As 3007.5 - Electrical Installations

AS 3007.5—1987

Australian StandardR

Electrical installations – Surface mines and associated processing plant

Accessed by HOMESTAKE GOLD of AUSTRALIA LTD on 18 Apr 2002

Part 5: Operating requirements

This Australian standard was prepared by Committee EL/33, Electrical Installations for Outdoor Sites Under Heavy Conditions (Including Open–cast Mines and Quarries). It was approved on behalf of the Council of the Standards Association of Australia on 27 February 1987 and published on 4 May 1987.

The following interests are represented on Committee EL/33: Association of Consulting Engineers Australia Australian Electrical and Electronic Manufacturers Association Australian Institute of Mining and Metallurgy Confederation of Australian Industry Department of Industrial Relations, N.S.W. Department of Mines, Qld Department of Mines, Tas. Electricity Supply Association of Australia

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Mining Interests

Review of Australian Standards. To keep abreast of progress in industry, Australian Standards are subject to periodic review and are kept up to date by the issue of amendments or new editions as necessary. It is important therefore that Standards users ensure that they are in possession of the latest edition, and any amendments thereto. Full details of all Australian Standards and related publications will be found in the Standards Australia Catalogue of Publications; this information is supplemented each month by the magazine ‘The Australian Standard’, which subscribing members receive, and which gives details of new publications, new editions and amendments, and of withdrawn Standards. Suggestions for improvements to Australian Standards, addressed to the head office of Standards Australia, are welcomed. Notification of any inaccuracy or ambiguity found in an Australian Standard should be made without delay in order that the matter may be investigated and appropriate action taken.

This Standard was issued in draft form for comment as DR 86011.

AS 3007.5—1987

Australian StandardR

Electrical installations – Surface mines and associated processing plant

Accessed by HOMESTAKE GOLD of AUSTRALIA LTD on 18 Apr 2002

Part 5: Operating requirements

First published . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1987

PUBLISHED BY STANDARDS AUSTRALIA (STANDARDS ASSOCIATION OF AUSTRALIA) 1 THE CRESCENT, HOMEBUSH, NSW 2140 ISBN 0 7262 4619 0

PREFACE

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This standard was prepared by the Association’s Committee on Electrical Installations for Outdoor Sites Under Heavy Conditions (Including Open–cast Mines and Quarries). It constitutes Part 5 of the AS 3007 series and is essentially identical with IEC 621–5* which was prepared by the corresponding IEC Technical Committee, i.e. TC 71. Where this standard deviates technically from IEC 621–5 by way of different or additional requirements, this is indicated by a rule in the margin against the clause, or part thereof, affected. A summary of such technical variations is given in the Annex. The Australian committee (EL/33) has actively participated in the work of IEC TC 71 which has as its objective the development of uniform and internationally acceptable rules for the safe use of electricity in open–cast mines, quarries, stockpiles and the like. Such applications present particularly onerous conditions for the electrical apparatus and systems, including continual alteration of the location of the apparatus and systems, extension of the operational area, and adverse environmental conditions. Because of the size of the plant and the need for mobility, supply is frequently at high voltage over long distances, by means of trailing cables. This should be compared with other industries where the electrical installations are generally fixed. The AS 3007 series specifies requirements for the installation and operation of electrical apparatus and systems in the above–mentioned locations, with the object of ensuring the safety of persons, livestock and property. AS 3007.1 outlines the scope of the composite standard and provides definitions for some of the terms used. AS 3007.2 specifies the measures which are required for protection against electric shock in normal service from direct contact with live parts; for protection against electric shock from parts which may become live in the event of a fault (indirect contact); and for protection against the effects of overcurrent resulting from overload or short circuit conditions. AS 3007.3 specifies general requirements for the equipment and ancillaries associated with the electrical installation. AS 3007.4 sets out the requirements which are specific to particular installations, together with any exemptions from the general requirements of AS 3007.2 and AS 3007.3 which apply for such installations. AS 3007.5 (this standard) sets out the normal operating procedures which should be carried out to ensure the safety of personnel. The AS 3007 series recognizes several types of power supply system and specifies the protective measures which are necessary for each system. Requirements for the protection of personnel from indirect contact (see Section 2 of AS 3007.2) are based on the concept of permissible voltage versus time limits, which take into account the patho–physiological effects of electric current passing through the human body, the typical industry conditions, and the probability of persons being in contact with the plant. In this and other respects the AS 3007 series differs in approach from the practically evolved requirements of AS 3000, SAA Wiring Rules. It will therefore be necessary for the regulatory authorities concerned to clearly delineate the respective areas of application for the AS 3007 series and for AS 3000. *

In course of publication based on IEC Document 71(Central Office)36.

E Copyright — STANDARDS AUSTRALIA Users of Standards are reminded that copyright subsists in all Standards Australia publications and software. Except where the Copyright Act allows and except where provided for below no publications or software produced by Standards Australia may be reproduced, stored in a retrieval system in any form or transmitted by any means without prior permission in writing from Standards Australia. Permission may be conditional on an appropriate royalty payment. Requests for permission and information on commercial software royalties should be directed to the head office of Standards Australia. Standards Australia will permit up to 10 percent of the technical content pages of a Standard to be copied for use exclusively in–house by purchasers of the Standard without payment of a royalty or advice to Standards Australia. Standards Australia will also permit the inclusion of its copyright material in computer software programs for no royalty payment provided such programs are used exclusively in–house by the creators of the programs. Care should be taken to ensure that material used is from the current edition of the Standard and that it is updated whenever the Standard is amended or revised. The number and date of the Standard should therefore be clearly identified. The use of material in print form or in computer software programs to be used commercially, with or without payment, or in commercial contracts is subject to the payment of a royalty. This policy may be varied by Standards Australia at any time.

CONTENTS Page SCOPE OF PART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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REFERENCED DOCUMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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RESTRICTIONS ON ACCESS BY PERSONNEL . . . . . . . . . . . . . . . . . . . . OPERATIONS INVOLVING PERSONNEL WORKING IN THE VICINITY OF EXPOSED LIVE PARTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . MOVEMENT OF VEHICLES AND MACHINERY IN THE VICINITY OF OVERHEAD LINES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OPERATIONS IN THE VICINITY OF COLLECTOR/TROLLEY WIRES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ALTERATIONS IN THE OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MOVING OF CABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PROTECTION OF CABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MOVING OF OVERHEAD LINES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ELECTRIC SHOT–FIRING OPERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . FIRE PREVENTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADDITIONAL REQUIREMENTS AND PRECAUTIONS . . . . . . . . . . . . . . TEMPORARY OPERATION OF EQUIPMENT . . . . . . . . . . . . . . . . . . . . . .

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APPENDIX A. RECOMMENDED MEASURES TO MINIMIZE THE POSSIBILITY OF INADVERTENT INITIATION OF ELECTRICALLY INITIATED EXPLOSIVE DEVICES . . . . . . .

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ANNEX. SUMMARY OF TECHNICAL DEVIATIONS BETWEEN THIS STANDARD AND IEC 621–5 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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STANDARDS ASSOCIATION OF AUSTRALIA Australian Standard for ELECTRICAL INSTALLATIONS — SURFACE MINES AND ASSOCIATED PROCESSING PLANT PART 5 — OPERATING REQUIREMENTS SCOPE OF PART This standard specifies the normal operating procedures which should be carried out to ensure the safety of personnel. These procedures may be varied in certain circumstances where a planned operation is performed under controlled conditions. NOTE: Att enti on is drawn to the fact that the requir ements of Regulatory Authorit ies may dif fer from the requir ements specifi ed in this standard.

REFERENCED DOCUMENTS

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The following standards are referred to in this standard: AS 2187.1 SAA Explosives Code Part 1 — Storage and Land Transport AS 2187.2

SAA Explosives Code Part 2 — Use of Explosives

AS 3007.2

Electrical Installations — Surface Mines and Associated Processing Plant Part 2 — General Protection Requirements

BS 6657

Guide to Prevention of Inadvertent Initiation of Electro-explosive Devices by Radio-frequency Radiation

IEC 621-5

Electrical Installations for Outdoor Sites Under Heavy Conditions (Including Open-cast Mines and Quarries) Part 5: Operating Requirements.

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1 RESTRICTIONS ON ACCESS BY PERSONNEL. 1.1 Access to normal operating areas. All personnel may have access to a normal operating area provided all barriers and enclosures required by Section 1 of AS 3007.2 are in place. Barriers or enclosures provided in accordance with Clause 2.3 of AS 3007.2 shall be removed only by skilled or instructed persons, unless of the type described in Items (b), (c), (d) or (e) of that clause. When these barriers or enclosures are removed and the exposed live parts are not isolated in accordance with Clause 2.3 of this standard, temporary barriers and warning signs shall be installed. 1.2 Access to electrical operating areas and closed electrical operating areas. Only the following persons shall be permitted access to an electrical operating area and a closed electrical operating area, unless all exposed live parts in the area have been isolated in accordance with Clause 2.3: (a) Skilled persons. (b) Appropriately instructed persons. (c) Ordinary persons when accompanied by skilled persons or appropriately instructed persons. 2 OPERATIONS INVOLVING PERSONNEL WORKING IN THE VICINITY OF EXPOSED LIVE PARTS. 2.1 General. When it is necessary to work in the vicinity of exposed live parts with voltages of more than 50 V a.c. or 120 V d.c., either — (a) the work shall be conducted observing the minimum approach distances specified in Clause 2.2; or (b) the exposed live parts shall be isolated in accordance with Clause 2.3; or (c) for instructed or skilled persons, the special procedures prescribed in Clause 2.4 shall be observed. 2.2 Minimum approach distances. Except where permitted by Clause 2.4, no part of any person or any object in contact with a person, other than specially insulated operating devices, shall approach closer to exposed live parts than the distances specified in Table 1. NOTES: 1. The use of ropes, barriers or similar measures may be necessary to facilitate observance of the minimum approach distances. 2. The minimum approach distances specified in Table 1 are based on work from a stable surface and exposed live parts which are fixed in position. Where these conditions do not apply the distances should be increased to take account of the expected movement. 3. The minimum approach distances specified in Table 1 may need to be increased when working in the vicinity of overhead lines.

Particular care shall be taken when it is necessary for persons working in the vicinity of exposed live parts to use long objects such as ladders, metal scaffolds, pipes, etc. It is recommended that such objects be carried in the horizontal position by at least two persons. 2.3 Isolation of exposed live parts. When it is necessary to work in the vicinity of exposed live parts in a position giving less than the minimum approach distances specified in Table 1, the power supply to the exposed live parts shall be isolated. However, this requirement shall not apply when instructed or skilled persons are working to the procedure specified in Clause 2.4.

AS 3007.5—1987

TABLE 1 MINIMUM APPROACH DISTANCES FOR PERSONNEL Nominal voltage (phase-t o-phase) *

Minimum approach distance *

kV, r.m.s.

mm

1.1 3.3 6.6

† 90 90

11 22 33

120 220 320

66 110 150 220

630 1100 1500 2100

*

The minimum approach distances specif ied take into account the fact that the system volt age may vary by up to 10 percent fr om the nominal volt age. † No minimum approach distance specifi ed. Contact with live part s is to be avoided.

For installations with voltages of more than 1000 V, isolation shall include short-circuiting and earthing of the parts concerned. A skilled person shall ensure that the isolation, short-circuiting and earthing have been satisfactorily completed, and shall give authorization before the commencement of any work. For testing purposes the short-circuiting and earthing may be temporarily removed provided appropriate measures are adopted to ensure the safety of personnel. A skilled person shall ensure that all persons who are to work on the parts are fully conversant with the area isolated and the work to be carried out. The skilled person shall be aware of the possibility of dangerous voltages being induced from adjacent energized conductors and, where necessary, shall ensure that appropriate precautions are taken. Where there are adjacent exposed live parts, the exposed live parts which have been isolated and, where applicable, short-circuited and earthed, shall be clearly identified and precautions taken to avoid contact with the adjacent exposed live parts. 2.4 Work on or in close proximity to exposed live parts. 2.4.1 General. When it is necessary to work on or in the vicinity of exposed live parts with voltages of more than 1000 V in a position giving less than the minimum approach distances specified in Table 1, and it has been established that it is not practical to isolate the parts in accordance with Clause 2.3, work may be carried out whilst the parts are live provided the measures prescribed in Clauses 2.4.2 and 2.4.3 are taken. 2.4.2 Responsible person. A skilled person shall be designated to be responsible for the operation. Before permitting work to commence the skilled person shall carry out the following: (a) Prepare a detailed description of the nature and location of the work to be carried out. (b) Prepare a detailed plan of the method and sequence to be used including details of the work to be carried out by each person.

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(c) Ensure that all persons involved are fully informed of their duties and the precautions to be carried out. The skilled person shall ensure that each person involved in the operation is under observation whilst the work is carried out. 2.4.3 Protective equipment. Suitable protective equipment shall be used and such equipment shall be periodically tested to ensure continued effectiveness.

TABLE 2 MINIMUM CLEARANCES FOR THE MOVEMENT OF VEHICLES AND MACHINERY UNDER AND IN THE VICINITY OF OVERHEAD LINES Nominal voltage (phase-t o-phase) * kV, r.m.s.

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NOTE: Standards for tools and equipment for use in live-line working are in course of preparation by IEC Technical committee No 78, Tools for Live Working.

3 MOVEMENT OF VEHICLES AND MACHINERY IN THE VICINITY OF OVERHEAD LINES. 3.1 General. The movement of vehicles and machinery in the vicinity of overhead lines shall be conducted in such a way that the minimum clearances specified in Clauses 3.2 and 3.3 are observed, excepting that these clearances may be reduced in the special circumstances described in Clause 3.4. The minimum clearances specified in Clauses 3.2 and 3.3 shall also be observed by persons on the vehicles or machinery. The minimum clearances specified in Clauses 3.2 and 3.3 do not apply where the overhead line has been isolated in accordance with the procedure specified in Clause 2.3. 3.2 Vertical clearances. The minimum clearances specified in Table 2 shall be observed when vehicles and machinery pass under overhead lines. The clearances apply from the highest point of the vehicles or machinery to the overhead lines. When it is necessary for vehicles or machinery to pass under overhead lines as part of their normal operation (i.e. at officially designated vehicular crossings) and there is a likelihood that the minimum clearances specified in Table 2 cannot be maintained, height gauges, such as goal posts, shall be provided at each side of the line to indicate the maximum height above the road surface permitted in terms of Table 2. 3.3 Horizontal clearances. Where vehicles or machinery are operated in the vicinity of overhead lines and the height of the vehicles or machinery is such that the minimum vertical clearances specified in Clause 3.2 cannot be achieved, a horizontal clearance of not less than the appropriate value specified in Table 2 shall be maintained. Where the horizontal movement of the vehicles or machinery cannot be adequately controlled, larger horizontal clearances shall be maintained. 3.4 Permissible reduction of clearances. The clearances specified in Clauses 3.2 and 3.3 may be reduced where any one of the following circumstances exist: (a) Where the vehicles or machinery move in a defined path, e.g. rail-mounted vehicles. (b) Where the movement of the vehicles or machinery is under the supervision of an instructed or skilled person. (c) Where the measures for protection against indirect contact specified in AS 3007.2 are applied to the vehicles or machinery. 4 OPERATIONS IN THE VICINITY OF COLLECTOR/ TROLLEY WIRES. (Requirements yet to be developed.)

≤ 1.1 > 1.1 > 33 > 66 > 110

≤ 33 ≤ 66 ≤ 110 ≤ 220

Minimum clearance *† mm 1000 2300 2500 3000 4000

*

The minimum clearances specif ied take into account the fact that the system voltage may vary by up to 10 percent fr om the nominal volt age. † Allowance should be made for the possible sag and swing of the line.

5 ALTERATIONS IN THE OPERATION. 5.1 Preservation of protection. Care shall be taken to ensure that the protection required by AS 3007.2 is maintained when the operation is altered. Such alterations may include extending the area of operation (requiring longer power lines or cables), construction of roads, addition of equipment, etc. Matters to be considered include clearances, guarding of electrical installations, protective conductor size, overload and short-circuit protection, undervoltage, exposure to lightning, prospective touch voltages, etc. 5.2 Reduction of clearances. Particular care shall be taken to ensure that the clearance of overhead lines to ground is not reduced below the minimum values permitted by dumping or tipping of material, landscaping, or by creating storage areas, or by the positioning of buildings or structures. 5.3 Excavation near electrical installations. Excavation for the extraction of minerals or any other purpose shall not affect the security of the foundation of any pole, tower or other support, nor disturb earthing conductors or electrodes. 5.4 Integrity of safety circuits and safety devices. Precautions shall be taken to ensure that safety circuits or safety devices are not rendered inoperative unless alternative safety measures are implemented. 6 MOVING OF CABLES. 6.1 Movable distribution cables. All movable distribution cables shall be isolated before relocation is commenced unless of a type which is specifically designed to be moved whilst energized. Movement of the cables shall be carried out in accordance with the manufacturer’s recommendations regarding the maximum tension and the minimum temperature and bending radius. Before reconnecting cable coupling boxes they shall be inspected and tested where appropriate to ensure that good conductivity and insulation is maintained. 6.2 Trailing cables and reeling cables. Where trailing cables and reeling cables are moved by a machine, means shall be provided to prevent direct strain being taken by the cable terminations at the machine. Movement of the cables shall be carried out

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in accordance with the manufacturer’s recommendations regarding the maximum tension and the minimum temperature and bending radius. For trailing cables it is recommended that an excess active cable length be provided close to the machine, and that such excess cable be stored in a figure of eight or zig-zag configuration. All trailing cables and reeling cables shall be so located that damage by rocks, stones, etc., will be minimized. All trailing cables and drum cables shall be examined at regular intervals to ensure freedom of movement and freedom from damage. Where the movement of trailing cables and reeling cables requires separation of cable couplers, the cable shall be isolated before the work is commenced. However, this requirement does not apply for low-voltage, low-current applications, e.g. control cables.

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7 PROTECTION OF CABLES. Cables which may be subject to damage as a result of the movement of vehicles and machinery shall be conspicuously located or appropriately protected. Such protection may take the form of — (a) use of ramps and covers; (b) covering with suitable loose material; (c) warning flags, markers or fences; (d) earth embankments; (e) burying in pipes under defined roads; (f) overhead cable bridges; or (g) supporting cables above ground level. 8 MOVING OF OVERHEAD LINES. Before moving an overhead line, all conductors shall be isolated in accordance with the procedure specified in Clause 2.3. In the event of an electrical storm in the area of the overhead line all work on the line shall cease. When persons are working above ground appropriate precautions shall be taken to minimize the risk of falling, e.g. use of safety belts. Precautions shall be taken to ensure that all poles or towers are structurally sound and that releasing the conductors will not cause instability to other sections of the line. All vehicles and machinery shall be prevented from passing under or over a line during dismantling and erection unless appropriate protective measures are taken.

AS 3007.5—1987

The removal of used poles from their original location shall be carried out in a manner which will not endanger the personnel involved. All poles shall be examined along their full length before re-erection, including insulators and cross arms. The re-erecting of overhead line poles shall be carried out on substantial and solid ground. Before re-erection conductors shall be examined to ensure their suitability for re-use. 9 ELECTRIC SHOT-FIRING OPERATIONS. Where electrically initiated explosive devices are used care shall be taken to guard against the danger of inadvertent initiation, or misfires, caused by the input of electrical energy from any source other than the intended initiating source. NOTE: Electrical current can flow in earth paths for a variety of reasons. Such currents, usually described as stray currents constitute possible initiating sources for electrically initiated explosive devices. Recommended measures to minimize the possibility of inadvertent initiation of electrically initiated explosive devices are set out in Appendix A. Attention is also drawn to requirements for the storage and use of explosives in AS 2187.1 and AS 2187.2, respectively.

10 FIRE PREVENTION. (Requirements yet to be developed.) 11 ADDITIONAL REQUIREMENTS AND PRECAUTIONS. 11.1 Precautions during lightning storms. Deenergized cables or overhead lines shall not be handled or repaired during lightning storms where there is a possible hazard from direct strikes or from induced voltages. 11.2 Warning notices. Warning notices shall be provided to draw attention to potential hazards and shall be properly maintained. 11.3 Removal of guards. Protective guards and enclosures shall be removed only when absolutely necessary and when appropriate precautions have been taken. Provision shall be made for prompt replacement of such guards and enclosures on completion of the work. 11.4 Operations involving long metallic structures. Care shall be taken when long metallic structures (e.g. movable conveyors, pipeline systems) are run parallel to overhead lines because of possible hazards from induced voltages. 12 TEMPORARY OPERATION OF EQUIPMENT. Temporary installations shall comply with the general protection requirements of AS 3007.2.

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APPENDIX A

RECOMMENDED MEASURES TO MINIMIZE THE POSSIBILITY OF INADVERTENT INITIATION OF ELECTRICALLY INITIATED EXPLOSIVE DEVICES (See Clause 9)

A1 GENERAL PRECAUTIONS. Procedures which may be used to guard against premature initiation of electrically initiated explosive devices include: (a) The use of adequately insulated initiation cables. (b) Avoidance of cable joints wherever possible. (c) Ensuring that joints are staggered in adjacent cores and are mechanically secure and well insulated. (d) Making the final connection to the initiating device only when the device is about to be used. At all other times the initiating cables should be short-circuited and insulated from earth. (e) Use of frequency sensitive detonators and initiating devices. Such devices are responsive to high frequency (15 000 Hz) only and are insensitive to frequencies of 50 Hz to 60 Hz. The recommendations of Clauses A2 to A9 inclusive outline specific additional measures which may be used to minimize the possibility of inadvertent initiation. A2 IT SYSTEMS WHICH CONTINUE TO OPERATE UNDER FIRST FAULT CONDITIONS. Electrically initiated explosive devices should not be stored or used in the vicinity of any electrical installation which is permitted to continue to operate under first fault conditions (see Clause 11.4 of AS 3007.2). A3 EXPOSED CONDUCTIVE PARTS AND EXTRANEOUS CONDUCTIVE PARTS. Electrically initiated explosive devices and connecting cables should not be used in the vicinity of exposed conductive parts and extraneous conductive parts to avoid premature initiation due to the possibility of voltages appearing on those parts in normal operation, e.g. from the use of PEN conductors, or under fault conditions. A4 OVERHEAD LINES. Electrically initiated explosive devices and connecting cables should not be used in the vicinity of overhead lines. Stray currents can be induced in the cables during fault conditions on the overhead line or in normal operation in the case of single wire earth return (SWER) lines. An additional hazard exists due to the possibility of overhead lines falling to the ground.

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A5 GALVANIC EFFECTS. The contact of dissimilar metals in an electrolytic environment (e.g. ground water, drilling mud) will produce an electric current. The use of metal liners, metal loading sticks or other conductive parts should therefore be avoided. A6 CATHODIC PROTECTION. Particular care should be taken when using electrically initiated explosive devices in the vicinity of pipelines and other structures which are provided with cathodic protection. A7 ELECTROMAGNETIC RADIATION. High frequency energy from radio, television, radar, etc., can under certain conditions, cause initiation of electrically initiated explosive devices. It is recommended that portable radio transmitters not be used in the vicinity of electrically initiated explosive devices and connecting cables. Cognizance should be taken of any fixed transmitting stations in the vicinity. NOTE: Guidance on the prevention of inadvertent initiation of electrically initiated explosive devices by radio-frequency radiation is provided in BS 6657.

A8 STATIC ELECTRICITY. Static electricity charges may be generated by dust storms, snow storms, moving conveyor systems, pneumatic loading systems, etc. If generated charges are allowed to accumulate and/or store on a person or object there is a possible danger of discharge into electrically initiated explosive devices.

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AS 3007.5—1987

It is recommended that shot-firing be suspended during dust storms or snow storms and that accumulation of static charges be avoided by connecting to earth all persons or equipment on which a static charge may accumulate. The electrical resistance of the earth connection should be high enough to restrict current flow yet low enough to dissipate the static charge (usually a resistance value of 10 MΩ is adequate for this purpose). This recommendation may be achieved by the use of semi-conductive products for personal footwear, hoses to pneumatic loading systems and conveyor belts.

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A9 LIGHTNING. Atmospheric disturbance can initiate electrically initiated explosive devices by inducing a current in the firing circuit. It is recommended that laying or firing operations be suspended, and personnel withdrawn from the area during lightning storms.

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ANNEX

SUMMARY OF TECHNICAL DEVIATIONS BETWEEN THIS STANDARD AND IEC 621-5 General. Throughout the text reference has been made to applicable Australian standards in lieu of IEC Publications. Scope. A note has been added warning that the requirements of Regulatory Authorities may differ from the requirements of this standard. Table 1. The minimum approach distances have been revised to align with the clearance distances specified in Table 1 of AS 3007.2 which differ from the corresponding values in IEC 621-2. The approach distances specified have been related to values of nominal system voltage in use within Australia. Table 2. The minimum clearances have been related to values of nominal system voltage in use within Australia. Clause 5.2. The words ‘or by the positioning of structures or buildings’ have been added at the end of the clause. Clause 6.1. In the second sentence, reference has been made to the ‘maximum tension’ to be applied in the relocation of movable distribution cables. Clause 6.2. A sentence has been added to the first paragraph (same as existing in Clause 6.1) concerning the manufacturer’s recommended parameters for the movement of trailing cables and reeling cables. Clause 8. The third paragraph of the clause has been amended to accord with Australian practice for work on overhead lines. Appendix A — Clause A3. The clause has been clarified to indicate that voltages may be transferred to exposed conductive parts and extraneous conductive parts both in normal operation and under fault conditions. Appendix A — Clause A4. Reference has been added to the possibility of stray currents being induced in normal operation in the case of single wire earth return (SWER) lines. Appendix A — Clauses A5 and A6. The two clauses have undergone minor revision to clarify the recommendations. Accessed by HOMESTAKE GOLD of AUSTRALIA LTD on 18 Apr 2002

Appendix A — Clause A7. A note has been added referring to a relevant British Standard.

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