As 3007.4 - Electrical Installations

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AS 3007.41987

Australian Standard

Electrical installations Surfacemines and associated processingplant

Part 4: Additional requirementsfor specific applications

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This Australian standard was prepared by Committee EL/33, Electrical Installations forOutdoor Sites Under Heavy Conditions (Including Opencast Mines and Quarries). It wasapproved on behalf of the Council of the Standards Association of Australia on27 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 MetallurgyConfederation of Australian Industry

Department of Industrial Relations, N.S.W.

Department of Mines, Qld

Department of Mines, Tas.

Electricity Supply Association of Australia

Mining Interests

Review of Australian Standards. To keep abreast of progress in industry, Australian Standards are subject toperiodic review and are kept up to date by the issue of amendments or new editions as necessary. It is importanttherefore that Standards users ensure that they are in possession of the latest edition, and any amendments thereto.

Fulldetails 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, whichsubscribing members receive, and which gives details of new publications, new editions and amendments, and ofwithdrawn Standards.

Suggestions for improvements to Australian Standards, addressed to the head office of Standards Australia, arewelcomed. Notification of any inaccuracy or ambiguity found in an Australian Standard should be made withoutdelay in order that the matter may be investigated and appropriate action taken.

ThisStandard was issued in draft form for comment as DR 86010.Accessedb

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AS 3007.41987

Australian Standard

Electrical installations Surfacemines and associated processingplant

Part 4: Additional requirements

for specific applications

First published 1985. . . . . . . . . . . . . . . . . . . . . . . . . . . . .Second edition 1987. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

PUBLISHED BY STANDARDS AUSTRALIA(STANDARDS ASSOCIATION OF AUSTRALIA)1 THE CRESCENT, HOMEBUSH, NSW 2140

ISBN0 7262 4618 2

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PREFACE

This standard was prepared by the Associations Committee on Electrical Installations forOutdoor Sites Under Heavy Conditions (Including Opencast Mines and Quarries tosupersede AS 3007, Part 41985.It is essentially identical with IEC 6214* which was prepared by the correspondingIEC Technical Committee, i.e. TC 71. Where this standard deviates technically from

IEC 6214 by way of different or additional requirements, this is indicated by a rule in themarginagainst the clause, or part thereof, affected. A summary of such technical variations isgiven in the Annex.Some requirements are repeated in different sections of the standard. This arises from adecision by IEC TC 71 to consider separately the requirements which should apply forparticular types of installation. The IEC committee intends that the requirements which arefound to be common should ultimately be transferred to IEC 6213 (Australian equivalent AS 3007.3) as a general requirement for all installations.TheAustralian committee (EL/33) has actively participated in the work of IEC TC 71 whichhas as its objective the development of uniform and internationally acceptable rules for thesafeuse of electricity in opencast mines, quarries, stockpiles and the like. Such applicationspresent particularly onerous conditions for the electrical apparatus and systems, includingcontinualalteration of the location of the apparatus and systems, extension of the operationalarea,and adverse environmental conditions. Because of the size of the plant and the need formobility,supply is frequently at high voltage over long distances, by means of trailing cables.

Thisshould be compared with other industries where the electrical installations are generallyfixed.The AS 3007 series specifies requirements for the installation and operation of electricalapparatus and systems in the abovementioned locations, with the object of ensuring thesafety of persons, livestock and property. AS 3007.1 outlines the scope of the compositestandard and provides definitions for some of the terms used. AS 3007.2 specifies themeasures which are required for protection against electric shock in normal service fromdirect contact with live parts; for protection against electric shock from parts which maybecome live in the event of a fault(indirect contact); and for protection against the effects ofovercurrent resulting from overload or short circuit conditions. AS 3007.3 specifies generalrequirements for the equipment and ancillaries associated with the electrical installation.AS 3007.4 (this standard) sets out the requirements which are specific to particularinstallations, together with any exemptions from the general requirements of AS 3007.2 andAS 3007.3 which apply for such installations. AS 3007.5 sets out the normal operatingprocedures which should be carried out to ensure the safety of personnel.

The AS 3007 series recognizes several types of power supply system and specifies theprotectivemeasures which are necessary for each system. Requirements for the protection ofpersonnel from indirect contact (see Section 2 of AS 3007.2) are based on the concept ofpermissible voltage versus time limits, which take into account the pathophysiologicaleffects 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 theAS 3007 series differs in approach from the practically evolved requirements of AS 3000,SAAWiring Rules.Itwill therefore be necessary for the regulatory authorities concerned to clearly delineate therespective areas of application for the AS 3007 series and for AS 3000.

* Including Amendment No 1 to IEC 6214 which is in course of publication based on Document 71 (Central

Office)35.

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Users of Standards are reminded that copyright subsists in all Standards Australia publications and software. Except where the Copyright Act allowsand except where provided for below no publications or software produced by Standards Australiamay be reproduced, stored in a retrieval system inanyform or transmitted by any means without prior permission in writing from Standards Australia. Permission may be conditional on an appropriateroyalty payment. Requests for permission and information on commercial software royalties should be directed to the head office of StandardsAustralia.

Standards Australia will permit up to 10 percent of the technical content pages of a Standard to be copied for use exclusively inhouse bypurchasers of the Standard without payment of a royalty or advice to Standards Australia.

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Careshould 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 orrevised. The number and date of the Standard should therefore be clearly identified.

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CONTENTS

Page

SCOPE OF PART 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

REFERENCED DOCUMENTS 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 1. WINNING, STACKING AND PRIMARY PROCESSING MACHINERY

1 SPECIAL ADDITIONAL REQUIREMENTS FOR AND EXEMPTIONS

FROM PROTECTION AGAINST DIRECT AND

INDIRECT CONTACT 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2 DRIVES 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3 EXTERNAL POWER SUPPLY SYSTEMS 5. . . . . . . . . . . . . . . . . . . . . . . . .

4 SELFCONTAINED POWER SYSTEMS 5. . . . . . . . . . . . . . . . . . . . . . . . . . .

5 CABLE TYPES 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6 CONTROL CIRCUITS AND CONTROL DEVICES 5. . . . . . . . . . . . . . . . . .

7 EMERGENCY STOPPING AND EMERGENCY DEVICES 6. . . . . . . . . . . .

8 PROVISION OF SUPPLY ISOLATION 6. . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 2. TRANSPORT CONVEYOR SYSTEMS


FROM PROTECTION AGAINST DIRECT AND INDIRECT

CONTACT 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10 CABLES 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11 STOP CONTROLS 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12 EMERGENCY STOPPING AND EMERGENCY DEVICES 7. . . . . . . . . . . .

13 PROVISION FOR SUPPLY ISOLATION 7. . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 3. PUMPING AND WATER SUPPLY SYSTEMS



CONTACT 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 4. SECONDARY PROCESSING MACHINERY



CONTACT 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16 DRIVES AND OTHER ELECTRICAL LOADS 9. . . . . . . . . . . . . . . . . . . . . .

17 EXTERNAL POWER SUPPLY SYSTEMS 9. . . . . . . . . . . . . . . . . . . . . . . . .

18 SELFCONTAINED POWER SYSTEMS 9. . . . . . . . . . . . . . . . . . . . . . . . . . .

19 CABLE TYPES AND PROTECTION 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

20 CONTROL CIRCUITS AND CONTROL DEVICES 9. . . . . . . . . . . . . . . . . .

21 EMERGENCY STOPPING AND EMERGENCY STOP CONTROLS 10. . . .22 PROVISION FOR SUPPLY ISOLATION 10. . . . . . . . . . . . . . . . . . . . . . . . . . .

23 EXPLOSIVE ATMOSPHERES 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

24 STATIC ELECTRICITY 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

25 ELECTROSTATIC PRECIPITATORS 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

26 RADIOACTIVE SOURCES 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

27 RAILMOUNTED EQUIPMENT 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

28 HAZARDS FROM INDUCTION 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

APPENDICES

A EXAMPLES OF CIRCUIT ARRANGEMENTS FOR EMERGENCY

DEVICES 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

B GUIDELINES FOR LOW SIGNAL LEVEL SYSTEMS ANDCOMMUNICATION SYSTEMS 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ANNEX. SUMMARY OF TECHNICAL DEVIATIONS BETWEEN THIS

STANDARD AND IEC 6214 18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Accessedb

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AS 3007.41987 4

STANDARDS ASSOCIATION OF AUSTRALIA

Australian Standard

for

ELECTRICAL INSTALLATIONS SURFACE MINES AND ASSOCIATED PROCESSING PLANT

PART 4 ADDITIONAL REQUIREMENTS FOR SPECIFIC APPLICATIONS

SCOPE OF PART

This standard sets out the requirements which are specific to particular installationswithin the scope of AS 3007.1, together with any exemptions from the generalrequirements of AS 3007.2 and AS 3007.3 which apply for such installations.

NOTE: Appendix B provides guidelines for t he installation of low signal level systems andcommunication systems.

REFERENCED DOCUMENTS

The following standards are referred to in this standard:

AS 1020 The Control of Undesirable Static Electricity

AS 1755 SAA Conveyor Safety Code

AS 2380 Electrical Equipment for Explosive AtmospheresExplosion ProtectionTechniques

AS 3007.1 Electrical InstallationsSurface Mines and Associated Processing PlantPart 1Scope and Definitions

AS 3007.2 Electrical InstallationsSurface Mines and Associated Processing Plant

Part 2General Protection RequirementsAS 3007.3 Electrical InstallationsSurface Mines and Associated Processing Plant

Part 3General Requirements for Equipment and Ancillaries

AS 3007.5 Electrical InstallationsSurface Mines and Associated Processing PlantPart 5Operating Requirements

IE C 353 Line Traps

IEC 481 Coupling Devices for Power Line Carrier Systems

IEC 495 Recommended Values for Characteristic Input and Output Quantities ofSingle Sideband Power Line Carrier Terminals

IEC 536 Classification of Electrical and Electronic Equipment with regard toProtection against Electric Shock

IEC 621-4 Electrical Installations for Outdoor Sites Under Heavy Conditions

(Including Open-cast Mines and Quarries)Part 4: Requirements for the Installation

IEC 663 Planning of (Single-sideband) Power Line Carrier Systems

BS 6657 Guide to Prevention of Inadvertent Initiation of Electro-explosiveDevices by Radio Frequency Radiation.

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5 AS 3007.41987

SECTION 1. WINNING, STACKING AND PRIMARY

PROCESSING MACHINERY

INTRODUCTION. This Section specifies therequirements which particularly apply to the electricalequipment of winning, stacking and primaryprocessing machinery.

The requirements of AS 3007.2 and AS 3007.3 shallapply except where specific exemptions are allowed inthis Section.

Where conveyor systems are incorporated as part ofwinning, stacking and primary processing machinery,the requirements of Section 2 shall also apply.

1 SPECIAL ADDITIONAL REQUIREMENTSFOR AND EXEMPTIONS FROM PROTECTIONAGAINST DIRECT AND INDIRECT CONTACT.

1.1 Off-board mobile and movable auxiliaryequipment. For off-board mobile and movableauxiliary equipment (e.g. welding equipment,vulcanizing t ransformers) which require the provisionof a protective conductor, either the protectiveconductor shall be visible throughout its length or oneor more of the following measures shall be adopted:

(a) The protective conductor shall be monitored forincrease in resistance.

(b) Sensitive earth leakage protection shall beprovided.

(c) A visible equipotential bonding conductor shallbe provided between the off-board mobile ormovable auxiliary equipment and the plant fromwhich it is supplied.

1.2 Insulation monitoring device for IT systems.In IT systems, insulation monitoring devices are notrequired for power circuits which are supplied by apower source from within the machine, such as by atransformer having electrically isolated windings, orby a generator or storage battery.

1.3 Insulation monitoring devices for vulcanizingheating platens. In IT systems, insulation monitoringdevices are not required for vulcanizing heatingplatens where the power circuit is supplied from atransformer having electrically isolated windings.

1.4 Electric hand tools. (No requirement at present)

1.5 Electric hand lamps. (No requirement atpresent)

2 DRIVES. The requirements of Clauses 2.1 and 2.2apply to drives with a periodic or cyclic duty as wellas to certain other drives with a continuous duty.

2.1 Effects on voltage levels. The effects ofequipment starting and of the duty cycle on voltagelevels, which may result in damage or the malfunctionof equipment, shall be taken into consideration toensure the safety of persons and equipment.

2.2 Supply systems. The effect of load fluctuationson the supply system shall be considered, takingaccount of any restrictions imposed by the electricitysupplier.

3 EXTERNAL POWER SUPPLY SYSTEMS.

3.1 System design. The supply system shall meet therequirements of cyclic or periodic loads, motorstarting, and inherent a.c. motor oscillations transient

load changes. For protection requirements againstdirect and indirect contact, see AS 3007.2.

3.2 Overcurrent protection. Overload and short-circuit protection for t ransformers, cables, etc., shalltake into consideration the start ing requirements andcyclic nature of the load.

3.3 Automatic reclosing or transferring. Whereregenera tion may de lay the operation of undervoltage devices, automatic reclosing ortransferring devices shall not be used in the powerdistribution system unless one or more of thefollowing conditions apply:

(a) Such devices have sufficient time delay toallow motor disconnection (see Clause 6.2).

(b) The device is fi t ted with out of stepprotection.

(c) The combination of supply system and motordesign characteristics is such as to permitautomatic re-energization.

3.4 System voltage. Consideration shall be givenas to whether the system voltage specified is underno-load or full load conditions.

4 SELF-CONTAINED POWER SYSTEMS.

4.1 System design. The power generation systemsshall meet the requirements of motor starting,regeneration, peak load, r.m.s. load and frequencystability.

4.2 Fire protection. Consideration shall be givento the need for special and/or additional fireprotection due to the fuels used (see Section 11 ofAS 3007.3).

4.3 Earthing. When the supply of electrical energyis self-contained within stationary, mobile, ormovable items of equipment and there is no externalsupply, such equipment need not be connected to thegeneral mass of the earth.

4.4 Supply to off-board equipment. When poweris supplied to off-board mobile and movableequipment the requirements of Clause 1.1 shallapply.

5 CABLE TYPES. (No requirement at present)

6 CONTROL CIRCUITS AND CONTROLDEVICES.

6.1 Shock, vibration and voltage fluctuations.The effect of shock, vibration or voltage fluctuationson control devices shall be taken into consideration,ensuring that the safety of persons and equipment isnot endangered by inadvertent operation of controldevices (see also Clause 5 of AS 3007.3).

When mechanically latched control devices are usedand re-energization following loss of supply powerwould endanger persons or equipment, means shallbe provided to automatically trip the latched control

device on loss of supply power. The device shallalso be tripped on operation of protective devices.

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AS 3007.41987 6

6.2 Synchronous motor control.

6.2.1 Automatic discharge of fie ld energy. Wheresynchronous motors are used, provision shall be madefor automatic discharge of the field energy (i.e. fieldremoval or suppression) upon disconnection of t he

motor .

6.2.2 Automat ic field exci tat ion control . Wheresynchronous motors are used to drive periodic orcyclic loads, an automatic field excitation control isrecommended .

6.2.3 Power loss protection. Where synchronousmotors are used to drive loads which may beregenerative, means shall be provided to trip themotor starting switch or incoming line switch uponloss of power supply. Frequency-sensitive devices arerecommended. When automatic reclosing ortransferring devices are used in the distribution

system, the requirements of Clause 3.3 shall apply.

6.3 Stop controls.

6.3.1 Use of stop controls . Stop controls shall not beused for the purpose of isolation or immobilization toallow work to be carried out on parts which wouldotherwise be electrically energized or capable ofmoving, except where permitted in AS 3007.5.

6.3.2 Location of stop controls. A stop control shallbe located near each start control, except for lift callcontrols. Additional stop controls may be provided.

6.4 Start controls. Where equipment is started

manually from one or more locations, suitable audibleand/or visual warning devices, together withappropriate notices, shall be provided to give advancewarning of equipment starting unless one or more ofthe following conditions apply:

(a) Personnel access to hazardous parts is limited.

(b) Danger to personnel does not exist fromequipment starting.

(c) The hazardous parts of the equipment beingstarted are in full and clear view from all startinglocations .

Where equipment is started automatically the abovewarning system shall be provided unless conditions (a)

and/or (b) apply.For sequential starting of a localized plant group, asingle warning system may be sufficient.

7 EMERGENCY STOPPING AND EMERGENCYDEVICES.

7.1 Emergency stop controls. Emergency stopcontrols shall be provided for all equipment which isaccessible to persons and which presents a hazard tothem. The emergency stop controls shall be readilyaccessible and located in a suitable position for safeoperation under all expected emergency conditions.

The circuits of emergency stop controls shall besimple and reliable. Direct acting controls arepreferred wherever practicable.

NOTE: Manually operated stop controls and conveyorpullwire stop controls may also provide the function of an

emergency stop control.

7.2 Emergency stopping. Effective means shall beprovided for stopping the drive under emergencyconditions. Consideration shall be given, not onlyto disconnection of supply as a means of safestopping, but also to other suitable means, whereavailable, such as electrical regenerative braking.

7.3 Emergency devices. Where the emergencydevices are actuated remotely they shall be ar rangedas a series-tripping system, excepting that shunttripping may be used providing the tripping deviceand its stored energy tripping supply are regularlychecked or monitored and regularly maintained.

Emergency devices may be arranged to operatesimultaneously in a number of different circuits. Anumber of emergency devices may be arranged ingroups; each group may operate in single or multiplecircuits.

Where several circuits are divided, the respectivecontact elements shall be connected in series,excepting that shunt tripping systems may be usedprovided the above-mentioned conditions aremaintained.

The emergency device may use remote controlsystems, for example, audio-frequency ortime-multiplex operations, providing that at least the

same protective measures as for the above devicesare applied to ensure positive, and reliableoperation. However, the simultaneous existence oftwo or more faults within the remote control systemneed not be expected.

NOTE: See diagrams in Appendix A for an illustration ofrequirements for the arrangement of emergency devices, a s

outlined in the above clause.

8 PROVISION OF SUPPLY ISOLATION. Ameans of mains supply isolation shall be provided toisolate the power-circuits from the equipment orparts thereof, inclusive of control and motor circuits,excepting that separate means of isolation may beprovided for control circuits, which may remainenergized after disconnection of power circuits,provided special measures for the safety of personsand equipment have been implemented, includingthe provision of a warning notice at the mainssupply isolator to indicate that it does not isolate thecontrol circuit(s).

NOTE: See also Clause 24 of AS 3007.3, regarding

provision for the locking of isolators.

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7 AS 3007.41987

SECTION 2. TRANSPORT CONVEYOR SYSTEMS

INTRODUCTION. This Section specifies therequirements which particularly apply to the electricalequipment of transport conveyor systems.

The requirements of AS 3007.2 and AS 3007.3 shallapply except where specific exemptions are allowed inthis Section.


9.1 Equipoten tial bondin g c on du ctor an dconductivity of structural parts. Where electricalequipment supplied at a voltage in excess of 50 V ismounted on a conveyor structure and the cable to theequipment does not include a protective conductor, anequipotential bonding conductor shall be provided tothe electrical equipment unless the structural parts of

the conveyor are mechanically fastened and/orelectrically bonded together. The conductivity of themetallic structural parts of the conveyor and itsfastenings shall be at least equal to that of theotherwise necessary equipotential bonding conductor.

9.2 Off-board mobile and movable auxiliaryequipment. The requirements of Clause l.l shallapply.

9.3 Insulation monitoring device for IT systems.The requirements of Clause 1.2 shall apply.

9.4 Insulation monitoring devices for vulcanizing

heating platens. The requirements of Clause 1.3shall apply.

9.5 Electric hand tools. (No requirement at present)

9.6 Electric hand lamps. (No requirement atpresent)

10 CABLES.

10.1 General. Where cables without semi-conductivesheaths, metallic screens, or armouring are suspendedfrom structures or frames of movable conveyors, suchstructures and frames shall be considered asextraneous conductive parts and shall be included aspart of the whole plant in the design of the protectivemeasures against indirect contact, i.e., by ensuringthat all metallic parts are linked together.

10.2 Power supply cables. (No requirement atpresent)

11 STOP CONTROLS.11.1 Use of stop controls. Stop controls shall notbe used for the purpose of i solation orimmobilization to allow work to be carried out onparts which would otherwise be electricallyenergized or capable of moving, except wherepermitted in AS 3007.5.

11.2 Stopping sequence.The operation of a stopcontrol on a conveyor shall stop that conveyor andshall stop all upstream conveyors to a controlledloading point, or cause the material from allupstream conveyors to be diverted to an alternativeroute.

On very long conveyor systems, however, theoperation of a stop control within one stop zoneneed not stop all upstream conveyors beyond thatzone, provided t hat the conveyor upstream of thezone is proved to be unloaded, for example bysensors.

Al though the stop control may be resetautomatically, restarting shall be manually initiated.

11.3 Location of stop controls. Stop controls shallbe provided in the locations required by AS 1755.

11.4 Pullwire stop controls. Stop controlsoperated by a pullwire shall be arranged so that a

pull on the wire in any direction transverse to theconveyor axis will stop the controlled equipment.The stop controls shall be of a type in which thecontacts are actuated by a positive mechanical actionand can be reset only by a further mechanicalaction.

12 E M ERGE NCY S TO P P I N G A NDEMERGENCY DEVICES. The requirements ofClause 7 shall apply.

13 PROVISION FOR SUPPLY ISOLATION.The requirements of Clause 8 shall apply.

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AS 3007.41987 8

SECTION 3. PUMPING AND WATER SUPPLY SYSTEMS

INTRODUCTION. This Section specifies therequirements which particularly apply to the electrical

equipment of pumping and water supply systems.The requirements of AS 3007.2 and AS 3007.3 shallapply except where specific exemptions are al lowed inthe Section.

NOTE: There are no requirements at present for thefollowing:

(a) Pumps other than deep-well types.

(b) Power supply cables

(c) Control circuits and control devices

(d) Safety circuits and safety devices.


14.1 Deep-well type pumps.

14.1.1 Risers as protective conductors . Where acontinuous metallic riser pipe is fitted between themotor and the well head, no protective conductor isrequired between the motor and the protectiveconductor connected directly to the fixed riserprovided that all of the following conditions apply:

(a) The supply cable is terminated close to the wellhead.

(b) The conductivity of the metallic riser (stand pipe)and the connections (couplings) is at least equalto t he conductivity of the protective conductorwhich would otherwise be necessary.

(c) Persons do not have access down the well.

14.1.2 Continued operation after first earth fault .Operation may continue after the first earth fault onlywhen all of the following conditions are met:

(a) An IT system is used.

(b) Persons do not have access down the well.

(c) Equipotential bonding is provided in accordancewith Clause 14.1.3.

14.1.3 Equipotential bonding . An equipotentialbonding conductor shall be installed between the

main earth terminals of the supply and the wellhead(s), where the conductor shall be connecteddirectly to the fixed riser. Where transformers arelocated at the well head, their enclosures shall beconnected to this bonding conductor.

The equipotential bonding conductor shall be sodimensioned that the voltage drop between any twopoints that may be contacted simultaneously will notexceed 50 V. That is:

where

R = the resistance value between thesetwo points, in ohms

In = the rated current of the power fusesor, in the case of circuit-breakers,0.2 times the r eleasing current forthe instantaneous or short-time delaytrip, in amperes

K = a constant (a recommended value forKis 2.5).

NOTE: The purpose of this requirement i s to ensure that thevoltage/time limits specified in Section 2 of AS 3007.2 arenot exceeded in r espect of indirect contact between t he

various parts of the equipotential conductor.

14.1.4 Exemption from insulation monitoring

device . For IT systems an insulation monitoringdevice (or earth fault detector) is not necessary toindicate the occurrence of the first earth fault wherethe prospective touch voltage does not exceed ULand the conditions of Clause 14.1.2 are fulfilled.

14.1.5 Double line to earth faul ts. For IT systemsa device, such as one which detects a change inneutral displacement on the occurrence of the firstand second earth faults, may be used to disconnectthe supply on the occurrence of the second earthfault, as required by Clause 11.4(b) of AS 3007.2.

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9 AS 3007.41987

SECTION 4. SECONDARY PROCESSING MACHINERY

INTRODUCTION. This Section specifies therequirements which particularly apply to the electricalequipment of secondary processing machinery.

The requirements of AS 3007.2 and AS 3007.3 shallapply, except where specific exemptions are allowedin this Section.


15.1 Insulation monitoring device for IT systems.In IT systems, insulation monitoring devices are notrequired for power circuits which are supplied by apower source from within the machine, such as by atransformer having separate windings, or by agenerator or storage battery.

15.2 Insulation monitoring devices for vulcanizingheating platens. In IT systems, insulation monitoring

devices are not required for vulcanizing heatingplatens where the power circuit is supplied from atransformer having separate windings.

16 DRIVES AND OTHER ELECTRICAL LOADS.

16.1 App lic at ion of r eq uir eme nt s. Therequirements of Clauses 16.2 and 16.3 apply to drivesand other electrical loads with a periodic or cyclicduty as well as to certain other drives and electricalloads with a continuous duty.

16.2 Effects on voltage levels. Voltage fluctuationsdue to equipment starting and/or the equipment dutycycle may cause malfunctions or damage to t heelectrical installation and shall be taken into account

in the selection of the system.16.3 Supply systems. The effect on the supplysystem of load fluctuations, power factor andharmonic currents shall be considered, taking accountof any restrictions imposed by the electricity supplier.

17 EXTERNAL POWER SUPPLY SYSTEMS.

17.1 System design. The supply system shall meetthe requirements of cyclic or periodic loads, motorstarting, and inherent a.c. motor oscillations due totransient load changes, taking account of anyrestrictions imposed by the electricity supplier.

17.2 Overcurrent protection. Overload and short-circuit protection for transformers, cables, etc., shall

take into account the starting requirements and cyclicor periodic nature of the load.

17.3 Automatic reclosing or transferring. Whereregeneration may delay the operation of undervoltagedevices, automatic reclosing or transferring devicesshall not be used in the power distribution systemunless one or more of the following conditions apply:

(a) The devices have sufficient t ime delay to allowmotor disconnection (see Clause 20.4.3).

(b) The device is fitted with out of step protection.

(c) The combination of supply system and motordesign characteristics is such as to permitautomatic re-energization.

17.4 Supply voltage. Where large variations in loadcan occur, it may be necessary to regulate the supplyvoltage to the installation.

Consideration shall be given as to whether thevoltage specified is under no load or full loadconditions.

18 SELF-CONTAINED POWER SYSTEMS.

18.1 System design.The power generation systemsshall meet the requirements of motor starting,regeneration, peak load, r.m.s. load and frequencystability.

18.2 Fire protection. Consideration shall be givento the need for special and/or additional fireprotection due to the fuels used (see Section 11 ofAS 3007.3).

18.3 Earthing. When the supply of electricalenergy is self-contained within stationary, mobile, ormovable items of equipment and there is no externalsupply, such equipment need not be connected to thegeneral mass of the earth.

19 CABLE TYPES AND PROTECTION. Cablesshall be installed and terminated in such a mannerthat they are protected from damage resulting fromcorona or from physical and environmentalconditions. Where installed in areas prone tocorrosive atmospheres, steam, extreme heat,ultraviolet radiation, material build-up, etc.,additional protection may be necessary.

Where cables are exposed to physical damage, theyshall be protected by enclosures, armouring or othersuitable means.

20 CONTROL CIRCUITS AND CONTROLDEVICES.

20.1 Stop controls.20.1.1 Location of stop controls. A stop controlshall be located near each start control, except forlift call controls. Additional stop controls may beprovided.

20.1.2 Stopping sequence . The operation of a stopcontrol for a piece of equipment shall stop thatequipment and shall

(a) stop all upstream equipment to a controlledloading point, or cause the material from allupstream equipment to be diverted to analternative route; and where required

(b) initiate braking to stop the equipment in a safe

time; and(c) prevent run back.

20.2 Start controls. Where equipment is startedmanually from one or more locations, suitableaudible and/or visual warning devices, together withappropriate notices, shall be provided to giveadvance warning of equipment starting unless one ormore of the following conditions apply:

(a) Personnel access to hazardous parts is limited.

(b) Danger to personnel does not exist fromequipment starting.

(c) The hazardous parts of the equipment beingstarted are in full and clear view from allstarting locations.

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Where equipment is started automatically, the abovewarning system shall be provided unless conditions (a)and/or (b) apply.

For sequential starting of a localized plant group, asingle warning system may be sufficient.

20.3 Shock, vibration and voltage fluctuations.The effect of shock, vibration and voltage fluctuationson control devices shall be taken into consideration,ensuring that the safety of personnel and equipment isnot endangered by inadvertent operation of controldevices (see also Clause 5 of AS 3007.3).

When mechanically latched control devices are usedand re-energization following loss of supply powerwould endanger personnel or equipment, means shallbe provided to automatically trip the latched controldevice on loss of supply power. The device shall alsobe tripped on operation of protective devices.

20.4 Synchronous motor control.

20.4.1 Automatic discharge of field energy. Wheresynchronous motors are used provision shall be madefor automatic discharge of the field energy (i.e. fieldremoval or suppression) upon disconnection of t hemotor .

20.4.2 Automatic fie ld exci tation control . Wheresynchronous motors are used to drive periodic orcyclic loads, an automatic field excitation control isrecommended.

20.4.3 Power loss protection. Where synchronousmotors are used to drive loads which may beregenerative, means shall be provided to trip themotor starter switch or incoming line switch upon lossof power supply. Frequency sensitive devices are

recommended. When automatic reclosing ortransferring devices are used in the distributionsystem, the requirements of Clause 17.3 shall apply.

2 1 E M E RG EN C Y S T O PP I NG A N DEMERGENCY STOP CONTROLS.

21.1 Emergency stopping. Effective means shall beprovided for stopping drives under emergencyconditions. Consideration shall be given, not only todisconnection of supply as the primary means of safestopping, but also to other effective means whereavailable, such as electrical regenerative braking.

21.2 Emergency stop controls. Emergency stopcontrols shall be provided for all equipment which isaccessible to persons and which presents a hazard to

them. The emergency stop controls shall be readilyaccessible and located in a suitable position for safeoperation under all expected emergency conditions.

The circuits of emergency stop controls shall besimple and reliable. Direct acting controls arepreferred wherever practicable.

NOTE: Manually operated stop controls and conveyorpullwire stop controls may also provide the function of an

emergency stop control.

22 PROVISION FOR SUPPLY ISOLATION. Ameans of mains supply isolation shall be provided toisolate the power-circuits from the equipment or partsthereof, inclusive of control and motor circuits,excepting that separate means of isolation may beprovided for control circuits (which may remainenergized after disconnection of power circuits)

provided special measures for the safety ofpersonnel and equipment have been implemented.

NOTE: See also Clause 24 of AS 3007.3 regarding

provision for the locking of isolators.

23 EXPLOSIVE ATMOSPHERES. Whereexplosive gas atmospheres exist, electricalequipment shall comply with the relevant standardsin the AS 2380 series.

It should be recognized that certain fine dustparticles in air can form an explosive atmosphere. Insuch cases precautions shall be taken to prevent theformation of explosive concentrations or,alternatively, equipment used in the area concernedshall be of a type which will not give rise to risk ofignition.

24 STATIC ELECTRICITY.

24.1 General. For the purpose of this clause,generation of static electricity is taken to mean theseparation of electric charges into equal quantities of

opposite polarity by disunion or relative movementbetween contacting surfaces of two substanceshaving a different physical and/or chemical st ructureat the contacting surfaces. The substances may beboth solids, both liquids, or one solid and one l iquid.No static is generated by disunion or relativemovement between gas and solids or gas andliquids, except where the gas contains entrainedsubstances.

NOTE: See AS 1020 for further information on the control

of static electricity.

24.2 Common sources of generation. Commonsources of generation of static electricity include thefollowing:

(a) Pulverized materials passing through chutes orpneumatic conveyors.

(b) Low conduct iv ity l iquids , e.g. l iquidhydrocarbons flowing at high velocity throughpipes and associated equipment.

(c) Steam, air or gas containing particulate matterflowing from any opening in a pipe or hose.

(d) Non-conductive drive belts or conveyor belts inmotion.

(e) Moving vehicles.

24.3 Fire and explosion dangers. The generationor presence of static electricity does not necessarily

create a danger of fire or explosion, but will initiateit only when all the following four conditions arefulfilled:

(a) An effective means of static electricitygeneration.

(b) A means of accumulating the separated chargesand attaining sufficient potential differencebetween them.

(c) A static discharge having sufficient energy forignition .

(d) The static discharge occurring in or on aflammable or explosive substance.

24.4 Removal of fire and explosion dangers.Measures for removing fire or explosion hazardsmay include one or more of the following:

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(a) Eliminate any source of generation of staticelectricity from localities where flammable orexplosive substances are present or are likely tobe present. Machinery which produces staticelectricity should not be used in these localities,

e.g. use direct coupled gear drives rather t hanbelt drives.

(b) Provide means for adequate dissipation andprevention of accumulation of static electricity,thereby ensuring that static discharges do notoccur, e.g. use of discharge pickups.

(c) Ensure that there are no flammable or explosivesubstances in areas where static discharges arelikely to occur.

25 ELECTROSTATIC PRECIPITATORS.Whereelectrostatic precipitators and separators operating athigh voltage are used, precautions shall be taken suchas coded locks and interlocking, to prevent access ofpersonnel to high-voltage areas having sufficient

energy to create a hazard for personnel.

26 RADIOACTIVE SOURCES. Where radioactivesources are used for applications such as slurrydensity measurements, bin-level detection or beltweighers, means shall be provided to

(a) effectively isolate the source, e.g. by the use ofmechanical locks and shutters;

(b) prevent persons from gaining access to theuseful beam; and

(c) either restrict the radiation level external to thesource enclosure to not more than the acceptedsafe level for persons, or control the access ofpersons to prevent exposure to dangerousdosages of radiation.

27 RAIL-MOUNTED EQUIPMENT. High dustlevels and corrosive atmospheres may causeproblems due to poor electrical conductivity betweenwheels and rails. Special precautions shall be takento ensure that protective conductor paths remaineffective under these conditions.

28 HAZARDS FROM INDUCTION. Considera-tion shall be given to the possibility of hazards

arising from induction from installations involvingextremely high currents such as may exist with potlines and arc furnaces. This applies particularly tothe installation of cables in the vicinity of suchequipment.

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AS 3007.41987 12

APPENDIX A

EXAMPLES OF CIRCUIT ARRANGEMENTS FOREMERGENCY DEVICES

(to illustrate the requirements of Clause 7.3)

Fig. A1. ARRANGEMENTOF EMERGENCY DEVICES FOR SERIES TRIPPING

Fig. A2. ARRANGEMENT OF EMERGENCY DEVICES IN A NUMBER OFDIFFERENT CIRCUITS WITH SERIES TRIPPING

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Fig. A3. ARRANGEMENT OF EMERGENCY DEVICES FOR SHUNT TRIPPING

Fig. A4. ARRANGEMENTOF EMERGENCY DEVICES IN A NUMBER OFDIFFERENT CIRCUITS WITH SHUNT TRIPPING

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AS 3007.41987 14

APPENDIX B

GUIDELINES FOR LOW SIGNAL LEVEL SYSTEMS ANDCOMMUNICATION SYSTEMS

INTRODUCTION. The purpose of this Appendix is to set out guiding principles forlow signal level systems (for transmitting measured values, control data, controlinstructions, etc.) and communication systems (for transmitting speech, sounds,pictures, characters, etc.) in order to protect persons and property against -

(a) the transfer of unsafe voltages f rom power systems or other circuits; and

(b) malfunctions due to interference originating either from within the system orfrom an external influence such as nearby overhead lines, radio transmitters orheavy electrical equipment.

It applies to the installation of low signal level systems and communication systemsin the locations covered by AS 3007.1. These systems should comply with the relevantrequirements of AS 3007.2 and AS 3007.3.

NOTE: This Appendix does not apply to railway signalling systems.

B1 ASSESSMENT OF GENERAL CHARACTERISTICS. An assessment shouldbe made of the following characteristics of the installation:

(a) Means of transmission, for example, cable, power line carrier, radio or opticalsystems.

(b) Signal type, e.g. analogue or digital.

(c) Interference to signal transmission by power supplies (e.g. harmonics, voltagetransients), other circuits, lightning, radio signals, etc.

(d) Interference by indirect t ransfer of voltage, e.g. inductive (electromagnetic),capacitive (electrostatic), resistive (ohmic), galvanic (electrolytic).

(e) Interference by direct t ransfer of voltage from power systems.

(f) Interference from fault current in the earthing system influencing the referencepotential.

(g) Power supply for the low signal level system and communication system,

including regulation of voltage, current and frequency, effects of fault current,effects of harmonics, maintenance of potential reference for the system, effectsof loss of power.

These characteristics should be t aken into account in the choice of methods ofprotection to ensure safety of persons and to avoid malfunction of equipment.

B2 PROTECTION OF PERSONS AGAINST THE TRANSFER OF UNSAFEVOLTAGES.

B2.1 Causes of voltage transfer. Unsafe voltages may be transferred to low signallevel systems and communication systems by -

(a) direct transfer of voltages due to insulation failure, mechanical damage, accidentalcontact, leakage between adjacent terminals, failure of equipment, etc.; and

(b) indirect transfer of voltages resulting from inductive and capacitive coupling wi th

other circuits.B2.2 Measures for protecting persons against direct transfer of unsafe voltages.One or more of the measures described in Items (a) to (k) below shall be adopted, orother measures providing equivalent protection. Not all of the measures listed areeffective for all types of TN, T T and IT systems described in Clause 8 of AS 3007.2.

(a) Use of safety extra-low voltage for the power system.

NOTE: See IEC 536 for a definition of the term safety extra-low voltage.

(b) Use of cables in the power system with metallic screens and/or armouring (seeClauses 29 and 33 of AS 3007.3).

(c) Use of cables in the power system with semi-conducting layers (see Clause 32 ofAS 3007.3).

(d) Use of cables in the power system with double insulation or reinforced insulation.

NOTE: See IEC 536 for definitions of the terms double insulation and reinforced insulation.

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(e) Inclusion of all exposed conductive parts of the low signal level system or communicationsystem which may become live in the event of a fault in the power system, in the protectivemeasures against indirect contact of the power system.

(f) Application of conductive shielding between conductors of the low signal level system orcommunication system and conductors of other circuits. The shielding should be connected toa protective conductor and sized in accordance with the prospective fault current.

(g) Use of isolating transformers or optical isolators to terminate the conductors of low signal levelsystems or communication systems for the purpose of providing isolation from other circuits.

(h) Installation of cables of low signal level systems or communication systems physically separatethroughout their entire length from other cables, with or without the use of barriers. Terminalsshould be grouped physically separate from terminals of other systems and, if necessary,provided with barriers, shrouds, etc.

(j) Use of cables provided with either armouring and/or double insulation or reinforced insulationfor the circuits of low signal level systems and communication systems.


(k) Use of fuses and/or overvoltage protection equipment for each conductor of low signal levelsystems or communication systems.

(l) Use of Class II equipment for low signal level systems or communication systems.

NOTE: Class II equipment is equipment in which protection against electric shock does not rely on basic insulationonly, but in which additional safety precautions such as double insulation or reinforced insulation are provided, there

being no provision for protective earthing or reliance upon installation conditions.

B2.3 Measures for protecting persons against indirect transfer of unsafe voltages. One or moreof the following measures should be adopted, or other measures providing equivalent protection:

(a) Use of isolating transformers or optical isolators to terminate the conductors of low signal levelsystems or communication systems for the purpose of providing isolation from other circuits.

(b) Use of fuses and/or overvoltage protection equipment for each conductor of the low signal levelsystem or communication system.

The above measures need not be taken if it is determined by calculation or measurement that themagnitude and the characteristics of the transferred voltage will not present a hazard. Values areunder consideration.

B3 PROTECTION OF LOW SIGNAL LEVEL SYSTEMS AGAINST MALFUNCTION DUETO INTERFERENCE.

B3.1 Basic principle. Where electrical interference can cause malfunctioning and can result in acondition dangerous to persons, or property, measures should be taken to reduce the effect of theinterference to an acceptable level. Examples of the measures which can be taken are given inClause B3.2. A combination of these measures may be required.

B3.2 Protection measures.

B3.2.1 Design feat ures. Design features which may be incorporated in the equipment to reduce itssusceptibility to interference include the following:

(a) Common mode rejection.

(b) Propagation delay methods at input interface.

(c) Majority logic.

(d) Feedback supervision.(e) Cross-monitoring techniques.

(f) Circuit isolation (for example optical isolators, isolating transformers).

(g) Coding of signals, parity checks, etc.

(h) Overvoltage protection equipment.

(j) Use of Class II equipment.

NOTE: Class II equipment is equipment in which protection gainst electric shock does not r ely on basic insulation only,but in which additional safety precautions such as double insulation or reinforced insulation are provided, there being

no provision for protective earthing or reliance upon installation conditions.

(k) Use of cables with double insulation or reinforced insulation.


B3.2.2 Other measures. Other measures which may be taken to minimize the effects of interfere

include the following:

(a) Screening against capacitive (electrostatic) interference.

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(b) Shielding against inductive (electromagnetic) interference.

(c) Physical separation of cables.

(d) Segregation of circuits.

(e) Physical isolation of sensitive components.

(f) Suppression of interference at source, e.g. of harmonics, voltage transients.

(g) Use of higher signal levels or signal amplification.

(h) Use of line fuses.

B3.3 Transmission by cable.

B3.3.1 Screening against capacitive (electrostatic) interference. Screening of cables by means ofconductive materials may be employed to eliminate or minimize capacitive interference. Thescreening should extend over the length of the cable and should be taken as close as practicable tothe cable terminations.

The screen should be insulated from earth along its entire length and left unearthed or connecteddirectly at one location only with the lowest practicable impedance to the low signal level systemcommon earthing point or zero potential common reference point.

Cable armouring, conduit or cable tray, if constructed of materials having good electrical

conductivity and installed as described above, can provide a measure of screening from capacitiveinterference, but will be less effective than the use of cables incorporating screens designedspecifically for the purpose.

The connection of spare cores in a cable to earth or to the common reference potential at thereceiving end will also afford a limited measure of screening against capacitive interferenceprovided the spare cores are connected as described above for a cable screen.

Extremely sensitive low signal level systems may require the use of cables incorporating screeningfor each signal circuit pair in addition to the overall screening of the cable.

B3.3.2 Shielding against inductive (electromagnetic) interference. Interference arising frominductive coupling may be minimized by keeping the area enveloped by the circuit as small aspossible, for example, when signal-carrying conductors run alongside the conductor serving as thecommon return or reference potential conductor. The most effective shielding against inductiveinterference is achieved by twisting a conductor serving as t he common reference potential with

each signal-carrying conductor in a multi-core twisted pair cable. This measure minimizes inductiveinterference from other cables and from other conductors incorporated in the cable.

Shielding of cables by means of ferrous materials (e.g. steel conduits, steel cable trays, steel cablearmouring) may be employed to minimise electromagnetic coupling with other cables.

The effectiveness of the shielding will generally be reduced where bonded to adjacent earthedmetallic parts, or where it is impracticable to maintain t he insulation of the shielding over it s entirelength.

The effectiveness of cable trays and cable armouring as shielding depends on the construction andmethod of earthing. Generally, cable tray and armouring is significantly l ess effective t han steelconduit enveloping the entire cable. Conduits and cable trays should be solidly connected andbonded, where necessary, to bridge any discontinuities in order to maintain electrical continuitythroughout their entire length .

B3.3.3 Physical separation from power cables and equipment. Where cables of low signal level

systems are run in parallel with power cables (or busbar systems), or in close proximity toequipment producing external variable magnetic fields, it may be necessary to separate the signalcables from the power cables with or without metallic barriers or equipment to minimizeinterference. This applies particularly where the signal cables are not screened in accordance withClause B3.3.1 or shielded in accordance with Clause B3.3.2.

The question of whether separation is required and the degree of separation which might benecessary will depend on factors such as the type of cables used (both signal and power cables); thesignal level employed, the distance over which the signal cable are run in parallel with the powercables, and the maximum expected current in the power cables (e.g. motor starting current, powercable fault current).

B3.3.4 Segregation of circuits. Circuits having widely different current or voltage levels shouldbe run i n separate cables or cable looms, particularly if none of the measures described inClauses B3.3.1, B3.3.2 and B3.3.3 are taken.

B3.4 Transmission by power line carrier. Attention is drawn to the following IEC publications

relating to power line carrier systems: IEC 353, IEC 481, IE C 495 and IEC 663.

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B3.5 Transmission by radio.

B3.5.1 Safety precautions relating to the use of radio . Precautions should be taken to preventaccidental ignition of detonators. See AS 3007.5.

NOTE: Guidance on the prevention of inadvertent initiation of electro-explosive devices by radio frequency radiation

is provided in BS 6657.

B3.5.2 Physical isolation of sensitive elements. Equipment of low signal level systems may beenclosed separately from power equipment (e.g. transformers, switchgear, etc.) in enclosuresconstructed of ferrous material (e.g. steel cabinets, cubicles), so as to provide effective shieldingfrom likely sources of interference.

B3.6 Transmission b y optical means. (No requirement at present)

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AS 3007.41987 18

ANNEX

SUMMARY OF TECHNICAL DEVIATIONS BETWEEN THISSTANDARD AND IEC 621-4

General. Throughout the text, reference is made to appropriate Australian standards in lieu of IEC

publications.

Introduction.Cross-reference is made to Section 2 of this standard for the requirements which wil lapply where conveyor systems are incorporated as part of winning, stacking and primary processingmachinery.

Clause 1. Clause 1.1 of IEC 621-4 has been omitted as the committee is of the view that, ingeneral, structural parts should not be used as a protective conductor.

Clause 1.1. Sensitive earth leakage protection is permitted as an alternative to the protectivemeasures specified in Clause 1.2 of IEC 621-4.

Clause 3.4. The text has been amended t o correspond with a later TC 71 document in order toremove the contractual nature of the clause existing in IEC 621-4.

Clause 6.2.1. The text has been amended to correspond with a later TC 71 document. Requirementspecified in terms of discharge of field energy instead of field removal.

Clause 6.3. The text previously i n Clause 6.3.2 of IEC 621-4 has been relocated within Clause 7.1as it was considered relevant to emergency stop controls, but it has been amended as agreed for alater TC 71 document.

Clause 6.3.4 of IEC 621-4 has been transferred to a new Clause 11.4 in Section 2 of this standardas the requirements relate to conveyor systems which are dealt wi th in Section 2. The requirementsof Section 2 are called up by the cross-reference which is included in the introduction to Section 1of this standard.

Clause 6.4. Clauses 6.4 and 6.5 of IEC 621-4 have been replaced by comparable text which hasbeen developed for a later TC 71 document.

Clause 7.1. A new clause has been added as agreed for a later TC 71 document.

Clause 7.2. This corresponds to Clause 7.1 of IEC 621-4 but the text has been revised in a formadopted for a later TC 71 document.

Clause 7.3. This corresponds to Clause 7.2 of IEC 621-4. However, regular checking of thetripping device and its stored energy tri pping supply is permitt ed as an alternative to monitoring.

Clause 8. A requirement for the provision of a warning notice at the mains supply isolator has beenadded.

Clause 9. Clause 9.1 of IEC 621-4 has been deleted for the reasons outlined in earlier remarksconcerning Clause 1.

Clause 11.2. The requirements of Items (b) and (c) of Clause 11.2 of IEC 621-4 have been deleted.

Clause 11.3. Reference has been made to AS 1755 for the locations of stop controls in lieu of therequirements existing in IEC 621-4.

Clause 11.4. See above remarks to Clause 6.3.

Clauses 12 and 13. The requirements of Clauses 7 and 8 in Section 1 of this standard have beencalled up as being also applicable to transport conveyor systems.

Clause 14.1.4. The conditions applying to the exemption given in this clause have been moreclearly specified.

Clause 15. Clause 15.1 of IEC 621-4 has been omitted because the committee is of the view that,in general, structural parts should not be used as a protective conductor. Clause 15.2 of IEC 621-4has also been omitted as the concept of off-board is not considered applicable t o secondaryprocessing machinery and, in any event, the specified requirements which derive from thosespecified for winning, s tacking and primary processing machinery (see Clause 1.1 of this standard)were considered unduly onerous.

Clause 18. Clause 15.4 of IEC 621-4 has been omitted since provisions relating to supply tooff-board equipment were not considered applicable for secondary processing machinery.

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Clause 20.4.1. The words i.e. field removal or suppression have been added to explain the phrasedischarge of the field energy.

Clause 24.1. A Note has been added referring to AS 1020 for further information on the controlof static electricity.

Appendix B Introduction. Different examples are given in (b).

Clause B2.2. Items (a) to ( l) are redesignations of Clauses B2.2.1 to B2.2.11 respectively ofIEC 621-4.

The clauses of IEC 621-3 which are cited in Clauses B2.2.2 and B2.2.3 of IEC 621-4 are incorrectand appropriate clauses in the corresponding Australian standard (AS 3007.3) have been referencedin items (b) and (c) of Clause B2.2 of this standard.

A Note has been added to item (l) in explanation of the term Class II equipment.

Clause B3.2.1. A Note has been added to item (j ) in explanation of the term Class II equipment.

Clause B3.5.1. A Note has been added referring to a relevant British Standard.

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Documents

As 3007.4 - Electrical Installations