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Mine Health And Safety > B3. Electricity > Flashcards

B3. Electricity Flashcards

1
Q

What is the definition of “Arc Flash”?

A

“Arc Flash” means an uncontrolled electrical discharge through the air between conductors or between a conductor and earth. The resulting discharge of energy can result in fire, serious damage to electrical apparatus and injury or death to a person.

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2
Q

What is the definition of “Armouring”?

A

“Armouring” means a metallic covering of an electric cable, in the form of tape, wire or tube enclosing one or more conductors to provide adequate mechanical protection against damage.

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3
Q

What is the definition of “Bus-coupler”?

A

“Bus-coupler” means a device, or set of devices, needed to facilitate the connection of two parallel circuits.

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4
Q

What is the definition of “Bus-section”?

A

“Bus-section” means a device, or set of devices, that will extend a bus-bar to another.

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5
Q

What is the definition of “Circuit”?

A

“Circuit” means an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources and switches which have a closed loop giving a return path for the current.

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6
Q

What is the definition of “Clearance”?

A

“Clearance” means a minimum distance any part of a person’s body or any work tool may encroach to any unearthed, bare conductor or to any unearthed and unscreened conductor.

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7
Q

What is the definition of “Collectively Screened”?

A

“Collectively Screened” means having a conductive covering enclosing all power conductors as well as all control conductors within the protective outer sheath of a cable.

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8
Q

What is the definition of “Conductor”?

A

“Conductor” means any substance or material which can transfer an electrical charge along or through it and is connected to an electrical circuit.

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9
Q

What is the definition of “Dead”?

A

“Dead” means at or about zero potential with respect to the general mass of earth and disconnected from any live reticulation system.

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10
Q

What is the definition of “Domestic Voltage”?

A

“Domestic Voltage” means a voltage not exceeding 230V ± 10% alternating current phase to neutral.

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11
Q

What is the definition of “Earthed”?

A

“Earthed” means connected to the general mass of earth in such a manner as will ensure at all times an immediate discharge of electrical energy without risk.

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12
Q

What is the definition of “Electrical Apparatus”?

A

“Electrical Apparatus” means any apparatus, machine and fitting in which conductors are used, or of which they form a part.

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13
Q

What is the definition of “Electrical Single-Line Diagram”?

A

“Electrical Single-Line Diagram” means a diagram that shows, by means of a single lines and graphic symbols, the general layout of an electric circuit or system of circuits.

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14
Q

What is the definition of “Flexible cable”?

A

“Flexible cable” means a cable of which the conductors consist of strands of diameter not exceeding 0,51 mm and of which the insulation and covering area are such that they afford flexibility and in which the nominal cross sectional are of each conductor exceeds 4mm², but shall not include signalling cable, telephone cable, blasting cable, or flexible cord used with electric apparatus at a voltage not exceeding domestic voltage alternating current on a single phase system.

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15
Q

What is the definition of “Flexible cord”?

A

“Flexible cord” means a cable of which the nominal cross sectional area of each conductor does not exceed 4mm² and of which each conductor consists of strands of diameter not exceeding 0,31mm.

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16
Q

What is the definition of “Hazard Classification”?

A

“Hazard Classification” – A system developed for categorizing electrical hazards based on the voltage and fault level ratings for electrical components.

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17
Q

What is the definition of “High Voltage (HV)”?

A

“High Voltage (HV)” a set of nominal voltage levels in the range 44kV and above to 220kV.

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18
Q

What is the definition of “Individually Screened?

A

“Individually Screened” means having a conductive covering enclosing power conductors individually within the protective outer sheath of a cable.

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19
Q

What is the definition of “Isolation”?

A

“Isolation” means disconnecting the apparatus from all possible sources of electrical potential and locking the apparatus in such a manner so that no energisation can take place.

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20
Q

What is the definition of “Insulated”?

A

“Insulated” means covered with any material that has the characteristic of low electrical conductivity such as to prevent an electrical discharge.

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21
Q

What is the definition of “Live”?

A

“Live” means electrically charged.

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22
Q

What is the definition of “Lockout-tagout”?

A

“Lockout-tagout” (LOTO) or lock and tag is a safety procedure which is used to ensure that machines/switchgear and Electrical equipment are properly isolated, de-energised and tagged.

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23
Q

What is the definition of “Low Voltage (LV)”?

A

“Low Voltage (LV)” means a set of nominal voltage levels that are used for the distribution of electricity, the upper limit of which is an a.c. voltage of 1000V to below 44kV.

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24
Q

What is the definition of “Metallic Covering” ?

A

“Metallic Covering” means iron or steel armouring or metal conduit surrounding two or more conductors with or without a lead or other metallic sheath as required in terms of operational conditions.

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25
Q

What is the definition of “Moveable Electrical Apparatus”?

A

“Moveable Electrical Apparatus” means electrical apparatus, excluding self-propelled mobile machines or portable electrical apparatus, which is not installed on permanent foundations and is intended to be moved from place to place.

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26
Q

What is the definition of “Overhead Power Line”?

A

“Overhead Power Line” means an overhead line erected to convey electrical energy for any purpose other than communication but excluding the overhead contact or catenary wires of an electrical traction system.

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27
Q

What is the definition of “Permit to work”?

A

“Permit to work” is a formal, written, safe system of work to control potentially hazardous activities. The permit details the work undertaken and the necessary precautions to be taken.

28
Q

What is the definition of “Portable Electric Apparatus”?

A

“Portable Electric Apparatus” means electric apparatus, which is designed to be carried by hand, and may require electric power while being used.

29
Q

What is the definition of “Reticulation System”?

A

“Reticulation System” means a circuit or combination of circuits.

30
Q

What is the definition of “Substation”?

A

“Substation” means a location containing medium or high voltage switchgear and associated equipment for the purpose of isolation, feeding , protecting and energising electrical equipment and reticulation systems.

31
Q

What is the definition of “Switchgear”?

A

“Switchgear” general term covering switching devices and their combination with associated control, measuring, protective and regulating equipment, also assemblies of such devices and equipment with associated interconnections, accessories, enclosures and supporting structures.

32
Q

What is the definition of “Trackless Mobile Machine”?

A

“Trackless Mobile Machine” means any self-propelled mobile machine that is used for the purpose of performing mining, transport or associated operations underground or on surface at a mine and is mobile by virtue of its movement on wheels, skids, tracks, mechanical shoes or any other device fitted to the machine, but excludes-

(a) rail bound equipment
(b) scraper winches, mono rail installations, static winches, winding machinery installations and any equipment attached thereto.

33
Q

What is the definition of “Trailing Cable”?

A

“Trailing Cable” means cable used to supply power to any mobile machine and movable electrical apparatus which is designed to be dragged across the ground.

34
Q

What reasonable practicable measures must the employer take with all electrical apparatus?

A
  1. 1 The employer must take reasonable practicable measures to ensure that-
  2. 1.(1) the design of all electrical apparatus and electrical reticulation systems are approved by a competent person;
  3. 1.(2) all electrical apparatus are under the control of a competent person; and
  4. 1.(3) all electrical apparatus are installed, repaired and maintained by a competent person.
35
Q

As a result of what must the employer take reasonable practicable measures to ensure that no person suffers any electrical shock, arc flash or electrocution?

A
  1. 2 The employer must take reasonable practicable measures to ensure that no person suffers any electrical shock, arc flash or electrocution as a result of-
    (a) exposure to electrical current flow;
    (b) a person coming into contact with live exposed parts of any electrical apparatus;
    (c) exposure to electricity, arc flash, all fault currents, overvoltage and surges;
    (d) any electrical apparatus failing due to electromagnetic interference from other equipment;
    (e) any electrical apparatus being incorrectly designed, installed, operated or maintained; and
    (f) any exposure to blasts, fires or arc flashes resulting from electrical faults.
36
Q

What measures must the employer take to ensure that no person gets electrocuted?

A
  1. 3 The measures contemplated in regulation 3.2 must include measures to ensure-
  2. 3.1 proper fencing off or enclosures or clearances of such electrical apparatus;
  3. 3.2 that an extension of any electrical reticulation system is approved by a competent person before being energised, taking into account the reticulation network and the effect thereon;
  4. 3.3 that only competent persons are permitted to energise, de-energise or isolate electrical apparatus where the operation of such apparatus poses a significant risk and that such apparatus are protected against unauthorised access and operation;
  5. 3.4 that only competent persons authorised in writing by the employer to do so, carry out switching procedures on MV or HV equipment; and
  6. 3.5 that where the interruption of electrical supply to any equipment could result in a significant risk, such electrical supply can be provided from another source or network, which can include an emergency supply alternator or generator, for power supply in the event of an interruption to the normal power supply.
37
Q

What reasonably practicable measures must the employer take at any place at a mine, where electrical apparatus is installed and which may constitute a danger to persons?

A
  1. 4 The employer must take reasonably practicable measures to ensure that at any place at a mine, where electrical apparatus is installed and which may constitute a danger to persons shall be-
    (a) of adequate size so as to provide safe and unobstructed clear working space for operating and maintenance staff;
    (b) constructed and ventilated in such a manner that the apparatus is kept at a safe temperature to safeguard persons;
    (c) constructed in such a manner as to proved protection where necessary against the ingress of vermin and water;
    (d) illuminated in such a manner as to prevent any danger to persons and to enable all equipment to be distinguished clearly and all instruments, labels and notices to be read clearly while it is live;
    (e) equipped with effective means to safely disconnect the energy source; and
    (f) equipped with an effective fire extinguishing system.
38
Q

What drawing must be at every substation?

A

3.5 The employer must take reasonably practicable measures to ensure that at every substation there must be a legible, up to date single line drawing of the reticulation system, highlighting ring feeds, of which that substation is a part, displayed in a conspicuous place. Every substation must be clearly identified, and its position clearly marked on such drawing.

39
Q

What shall be displayed at every point of entry to a substation?

A
  1. 6 The employer must take reasonably practicable measures to ensure that the area in which a substation is located is clearly demarcated and that notices are displayed at every point of entry to such an area. These notices shall-
    (a) prohibit access of any unauthorised person from accessing that area;
    (b) set out the procedures to be followed in the event of a fire;
    (c) set out the first aid treatment measures to be given to persons suffering from the effects of electric shock and burns;
    (d) indicate the presence of electricity;
    (e) describe measures to safely remove any person incapacitated as a result of contact with electricity; and
    (f) have available an effective means of communication.
40
Q

What reasonably practicable measures must the employer take with to all suspended cables?

A
  1. 7 The employer must take reasonably practicable measures to ensure that all suspended cables that could cause a fire due to faults or mechanical damage, in stopes, haulages or shafts either through damage by moving machinery or by fall of ground are properly protected by-
    (a) switchgear which is electrically supplied and commissioned with discrimination settings for overload and earth fault protection to prevent fire;
    (b) switchgear installed which is correctly rated to prevent a fire or explosion;
    (c) all cables in areas where a fire can occur must be fire retardant cables or be coated with fire retardant material at areas in close proximity with timber; and
    (d) the employer must have a procedure to be followed in the event of such a fire.
41
Q

What measures must the employer take with all new main reticulation underground substations?

A

3.8 The employer of every coal mine must take reasonably practicable measure to ensure that all new main reticulation underground substations are designed and located such that they vent into the return air-way.

42
Q

What measures must the employer take with mineral oil used in electrical apparatus?

A

3.9 The employer must take reasonably practicable measures to ensure that where mineral oil is used as the medium for insulation or cooling of electrical apparatus, adequate precautions are in place to address any significant risk in the event of an explosion, spillage or burning of the oil.

43
Q

How must electrical apparatus be identifiable?

A
  1. 10 The employer must take reasonably practicable measures to ensure that where electrical apparatus is accessible from the front and the back, each apparatus are identifiable by clearly labelled and legible markings on the front and the back fixed portions of such apparatus and on switchgear shutters.
  2. 11 The employer must take reasonably practicable measures to ensure that where ring feeds including bus-sections and bus-couplers are accessible from the front and the back, each apparatus are identifiable by clearly labelled and legible markings on the front and back fixed portions of such apparatuses and on switchgear shutters.
  3. 12 The employer must take reasonably practicable measures to ensure that all electrical apparatus used for the distribution of electrical power, except electrical apparatus which contains domestic voltage, are clearly marked with the maximum voltage that may present therein.
44
Q

May you work on live electrical apparatus?

A

3.13 The employer must take reasonably practicably measures to ensure that no examination, adjustment, testing, repair or other network necessitating the dangerous approach to or the handling of electrical apparatus shall be carried out unless such apparatus is dead: Provided that where such equipment must be live for the purpose of examination, adjustment, repair or other work it may be done by or under the direct supervision of a competent person.

45
Q

Who may enter a where electric apparatus is installed?

A

3.14 The employer must take reasonably practicable measures to ensure that no person other than a competent person authorised in writing by the employer to do so, enters a place where electric apparatus is installed unless all live conductors therein are insulated adequately or otherwise protected effectively against inadvertent contact: Provided that such authorised competent person may in case of an emergency be assisted by a person acting under the immediate personal supervision of such authorised competent person.

46
Q

What precautions must be taken to ensure that when work is to be carried out on electrical apparatus that it has been isolated from all sources of electrical supply?

A
  1. 15 The employer must take reasonably practicable measures to ensure that when work is to be carried out on electrical apparatus which have been isolated from all sources of electrical supply, effective precautions shall be taken-
    (i) by discharging all stored electrical energy, and
    (ii) testing for dead including any ring feeds by earthing such apparatus and, in the case of ring-feeds or dual supplies of power, by earthing both sides of the associated electrical apparatus worked on, so as to prevent any conductor or apparatus from being made live while any person is working thereon.
  2. 17 The employer must take reasonably practicable measures to ensure that whenever work is to be carried out on electrical apparatus which has been isolated from all sources of supply, effective precautions shall be taken by earthing or other means to discharge electrically such electrical apparatus or any adjacent electrical apparatus to prevent any conductor or apparatus from being made live accidentally or inadvertently while any person is working thereon.
47
Q

What measures must be taken with any accessible metallic portion of electric apparatus which, though not normally forming part of an electric circuit, may inadvertently become live?

A

3.16 The employer must take reasonably practicable measures to ensure that any accessible metallic portion of electric apparatus which, though not normally forming part of an electric circuit, may inadvertently become live, is insulated or earthed by a conductor of adequate cross-sectional area capable of withstanding the maximum possible earth fault current condition, so as to prevent any significant risk to persons for the duration that the fault current may be flowing in the circuit.

48
Q

What ladders must be used when working near electrical apparatus?

A

3.18 The employer must take reasonably practicable measures to ensure that no metal ladder or ladder with reinforced stiles is used for examination, repair, or other work necessitating the dangerous approach to or work on electrical apparatus.

49
Q

How shall conductors be connected to earth?

A
  1. 19 The employer must take reasonably practicable measures to ensure that any accessible metallic portion of electrical plant or apparatus which, though not forming part of an electrical circuit, may accidentally become live shall either be protected by an insulating material or shall be connected to earth by a conductor of adequate cross-section so as to prevent danger to persons.
  2. 20 The employer must take reasonably practicable measures to ensure that the cross-sectional area of any earthing conductor is calculated to be capable of withstanding the maximum possible earth fault current condition.
50
Q

What procedure must the employer draw up for high voltage electrical apparatus?

A

3.21 The employer must take reasonably practicable measures to draw up and implement a procedure for all energising, de-energising and isolation of medium or high voltage electrical apparatus.

51
Q

How must electrical cable be buried in the ground or installed?

A

3.22 The employer must take reasonably practicable measures to ensure that where any electrical cable is buried in the ground or installed in such a position that mechanical damage to it may occur, it is protected by armouring.

52
Q

Where may flexible cables or trailing cables only be used?

A
  1. 23 The employer must take reasonably practicable measures to ensure that all flexible cables or trailing cables may only be used in connection with the operation of-
    (a) any self-propelled mobile machine which requires electric power to operate such machine;
    (b) movable electric apparatus; or
    (c) portable electric apparatus.
53
Q

How shall trailing cable be screened and repaired?

A
  1. 24 The employer must take reasonably practicable measures to ensure that any flexible cable or trailing cable used in or on a mine or works shall be screened either individually or collectively and such screens shall be earthed: Provided that a cable used in a hazardous area shall be screened individually.
  2. 25 The employer must take reasonably practicable measures to ensure that no flexible cable or trailing cable shall have more than fifteen joint repairs, including sheath patches over a length of 200 metres and no joint repair or patch shall be closer than 5 metres to an adjacent joint, repair or patch and no joint, repair or patch shall be closer than 3 metres to the cable plug or its terminal connections at the machine or apparatus.
54
Q

With what shall a cable reel used in connection with a self-propelled mobile machine be provided with?

A

3.26 The employer must take reasonably practicable measures to ensure that any cable reel used in connection with self-propelled mobile machine shall be provided with a device which shall interrupt the power supply to the cable before the complete cable is unreeled so that at least one complete turn of the cable shall remain on the reel when the interruption of the power supply has been affected, unless the machine’s maximum range of travel is limited to less than that permitted by the cable on the reel for reasons other than the length of the cable.

55
Q

What must happen with every electrical cable trench or duct?

A

3.27 The employer must take reasonably practicable measures to ensure that no electrical cable trench or duct is left open, uncovered or unprotected, except when persons are working in such trench or duct or where precautions have been taken to prevent persons from inadvertently falling into such trench or duct.

56
Q

From what must the employer prevent that persons have inadvertent contact with overhead power lines

A

3.28 The employer must take reasonably practicable measures to ensure that persons are prevented from significant risks arising from inadvertent contact with overhead power lines by trackless mobile machines/rail bound equipment or while erecting or moving structures or other objects.

57
Q

From what must the employer prevent persons carrying out examinations, repairs or other work at elevated positions in close proximity to exposed electrical apparatus?

A

3.29 The employer must take reasonably practicable measures to ensure that persons carrying out examinations, repairs or other work at elevated positions in close proximity to exposed electrical apparatus are protected from live electrical contact.

58
Q

How shall surface residential and commercial buildings be wired?

A

3.30 The employer must take reasonably practicable measures to ensure that surface residential and commercial buildings are to be wired and protected in accordance with South African Bureau of Standards Code of Practice SANS 10142-1, 2006, “Wiring of premises and installations not exceeding 1kV”. The normative references of SANS 10142-1, 2006 are not applicable to the employer.

59
Q

How must the employer ensure that the design and construction of overhead power lines is correct?

A

3.31 The employer must take reasonably practicable measures to ensure that the design and construction of overhead power lines are in accordance with South African Bureau of Standards Code of Practice SANS 10280, 1995 “Overhead power lines for conditions prevailing in South Africa”. The normative references in SANS 10280, 1995 are not applicable to the employer.

60
Q

How must electrical security fencing be erected and maintained?

A

3.32 The employer must take reasonably practicable measures to ensure that electrical security fencing is erected and maintained in accordance with the South African Bureau of Standards Code of Practice SANS 10222 : 2002, Part 3, “Electrical Security Fences (non lethal)”. The normative references of SANS 10222, 2002 are not applicable to the employer.

61
Q

What helmet light assemblies may be us d underground at a mine?

A
  1. 33 The employer must take reasonably practicable measures to ensure that any helmet light assemblies underground at a mine complies with SANS 1438, 2013 “Helmet light assemblies for miners”. The normative references of SANS 1438, 2013 are not applicable to the employer.
  2. 34 The employer must take reasonably practicable measures to ensure that any helmet light assemblies used underground are tested in accordance with the requirements of ARP 0108: 2013.
62
Q

What shall the operating voltage of any portable lamp used at a mine be?

A

3.35 The employer must take reasonably practicable measures to ensure that the operating voltage of any portable lamp used at a mine does not exceed 32 volts.

63
Q

What must the employer ensure about electric apparatus?

A

3.36 The employer must take reasonably practicable measures to ensure that all electric apparatus are selected, installed, worked and maintained in such a manner as not to constitute a hazard and shall be placed and protected in such a manner that no person can be injured by inadvertent contact with any live portion.

64
Q

What must the employer ensure about electric apparatus used in a hazardous area?

A
  1. 37 The employer must take reasonably practicable measures to ensure that all electric apparatus used in a hazardous area shall be explosion protected and certified as such by an inspection authority (la) certificate issued by an accredited test laboratory.
  2. 38 The employer must take reasonably practicable measures to ensure that any type and design of explosion protected apparatus shall at all times be identified in an inspection authority (la) certificate and an identification number shall be allocated to such apparatus by the accredited test laboratory.
  3. 39 The employer must take reasonably practicable measures to ensure that explosion protected apparatus is not used at a mine unless the manager is in possession of a copy of the inspection authority certificate. The identification number referred to in regulation 3.36 must be clearly and indelibly marked on the apparatus or on a metal plate (other than a light metal) permanently fixed to the apparatus.
65
Q

What is the definition of “Accredited Test Laboratory”?

A

“Accredited Test Laboratory” (ATL) means an organisation that is accredited by the South African National Accreditation System (SANAS)

Mine Health And Safety (52 decks)

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