IEC IEC60287-1-1 Edition3.02023-05 INTERNATIONAL STANDARD Electriccables-Calculationofthecurrentrating- Part1-1:Currentratingequations(1oo%loadfactor)andcalculationoflosses General IEC60287-1-1:2023-05(en THISPUBLICATIONISCOPYRIGHTPROTECTED Copyright2023IEC,Geneva,Switzerland orbyanymeans,electronic ormechanical,includingphotocopyingandmicrofilm,withoutpermissioninwritingfrom either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or your local IEC member National Committee for further information. IECSecretariat Tel.: +41 22 919 02 11 3,rue deVarembe [email protected] CH-1211Geneva 20 www.iec.ch Switzerland About the IEC The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes International Standardsforall electrical, electronic and relatedtechnologies. About IEC publications The technical content of IEC publications is kept under constant reviewby the IEC.Please make sure that youhave the latestedition,acorrigendumoranamendmentmighthavebeenpublished IECpublicationssearch-webstore.iec.ch/advsearchform IECProducts&ServicesPortal-products.iec.ch The advanced search enables to find IEC publications by a Discover our powerful search engine and read freely all the varietyof criteria (referencenumber,text, technical publicationspreviews.Withasubscriptionyouwillalwayshave committee,..).Italsogivesinformationonprojects,replaced access to up to date content tailored to your needs. andwithdrawnpublications. Electropedia-www.electropedia.org IECJustPublished-webstore.iec.ch/justpublished The world's leading online dictionary on electrotechnology, Stay up to date on all new IEC publications. Just Published detailsallnewpublicationsreleased.Availableonlineandonce and French, with equivalent terms in 19 additional languages. amonthbyemail. Also known as the International Electrotechnical Vocabulary IEc Customer Service Centre-webstore.iec.ch/csc (IEV)online If you wish to give us yourfeedback on this publication or need further assistance, please contact the Customer Service Centre:[email protected] IEC IEC 60287-1-1 Edition 3.02023-05 INTERNATIONAL STANDARD Electric cables -Calculation of the current rating Part 1-1:Current ratingequations(1o0 %loadfactor)andcalculationoflosses General INTERNATIONAL ELECTROTECHNICAL COMMISSION ICS29.060.20 ISBN 978-2-8322-6937-4 Warning! Make sure that you obtained this publication from an authorized distributor. ? Registered trade k of th echnical Commissio - 2 - IEC60287-1-1:2023@IEC2023 CONTENTS FOREWORD INTRODUCTION.. .6 1 Scope.... 2 Normative references ... 3 Terms, definitions and symbols. 3.1 Terms and definitions...... 8 3.2 Symbols... 8 4 Permissible current rating of cables.. 4.1 General.. 4.2 Buried cables where drying out of the soil does not occur or cables in air 4.2.1 AC cables.. .12 4.2.2 DC cables up to 5 kV. .13 4.3 Buried cables where partial drying-out of the soil occurs .13 4.3.1 AC cables... 13 4.3.2 DC cables up to 5 kV. .14 4.4 Buried cables where drying-out of the soil shall be avoided .14 4.4.1 Ac cables...... 4.4.2 DC cables up to 5 kV... 4.5 Cables directly exposed to solar radiation.. 4.5.1 General .... .15 4.5.2 Ac cables...... .15 5 Calculation of losses . 16 5.1 AC resistance of conductor 16 5.1.1 General.. 16 5.1.2 DC resistance of conductor... 16 5.1.3 Skin effect factor y's .. 16 5.1.4 Proximity effect factor yp for two-core cables and for two single-core cables.... 5.1.5 Proximity effect factor yp for three-core cables and for three single-core cables... .17 5.1.6 Skin and proximity effects in pipe-type cables. .18 5.2 Dielectric losses (applicable to AC cables only) .18 5.3 Loss factor for sheath and screen (applicable to power frequency AC cables only) .19 5.3.1 General... 5.3.2 Two singie-core cabies, and three singie-core cabies (in trefoi format