IEC_60364-4-442-1993_scan.pdf

364-4-442IEC:1993-3CONTENTSPageFOREWORDINTRODUCTION.7Clause442.1General.442.1.19442.1.2Scope and object.。9442.1.3Faut-voltage9442.1.4Stress-voltageNormative references.9442.211Earthing systems in transformer sub-stations.442.311Earthing arrangements in transformer sub-stations442.411Earthing arrangements with regard to type of earthing systemsin LV installations13442.4.1442.4.2Symbols13442.4.3TN-SystemsTT-systems13442.4.4IT-systems.13442.515Limitation of stress-voltage in LV equipment of transformer sub-stations.15442.5.1 TN-and TT-systems.442.5.2lT-systems545444444444*15Figures.1517Annex A-Explanatory notes.37364-4-442IEC:1993-5-INTERNATIONAL ELECTROTECHNICAL COMMISSIONELECTRICAL INSTALLATIONS OF BUILDINGSPart 4:Protection for safetyChapter 44:Protection against overvoltagesSection 442-Protection of low-voltage installationsagainst faults between high-voltage systems and earthFOREWORD1)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.2)They have the form of recommendations for international use and they are accepted by the NationalCommittees in that sense.3)In order to promote international unification,the IEC expresses the wish that all National Committeesshould adopt the text of the IEC recommendation for their national rules in so far as national conditions willpermit.Any divergence between the IEC recommendation and the corresponding national rules should,asfar as possible,be clearly indicated in the latter.This International Standard has been prepared by Technical Committee No.64:Electricalinstallations of buildings.The text of this standard is based on the following documents:Six Months RuleReport on Voting64(CO)17564(CO)213Full information on the voting for the approval of this standard can be found in the VotingReport indicated in the above table.Annex A is for information only.