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1、BRITISH STANDARD BS 7626:1993 Incorporating Amendment No. 1 Specification for Current transformers (Implementation of CENELEC HD 553 S2) UDC 621.314.6 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:30:21 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7626:199
2、3 This British Standard, having been prepared under the direction of the Power Electrical Engineering Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 15 February 1993 BSI 02-1999 The following BSI references relate to the work on this sta
3、ndard: Committee reference PEL/59 Draft for comment 92/03129 DC ISBN 0 580 21575 X Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Power Electrical Engineering Standards Policy Committee (PEL/-) to Technical Committee PEL/59, upon which
4、the following bodies were represented: Association of Consulting Engineers Department of Energy (Electricity Division) Electricity Association Transmission and Distribution Association (BEAMA Limited) Amendments issued since publication Amd. No.DateComments 8036November 1993 Indicated by a sideline
5、in the margin Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:30:21 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7626:1993 BSI 02-1999i Contents Page Committees responsible Inside front cover National forewordii Foreword2 Text of HD 553 S27 National annex NA
6、 (informative) Original IEC text amended by CENELEC common modifications37 National annex NB (informative) Cross-referencesInside back cover Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:30:21 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7626:1993 ii BSI 0
7、2-1999 National foreword This British Standard has been prepared under the direction of the Power Electrical Engineering Standards Policy Committee. It implements Harmonization Document HD 553 S2:1993, published by the European Committee for Electrotechnical Standardization (CENELEC) which was deriv
8、ed from IEC 185:1987 plus Amendment No.1 (1990), published by the International Electrotechnical Commission (IEC). The CENELEC common modifications have been implemented at the appropriate places in the text and are indicated by a side line in the margin. Parts of the original IEC text that have bee
9、n modified by CENELEC have been quoted in National annex NA. This British Standard supersedes BS 3938:1973 which is declared obsolescent. Products may continue to be manufactured to BS 3938:1973 until 1 June 1998. A British Standard does not purport to include all the necessary provisions of a contr
10、act. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, the EN title page, pages 2 to 40
11、 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:30:21 GMT+00:00 2006, Unc
12、ontrolled Copy, (c) BSI EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM HD 553 S2 May 1993 UDC 621.314.6 Descriptors: Instrument transformer, current transformer, specification, test, marking English version Current transformers (IEC 185:1987 + A1:1990, modified) Transformateurs de courant (CEI 18
13、5:1987 + A1:1990, modifis) Stromwandler (IEC 185:1987 + A1:1990, modifiziert) This Harmonization Document was approved by CENELEC on 1993-03-09. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for implementation of this Harmonization Docum
14、ent on a national level. Up-to-date lists and bibliographical references concerning national implementation may be obtained on application to the Central Secretariat or to any CENELEC member. This Harmonization Document exists in three official versions (English, French, German). CENELEC members are
15、 the national electrotechnical committees of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CENELEC European Committee for Electrotechnical Standardization Comit Europen d
16、e Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B-1050 Brussels 1993 Copyright reserved to CENELEC members Ref. No. HD 553 S2:1993 E Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:30:
17、21 GMT+00:00 2006, Uncontrolled Copy, (c) BSI HD 553 S2:1993 BSI 02-1999 2 Foreword At the request of the BTTF 56-3, CENELEC 71st Technical Board decided to submit the international standard IEC 185:1987 and its amendment 1:1990 to the CENELEC Unique Acceptance Procedure (UAP) for acceptance as a Ha
18、rmonization Document. The reference documents, together with the common modifications previously accepted for HD 553 S1, were submitted to this procedure in April 1992. The text of the draft was approved by CENELEC as HD 553 S2 on 9 March 1993. The following dates were fixed: For products which have
19、 complied with HD 553 S1:1992 before 1993-12-01, as shown by the manufacturer or by a certification body, this previous standard may continue to apply for production until 1988-12-01. Annexes designated “normative” are part of the body of the standard. In this standard, Annex ZA (Cross-references) i
20、s normative and Annex ZB (B-deviations) is informative. latest date of announcement of the HD at national level(doa)1993-06-01 latest date of publication of a harmonized national standard(dop)1993-12-01 latest date of withdrawal of conflicting national standards(dow) 1993-12-01 Licensed Copy: London
21、 South Bank University, London South Bank University, Fri Dec 08 12:30:21 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7626:1993 BSI 02-19993 Common modifications 2 Service conditions 2.1 Ambient air temperatures Replace by: In extreme cases, for outdoor transformers, lower minimum ambient temperat
22、ures (i.e. 50 C) may be required. 3 Definitions 3.16 Add “(Um)” in the title. 8 Short-time current rating 8.1 Add: NOTEWhen a current transformer is a part of another equipment (i.e. switchgear), a rated time other than 1 s may be specified. 10 Insulation requirements 10.1.1 Replace “Tables IIA and
23、IIB” by “Table IIA”. To Table IIA, add the value Um = 100 kV with the following withstand voltages: Delete Table IIB. Move the Note under Table IIE to subclause 10.2.2. 10.2.3 Replace the text by: If additionally specified, the primary windings shall also be capable of withstanding chopped lightning
24、-impulse voltages as per clause 20. 19 Test of interturn insulation Replace the text of test procedure A by: Procedure A With the secondary winding open-circuited (or connected to a high impedance device which reads peak voltage), a substantially sinusoidal current at a frequency between 40 Hz and 6
25、0 Hz (in accordance with IEC Publication 60) and of r.m.s. value equal to the rated primary current (or rated extended current when applicable) shall be applied for 1 min to the primary winding. If the voltage produced at the secondary terminals has a peak value greater than the prescribed test volt
26、age, the applied current shall be reduced accordingly. Replace the second paragraph of test procedure B by: The value of the test frequency shall be no greater than ten times the rated frequency; at this frequency value, the prescribed test voltage may be the value obtained at the rated secondary cu
27、rrent (extended range current when applicable). maximum 40 C daily mean, not exceeding30 C minimum, for indoor type transformers 5 C minimum, for class 25 outdoor type transformers 25 C minimum, for class 40 outdoor type transformers 40 C Licensed Copy: London South Bank University, London South Ban
28、k University, Fri Dec 08 12:30:21 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7626:1993 4 BSI 02-1999 When the test frequency exceeds twice the rated frequency, the duration of the test may be reduced from 1 min as below: with a minimum of 15 s. 20 Chopped lightning-impulse test on primary winding
29、s Modify the value of the chopped impulses as follows: a) Windings having Um Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:30:21 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7626:1993 BSI 02-199927 34.2 composite error1) under steady-state conditions, the
30、r.m.s. value of the difference between: a) the instantaneous values of the primary current and b) the instantaneous values of the actual secondary current multiplied by the rated transformation ratio, the positive signs of the primary and secondary currents corresponding to the convention for termin
31、al markings. the composite error is generally expressed as a percentage of the r.m.s. values of the primary current according to the mathematical expression: where: 34.3 rated accuracy limit primary current the value of primary current up to which the transformer will comply with the requirements fo
32、r composite error 34.4 accuracy limit factor the ratio of the rated accuracy limit primary current to the rated primary current 34.5 secondary limiting e.m.f. the product of the accuracy limit factor, the rated secondary current and the vectorial sum of the rated burden and the impedance of the seco
33、ndary winding 34.6 exciting current the r.m.s. value of the current taken by the secondary winding of a current transformer when sinusoidal voltage of rated frequency is applied to the secondary terminals, the primary and any other windings being open-circuited Section 13. Accuracy requirements 35 S
34、tandard accuracy limit factors The standard accuracy limit factors are: 5 10 15 20 30. 36 Accuracy classes 36.1 Accuracy class designation For protective current transformers, the accuracy class is designed by the highest permissible percentage composite error at the rated accuracy limit primary cur
35、rent prescribed for the accuracy class concerned, followed by the letter “P” (meaning protection). 1) See Appendix A. Kn= the rated transformation ratio Ip= the r.m.s. value of the primary current ip= the instantaneous value of the primary current is= the instantaneous value of the secondary current
36、 T= the duration of one cycle Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:30:21 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7626:1993 28 BSI 02-1999 36.2 Standard accuracy classes The standard accuracy classes for protective current transformers are: 5
37、P and 10 P. 37 Limits of error At rated frequency and with rated burden connected, the current error, phase displacement and composite error shall not exceed the values given in Table VI. For testing purposes when determining current error and phase displacement, the burden shall have a power-factor
38、 of 0.8 inductive except that, where the burden is less than 5 VA, a power-factor of 1.0 is permissible. For the determination of composite error, the burden shall have a power-factor of between 0.8 inductive and unity at the discretion of the manufacturer. Table VI Limits of error Section 14. Tests
39、 for accuracy 38 Type and routine tests for current error and phase displacement Tests shall be made at rated primary current to prove compliance with Clause 37 in respect of current error and phase displacement. 39 Type tests for composite error a) Compliance with the limits of composite error give
40、n in Table VI shall be demonstrated by a direct test in which a substantially sinusoidal current equal to the rated accuracy limit primary current is passed through the primary winding with the secondary winding connected to a burden of magnitude equal to the rated burden but having, at the discreti
41、on of the manufacturer, a power-factor between 0.8 inductive and unity (see Appendix A). The test may be carried out on a transformer similar to the one being supplied except that reduced insulation may be used provided that the same geometrical arrangement is retained. NOTEWhere very high primary c
42、urrents and single bar-primary winding current transformers are concerned, the distance between the return primary conductor and the current transformer should be taken into account from the point of view of reproducing service conditions. b) For current transformers having substantially continuous
43、ring cores, uniformly distributed secondary windings and having either a centrally located primary conductor(s) or a uniformly distributed primary winding, the direct test may be replaced by the following indirect test provided that the effect of the return primary conductor(s) is negligible. With t
44、he primary winding open-circuited, the secondary winding is energized at rated frequency by a substantially sinusoidal voltage having an r.m.s. value equal to the secondary limiting e.m.f. The resulting exciting current, expressed as a percentage of the rated secondary current multiplied by the accu
45、racy limit factor, shall not exceed the limit of composite error given in Table VI. NOTE 1In calculating the secondary limiting e.m.f., the secondary winding impedance should be assumed to be equal to the secondary winding resistance measured at room temperature and corrected to 75 C. NOTE 2In deter
46、mining the composite error by the indirect method, a possible difference between turns ratio and rated transformation ratio need not be taken into account. Accuracy class Current error at rated primary current % Phase displacement at rated primary current Composite error at rated accuracy limit prim
47、ary current % minutescentiradians 5 P 1 60 1.85 10 P 310 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:30:21 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7626:1993 BSI 02-199929 40 Routine tests for composite error For all transformers qualifying under Ite
48、m b) of Clause 39, the routine test is the same as the type test. For other transformers, the indirect test of measuring the exciting current may be used, but a correction factor shall be applied to the results, the factor being obtained from a comparison between the results of direct and indirect t
49、ests applied to a transformer of the same type as the one under consideration (see Note 2), the accuracy limit factor and the conditions of loading being the same. In such cases, certificates of test should be held available by the manufacturer. NOTE 1The correction factor is equal to the ratio of the composite error obtained by the direct method and the exciting current expressed as a percentage of the rated secondary current multiplied by the accuracy limit factor, as determined by the indirect method specified in