IEC_60364-2-21-1993_scan.pdf

8RAPPORTCEITECHNIQUEIECTECHNICAL364-2-21REPORTPremiere editionFirst edition1993-01Installations electriques des batimentsPartie 2:DefinitionsChapitre 21:Guide pour les termes generauxElectrical installations of buildingsPart 2:DefinitionsChapter 21:Guide to general termsCEl 1993 Droits de reproduction rservs-Copyright-all rights reservedAuoune partie de cette publication ne peut tre reproduite niNo part of this publication may be reproduoed or utized inany form or by any means,eleoronio or mechanical,nannique,y compris a photooopie etincluding photooopying and miorofilm,without permissionin writing from the publisher.Bureau Central de la Commission Electrotechnique Intemationale 3.rue de Varemb6 Gendve,SuisseCommission Electrotechnique InternationaleCODE PRIXInternational Electrotechnical CommissionPRICE CODEHMexayHapo HaR 3neKTpoTexHvecka HoMHCCHAPour prix,voir catelogue en vigueurFor price,see current catalogueIECVoL 12.364-2-21IEC-3-INTERNATIONAL ELECTROTECHNICAL COMMISSIONELECTRICAL INSTALLATIONS OF BUILDINGSPart 2:DefinitionsChapter 21:Guide to general termsFOREWORD1)The IEC(International Electrotechnical Commission)is a worldwide organization for standardizationcomprising all national electrotechnical committees(IEC National Committees).The object of the IEC is topromote international cooperation on all questions concerning standardization in the electrical andelectronic fields.To this end and in addition to other activities,the IEC publishes International Standards.Their preparation is entrusted to technical committees;any IEC National Committee interested in thesubject dealt with may participate in this preparatory work.International,governmental andnon-governmental organizations liaising with the IEC also participate in this preparation.The IECcollaborates closely with the International Organization for Standardization(ISO)in accordance withconditions determined by agreement between the two organizations.2)The formal decisions or agreements of the IEC on technical matters,prepared by technical committees onwhich all the National Committees having a special interest therein are represented,express,as nearly aspossible,an international consensus of opinion on the subjects dealt with.3)They have the form of recommendations for international use published in the form of standards,technicalreports or guides and they are accepted by the National Committees in that sense.4)In order to promote international unification,IEC National Committees undertake to apply IEC InternationalStandards transparently to the maximum extent possible in their national and regional standards.Anydivergence between the IEC Standard and the corresponding national or regional standard shall be clearlyindicated in the latter.The main task of IEC technical committees is to prepare International Standards.In excep-tional circumstances,a technical committee may propose the publication of a technicalreport of one of the following types:.type 1,when the required support cannot be obtained for the publication of an Inter-national Standard,despite repeated efforts;.type 2,when the subject is still under technical development or where for any otherreason there is a future but not immediate possibility of an agreement on an Inter-national Standard;type 3,when a technical committee has collected data of a different kind from thatwhich is normally published as an International Standard,for example state of the art.Technical reports of types 1 and 2 are subject to review within three years of publication todecide whether they can be transformed into International Standards.Technical reports oftype 3 do not necessarily have to be reviewed until the data they provide are consideredto be no longer valid or useful.IEC 364-2-21,which is a technical report of type 3,has been prepared by IEC technicalcommittee 64:Electrical installations of buildings.It is of a purely informative nature and isnot to be regarded as an International Standard.364-2-21IEC-5-The text of this technical report is based on the following documents:Six Months RuleReport on Voting64(CO)17264(CO)204Full information on the voting for the approval of this technical report can be found in thereport on voting indicated in the above table.364-2-21IEC-7-ELECTRICAL INSTALLATIONS OF BUILDINGSPart 2:DefinitionsChapter 21:Guide to general terms21.0ScopeThis guide is applicable to electrical installations of buildings.It contains explanatorynotes on terms used in IEC 364,listed in sections 01 to 08 of IEC 50(826)*.The notes areintended to facilitate the application of terms.TermNote21.1Characteristics of installations(section 01)21.1.1Origin of an electrical installation;An electrical installation may have more thanService entrance(USA)one origin.(826-01-02)21.1.2 Neutral conductorThe neutral point(of a polyphase system)(symbol N)is defined in IEV(601)as follows:(826-01-03)Common point of the n-windings in a star-connected power transformer or earthingtransformer,in a substation.In certain instances,and under specifiedconditions,the functions of neutral con-ductor and protective conductor may becombined in a single conductor(see defi-nition of PEN conductor 826-04-06).21.1.3 Ambient temperatureIt is assumed that the ambient tempera-(826-01-04)ture includes the effects of all other equip-ment installed in the same location.The ambient temperature to be consideredfor the equipment is the temperature atthe place where the equipment is to beinstalled resulting from the influence of allother equipment and heat sources in thesame location,when operating,not takinginto account the thermal contribution ofthe equipment to be installed.IEC 50(826):1982,International Electrotechnical Vocabulary(IEV)-Chapter 826:Electrical installations ofbuildings.364-2-21IEC-9-TermNote21.1.4(Supply system for)Safety services;Safety services are often a statutory re-Emergency power system(USA)quirement in premises open to the public,(826-01-05)in very high buildings and in certainindustrial premises.21.1.5 Standby supply system(826-01-06)Standby supplies are necessary,forexample,to avoid interruption ofcontinuous industrial processes or dataprocessing.21.2Voltages(section 02)21.2.1Nominal voltageTransient overvoltages,due for example(of an installation)(826-02-01)to switching operations,and temporaryvariations in the voltage due to abnormalconditions,such as faults in the supplysystem,are ignored.21.3 Electric shock(section 03)21.3.1 Extraneous-conductive-partExtraneous-conductive-parts may be:(826-03-03)-metallic parts of the buildingstructure;-metal pipe systems for gas,water,heating,etc.;-non-insulating floors and walls.21.3.2 Simultaneously accessible partsIn the context of protection against direct(826-03-10)contact,a live part may be accessiblewith:-another live part;or-an exposed-conductive-part;or-an extraneous-conductive-part;or-a protective conductor.The following may constitute simulta-neously accessible parts in the context ofprotection against indirect contact:-exposed-conductive-parts;-extraneous-conductive-parts;-protective conductors.