IEC_60364-4-44_A2_64_1344_CD.pdf

64/1344/CDCOMMITTEE DRAFT(CD)IEC/TC or SC:TC 64Project numberIEC 60364-4-44,A2,f1,Ed.1Title of TC/SC:Electrical installations and protection againstelectrical shockDate of circulation2003-10-17Closing date for comments2004-01-23Also of interest to the following committeesTC 99Supersedes document64/1343/MCRFunctions concerned:Safety EMC Environment Quality assuranceSecretary:Dipl.-Ing.R.Pelta(Germany)E-mail:THIS DOCUMENT IS STILL UNDER STUDY AND SUBJECT TOCHANGE.IT SHOULD NOT BE USED FOR REFERENCE PURPOSES.RECIPIENTS OF THIS DOCUMENT ARE INVITED TO SUBMIT,WITHTHEIR COMMENTS,NOTIFICATION OF ANY RELEVANT PATENTRIGHTS OF WHICH THEY ARE AWARE AND TO PROVIDESUPPORTING DOCUMENTATION.Title:Amendment 2 and f1 to IEC 60364-4-44,Ed.1:Electrical installations of buildings-Part 4:Protection for safety-Part 4-44:Protection against voltage disturbances and measures againstelectromagnetic influences-Clause 442:Protection of low-voltage installations against temporaryovervoltages and faults between high-voltage systems and earth(Titre):Introductory noteThis draft has been prepared by TC 64/WG 9 in the frame of maintenance of Part 44 of IEC 60364.FORM CD(IEC)2002-05-14Copyright 2003 International Electrotechnical Commission,IEC.All rights reserved.It ispermitted to download this electronic file,to make a copy and to print out the content for the solepurpose of preparing National Committee positions.You may not copy or mirror the file orprinted version of the document,or any part of it,for any other purpose without permission inwriting from IEC.XXX IEC:200X 2 64/1344/CDINTERNATIONAL ELECTROTECHNICAL COMMISSIONELECTRICAL INSTALLATIONS OF BUILDINGS Part 4-44:Protection for safety Protection against voltage disturbances andelectromagnetic disturbances440 IntroductionPart 4-44 of IEC 60364 provides rules for the protection against the effects of disturbancesgenerated,conducted and radiated for different reasons on electrical installations.The rules of this standard do not apply to systems which are wholly or partly under control ofpublic power supply companies(see scope of IEC 60364-1)although disturbances influencingthe electrical installations may be conducted via these supply systems.Clause 442 is intended to describe means by which the safety of persons and equipment in thelow-voltage installation in the event of a fault between the high-voltage system and earth in thetransformer sub-station supplying the low-voltage installation is provided.The fault-current flowing in the earth electrode of the exposed-conductive-parts of the sub-station causes a significant rise of the potential of the exposed-conductive-parts of the sub-station to the general mass of the earth,i.e.a fault-voltage,whose magnitude is governed by the fault-current magnitude,and the resistance of the earth electrode to which the exposed-conductive-parts of the sub-station are connected.The fault-current may cause a general rise of the potential of the low-voltage system with respect to earth,i.e.stress-voltages which may cause a breakdown of the insulation in low-voltage equipment,a general rise of the potential at the exposed-conductive-parts of equipment of the low-voltage system with respect to earth,which may give rise to fault-voltage and touchvoltages.NOTE In this standard,the expression high-voltage(HV)refers to voltages exceeding the upper limit ofvoltage band II.The expression low-voltage(LV)refers to voltages not exceeding the upper limit of voltageband II.Clause 443 is intended to describe the means by which transient overvoltages originatingfrom atmospheric events or from switching and transmitted from some distance via the supplylines of the system or from other electrical installations via the system can be limited.Such alimitation reduces the risk of failures in the installation,and in electrical equipment connectedto it,to an acceptable level.This approach is in line with the principles of insulation co-ordination in IEC 60664.IEC 60664-1 requires technical committees to specify an appropriateimpulse withstand category(overvoltage category)for their equipment,that means aminimum impulse withstand voltage of equipment,according to its application and therelated impulse withstand categories.NOTE Following 2.2.2 of IEC 60664-1,technical committees should specify the relevant information.It isrecommended to indicate the rated impulse withstand voltage to be supplied with the equipment and the way inwhich this should be done.XXX IEC:200X 3 64/1344/CDClause 444 provides basic recommendations for the mitigation of electromagneticdisturbances.Electromagnetic Interferences(EMI)may disturb or damage informationtechnology systems or IT-equipment and equipment with electronic components or circuits aswell.Currents due to lightning,switching operations,short-circuits and other electromagneticphenomena may cause overvoltages and electromagnetic interference.These effects appear where large metal loops exist1);and where different electrical wiring systems ar