IEC 60287 3 1 Edition 2 0 201 7 06 INTERNATIONAL STANDARD NORME INTERNATIONALE Electric cables – Calculation of the current rating – Part 3 1 Operating conditions – Site reference conditions Câbles él[.]
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webstore i ec ch /csc Si vous désirez nous donner des commentaires sur cette publication ou si vous avez des questions contactez-nous: csc@iec.ch I E C 60 -3 -1 ® Edition 2.0 201 7-06 I N TE RN ATI ON AL S TAN D ARD N ORM E I N TE RN ATI ON ALE E l ectri c cabl es – C al cu l ati on of th e cu rre n t rati n g – P art -1 : O perati n g d i ti on s – S i te re fere n ce d i ti on s C âbl e s é l ectri q u es – C al cu l d u cou ran t ad m i s s i bl e – P arti e -1 : C on d i ti on s d e fon cti on n em en t – C on d i ti on s d u s i te d e ré fére n ce INTERNATIONAL ELECTROTECHNICAL COMMISSION COMMISSION ELECTROTECHNIQUE INTERNATIONALE ICS 29.060.20 ISBN 978-2-8322-4348-0 Warn i n g ! M ake su re th at you ob tai n ed th i s pu bl i ca ti on from an au th ori zed d i s tri bu tor Atten ti on ! Veu i l l ez vou s as s u rer q u e vou s avez ob ten u cette p u b l i cati on vi a u n d i s tri bu teu r ag ré é ® Registered trademark of the International Electrotechnical Commission Marque déposée de la Commission Electrotechnique Internationale –2– I EC 60287-3-1 : 201 © I EC 201 CONTENTS FOREWORD I NTRODUCTI ON Scope Norm ative references Terms and definitions Reference ambient temperatures and therm al resistivities of soil in various countries Operating conditions – Site reference conditions Procedure when values are not provided in national tables General 2 Ambient tem peratures at sea level Thermal resistivity of soil 4 Solar radiation Annex A (informative) Values relating to the operating conditions in various countries A Australia A Austria A Canada A China A Eg ypt A Finland 1 A France A German y A I tal y A Japan A 1 Mexico A Netherlands A New Zealand A Norway A Om an A Poland A Portugal 20 A Spain 20 A South Africa 21 A 20 Sweden 21 A 21 Switzerland 22 A 22 United Kingdom 22 A 22 HV 22 A 22 LV/M V 23 A 23 United States of America 23 Bibliograph y 24 Table – Am bient tem peratures at sea level Table – Therm al resistivity of soil I EC 60287-3-1 : 201 © I EC 201 –3– INTERNATI ONAL ELECTROTECHNI CAL COMMISSI ON E L E C T RI C C AB L E S – C AL C U L AT I O N O F T H E C U RRE N T R AT I N G – P a rt -1 : O p e ti n g c o n d i ti o n s – S i te re fe re n c e c o n d i ti o n s FOREWORD ) The I nternati on al Electrotechni cal Comm ission (I EC) is a worl d wid e organization for stan dardization com prisin g all n ation al el ectrotechnical comm ittees (I EC National Comm ittees) The object of I EC is to prom ote internati onal co-operation on all q uestions concerni ng stand ardi zati on in the el ectrical an d electronic fi elds To this en d and in additi on to other acti vities, I EC pu blish es I nternational Stan dards, Techn ical Specificati ons, Technical Reports, Publicl y Avail abl e Specificati ons (PAS) an d Gu ides (h ereafter referred to as “I EC Publication(s)”) Th ei r preparation is entrusted to tech nical comm ittees; any I EC N ational Comm ittee interested in the subj ect dealt with m ay partici pate in this preparatory work I nternational, governm ental an d n on governm ental organ izations l iaising with th e I EC also participate i n this preparation I EC collaborates closel y with the I ntern ational Organi zation for Stand ardization (I SO) in accordance with ditions determ ined by agreem ent between th e two organi zati ons 2) The form al decisions or ag reem ents of I EC on tech nical m atters express, as n early as possible, an i nternati onal consensus of opi nion on the rel evant subjects since each technical com m ittee has representati on from all interested I EC N ational Com m ittees 3) I EC Publications have the form of recom m endations for international use an d are accepted by I EC National Com m ittees in that sense While all reasonable efforts are m ade to ensure that the tech nical content of I EC Publications is accu rate, I EC cann ot be h eld responsi ble for th e way in which th ey are used or for an y m isinterpretation by an y en d u ser 4) I n order to prom ote intern ational u niform ity, I EC National Com m ittees und ertake to apply I EC Publications transparentl y to the m axim um extent possible i n their national an d regi on al publicati ons Any d ivergence between an y I EC Publication and the correspondi ng national or regi on al publicati on sh all be clearl y in dicated in the latter 5) I EC itself d oes n ot provi de an y attestation of conform ity I n depend ent certificati on bodies provi de conform ity assessm ent services and, in som e areas, access to I EC m arks of conform ity I EC is not responsi ble for any services carri ed out by ind ependent certification bodi es 6) All users shou ld ensure that th ey have the l atest editi on of thi s publicati on 7) No liability shall attach to I EC or its directors, em ployees, servants or ag ents inclu din g in divi dual experts an d m em bers of its technical com m ittees and I EC Nati on al Com m ittees for any person al i njury, property d am age or other dam age of any n ature whatsoever, wheth er di rect or indirect, or for costs (includ i ng leg al fees) and expenses arisi ng out of the publ ication, use of, or relian ce upon, this I EC Publicati on or any other I EC Publications 8) Attention is drawn to th e N orm ative references cited in th is publ ication Use of the referenced publ ications is indispensable for the correct applicati on of this publication 9) Attention is drawn to the possibility that som e of the elem ents of this I EC Publication m ay be the su bject of patent rig hts I EC shall not be held responsibl e for identifyi ng any or all such patent ri ghts I nternational Standard I EC 60287-3-1 has been prepared by I EC technical com mittee 20: Electric cables This second edition cancels and replaces the first edition publ ished in 995 and Amendm ent : 999 This edition constitutes a technical revision This edition includes the following significant technical changes with respect to the previous edition: a) the updated list of national laying conditions is now covered in Annex A; b) Clause about the information required from the purchaser for the selection of the appropriate type of cable has been rem oved –4– I EC 60287-3-1 : 201 © I EC 201 The text of this standard is based on the following documents: FDI S Report on votin g 20/1 71 4/FDI S 20/1 730/RVD Full information on the voting for the approval of this standard can be found in the report on voting indicated in the above table This publication has been drafted in accordance with the I SO/I EC Directives, Part A list of all parts in the I EC 60287 series, published under the general title Electric cables – Calculation of the current rating, can be found on the I EC website The reader's attention is drawn to the fact that Annex A lists all of the “in -som e-country” clauses on differing practices of a less perm anent nature relating to the subject of this standard The comm ittee has decided that the contents of this publication will remain unchanged until the stability date indicated on the I EC website under "http: //webstore.iec.ch" in the data related to the specific publication At this date, the publication will be • • • • reconfirmed, withdrawn, replaced by a revised edition, or am ended I EC 60287-3-1 : 201 © I EC 201 –5– INTRODUCTION I EC 60287 has been divided into three parts so that revisions of, and additions to the document can be carried out m ore convenientl y Each part is subdivided into subparts which are published as separate standards Part : Form ulae for ratings (1 00 % load factor) and power losses Part 2: Form ulae for therm al resistance Part 3: Operating conditions This part of I EC 60287-3 contains reference am bient tem peratures and thermal resistivities of soil in various countries Quantities related to the operating conditions of cables are liable to vary considerabl y from one country to another For instance, with respect to the ambient tem perature and soil thermal resistivity, the values are governed in various countries by different considerations Superficial com parisons between the values used in the various countries may lead to erroneous conclusions if they are not based on comm on criteria: for example, there m ay be different expectations for the life of the cables, and in som e countries design is based on maximum values of soil thermal resistivity, whereas in others average values are used Particularl y, in the case of soil thermal resistivity, it is well known that this quantity is very sensitive to soil m oisture content and may vary significantl y with tim e, depending on the soil type, the topographical and meteorological conditions, and the cable loading The following procedure for choosing the values for the various param eters should, therefore, be adopted Numerical values should preferabl y be based on results of suitable m easurements Often such results are alread y included in national specifications as recomm ended values, so that the calculation m ay be based on these values generall y used in the country in question; a survey of such values is given in this part of I EC 60287-3 –6– I EC 60287-3-1 : 201 © I EC 201 E L E C T RI C C AB L E S – C AL C U L AT I O N O F T H E C U RRE N T R AT I N G – P a rt -1 : O p e ti n g c o n d i ti o n s – S i te re fe re n c e c o n d i ti o n s S cop e This part of I EC 60287-3 is applicable to the conditions of stead y-state operation of cables at all voltages, buried directl y in the ground, in ducts, troughs or in steel pipes, both with and without partial drying-out of the soil, as well as cables in air The term "stead y state" is intended to mean a continuous constant current (1 00 % load factor) just sufficient to produce asym ptoticall y the maximum conductor temperature, the surrounding am bient conditions being assumed constant This document defines site reference conditions, however the general values are superseded by specific national requirements N o rm a t i ve re fe re n c e s There are no normative references in this docum ent T e rm s a n d d e fi n i t i o n s No terms and definitions are listed in this document I SO and I EC maintain term inological databases for use in standardization at the following addresses: I EC Electropedia: available at http://www electropedia org/ I SO Online browsing platform : available at http: //www iso org/obp • • Re fe re n c e a m b i e n t t e m p e t u re s a n d t h e rm a l re s i s t i vi t i e s o f s o i l i n va ri o u s c o u n t ri e s O p e t i n g c o n d i t i o n s – S i t e re fe re n c e c o n d i t i o n s I n order to use the formulae given in the various parts of I EC 60287, num erical values for the ph ysical quantities should be chosen relating to the operating conditions It is obviousl y possible to com pare the results of two calculations of current rating onl y when the assum ptions m ade and the numerical values of th e param eters are known In particular, the quantities related to the operating conditions of cables are likel y to vary considerabl y from one country to another An enquiry into this subj ect has been carried out and a number of countries have replied An nex A summ arizes th e operatin g di ti ons u sed in various coun tri es Attention is drawn to th e fact that th e i nform ation i n Ann ex A is inten ded on l y as a gu i de for cable instal lati on designers when d ata provi ded by a user is incom plete Care shoul d be taken not to draw unj ustifi ed conclusions from com parisons of val ues for d ifferent coun tries I t shoul d be rem em bered th at th e val ues ad opted in an y parti cul ar coun try are govern ed by m an y factors som e of which m igh t not be of equ al im portance i n oth er coun tri es Values relating to the operating conditions are given in Annex A for the following countries: Australia I taly Portug al Austria J apan Spain I EC 60287-3-1 : 201 © I EC 201 –7– Can ad a Mexico South Africa Chin a Neth erl ands Swed en Egypt New Zeal and Switzerland Finland Norway United King dom France Om an United States of Am erica Germ any Polan d 4.2 Procedure when values are not provided in national tables 4.2.1 General I t is recomm ended that when there is no value laid down in the national tables for the reference ambient temperature, thermal resistivity of the soil or solar radiation, the values given in 4.2.2, 4.2.3 and 4 should be adopted 4.2.2 Ambient temperatures at sea level See Table Table – Ambient temperatures at sea level Ambient air temperatu re Min Max °C °C Climate 25 10 Tropical Subtropical Tem perate 55 40 25 Ambient ground temperature at a depth of m Min Max °C °C 40 30 20 25 15 10 I t is essential that current ratings should be valid for the m aximum temperatures given The lower values are for winter ratings if required The values correspond with the tem perature limits of winter and summer, alternativel y rain y and dry seasons When no inform ation about the depth of laying is given, the standard depth is to be taken as m 4.2.3 Thermal resistivity of soil See Table Table – Thermal resistivity of soil Thermal resisti vity K m/W Soil conditions Weather conditions Very m oist Moist Dry Very dry Conti nu ously m oist Reg ular rainfall Seldom rains Little or no rai n ∙ 0, ,0 2, 3, 4.2.4 Solar radiation When no inform ation about the intensity of solar radiation a value of 000 W/m is adopted –8– I EC 60287-3-1 : 201 © I EC 201 An nex A (informative) Valu es relating to the operati ng cond iti ons in variou s cou n tries A Au stral i a Th erm al ch aracteri s ti cs of th e soi l Thermal resistivity, nominal ,2 K· m /W Soil ambient temperature, summer 25 °C Soil ambient temperature, winter 18 °C Voltage range : L V cables und er footways und er roadways 0, 0, 75 m m Voltage range 2: 1 kV cables und er footways an d road ways 0, m ,0 m Maximum , summ er + 40 °C Maxim um , winter + 30 °C Depth of l a yi n g of cabl es a Voltage range 3: 33 kV cables and hi gher voltages und er footways an d road ways Ai r am bi en t tem peratu re a A Measured from the groun d surface to the centre of the cabl e, or to th e centre of a trefoil group Au stri a Th erm al ch aracteri sti cs of th e soi l Thermal resistivity, nominal, season (wet) ,0 K· m /W Thermal resistivity, dry zone, season (dry) 2, K· m /W Temperatu re, season 20 °C up to kV 0, m Voltage range 2: > kV up to 30 kV 0, m Voltage range 3: > 30 kV ,2 m Averag e valu e 20 °C Maximum + 40 °C Minimum -20 °C Depth of l a yi n g of cabl es Voltage range : Ai r am bi en t tem peratu re