BS 7970-2012 Electric cables Metal foil and longitudinally welded aluminium sheath constructions of power cables having XLPE insulation for rated voltages from 66 kV (Um = 72 5 kV).pdf

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1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS 7970:2012Electric cables Metal foiland longitudinally weldedaluminium sheathconstructions of powercables having XLPEinsulation for rated voltagesfrom 66 kV (Um= 72.5 kV)to 132

2、 kV (Um= 145 kV)Publishing and copyright informationThe BSI copyright notice displayed in this document indicates when the documentwas last issued. The British Standards Institution 2012Published by BSI Standards Limited 2012ISBN 978 0 580 74984 1ICS 29.035.20; 29.060.20The following BSI references

3、relate to the work on this standard:Committee reference GEL/20/16Draft for comment 12/30244364 DCPublication historyFirst published, November 2005Second (current) edition, December 2012Amendments issued since publicationDate Text affectedBS 7970:2012 BRITISH STANDARDContentsForeword ii1 Scope 12 Nor

4、mative references 13 Terms and definitions 14 Construction of metal wire and foil sheaths 15 Marking of cables 36 Routine tests on cables 47 Sample tests on cables 48 Type tests on cables and components 5AnnexesAnnex A (normative) Die penetrant test for weld integrity 7Annex B (normative) Test for p

5、eel strength of overlapped metal foil 7Annex C (normative) Test for adhesion strength of metal foil 9Annex D (normative) Test for impact 9Annex E (normative) Test for sidewall loading 10Annex F (normative) Test for corrosion 12Bibliography 13List of figuresFigure B.1 Peel strength of metal foil shea

6、th overlap Preparation of testsample 8Figure B.2 Peel strength of metal foil sheath overlap Test arrangement 8Figure C.1 Peel strength of metal foil sheath to the oversheath 9Figure D.1 Impact test 10Figure E.1 Example (Arrangement A) for the sidewall loading test 11Figure E.2 Example (Arrangement B

7、) for the sidewall loading test 12Summary of pagesThis document comprises a front cover, an inside front cover, pages i to ii,pages 1 to 14, an inside back cover and a back cover.BRITISH STANDARD BS 7970:2012 The British Standards Institution 2012 iForewordPublishing informationThis British Standard

8、 is published by BSI Standards Limited, under licence fromThe British Standards Institution, and came into effect on 31 December 2012. Itwas prepared by Subcommittee GEL/20/16, Medium/high voltage cables, underthe authority of Technical Committee GEL/20, Electric cables. A list oforganizations repre

9、sented on this committee can be obtained on request to itssecretary.SupersessionThis British Standard supersedes BS 7970:2005, which is withdrawn.Relationship with other publicationsThis British Standard is intended to be read in conjunction with BS 7912 which,together with the additional tests in B

10、S 7970, implements the nationallyapplicable parts (part 5, section H) of Harmonization Document HD 632 S2:2008published by the European Committee for Electrotechnical Standardization(CENELEC) in accordance with the decision of the CENELEC Technical Board.Information about this documentThis is a full

11、 revision of the standard, and introduces the following principalchanges: alignment with the parallel revision of BS 7912, and removal of unnecessaryduplication; introduction of requirements for designs with longitudinally weldedaluminium sheaths.Product certification/inspection/testingUsers of this

12、 British Standard are advised to consider the desirability ofthird-party certification/inspection/testing of product conformity with this BritishStandard. Users seeking assistance in identifying appropriate conformityassessment bodies or schemes may ask BSI to forward their enquiries to therelevant

13、association.Hazard warningsWARNING. This British Standard calls for the use of substances and/orprocedures that can be injurious to health if adequate precautions are nottaken. It refers only to technical suitability and does not absolve the userfrom legal obligations relating to health and safety a

14、t any stage.Presentational conventionsThe provisions of this standard are presented in roman (i.e. upright) type. Itsrequirements are expressed in sentences in which the principal auxiliary verb is“shall”.Commentary, explanation and general informative material is presented insmaller italic type, an

15、d does not constitute a normative element.Contractual and legal considerationsThis publication does not purport to include all the necessary provisions of acontract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legalobligations.BRIT

16、ISH STANDARDBS 7970:2012ii The British Standards Institution 20121 ScopeThis British Standard specifies requirements for construction and performance,and gives methods of test, for metal wire and foil sheath, or metal wire andlongitudinally welded aluminium, or longitudinally welded aluminiumconstru

17、ctions of power cables having XLPE insulation for rated voltages from66 kV (Um= 72.5 kV) to 132 kV (Um= 145 kV). The tests and requirements in thisBritish Standard are additional to the tests and requirements for cables and theiraccessories specified in BS 7912.NOTE 1 In exceptional cases, with very

18、 low fault currents, foil sheath designswithout metal wires may also be used.NOTE 2 Tests described in BS 7912:2012, 15.2, 15.3 and 15.4 are not required in thisstandard.This British Standard is applicable to single-core cables for usual conditions ofinstallation and operation, but not to special ca

19、bles, such as those designed forsubmarine applications.NOTE 3 Annex A gives requirements for a die penetrant test for weld integrity.Annex B lists a test for peel strength of overlapped metal foil. Annex C lists testrequirements for adhesion strength of metal foil. Annex D covers the test for impact

20、and Annex E the test for sidewall loading. Annex F covers the test for corrosion.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in thisdocument and are indispensable for its application. For dated references, onlythe edition cited applies. For undated

21、references, the latest edition of thereferenced document (including any amendments) applies.BS 7870-2:2011, LV and MV polymeric insulated cables for use by distributionand generation utilities Part 2: Methods of testBS 7912:2012, Power cables with XLPE insulation and metal sheath, and theiraccessori

22、es, for rated voltages from 66 kV (Um= 72.5 kV) to 132 kV (Um= 145 kV)(Implementation of HD 632)BS EN 60228, Conductors of insulated cablesIEC 60050-461, International Electrotechnical Vocabulary Part 461 ElectriccablesIEC 60840, Power cables with extruded insulation and their accessories for ratedv

23、oltages above 30 kV (Um= 36 kV) up to 150 kV (Um= 170 kV) Test methodsand requirements3 Terms and definitionsFor the purposes of this British Standard, the terms and definitions given inIEC 60050-461 and BS 7912 apply.4 Construction of metal wire and foil sheaths4.1 Metal wiresFor foil sheath constr

24、uctions, and where required for longitudinally weldedaluminium, a layer of metal wires shall be applied over the semi-conductinginsulation screen in a single helical layer.NOTE In exceptional cases, with very low fault currents, foil sheath designs withoutmetal wires may also be used.BRITISH STANDAR

25、D BS 7970:2012 The British Standards Institution 2012 1The wires shall be spaced with an average gap not greater than 4 mm and nogap shall exceed 8 mm. No wires shall cross other wires.A metal tape or wires shall be applied helically over, and in contact with, thelayer of metal wires in order to equ

26、alize the current flowing in the individualwires forming the layer of wires.4.2 Water blockingThe requirements of BS 7912:2012, 4.6, shall apply.4.3 Metal sheath4.3.1 GeneralThe metal sheath shall conform to 4.3.2 or to 4.3.3, as appropriate.4.3.2 Metal foil sheathA continuous metal foil sheath shal

27、l be longitudinally applied over the waterblocking tapes with a minimum overlap of 7 mm. The foil shall either be a metalfoil or a metal foil/polymer laminate. Joins in the foil shall have the sameelectrical performance as a continuous piece of foil. The metal foil overlap shallbe sealed to prevent

28、ingress of moisture.4.3.3 Longitudinally welded aluminium sheathA continuous metal strip sheath shall be longitudinally applied over the waterblocking tapes and the edges of the strip shall be welded to form a join withthe same thickness as the strip material. If the strip material is joined to anot

29、herstrip then the join shall have the same electrical performance as the unjoinedstrip. The weld shall be continuous and without porosity. The integrity of theweld shall be monitored continuously during manufacture.4.4 Earth fault capabilityThe earth fault capability in current (kA) and duration (se

30、conds) shall be asspecified by the purchaser. The cross-sectional area, approximate number andapproximate diameter of the metal wires shall be as specified by themanufacturer.4.5 OversheathThe oversheath shall be an extruded layer of black medium density polyethylene(MDPE) conforming to the requirem

31、ents specified for ST3or ST7as given inBS 7912:2012, Table 5 and Table 9, unless otherwise agreed.NOTE Alternative materials to ST3and ST7may be provided by agreement betweenthe manufacturer and the purchaser.The thickness of the oversheath shall be as agreed between the manufacturerand the purchase

32、r.The oversheath shall be bonded to metal foil or longitudinally welded sheath.An outer semi-conducting coating shall be applied to serve as an electrode for avoltage test on the oversheath.BRITISH STANDARDBS 7970:20122 The British Standards Institution 20125 Marking of cables5.1 External markingThe

33、 external surface of all cables shall be legibly marked with the followingelements.Element Example of markinga) Electric cable ELECTRIC CABLEb) Voltage designation 66000 V or 110000 V or 132000 Vc) British Standard number BS 79701)d) Manufacturers identification XYZe) Number of cores and nominal are

34、aand type (CU or AL) of conductor,e.g. single-core cable with 300 mm2copper conductor1 300 CUThe marking of elements a) to d) shall be by embossing or indenting on theoversheath.The marking of element e) shall be by embossing, indenting or printing on theoversheath.Elements a), b) and c) shall appea

35、r on two or more primary lines along the axisof the cable, approximately equally spaced around the circumference of thecable.Elements d) and e) shall appear on at least one line.NOTE Elements d) and e) may be on one of the primary lines or a secondary line orlines and need not be on the same line.Th

36、e letters and figures shall consist of upright block characters. The charactersshall have a height of not less than 3 mm.The distance between the end of the one element of marking and thebeginning of the next identical element of marking shall be not greater than550 mm for elements a), b) and c), an

37、d not greater than 1 100 mm forelements d) and e).5.2 Identification of year and month of manufactureA means of identifying the year and month of manufacture of the cable shall beprovided throughout the length of the cable by marking on the surface of thecable.The marking shall be by embossing or in

38、denting on the oversheath. Thecharacters shall have a height of not less than 3 mm and the distance betweenthe end of the one element of marking and the beginning of the next identicalelement of marking shall be not greater than 1 100 mm.5.3 Mark of an approval organizationIf the mark of an approval

39、 organization is used, it shall be provided throughoutthe length of the cable.1)Marking BS 7970 or BS 7970:2012 on or in relation to a product represents amanufacturers declaration of conformity, i.e. a claim by or on behalf of themanufacturer that the product meets the requirements of the standard.

40、 The accuracyof the claim is solely the claimants responsibility. Such a declaration is not to beconfused with third-party certification of conformity.BRITISH STANDARD BS 7970:2012 The British Standards Institution 2012 36 Routine tests on cables6.1 GeneralCOMMENTARY ON 6.1“Routine test” is defined

41、in BS 7912:2012, 3.4.In addition to the requirements specified in BS 7912:2012, Clause 9, the cableshall conform to the requirements specified in 6.2, 6.3 and 6.4.6.2 Metal screen resistanceWhen measured in accordance with BS 7870-2:2011, 3.1.1, and corrected to 20 Cin accordance with BS EN 60228, t

42、he d.c. resistance of the metal screen shall notexceed the value specified by the manufacturer.6.3 Examination6.3.1 SamplingTwo samples 0.5 m in length shall be taken, one from each end of the drumlength.6.3.2 Metal foil sheath overlapWhen measured at each end of two samples, none of the metal foil

43、sheathoverlaps shall be less than 7 mm.6.3.3 Metal foil sheath visual examinationWhen the metal foil sheath/oversheath assembly is cut longitudinally from thetwo 0.5 m samples and examined with normal or corrected vision, withoutmagnification, the metal foil sheath shall show no evidence of cracking

44、, splittingor annular wrinkling and there shall be no voids at the metal foilsheath/oversheath interface.6.3.4 Longitudinally welded aluminium visual examinationThe longitudinally welded aluminium sheath/oversheath assembly shall be cutlongitudinally from the two 0.5m samples such that the weld is a

45、t the centre ofone of the samples. The weld shall be examined with normal or corrected vision,without magnification. There shall no evidence of voids or fractures, and thethickness of the weld shall be at least equal to that of the adjacent aluminiumstrip.The insulation screen of the two 0.5 m sampl

46、es shall be examined to confirmthat there is no damage due to the aluminium sheath welding process.6.4 Longitudinally welded aluminium die penetrant testWhen tested in accordance with Annex A, there shall be no indication of defectin the weld.7 Sample tests on cables7.1 GeneralCOMMENTARY ON 7.1“Samp

47、le test” is defined in BS 7912:2012, 3.5.In addition to the requirements specified in BS 7912: 2012, Clause 10, the cableshall conform to the requirements specified in 7.2 and 7.3.BRITISH STANDARDBS 7970:20124 The British Standards Institution 20127.2 Peel strength7.2.1 Peel strength of metal foil s

48、heath overlapWhen tested in accordance with Annex B, the minimum value of the peelstrength shall be not less than 0.5 N/mm.NOTE When the peel strength is greater than the tensile strength of the metal foilso that the latter breaks before peeling, the test should be terminated and thebreak point shou

49、ld be recorded.7.2.2 Peel strength of metal sheath to oversheathThe metal foil sheath shall be tested in accordance with Annex C.The adhesion strength shall be calculated by dividing the peel force, in Newtons,by the width of the specimen, in millimetres. At least five specimens shall besubmitted to the test and the minimum value of the adhesion strength shall benot less than 0.5 N/mm.NOTE When the adhesion strength is greater than the tensile strength of the metalfoil so that the latter breaks before peeling, the test should be term