Light and Power Acts, 1896 to 1962," the relevant Standard Specifications and Wiring Rules of the Standards Association of Australia, or amendments thereof, ami in vogue at the time of purchase and installation of the conductors and associated apparatus.
228. Power lines near magazines. Aerial lines where near an explosive magazine shall be separated from the latter by a distance of not less than 50 feet, which minimum distance may be increased by the electrical inspector if the span between supports is greater than 150 feet.
229. Use of trailing cables. (1) Trailing cables having a flexible metallic covering may be used to connect armoured cables to portable or transportable apparatus or mobile machines or to connect such apparatus to the switchgear by means of which it is controlled.
(2) Trailing cables having a flexible metallic screen may be used to connect portable or transportable apparatus or mobile machines to the switchgear by means of which it is controlled.
( 3) Trailing cables of an approved type without a flexible metallic covering ,or a flexible metallic screen may be used to connect portable or transportable apparatus or mobile machines in use at or in the vicinity of the working face to the switchgear by means of which it is controlled if the voltage does not exceed medium pressure.
( 4) If the voltage of the circuit exceeds medium pressure flexible cables shall include a flexible metallic covering.
( 5) The length of a trailing cable in use as set out in sub- regulations (1) and ( 2) of this regulation shall be governed in terms of voltage drop, loading and temperature rise, as required by the Standards Association of Australia Wiring Rules.
( 6) Trailing cables used with portable and transportable apparatus shall include an earthing core. When used with transportable apparatus or a dredge this requirement is not obligatory for cables having a flexible metallic covering or a flexible metallic screen provided the screen has a conductance equal to that of the largest power core enclosed by it.
230. Defects. Should the trailing cable be found to be damaged or defective it shall forthwith be repaired or replaced by a spare cable in good and substantial repair.
The defective cable shall not again be used until after it has been repaired and tested, in a manner prescribed by these regulations either at the surface of the mine or at an approved workshop underground or in the open-cut and approved for use by a competent person.
231. Persons using to observe. Every person using a trailing cable shall carefully observe the trailing cable while in use so as to detect defects; and, on observing any defect therein, he shall immediately report the same to the manager or mine electrician.
232. Clear of rails and traffic. Trailing cables shall at all times be kept clear of rails and traffic and where practicable be suspended within a reasonable distance of the machine to which they are connected.
Regulations rr. 233-239 91 233. Care while machine in operation. Special care shall be taken to prevent injury to and undue strain on the trailing cable while any machine to which it is attached is in operation or being removed from place to place.
234. Repairs to trailing cables. All repairs to trailing cables shall be properly made and the repair shall be completed by vulcanising.
235. Joining of trailing cables. (1) Lengths of trailing cable can only be coupled together or terminated by means of an approved bolted coupling, such as a flit plug, except that a free plug and socket coupling of an approved design may be used provided that the system is protected in such a manner that removal of the plug from the socket shall automatically disconnect the supply from the trailing cable.
(2) A trailing cable may be joined to a main cable through a fixed or bolted terminal or joint box or the like.
( 3) Where separate lengths of cable are required to be joined together, the cross-sectional area of the larger cable shall not be reduced unless it first passes through a switch-fuse or other equally effective means capable of adequately protecting the smaller cable in the event of a fault.
( 4) Where a trailing cable is joined to a larger cable as in sub- regulation (3) and a free plug is used, an interlock shall be provided to prevent the trailing cable being connected or disconnected whilst the power is switched on.
236. Insulation resistance. · The insulation resistance of trailing cables shall not be less than one megohm measured between conductors and between the conductors and earth screen.
237. Connection to apparatus. The separate conductors of a twin or multi-core trailing cable shall be divided only for such length as is necessary for the making of connections. The cable, with its outer covering complete, shall be securely held by suitable clamps in such a manner as to protect the trailing cable from injury and to prevent any mechanical strain at the terminals.
238. Identification. Each trailing cable shall have a distinguishing number, which shall be clearly indicated on the cable or its attached fitting.
DIVISION Vlll
CONTROL AND PROTECTION
239. Fault detectors. In every system which is not earthed at the point of supply, earth or fault detectors shall be kept connected up in every generating and transformer station, to show immediately any defect in the insulation of the system, except in the following cases:-
(a) Circuits which are included within a circle of Jess than 100 feet radius.
(h) Circuits having approvt:d automatic earth leakage protection cquipmt:nt operating on 15 per cent. or Jess of the normal full load current.
(c) Signalling and telephone circuits.
These detectors shall he inspected daily by an authorised person.
240. Protection of circuits. Every circuit shall be protected by one of the following methods:-
( a) By an automatic circuit breaker controlling each active pole with suitable overcurrent protection;
(b) By a switch and fuse combination unit controlling each active pole:
except where the system has a solidly-earthed neutral or mid-wire, in which case no cut-out or unlinked switch shall be inserted in the neutral conductor.
241. Control of circuits. (1) The current in the system or in any portion of the installation shall be so controlled that when in any circuit the current exceeds the rated current, so as to involve danger, such current shall be cut off automatically.
(2) The current in an alternating system, either underground or in an open-cut, in which the voltage exceeds 125 volts shall be so con- trolled that when, in any circuit the leakage current to earth exceeds 15 per cent. of the rated current for the circuit, or 5 amperes, whichever is the greater, the circuit shall be isolated automatically.
. 242. Provision of linked switches. Where switches are required to control more than one conductor of a circuit, they shall be linked switches and shall operate simultaneously in all active conductors, except- ing single pole link stick operated links, which may be installed for isolating purposes and for testing.
243. Insertion of switch in any conductor. Nothing in these regulations shall prevent the insertion of a switch in any conductor pro- vided it is linked with corresponding switches in all active conductors in the circuit. In the case of a three-wire direct current supply and multi- phase alternating current supply the linked switch shall be so arranged that the neutral switch will not close after the active switches and will not open before the active switches.
244. Isolating links or switches. Where necessary to prevent danger means shall be provided near apparatus to enable all pressure to be cut off from it, or from any circuit forming a part of a system.
245. Protection against lightning. Suitable means shall be provided at the surface of the mine to protect the installation in, on or about the mine from abnormal voltage due to atmospheric electricity.
246. Setting of circuit breakers. The current setting of circuit breakers shall not be adjusted by anyone except the mine electrician or assistant electrician.
247. Replacement of fuses. Fuses shall not be replaced by anyone except a competent person, or where such a person is not immediately available, some person authorised by the manager. When fuses are renewed by other than a competent person such fuses shall, as soon thereafter as practicable, be examined by a competent person. Before any fuse is replaced the electrical power shall be switched off.
248. Switch gear near entrance to mine. Switch gear, in a readily accessible position, shall be provided near the main shaft or near any other openings where power is taken underground or into an open-cut to enable the electrical power to be cut off from the installation supplied through the main shaft or other openings. The switch gear shall be of the approved type giving automatic protection to the conductors and
Regulations rr. 249-256 93 apparatus and shall be installed in a room built for the purpose or other- wise enclosed and adequately protected from the weather, and such room or enclosure shall be either kept locked or closed with instructions posted prohibiting unauthorised interference. Effective telephonic communica- tion, between the position of such switch gear and the main shaft or other openings, shall be provided when the distance exceeds 400 yards.