C. 21. Electricity Flashcards
(93 cards)
0
Q
Complete the sentence:
21.1.1.1 All electric apparatus shall be ___________, _________, _________, __________ and __________ 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 thereof.
A
selected, installed, worked, marked and maintained
1
Q
What does the regulation say about electrical apparatus where unauthorised persons can make the incorrect switching of unattended switchgear that may constitute a danger to persons?
A
- 1.1.2 Where the incorrect switching of unattended switchgear by an unauthorised person may constitute danger to persons, the switchgear shall be enclosed in the manner specified in regulation 21.1.2 or the switching mechanism must be suitably locked to prevent unauthorised operation.
- 1.2 Any place where electrical apparatus is installed and which may constitute danger to persons shall be-
(a) fenced off or enclosed effectively;
(b) provided with notices at all entrances prohibiting unauthorised access; and
(c) kept closed and locked at all entrances, if unattended by an authorised person to prevent unauthorised access.
2
Q
What does the regulation stipulate about fenced off or enclosed places?
A
- 1.3 Any fenced off or enclosed place referred to in regulation 21.1.2 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 provide 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) subject to regulation 21.5.4, constructed in such a manner that no exposed live parts of electric apparatus are within reach of windows or external wall openings;
(f) designed in such a manner as to provide, in an emergency, unobstructed egress for persons from a door or doors which shall not open inwards and such door or doors shall be provided with notices on both sides;And no work which may result in danger to persons shall be carried out in such a place unless adequate illumination is available.
3
Q
What does the regulations say about cable trenches?
A
21.2 No cable trench shall be left open, uncovered or unprotected, except at a place where work is being carried out in such trench.
4
Q
What does the regulation stipulate about electrical switching apparatus?
A
- 3.1 All electric apparatus in which a fault may develop which may endanger persons shall be provided with effective switching, controlling or protective devices which, in the event of a fault, shall be capable of automatically isolating the power supply to such apparatus.
- 3.2 Where electric switching or controlling apparatus is accessible from the front and the back, the markings referred to in regulation 21.1.1 shall be on a fixed portion of the front and the back of such switching or controlling apparatus.
- 3.3 Where a ring feed or the possibility of electrical back feed exists at any apparatus a prominent notice to that effect shall be fixed to such apparatus.
5
Q
Complete the sentence:
21.3.1 All electric apparatus in which a fault may develop which may endanger persons shall be provided with effective _________, ____________ or _________ devices which, in the event of a fault, shall be capable of automatically isolating the power supply to such apparatus.
A
switching,
controlling or
protective
6
Q
Complete the sentence:
21.3.2 Where electric switching or controlling apparatus is accessible from the front and the back, the markings referred to in regulation 21.1.1 shall be
A
on a fixed portion of the front and the back of such switching or controlling apparatus.
7
Q
What does the regulation stipulate about ring feed apparatus?
A
21.3.3 Where a ring feed or the possibility of electrical back feed exists at any apparatus a prominent notice to that effect shall be fixed to such apparatus.
8
Q
When may a person interfere with or render ineffective any electric apparatus provided for safety or protection?
A
21.4 No person shall interfere with or render ineffective any electric apparatus provided for safety or protection unless it is necessary to do so to perform work associated with such apparatus.
9
Q
What does the regulation stipulate about switchboards?
A
- 5.1. A switchboard shall have a clearance of not less than 1,2 metres in the front of such switchboard for operating and maintenance purposes.
- 5.2. Any switchboard to which access is required from the back and which has no live conductors accessible from the back when the doors, covers or panels enclosing the back of such switchboard are in position shall have a clearance of at least 0,75 metres at the back and such space shall not be obstructed in any manner.
- 5.3.1 Any switchboard of which the back is accessible only through an opening in a wall or partition against which it is placed shall have a clearance at the back which shall be sufficient for the purpose of electrical insulation between conductors and the wall or partition;
- 5.3.2 The opening referred to in 21.5.3.1 shall be kept closed and locked to prevent unauthorised entrance.
- 5.4 Any switchboard that has live conductors accessible only from the back and that has no doors, covers or panels enclosing the back shall have a clearance of at least 1,2 metres behind it and such space shall not be obstructed in any manner and access to this space shall-
(a) as far as is practicable, be permitted only when the conductors at the back of such switchboard are dead or earthed; and
(b) only be through doors which shall be kept closed and locked to prevent unauthorised access.
10
Q
What does the regulation say about any switchboard that has live conductors accessible only from the back and that has no doors, covers or panels enclosing the back?
A
- 5.4 Any switchboard that has live conductors accessible only from the back and that has no doors, covers or panels enclosing the back shall have a clearance of at least 1,2 metres behind it and such space shall not be obstructed in any manner and access to this space shall-
(a) as far as is practicable, be permitted only when the conductors at the back of such switchboard are dead or earthed; and
(b) only be through doors which shall be kept closed and locked to prevent unauthorised access.
11
Q
What does the regulation say about the examination, adjustment, testing, repair or other work necessitating the dangerous approach to or the handling of electric apparatus?
A
- 6.1 No examination, adjustment, testing, repair or other work necessitating the dangerous approach to or the handling of electric apparatus shall be carried out unless such apparatus is dead; Provided that where the apparatus must be live for the purpose of examination, adjustment, testing, repair or other work it may be done by or under the direct supervision of a competent person.
- 6.2 No person other than a duly authorised competent person shall enter a place where electric apparatus is installed unless all live conductors therein are insulated adequately or otherwise protected effectively against inadvertent contact; Provided that an authorised competent person may in an emergency be assisted by a person acting under the immediate personal supervision of such authorised competent person.
- 6.3 Whenever work is to be carried out on electric apparatus which has been isolated from all sources of supply, effective precautions shall be taken by earthing or other means to discharge electrically such apparatus and any adjacent apparatus to prevent any conductor or apparatus from being made live accidentally or inadvertently while any person is working thereon.
- 6.4 No metal ladder or ladder with metal reinforced stiles may be used for examination, repair or other work necessitating the dangerous approach to or work on electric apparatus.
12
Q
When may any person enter a place where electric apparatus is installed?
A
21.6.2 No person other than a duly authorised competent person shall enter a place where electric apparatus is installed unless all live conductors therein are insulated adequately or otherwise protected effectively against inadvertent contact; Provided that an authorised competent person may in an emergency be assisted by a person acting under the immediate personal supervision of such authorised competent person.
13
Q
What effective precautions shall be taken when work is to be carried out on electric apparatus which has been isolated from all sources of supply?
A
21.6.3 Whenever work is to be carried out on electric apparatus which has been isolated from all sources of supply, effective precautions shall be taken by earthing or other means to discharge electrically such apparatus and any adjacent apparatus to prevent any conductor or apparatus from being made live accidentally or inadvertently while any person is working thereon.
14
Q
What ladders may not be used for examination, repair or other work necessitating the dangerous approach to or work on electric apparatus?
A
21.6.4 No metal ladder or ladder with metal reinforced stiles may be used for examination, repair or other work necessitating the dangerous approach to or work on electric apparatus.
15
Q
What does the regulation say about any accessible metallic portion of an electric plant or apparatus, though not normally forming part of an electric circuit, that may accidentally become live?
A
- 7.1 Any accessible metallic portion of electric plant or apparatus, though not normally forming part of an electric circuit, may accidentally become live shall either be protected by insulating material or shall be connected to earth by a conductor of adequate cross-sectional area so as to prevent danger to persons.
- 7.2 The cross-sectional area of any earthing conductor shall be calculated to be capable of withstanding the maximum possible earth fault current condition.
- 7.3 Where an earth fault gives rise to a condition dangerous to persons, adequate electrical protection shall be provided.
16
Q
What does the regulation stipulate about overhead conductors?
A
- 8.1 Any lattice-type support which carries overhead conductors shall be protected adequately to prevent any unauthorised person from coming into dangerous proximity to the conductors by climbing up such support: Provided that a Principal Inspector of Mines may require that a support of any other type shall be protected similarly.
- 8.2 Every overhead service line shall be connected to a line conductor at a point of support only and every portion of such service line which is accessible from a building or from a ladder leaning against a building shall consist of suitably insulated wire.
- 8.3 Where any portion of an overhead service line passes a building, structure or any place from which access is possible, such portion of the line shall be insulated in a manner similar to that provided for in regulation 21.8.2.
- 8.4 No portion of any uninsulated or unprotected live electric apparatus or conductor shall be permitted within a horizontal distance of 1,5 metres or within a vertical distance of 3,0 metres from any landing, walkway or permanently fixed ladderway.
17
Q
How shall any lattice-type support which carries overhead conductors be protected?
A
21.8.1 Any lattice-type support which carries overhead conductors shall be protected adequately to prevent any unauthorised person from coming into dangerous proximity to the conductors by climbing up such support: Provided that a Principal Inspector of Mines may require that a support of any other type shall be protected similarly.
18
Q
How shall every overhead service line be connected?
A
- 8.2 Every overhead service line shall be connected to a line conductor at a point of support only and every portion of such service line which is accessible from a building or from a ladder leaning against a building shall consist of suitably insulated wire.
- 8.3 Where any portion of an overhead service line passes a building, structure or any place from which access is possible, such portion of the line shall be insulated in a manner similar to that provided for in regulation 21.8.2.
- 8.4 No portion of any uninsulated or unprotected live electric apparatus or conductor shall be permitted within a horizontal distance of 1,5 metres or within a vertical distance of 3,0 metres from any landing, walkway or permanently fixed ladderway.
19
Q
What distance shall any uninsulated or unprotected live electric apparatus or conductor be from any landing, walkway or permanently fixed ladderway?
A
21.8.4 No portion of any uninsulated or unprotected live electric apparatus or conductor shall be permitted within a horizontal distance of 1,5 metres or within a vertical distance of 3,0 metres from any landing, walkway or permanently fixed ladderway.
20
Q
What does the regulation say about an electricity scheme at a mine or works that is being constructed or extended?
A
- 9.1 Where an electricity scheme at a mine or works is being constructed or extended the-
(a) supplier of electricity shall submit its complete proposals in advance, with the exception of a service connection, in duplicate to the Postmaster-General; and
(b) Postmaster-General shall on request provide plans of existing and proposed communication lines in a particular area to the supplier of electricity,So that they may mutually agree on which methods or apparatus should be used by the suppliers of electricity to prevent the creation of a dangerous condition in respect of any such communication lines.
- 9.2 If dangerous condition as referred to in regulation 21.9.1 can be prevented by amendment either to the proposed plans of the supplier of electricity or to those of the Postmaster-General, such amendments shall be made.
- 9.3 The Postmaster-General shall on request supply plans of his existing and proposed works in any specified area to the appropriate supplier of electricity.
- 9.4 If the supplier of electricity and the Postmaster-General cannot reach agreement as referred to in regulation 21.9.1, the decision of the Chief Inspector shall be decisive.
- 9.5 During the design or construction of an electricity scheme at a mine or works all methods and devices required for the protection of the public shall be provided by and at the expense of the supplier of electricity.
- 9.6 Any alteration, modification or addition to the design or construction of existing power lines or existing devices resulting from any request made by the Department of Posts and Telecommunications or any other body shall be carried out by the supplier of electricity at the expense of the said Department or body by whom the request was made.
21
Q
When shall the provisions of regulation 21.10.1 (minimum clearances) not apply?
A
- 10.2 The provisions of regulation 21.10.1 shall not apply in the case of overhead power lines, electric trolley lines and service mains-
(a) not having a voltage in excess of 1,1kV; and
(b) consisting of suitably insulated wire.
22
Q
What does the regulation stipulate about the clearances in respect of electrical conductors and other conductors of overhead power lines?
A
- 10.2 The provisions of regulation 21.10.1 shall not apply in the case of overhead power lines, electric trolley lines and service mains-
(a) not having a voltage in excess of 1,1kV; and
(b) consisting of suitably insulated wire. - 10.3 Any clearance shall be determined-
(a) for a minimum conductor temperature of 50 degrees C and with a swing angle corresponding to a wind pressure of 500 Pascals; or
(b) in such a manner that, in the case of power line conductors operating normally under conditions at a temperature higher than 50 degrees C, the clearance at such higher temperature at which the conductors operate shall be in accordance with the clearances indicated in regulation 21.10.1.
23
Q
What does the regulation stipulate about overhead power lines in regulation 21.10
A
- 10.4 No person shall, except for the purpose of inspection, maintenance and repairs construct or place any road, railway, rail track, communication line, power line, building, structure or any other object under or in the vicinity of an overhead line if such construction or placing will affect the minimum clearances referred to in regulation 21.10.1.
- 10.5 No object shall be brought closer to a live power line at any mine or works than the distance specified in the following table-
Up to 250kV - 2 metres 250kV to 400kV - 3 metres Above 400kV - 4 metres - 10.6 Notices and signs indicating the maximum height of any object permitted to pass beneath a live overhead power line shall be displayed at suitable places not less than 150 metres from the point where such object is likely to pass beneath such power line.
- 10.7 Where the maximum height of an object is greater than the height indicated on any notice or sign referred to in regulation 21.10.5, the person in charge of the movement of such object shall stop the movement and inform the responsible engineer or the competent person appointed in terms of regulation 2.13.2, and such engineer or competent person shall thereafter supervise any further movement of such object.
- 10.8 Any machine with a movable or extendable boom may be operated in close proximity to overhead power lines only if the-
(a) (i) operator of such machine is competent and has been authorised thereto by the responsible engineer or the competent person appointed in terms of regulation 2.13.2; and
(ii) clearance between any part of the machine or its load and the overhead power line is not less than the distance referred to in regulation 21.10.4 when the boom is fully extended; or
(b) power lines are disconnected and earthed; or
(c) power lines are shielded against contact by any part of the machine or its load.
24
What are the distances that no object shall be brought closer to a live power line at any mine or works?
21.10.5 No object shall be brought closer to a live power line at any mine or works than the distance specified in the following table-
Up to 250kV - 2 metres
250kV to 400kV - 3 metres
Above 400kV - 4 metres
25
How far shall notices and signs indicating the maximum height of any object permitted to pass beneath a live overhead power line be?
21.10.6 Notices and signs indicating the maximum height of any object permitted to pass beneath a live overhead power line shall be displayed at suitable places not less than 150 metres from the point where such object is likely to pass beneath such power line.
26
What does the regulation say what need to happen when the maximum height of an object is greater than the height of an overhead power line?
21.10.7 Where the maximum height of an object is greater than the height indicated on any notice or sign referred to in regulation 21.10.5, the person in charge of the movement of such object shall stop the movement and inform the responsible engineer or the competent person appointed in terms of regulation 2.13.2, and such engineer or competent person shall thereafter supervise any further movement of such object.
27
When may any machine with a movable or extendable boom be operated in close proximity to overhead power lines?
21. 10.8 Any machine with a movable or extendable boom may be operated in close proximity to overhead power lines only if the-
(a) (i) operator of such machine is competent and has been authorised thereto by the responsible engineer or the competent person appointed in terms of regulation 2.13.2; and
(ii) clearance between any part of the machine or its load and the overhead power line is not less than the distance referred to in regulation 21.10.4 when the boom is fully extended; or
(b) power lines are disconnected and earthed; or
(c) power lines are shielded against contact by any part of the machine or its load.
28
With what requirements shall you also comply where an overhead power line crosses a road, railway, rail truck or important communication line proclaimed by the Postmaster-General and the minimum clearance is in accordance with the provisions of regulation 21.10.1 and 21.10.2?
21. 11.1 Where an overhead power line crosses a road, railway, rail truck or important communication line proclaimed by the Postmaster-General, the minimum clearance shall be in accordance with the provisions of regulation 21.10.1 and 21.10.2 and shall also comply with the following requirements:
(a) Any structure supporting a crossing span shall be-
(i) designed in such a manner that it is able to withstand any load imposed by the breakage of any phase conductor or earth conductor; and
(ii) as far as is practicable be located in such a manner that it will not touch the service crossed when overturned.
(b) Subject to the provisions of paragraph (a)(ii), one of the structures supporting a crossing span shall be located as close to the point of crossing as is practicable.
(c) Where a power line crosses a road the clearance above the road shall not be less than 4,5 metres in the case of broken phase conductor in a span other than the crossing span.
(d) A crossing span shall not have any joints.
(e) When the maximum voltage for which the power line is designed exceeds 1,1kV-
(i) armour rods or arcing horn shall be fitted at the live ends of the suspension and rigid insulators on at least the first three structures on both sides of the crossing; or
(ii) duplicate conductors, tied together at intervals of not more than 1,5 metres beyond the supported by duplicate parallel insulators:
Provided that in the case of power lines on rigid insulators, the duplicate conductor shall extend at least 1,5 metres beyond the supports on each side of the crossing span:
(f) The deviation from a right-angled crossing over a communication line shall not be greater than-
(i) 30 degrees for a line with a voltage of 48kV and higher: and
(ii) 45 degrees for a line less than 48kV:
(g) Where a power line crosses another power line, the clearance shall comply with the provisions of regulation 21.10.3 and paragraphs (b) and (c) of this regulation: Provided that the Chief Inspector may grant exemption from the said conditions subject to such conditions as he may determine.
29
What does the regulation say about any structure supporting a crossing span
21. 11.1 (a) Any structure supporting a crossing span shall be-
(i) designed in such a manner that it is able to withstand any load imposed by the breakage of any phase conductor or earth conductor; and
(ii) as far as is practicable be located in such a manner that it will not touch the service crossed when overturned.
(b) Subject to the provisions of paragraph (a)(ii), one of the structures supporting a crossing span shall be located as close to the point of crossing as is practicable.
(d) A crossing span shall not have any joints.
30
What must the clearance be in the case of a broken phase conductor in a span other than the crossing span above a road when a electrical power line crosses a road?
(c) Where a power line crosses a road the clearance above the road shall not be less than 4,5 metres in the case of broken phase conductor in a span other than the crossing span.
31
What does the regulation say when the maximum voltage for which power lines is designed exceeds 1,1kV at a crossing?
(e) When the maximum voltage for which the power line is designed exceeds 1,1kV-
(i) armour rods or arcing horn shall be fitted at the live ends of the suspension and rigid insulators on at least the first three structures on both sides of the crossing; or
(ii) duplicate conductors, tied together at intervals of not more than 1,5 metres beyond the supported by duplicate parallel insulators:
Provided that in the case of power lines on rigid insulators, the duplicate conductor shall extend at least 1,5 metres beyond the supports on each side of the crossing span:
32
What does the regulation say about the deviation from a right-angled crossing over a communication line?
(f) The deviation from a right-angled crossing over a communication line shall not be greater than-
(i) 30 degrees for a line with a voltage of 48kV and higher: and
(ii) 45 degrees for a line less than 48kV:
33
When may a power line cross another power line?
(g) Where a power line crosses another power line, the clearance shall comply with the provisions of regulation 21.10.3 and paragraphs (b) and (c) of this regulation 21.11.1: Provided that the Chief Inspector may grant exemption from the said conditions subject to such conditions as he may determine.
34
What does the regulation say about overhead service mains?
21. 11.2.1 Where an overhead service main crosses over any bare overhead communication line, the minimum clearance at the crossing between the overhead service main and the overhead communication line shall not be less than 0,5 metres.
21. 11.2.2 Any overhead service main shall not cross underneath bare communication lines.
35
What does the regulation say about an overhead service main that crosses any bare overhead communication line?
21. 11.2.1 Where an overhead service main crosses over any bare overhead communication line, the minimum clearance at the crossing between the overhead service main and the overhead communication line shall not be less than 0,5 metres.
21. 11.2.2 Any overhead service main shall not cross underneath bare communication lines.
21. 12.2 For the purpose of regulation 21.12.1 it shall be assumed that-
(a) the structure concerned has no broken conductors;
(b) every line conductor, cable or wire supported by the structure is at a temperature of -5 degrees C; and
(c) the line conductor and the structure are subjected to a wind pressure of 700 Pascals: Provided that the area for calculating the force due of wind pressure shall, in the case of-
(i) a lattice structure, be 1,5 times; and
(ii) round, elliptical or hexagonal poles, conductors and wires be 0,6 times,
the projected area of the structure or component
21. 12.3.1 The factor of safety of any line conductor shall be not less than 2,5 and based on the rated ultimate tensile strength of the conductor.
21. 12.3.2 For the purpose of calculating the factor of safety referred to in regulation 21.12.3.1, the line conductor shall be deemed to be-
(a) at a temperature of -5 degrees C; and
(b) simultaneously subjected to a wind pressure at right angles to the line equivalent to 700 Pascals on 0,6 times the projected area of the conductors.
36
The supports of overhead power lines, how shall the structure be?
21. 12.2 For the purpose of regulation 21.12.1 it shall be assumed that-
(a) the structure concerned has no broken conductors;
(b) every line conductor, cable or wire supported by the structure is at a temperature of -5 degrees C; and
(c) the line conductor and the structure are subjected to a wind pressure of 700 Pascals: Provided that the area for calculating the force due of wind pressure shall, in the case of-
(i) a lattice structure, be 1,5 times; and
(ii) round, elliptical or hexagonal poles, conductors and wires be 0,6 times,
the projected area of the structure or component
37
What must the factor of safety be for a line conductor and how do you calculate it?
21. 12.3.1 The factor of safety of any line conductor shall be not less than 2,5 and based on the rated ultimate tensile strength of the conductor.
21. 12.3.2 For the purpose of calculating the factor of safety referred to in regulation 21.12.3.1, the line conductor shall be deemed to be-
(a) at a temperature of -5 degrees C; and
(b) simultaneously subjected to a wind pressure at right angles to the line equivalent to 700 Pascals on 0,6 times the projected area of the conductors.
38
What does the regulation say about an overhead power line that is erected in the vicinity of an explosives magazine?
21. 13 When an overhead power line is erected in the vicinity of an explosives magazine, the power line shall be separated from the magazine by a horizontal distance of not less than-
(a) 15 metres in the case of power lines with spans of up to 30 metres;
(b) 20 metres in the case of power lines with spans greater than 30 metres and up to 150 metres; and
(c) 30 metres in the case of power lines with spans greater than 150 metres.
39
When shall any cable other than a trailing cable, a cable of intrinsically safe circuit or a flexible cable for moveable electric apparatus or portable electric apparatus be protected by armouring?
21. 14.1 Any cable other than a trailing cable, a cable of intrinsically safe circuit or a flexible cable for moveable electric apparatus or portable electric apparatus shall be protected by armouring if-
(a) the cable is buried directly in the ground;
(b) the cable is installed in such a position that mechanical damage may occur; or
(c) there may be risk of igniting gas, coal dust or other flammable material.
40
What does the regulation stipulate about flexible cables or trailing cables used on a mine or works?
21. 14.2 A flexible cable or trailing cable may be used only 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.
21. 14.3 Any flexible cable or trailing cable used in or on a mine or at a 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.
21. 14.4 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 connection at the machine or apparatus.
21. 14.5 Any cable reel used in connection with a 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 effected, 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.
41
When may a flexible cable or trailing cable be used for operation?
21. 14.2 A flexible cable or trailing cable may be used only 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.
42
How shall any flexible cable or trailing cable used in or on a mine or at a works be screened?
21.14.3 Any flexible cable or trailing cable used in or on a mine or at a 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.
43
What does the regulation stipulate about joints, repairs and patches on any flexible cable or trailing cable?
21.14.4 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 connection at the machine or apparatus.
44
What does the regulation stipulate about the use of a cable reel used in connection with a self-propelled mobile machine?
21.14.5 Any cable reel used in connection with a 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 effected, 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.
45
What does the regulation say about any flexible trailing cable used in a hazardous area?
21. 14.6 Any flexible trailing cable used in a hazardous area shall be-
(a) provided with an intrinsically safe pilot circuit which will prevent power from being supplied to the cable unless the earth conductor is in good working condition; and
(b) provided with a means (system) to prevent arcing of power contacts of any plug used in conjunction with the cable while such plug is being inserted or withdrawn; and
(c) connected to a supply on which the earth fault current is limited to prevent danger to persons.
46
What provisions shall apply for any installation in a hazardous area?
21. 15 Subject to the provisions of this Chapter the following provisions shall apply to any installation in a hazardous area-
(a) Any cable shall, as far as is practicable, be so suspended or placed in such a manner that it cannot be damaged.
(b) The responsible engineer or competent person appointed in terms of regulation 2.13.2 shall appoint a competent person or person who shall carry out-
(i) at least once in each calendar month at intervals not exceeding 45 days a thorough examination and test for continuity of all electric apparatus and every earth conductor, transformer neutral earthing system, armouring or screening, except in cases where a continuous earth monitoring system has been installed or a satisfactory equivalent system has been approved by the regional director, under such conditions as he may prescribe; and
(ii) an examination and test of all new and re-erected electric apparatus before it is put into service.
(c) The person or persons carrying out the examinations or tests referred to in paragraphs (b)(i) or (ii) shall record the results thereof in a log book, which shall be scrutinised by the engineer or competent person appointed in terms of regulation 2.13.2.
47
What examinations shall be done on any installations in a hazardous area?
21. 15 Subject to the provisions of this Chapter the following provisions shall apply to any installation in a hazardous area-
(b) The responsible engineer or competent person appointed in terms of regulation 2.13.2 shall appoint a competent person or person who shall carry out-
(i) at least once in each calendar month at intervals not exceeding 45 days a thorough examination and test for continuity of all electric apparatus and every earth conductor, transformer neutral earthing system, armouring or screening, except in cases where a continuous earth monitoring system has been installed or a satisfactory equivalent system has been approved by the regional director, under such conditions as he may prescribe; and
(ii) an examination and test of all new and re-erected electric apparatus before it is put into service.
(c) The person or persons carrying out the examinations or tests referred to in paragraphs (b)(i) or (ii) shall record the results thereof in a log book, which shall be scrutinised by the engineer or competent person appointed in terms of regulation 2.13.2.
48
Fill in the missing words:
21.15 Subject to the provisions of this Chapter the following provisions shall apply to any installation in a hazardous area-
(b) The responsible engineer or competent person appointed in terms of regulation 2.13.2 shall appoint a competent person or person who shall carry out-
(i) at least once in each calendar month at intervals not exceeding 45 days a thorough examination and test for _____________ of all __________ and every ______________, ________________, _____________ or ______________, except in cases where a ________________ has been installed or a satisfactory equivalent system has been approved by the regional director, under such conditions as he may prescribe; and
```
continuity
electric apparatus
earth conductor,
transformer neutral earthing system,
armouring or
screening
continuous earth monitoring system
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49
How shall all buildings be wired on a mine or works?
21.16 At every mine or works all building situated thereon shall be wired in accordance with a code of practice approved by the Chief Inspector.
50
Who shall identify and define any hazardous area referred to in regulation 1 (11A)(ii) in or on a mine or at a works?
21.17.1 The manager shall identify and define any hazardous area referred to in regulation 1 (11A)(ii) in or on a mine or at a works and record it on a plan or in a register provided for that purpose.
51
What does the regulation say about explosion protected apparatus?
21. 17.2 Except where written exemption has been granted by the Principal Inspector of Mines, all electrical apparatus used in a hazardous area shall be explosion protected and certified as such in a test report by an inspection authority approved by the Chief Inspector: Provided that the Principal Inspector of Mines may require codes of practice for the use of such apparatus.
21. 17.3.1 Any type and design of explosion protected apparatus shall at all times be identified in a test report referred to in regulation 21.17.2, and an identification number shall be allocated to such apparatus by the inspection authority.
21. 17.3.2 Explosion protected apparatus shall not be used unless the manager is in possession of a copy of the test report and the identification number referred to in regulation 21.17.2 is marked clearly and indelibly on the apparatus or on a metal plate (other than light metal) permanently fixed to the apparatus.
21. 17.4 Prior to the use of any explosion-protected equipment a copy of the test report shall be forwarded by the manager to the Principal Inspector of Mines, who may enforce restrictions and conditions for the use of the apparatus as deemed necessary in the interest of safety.
21. 17.5 If any repair or modification which may affect its explosive-protected apparatus characteristics is carried out on explosion-protected apparatus by an organisation not licensed by the approved inspection authority, the apparatus shall not be put into service in a hazardous area unless a new test report has been issued by the inspection authority.
21. 17.6 The manager shall take all reasonable precautionary measures to ensure that all persons operating, running and maintaining explosion-protected apparatus are properly instructed in the conditions and requirements contained in the appropriate specifications in accordance with which the apparatus was tested.
52
What are the conditions for all electrical apparatus to be used in a hazardous area?
21.17.2 Except where written exemption has been granted by the Principal Inspector of Mines, all electrical apparatus used in a hazardous area shall be explosion protected and certified as such in a test report by an inspection authority approved by the Chief Inspector: Provided that the Principal Inspector of Mines may require codes of practice for the use of such apparatus.
53
Fill in the missing words:
21.17.3.1 Any type and design of explosion protected apparatus shall at all times be identified in a ___________ referred to in regulation 21.17.2, and an _______________ shall be allocated to such apparatus by the inspection authority.
21.17.3.1 Any type and design of explosion protected apparatus shall at all times be identified in a test report referred to in regulation 21.17.2, and an identification number shall be allocated to such apparatus by the inspection authority.
54
Explosion protected apparatus shall not be used before what has been done?
21. 17.3.2 Explosion protected apparatus shall not be used unless the manager is in possession of a copy of the test report and the identification number referred to in regulation 21.17.2 is marked clearly and indelibly on the apparatus or on a metal plate (other than light metal) permanently fixed to the apparatus.
21. 17.4 Prior to the use of any explosion-protected equipment a copy of the test report shall be forwarded by the manager to the Principal Inspector of Mines, who may enforce restrictions and conditions for the use of the apparatus as deemed necessary in the interest of safety.
55
What does the regulation say about any repair and modification of any explosive protected apparatus?
21.17.5 If any repair or modification which may affect its explosive-protected apparatus characteristics is carried out on explosion-protected apparatus by an organisation not licensed by the approved inspection authority, the apparatus shall not be put into service in a hazardous area unless a new test report has been issued by the inspection authority.
56
What does the regulation say about the operating, running and maintenance of any explosion protected apparatus?
21.17.6 The manager shall take all reasonable precautionary measures to ensure that all persons operating, running and maintaining explosion-protected apparatus are properly instructed in the conditions and requirements contained in the appropriate specifications in accordance with which the apparatus was tested.
57
Define “competent person”
“competent person” means a person who-
(a) (i) is qualified by virtue of his knowledge, training, skills and experience to organise work and its performance;
(ii) is familiar with the provisions of this Act and the regulations which apply to the work to be performed; and
(ii) has been trained to recognise any potential or actual danger to health and safety in the performance of the work; or
(b) is in possession of the appropriate certificate of competency where such certificate is required by these regulations;
58
Define “circuit”
“circuit” means an electrical circuit forming a system or branch of a system.
59
Define “collectively screened”
“collectively screened” means having a conductive covering enclosing all power conductors as well as all control conductors within the protective outer sheave of a cable.
60
Define “dead”
“dead” means at or about zero potential and disconnected from any live system.
61
Define “earthed”
“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 danger.
62
Define “flexible cable”
“flexible cable” means a cable having flexible insulated conductors and earthing conductors within a protective sheath, but shall not include signalling cable, telephone cable, blasting cable or flexible electric cord used with electric apparatus at a voltage not exceeding 250 volts alternating current on a single–phase system.
63
Define “individually screened”
“individually screened” means having a conductive covering enclosing power conductors individually within the protective outer sheave of a cable.
64
Define “intrinsically safe apparatus”
“intrinsically safe apparatus” means electric apparatus constructed in such a manner that, when connected and used, any sparking that may occur under any service or fault condition (either in the apparatus or in the circuit associated with the apparatus) is not capable of igniting flammable gas.
65
Define “live"
“live" means electrically charged.
66
Define “system”
“system” means an electrical system in which all the conductors and apparatus are electrically connected to a common source of electromotive force.
67
Define “trailing cable”
“trailing cable” means a flexible cable used to supply power to any mobile machine and which is dragged across the ground.
68
Define "hazardous area"
"hazardous area" means-
(i) in respect of a coal mine-
(aa) a return airway; or
(bb) an area within 180 metres of any working face; or
(ii) any area in or at a mine or at a works in addition to an area referred to in regulation 1(11A)(i) where there may be a risk of igniting gas, dust, vapour or any other explosive material
69
What is the definition of "armouring"?
“Armouring” means a metallic covering of an electric of an electric cable, in the form of tape, wire or tube enclosing one or more conductors to provide adequate mechanical protection.
70
What is the definition of "conductor"?
“Conductor” means an electrical conductor arranged to be electrically connected to a system.
71
What is the definition of "covered in insulating material"?
“Covered with insulating material" means adequately covered with insulating material of such quality and thickness that there is no danger.
72
What is the definition of "electric apparatus"?
"Electric apparatus" means all apparatus, machines and fitting in which conductors are used, or of which they form a part.
73
What is the definition of "extra high pressure"?
“Extra high pressure” means a pressure normally exceeding 3000 volts
74
What is the definition of "high pressure"?
“High pressure” means a pressure normally above 650 volts, but not exceeding 3000 volts.
75
What is the definition of "low pressure"?
“Low pressure” means a pressure normally not exceeding 250 volts.
76
What is the definition of "medium pressure"?
“Medium pressure” means a pressure above 250 volts, but not exceeding 650 volts.
77
What is the definition of "metallic covering"?
“Metallic covering” means iron or steel armouring, with or without a lead or other metallic sheath as the conditions of the case may require, or an iron or steel pipe surrounding two or more conductors.
78
What is the definition of "movable electric apparatus"?
“Moveable electric apparatus” means apparatus which does not fall within the definitions of “self-propelled mobile machine”” or “portable electric apparatus” and which is not installed on permanent foundations and is intended to be moved from place to place when it is in use.
79
What is the definition of "pressure"?
“Pressure” means the difference of electrical potential between any two conductors, or between a conductor and earth.
80
What is the definition of "workings"?
"Workings" means any excavation of a mine made or being made for the purpose of searching for or winning minerals.
81
What is the definition of "conductor"?
“Conductor” means an electrical conductor arranged to be electrically connected to a system.
82
What is the definition of "covered in insulating material"?
“Covered with insulating material" means adequately covered with insulating material of such quality and thickness that there is no danger.
83
What is the definition of "electric apparatus"?
"Electric apparatus" means all apparatus, machines and fitting in which conductors are used, or of which they form a part.
84
What is the definition of "extra high pressure"?
“Extra high pressure” means a pressure normally exceeding 3000 volts
85
What is the definition of "high pressure"?
“High pressure” means a pressure normally above 650 volts, but not exceeding 3000 volts.
86
What s the definition of "increased safety apparatus"?
“Increased safety apparatus” means apparatus in which special precautions have been taken to prevent sparking, arcing and the occurrence of temperatures high enough to ignite flammable gas.
87
What is the definition of "low pressure"?
“Low pressure” means a pressure normally not exceeding 250 volts.
88
What is the definition of "medium pressure"?
“Medium pressure” means a pressure above 250 volts, but not exceeding 650 volts.
89
What is the definition of "metallic covering"?
“Metallic covering” means iron or steel armouring, with or without a lead or other metallic sheath as the conditions of the case may require, or an iron or steel pipe surrounding two or more conductors.
90
What is the definition of "movable electric apparatus"?
“Moveable electric apparatus” means apparatus which does not fall within the definitions of “self-propelled mobile machine”” or “portable electric apparatus” and which is not installed on permanent foundations and is intended to be moved from place to place when it is in use.
91
What is the definition of "pressure"?
“Pressure” means the difference of electrical potential between any two conductors, or between a conductor and earth.
92
What is the definition of "workings"?
"Workings" means any excavation of a mine made or being made for the purpose of searching for or winning minerals.
