1、BRITISH STANDARDBS EN 60076-5:2006Power transformers Part 5: Ability to withstand short-circuit The European Standard EN 60076-5:2006 has the status of a British StandardICS 29.180g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36
2、g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN 60076-5:2006This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 June 2006 BSI 2006ISBN 0 580 48784 9National forewordThis British Standard is the official En
3、glish language version of EN 60076-5:2006. It is identical with IEC 60076-5:2006. It supersedes BS EN 60076-5:2001 which will be withdrawn on 1 April 2009.The UK participation in its preparation was entrusted to Technical Committee PEL/14, Power transformers, which has the responsibility to: A list
4、of organizations represented on this committee can be obtained on request to its secretary.Cross-referencesThe British Standards which implement international or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards C
5、orrespondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does n
6、ot of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep UK interests informed; monitor related international and European developments
7、 and promulgate them in the UK.Summary of pagesThis document comprises a front cover, an inside front cover, the EN title page, pages 2 to 36, an inside back cover and a back cover.The BSI copyright notice displayed in this document indicates when the document was last issued.Amendments issued since
8、 publicationAmd. No. Date CommentsEUROPEAN STANDARD EN 60076-5 NORME EUROPENNE EUROPISCHE NORM June 2006 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassa
9、rt 35, B - 1050 Brussels 2006 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 60076-5:2006 E ICS 29.180 Supersedes EN 60076-5:2000English version Power transformers Part 5: Ability to withstand short-circuit (IEC 60076-5:2006) Tra
10、nsformateurs de puissance Partie 5: Tenue au court-circuit (CEI 60076-5:2006) Leistungstransformatoren Teil 5: Kurzschlussfestigkeit (IEC 60076-5:2006) This European Standard was approved by CENELEC on 2006-04-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which st
11、ipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member. This European Stan
12、dard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the natio
13、nal electrotechnical committees of Austria, Belgium, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerl
14、and and the United Kingdom. Foreword The text of document 14/518/FDIS, future edition 3 of IEC 60076-5, prepared by IEC TC 14, Power transformers, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 60076-5 on 2006-04-01. This European Standard supersedes EN 60076-5:2000
15、. This European Standard includes the following significant technical changes with respect to EN 60076-5:2000: a) introduction of Annex A (informative) “Theoretical evaluation of the ability to withstand the dynamic effects of short circuit“, in place of previous Annex B (normative) “Calculation met
16、hod for the demonstration of the ability to withstand short circuit“ (blank); b) introduction of Annex B (informative) “Definition of similar transformer“, in place of previous Annex A (informative) “Guidance for the identification of a similar transformer“. The following dates were fixed: latest da
17、te by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2007-01-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2009-04-01 Annex ZA has been added by CENELEC. _ Endorsement n
18、otice The text of the International Standard IEC 60076-5:2006 was approved by CENELEC as a European Standard without any modification. _ EN 60076-5:2006 2 3 EN 60076-5:2006 CONTENTS 1 Scope 4 2 Normative references .4 3 Requirements with regard to ability to withstand short circuit .4 3.1 General .4
19、 3.2 Overcurrent conditions.5 4 Demonstration of ability to withstand short circuit 8 4.1 Thermal ability to withstand short circuit.8 4.2 Ability to withstand the dynamic effects of short circuit .11 Annex A (informative) Theoretical evaluation of the ability to withstand the dynamic effects of sho
20、rt circuit .20 Annex B (informative) Definition of similar transformer35 Annex ZA (normative) Normative references to international publications with their corresponding European publications36 Figure 1 Star/delta connected transformer 14 Figure 2 Star/star auto-transformer.15 Table 1 Recognized min
21、imum values of short-circuit impedance for transformers with two separate windings .6 Table 2 Short-circuit apparent power of the system.6 Table 3 Maximum permissible values of the average temperature of each winding after short circuit.10 Table 4 Values for factor k 2 12 Table A.1 Comparison of for
22、ces and stresses in core-type transformers30 Table A.2 Comparison of forces and stresses in shell-type transformers .32 Table A.3 Values for factor K3.34 Table A.4 Values for factor K4.34 EN 60076-5:2006 4 POWER TRANSFORMERS Part 5: Ability to withstand short circuit 1 Scope This part of IEC 60076 i
23、dentifies the requirements for power transformers to sustain without damage the effects of overcurrents originated by external short circuits. It describes the calculation procedures used to demonstrate the thermal ability of a power transformer to withstand such overcurrents and both the special te
24、st and the theoretical evaluation method used to demonstrate the ability to withstand the relevant dynamic effects. The requirements apply to transformers as defined in the scope of IEC 60076-1. 2 Normative references The following referenced documents are indispensable for the application of this d
25、ocument. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60076-1:1993, Power transformers Part 1: General Amendment 1 (1999)1IEC 60076-3:2000, Power Transformers Part 3: Insulation lev
26、els, dielectric tests and external clearances in air IEC 60076-8:1997, Power transformers Part 8: Application guide IEC 60076-11:2004, Power transformers Part 11: Dry-type transformers 3 Requirements with regard to ability to withstand short circuit 3.1 General Transformers together with all equipme
27、nt and accessories shall be designed and constructed to withstand without damage the thermal and dynamic effects of external short circuits under the conditions specified in 3.2. External short circuits are not restricted to three-phase short circuits; they include line-to-line, double-earth and lin
28、e-to-earth faults. The currents resulting from these conditions in the windings are designated as overcurrents in this part of IEC 60076. 1There exists a consolidated edition 2.1 (2000) that includes edition 2.0 and its amendment. 5 EN 60076-5:2006 3.2 Overcurrent conditions 3.2.1 General considerat
29、ions 3.2.1.1 Application conditions requiring special consideration The following situations affecting overcurrent magnitude, duration, or frequency of occurrence require special consideration and shall be clearly identified in transformer specifications: regulating transformers with very low impeda
30、nce that depend on the impedance of directly connected apparatus to limit overcurrents; unit generator transformers susceptible to high overcurrents produced by connection of the generator to the system out of synchronism; transformers directly connected to rotating machines, such as motors or synch
31、ronous condensers, that can act as generators to feed current into the transformer under system fault conditions; special transformers and transformers installed in systems characterized by high fault rates (see 3.2.6); operating voltage higher than rated maintained at the unfaulted terminal(s) duri
32、ng a fault condition. 3.2.1.2 Current limitations concerning booster transformers When the combined impedance of the booster transformer and the system results in short-circuit current levels for which the transformer cannot feasibly or economically be designed to withstand, the manufacturer and the
33、 purchaser shall mutually agree on the maximum allowed overcurrent. In this case, provision should be made by the purchaser to limit the overcurrent to the maximum value determined by the manufacturer and stated on the rating plate. 3.2.2 Transformers with two separate windings 3.2.2.1 For the purpo
34、se of this standard, three categories for the rated power of three-phase transformers or three-phase banks are recognized: category I: 25 kVA to 2 500 kVA; category II: 2 501 kVA to 100 000 kVA; category III: above 100 000 kVA. 3.2.2.2 In the absence of other specifications, the symmetrical short-ci
35、rcuit current (for the r.m.s. value, see 4.1.2) shall be calculated using the measured short-circuit impedance of the transformer plus the system impedance. For transformers of category I, the contribution of the system impedance shall be neglected in the calculation of the short-circuit current if
36、this impedance is equal to, or less than, 5 % of the short-circuit impedance of the transformer. The peak value of the short-circuit current shall be calculated in accordance with 4.2.3. 3.2.2.3 Commonly recognized minimum values for the short-circuit impedance of transformers at the rated current (
37、principal tapping) are given in Table 1. If lower values are required, the ability of the transformer to withstand short circuit shall be subject to agreement between the manufacturer and the purchaser. EN 60076-5:2006 6 Table 1 Recognized minimum values of short-circuit impedance for transformers w
38、ith two separate windings Short-circuit impedance at rated current Rated power kVA Minimum short-circuit impedance % 25 to 630 631 to 1 250 1 251 to 2 500 2 501 to 6 300 6 301 to 25 000 25 001 to 40 000 40 001 to 63 000 63 001 to 100 000 above 100 000 4,0 5,0 6,0 7,0 8,0 10,0 11,0 12,5 12,5 NOTE 1 V
39、alues for rated power greater than 100 000 kVA are generally subject to agreement between manufacturer and purchaser. NOTE 2 In the case of single-phase units connected to form a three-phase bank, the value of rated power applies to three-phase bank rating. 3.2.2.4 The short-circuit apparent power o
40、f the system at the transformer location should be specified by the purchaser in his enquiry in order to obtain the value of the symmetrical short-circuit current to be used for the design and tests. If the short-circuit apparent power of the system is not specified, the values given in Table 2 shal
41、l be used. Table 2 Short-circuit apparent power of the system Short-circuit apparent power MVA Highest voltage for equipment, UmkV Current European practice Current North American practice 7,2; 12; 17,5 and 24 36 52 and 72,5 100 and 123 145 and 170 245 300 362 420 525 765 500 1 000 3 000 6 000 10 00
42、0 20 000 30 000 35 000 40 000 60 000 83 500 500 1 500 5 000 15 000 15 000 25 000 30 000 35 000 40 000 60 000 83 500 NOTE If not specified, a value between 1 and 3 should be considered for the ratio of zero-sequence to positive-sequence impedance of the system. 7 EN 60076-5:2006 3.2.2.5 For transform
43、ers with two separate windings, normally only the three-phase short circuit is taken into account, as the consideration of this case is substantially adequate to cover also the other possible types of fault (exception is made in the special case considered in the note to 3.2.5). NOTE In the case of
44、winding in zigzag connection, the single-line-to-earth fault current may reach values higher than the three-phase short-circuit current. However, these high values are limited, in the two limbs concerned, to a half of the coil and furthermore the currents in the other star-connected winding are lowe
45、r than for a three-phase short circuit. Electrodynamic hazard to the winding assembly may be higher either at three- or single-phase short circuit depending on the winding design. The manufacturer and the purchaser should agree which kind of short circuit is to be considered. 3.2.3 Transformers with
46、 more than two windings and auto-transformers The overcurrents in the windings, including stabilizing windings and auxiliary windings, shall be determined from the impedances of the transformer and the system(s). Account shall be taken of the different forms of system faults that can arise in servic
47、e, for example, line-to-earth faults and line-to-line faults associated with the relevant system and transformer earthing conditions (see IEC 60076-8). The characteristics of each system (at least the short-circuit apparent power level and the range of the ratio between zero-sequence impedance and p
48、ositive-sequence impedance) shall be specified by the purchaser in his enquiry. Delta-connected stabilizing windings of three-phase transformers shall be capable of withstanding the overcurrents resulting from different forms of system faults that can arise in service associated with relevant system
49、 earthing conditions. In the case of single-phase transformers connected to form a three-phase bank, the stabilizing winding shall be capable of withstanding a short circuit on its terminals, unless the purchaser specifies that special precautions will be taken to avoid the risk of line-to-line short circuits. NOTE It may not be economical to design auxiliary windings to withstand short circuits on their terminals. In such cases, the overcurrent level should be limited by
