IEC 60853-2 AMD 1-2008 Calculation of the cyclic and emergency current rating of cables - Part 2 Cyclic rating of cables greater than 18 30 (36) kV and emergenc.pdf

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1、 IEC 60853-2 Edition 1.0 2008-10 INTERNATIONAL STANDARD NORME INTERNATIONALE Calculation of the cyclic and emergency current rating of cables Part 2: Cyclic rating of cables greater than 18/30 (36) kV and emergency ratings for cables of all voltages Calcul des capacits de transport des cbles pour le

2、s rgimes de charge cycliques et de surcharge de secours Partie 2: Rgime cyclique pour des cbles de tensions suprieures 18/30 (36) kV et rgimes de secours pour des cbles de toutes tensions IEC 60853-2:1989/A1:2008 AMENDMENT 1 AMENDEMENT 1 THIS PUBLICATION IS COPYRIGHT PROTECTED Copyright 2008 IEC, Ge

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17、Fax: +41 22 919 03 00 IEC 60853-2 Edition 1.0 2008-10 INTERNATIONAL STANDARD NORME INTERNATIONALE Calculation of the cyclic and emergency current rating of cables Part 2: Cyclic rating of cables greater than 18/30 (36) kV and emergency ratings for cables of all voltages Calcul des capacits de transp

18、ort des cbles pour les rgimes de charge cycliques et de surcharge de secours Partie 2: Rgime cyclique pour des cbles de tensions suprieures 18/30 (36) kV et rgimes de secours pour des cbles de toutes tensions INTERNATIONAL ELECTROTECHNICAL COMMISSION COMMISSION ELECTROTECHNIQUE INTERNATIONALE K ICS

19、29.060.20 PRICE CODE CODE PRIX ISBN 2-8318-1013-2 AMENDMENT 1 AMENDEMENT 1 Registered trademark of the International Electrotechnical Commission Marque dpose de la Commission Electrotechnique Internationale 2 60853-2 Amend. 1 IEC:2008 FOREWORD This amendment has been prepared by IEC technical commit

20、tee 20: Electric cables. The text of this amendment is based on the following documents: FDIS Report on voting 20/965/FDIS 20/991/RVD Full information on the voting for the approval of this amendment can be found in the report on voting indicated in the above table. The committee has decided that th

21、e contents of this amendment and the base publication will remain unchanged until the maintenance result date indicated on the IEC web site 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 At this date, the publication will be reconfirmed, withdrawn, replaced by a revis

22、ed edition, or amended. _ PREFACE Replace the quoted IEC publication “287(1982)”, by the following: IEC 60287-1-1, Electric cables Calculation of the current rating Part 1-1: Current rating equations (100 % load factor) and calculation of losses General IEC 60287-2-1, Electric cables Calculation of

23、the current rating Part 2-1:Thermal resistance Calculation of thermal resistance IEC 60287-3-1, Electric cables Calculation of the current rating Part 3-1:Sections on operating conditions Reference operating conditionsand selection of cable type Throughout the standard, replace all references to “IE

24、C Publication 287” by “the IEC 60287 series”. Add the following new reference: IEC 60853-3, Calculation of the cyclic and emergency current rating of cables Part 3: Cyclic rating factor for cables of all voltages, with partial drying of the soil 1.1 General Replace the first paragraph by the followi

25、ng: This standard gives manual methods for calculating cyclic rating factors for cables whose internal thermal capacitance cannot be neglected; in general this applies to cables for voltages greater than 18/30 (36) kV. It also gives a method for calculating the emergency rating for cables of any vol

26、tage. IEC 60853-1 deals with cyclic rating factors for cables of voltages not greater than 18/30 (36) kV where the internal thermal capacitance could be 60853-2 Amend. 1 IEC:2008 3 neglected. IEC 60853-3 deals with cyclic rating factors for cables of all voltages when partial drying of the soil occu

27、rs. Delete the fourth paragraph. Add the following three new paragraphs at the end of 1.1: When the load current changes in discrete and multiple steps the method set out in Clause 4 can be used to determine the temperature response of the cable. This method shall be used carefully where a large num

28、ber of steps is considered, or long duration steps are dealt with, or large variations of the load current occur. As the method involves an iterative process, the convergence criterion shall be adapted to the different situations. 2 Symbols Replace the word “sheath” by “metallic sheath or screen” un

29、der definitions Q s , q a, q j and q s.Throughout the text, starting with the “Unit” column, replace “J/m.K” with “J/Km” also replace “K.m/W” with “Km/W”. Replace the definition for N with “N = number of cables in a group, or, for touching cables, the number of circuits, see 7.4 b)” Replace “ ” by ”

30、 in order to align with the French version. Also in the “Unit” column, replace “J/K.m 3 “ by “J/Km 3 ”. Add the following new definition: d Steady-state conductor temperature rise above ambient due to dielectric losses 4.2.1.1 Single-core cables Replace, in the second line, the word “sheath” by “met

31、allic sheath or screen”. 4.2.1.2 Three-core cables Replace the existing Equation (4-2) by the following new Equation (4-2): = i 1 2i c T e D d (4-2) Replace, in the first line after Equation (4-2) and in the first line of 4.2.1.2 b), the word “sheath” by “metallic sheath or screen”. 4.2.2.1 General

32、Add, at the end of the subcause, a third paragraph as follows: For single-core cables in trefoil formation, the values of T 1and T 3are adjusted by the appropriate factors given in IEC 60287-2-1. 4 60853-2 Amend. 1 IEC:2008 4.2.2.2 Representation of common types of cable Replace, after Equation (4-6

33、), in the definition for Q sand twice in the definition for q s , the word “sheath” by “metallic sheath or screen”. 4.2.4.1 Buried cables (directly or in ducts) Replace the existing Equation (4-36) by the following new Equation (4-36): 4 ) ( - 4 ) ( 16 4 ) ( 1 1 2 pk 2 pk 2 2 e T e + = = = N k k I t

34、 d Ei t d Ei t L Ei t D Ei W t (4-36) Replace the final sentence of 4.2.4.1 beginning “This formula has been simplified “ by the following new paragraph: Equation (4-36) is the general equation for the transient response of buried cables and its application for cyclic rating purposes is given in Cla

35、use 7. It is noted that this equation cannot be used directly for cables in unfilled troughs. 4.3.2.1 General Add, at the end of this subclause, a new paragraph as follows: For single-core cables in trefoil formation the values of T 1and T 3are adjusted by the appropriate factors given in IEC 60287-

36、2-1. 4.3.2.2 Representation of common types of cable Replace the existing Equation (4-47) by the following new equation: 3 2 1 2 1 T q T q T q T T j a f s B + + + = (4-47) 4.4.1 Transient temperature response Add the following new text after item b). When the temperature response to a current that c

37、hanges in discrete and multiple steps is calculated, the calculations described in this clause should be repeated for every partial step of the current. In the calculation of these partial transients, the correct heat source (the heat gained or lost in the partial current step) and the correct tempe

38、ratures (for the calculation of electrical resistances) shall be used in the formulas above. One way of accomplishing this is to perform iterative calculations for each load step as follows: 1) Start with the temperature achieved at the end of the previous load step. 2) Calculate the electrical resi

39、stances corresponding to this temperature and obtain power losses. 3) With these losses calculate the temperature at the end of the time step. 4) Use this temperature to recalculate the electrical resistances and power losses and go to step 3. 5) Repeat steps 3 and 4 until convergence is achieved an

40、d go to the next load step. The total temperature response per partial step will be found by using the appropriate formulae in this clause. The complete total temperature response of the cable circuit will be 60853-2 Amend. 1 IEC:2008 5 found by adding all the partial transients, thereby taking the

41、time differences between the partial steps into account. 4.4.1.2 Cables in air Replace the last paragraph by the following: T 4is the external thermal resistance due to air in the steady-state, calculated according to IEC 60287-2-1, and shall be expressed as a quantity per conductor or equivalent co

42、nductor. 4.4.2 Correction to transient temperature response for variation in conductor losses with temperature (emergency ratings only) Replace the heading of this subclause with the words “Not used”. Delete the text of this subclause, including Equation (4-73). 4.4.3.2 Cables at voltages higher tha

43、n 275 kV Replace, in the third line, and in the penultimate paragraph, the word “sheath” by “metallic sheath or screen”. Add, at the end of the subclause, the following new text: Information on the voltages above which dielectric losses should be considered is given in IEC 60287-1-1. 5.1 General Rep

44、lacethe existing Equation (5-1) by the following new Equation (5-1): () (6) ) ( (5) (6) (2) (3) 1 (2) (1) R R R R 5 R R 2 R 1 R 0 max + + + + = Y Y Y Y R(5-1) 5.2.1 Any load cycle of known shape Replace the existing Equation (5-3) by the following new Equation (5-3): () () () () () () 2 1 5 0 6 1 1

45、1 / R R R R R R i i i i Y M + + = =(5-3) 5.2.2 Flat top load cycle Replace the existing Equation (5-5) by the following new Equation (5-5): () () 2 1 (6) 1 (6) (6) 1 1 1 1 / k M + = (5-5) 7.2 Single isolated circuit Under item a) 1), replace ” for cables in ducts, in trefoil or flat touching formati

46、on.” by ”.for cables in trefoil or flat touching formation or in ducts “ 6 60853-2 Amend. 1 IEC:2008 7.4 Group of “N”circuits, each of three single-core identical touching cables or ducts, all cables having equal losses Replace the existing title and text of this subclause by the following: 7.4 Grou

47、p of circuits, each of three single-core identical touching cables or ducts, all cables having equal losses The methods are the same as those given in 7.3 above, except that: a) The external thermal resistance 4 T , on which the value of 1 k is dependent, relates to = 630 , 0 4 In 5 , 1 e 4 D L T T (7-13) for metallic sheathed and part-metallic covered cables (where helically laid armour or screen wires cover from 20 % to 50 % of the cable circumference), or + = e e 4 2 In 2 4 In 2 1 D D L P T L T(7-14) for non-m