Bsi bs en 61109 2008

BS EN 61 09:2008 BSI Standards Publication Insul ators for overhead l i nes — Composi te suspensi on and tensi on i nsul ators for a.c systems wi th a nomi nal vol tage greater than 000 V — Defi ni ti ons, test methods and acceptance cri teri a BS EN 61 09:2008 BRITISH STANDARD National foreword This British Standard is the UK implementation of EN 61 09:2008 It is identical to IEC 61 09:2008 The UK participation in its preparation was entrusted to Technical Committee PEL/36, Insulators for power systems A list of organizations represented on this committee can be obtained on request to its secretary The attention of users is drawn to the flammability test in Tables and of BS EN 61 09:2008, which references BS EN 6221 7:2005, and is used as an indicator of power arc ignition and extinction performance The UK Committee is of the opinion that work carried out before and after BS EN 6221 7:2005 was published shows that the flammability test is not suitable for assessing the power arc performance of insulators The correlation between performance in different flammability tests, laboratory power arc tests and behaviour in service is currently under investigation by the International Council on Large Electric Systems study committee on Materials and Emerging Technologies (CIGRE SC D1 ) When applying this standard, users are recommended to consult the power arc tests in ANSI C29.1 or IEC 60099-4 surge arrestor specifications in addition to the test in Tables and The ANSI test also usefully includes an end fitting seal test after power arc damage This publication does not purport to include all the necessary provisions of a contract Users are responsible for its correct application © BSI 2009 ISBN 978 580 67052 ICS 29.080.1 Compliance with a British Standard cannot confer immunity from legal obligations This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 March 2009 Amendments issued since publication Amd No Date Text affected EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM EN 61 09 October 2008 ICS 29.080.1 English version Insulators for overhead lines Composite suspension and tension insulators for a.c systems with a nominal voltage greater than 000 V Definitions, test methods and acceptance criteria (IEC 61 09:2008) Isolateurs pour lignes aériennes Isolateurs composites de suspension et d'ancrage destinés aux systèmes courant alternatif de tension nominale supérieure 000 V Définitions, méthodes d'essai et critères d'acceptation (CEI 61 09:2008) Isolatoren für Freileitungen Verbund-Hänge- und -Abspannisolatoren für Wechselstromsysteme mit einer Nennspannung über 000 V Begriffe, Prüfverfahren und Annahmekriterien (IEC 61 09:2008) This European Standard was approved by CENELEC on 2008-09-01 CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate 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 Standard 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 national electrotechnical committees of Austria, Belgium, Bulgaria, 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, Switzerland and the United Kingdom CENELEC European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 050 Brussels © 2008 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members Ref No EN 61 09:2008 E BS EN 61 09:200 EN 61 09: 2008 -2- Foreword The text of document 36B/274/FDIS, future edition of IEC 61 09, prepared by SC 36B, Insulators for overhead lines, of IEC TC 36, Insulators, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 61 09 on 2008-09-01 The following dates were fixed: – latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) – latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 201 -09-01 2009-06-01 Annex ZA has been added by CENELEC Endorsement notice The text of the International Standard IEC 61 09:2008 was approved by CENELEC as a European Standard without any modification -3- BS EN 61 09:200 EN 61 09: 2008 Annex ZA (normative) Normative references to international publications with their corresponding European publications The following referenced documents are indispensable for the application of this document For dated references, only the edition cited applies For undated references, the latest edition of the referenced document (including any amendments) applies NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD applies Publication IEC 60383-1 IEC 60383-2 IEC 61 466-1 IEC 6221 ISO 3452 Year - 1) Title EN/HD Insulators for overhead lines with a nominal EN 60383-1 voltage above kV + A1 Part : Ceramic or glass insulator units for a.c systems - Definitions, test methods and acceptance criteria 1) Insulators for overhead lines with a nominal EN 60383-2 voltage above kV Part 2: Insulator strings and insulator sets for a.c systems - Definitions, test methods and acceptance criteria 1) Composite string insulator units for EN 61 466-1 overhead lines with a nominal voltage greater than kV Part : Standard strength classes and end fittings 2005 Polymeric insulators for indoor and outdoor EN 6221 use with a nominal voltage > 000 V + corr December General definitions, test methods and acceptance criteria Series Non-destructive testing - Penetrant EN ISO 3452 inspection 1) Un dated reference 2) Valid edition at d ate of issue Year 996 2) 999 995 2) 997 2) 2006 2006 Series BS EN 61 09:200 –2– 61 09 ? I EC: 2008 CON TENTS I N TRODU CTI ON Scope and obj ect N orm ative references Term s, definitions and abbreviations Term s and definitions Abbreviations I dentification Environm ental conditions Transport, storage and installation H ybrid insulators Tolerances Classification of tests 1 Design tests 1 Type tests 1 Sam ple tests 1 Routine tests 1 Design tests 1 General 2 Test specim ens for I EC 6221 Tests on interfaces and connections of end fittings 2 Tracking and erosion test 3 Tests on core m aterial Product specific pre-stressing for I EC 6221 Sud den load release Therm al-m echanical pre-stress 4 Assem bled core load -tim e tests 4 Test specim ens 4 Mechanical load test 1 Type tests 1 Electrical tests 1 Dam age lim it proof test and test of the tightness of the interface between end fittings and insulator housing 1 Test specim ens 1 2 Perform ance of the test 1 Evaluation of the test Sam ple tests General rules 2 Verification of dim ensions (E1 + E2) Verification of the end fittings (E2) Verification of tightness of the interface between end fittings and insulator housing (E2) and of the specified m echanical load, SML (E1 ) Galvanizing test (E2) Re-testing proced ure Routine tests M echanical routine test BS EN 61 09:200 61 09 ? I EC: 2008 –3– Visual exam ination Annex A (inform ative) Principles of the dam age lim it, load coordination and testing for com posite suspension and tension insulators 21 Annex B (inform ative) Exam ple of two possible devices for sudden release of load 25 Annex C (inform ative) Guidance on non-standard m echanical stresses and dynam ic m echanical loading of com posite tension/suspension insulators 27 Bibliography 29 Figure − Therm al-m echanical test 20 Figure A − Load-tim e strength and dam age lim it of a core assem bled with fittings 22 Figure A – Graphical representation of the relationship of the dam age lim it to the m echanical characteristics and service loads of an insulator with a m m d iam eter core 23 Figure A – Test load s 24 Figure B − Exam ple of possible d evice for sudden release of load 25 Figure B − Exam ple of possible d evice for sudden release of load 26 Table Table Table Table – – – – Tests to be carried out after design changes Design tests Mounting arrangem ents for electrical tests Sam ple sizes BS EN 61 09:200 –6– 61 09 ? I EC: 2008 I N TRODUCTI ON Com posite insulators consist of an insulating core, bearing the m echanical load protected by a polym eric housing, the load being transm itted to the core by end fittings Despite these com m on features, the m aterials used and the construction details em ployed by different m anufacturers m ay be quite different Som e tests have been grouped together as "Design tests", to be perform ed only once on insulators which satisfy the sam e design conditions For all d esign tests of com posite suspension and tension insulators, the appropriate com m on clauses defined in I EC 6221 are applied As far as practical, the influence of tim e on the electrical and m echanical properties of the com ponents (core m aterial, housing, interfaces etc ) and of the com plete com posite insulators has been considered in specifying the design tests to ensure a satisfactory life-tim e under norm ally known stress conditions of transm ission lines An explanation of the principles of the dam age lim it, load coordination and testing is presented in Annex A I t has not been considered useful to specify a power arc test as a m and atory test The test param eters are m anifold and can have very d ifferent values depending on the configurations of the network and the supports and on the design of arc-protection devices The heating effect of power arcs should be considered in the design of m etal fittings Critical dam age to the m etal fittings resulting from the m agnitude and d uration of the short-circuit current can be avoided by properly designed arc-protection d evices This standard, however, does not exclude the possibility of a power arc test by agreem ent between the user and m anufacturer I EC 61 467 [1 ] gives details of a c power arc testing of insulator sets Com posite insulators are used in both a c and d c applications I n spite of this fact, a specific tracking and erosion test procedure for d c applications as a design test has not yet been defined and accepted The 000 h a c tracking and erosion test of I EC 6221 is used to establish a m inim um requirem ent for the tracking resistance of the housing m aterial The m echanism of brittle fracture has been investigated by CI GRE B2 03 and conclusions are published in [2, 3] Brittle fracture is a result of stress corrosion induced by internal or external acid attack on the resin bond ed glass fibre core CI GRE D1 has d eveloped a test procedure for core m aterials based on tim e-load tests on assem bled cores exposed to acid, along with chem ical analysis m ethods to verify the resistance against acid attack [4] I n parallel I EC TC36WG is studying preventive and predictive m easures Com posite suspension/tension insulators are not norm ally intended for torsion or other nontensile loads Guidance on non-standard loads is given in Annex C Wherever possible, I EC Guide 1 [5] has been followed for the drafting of this standard _ Fi gu res i n sq uare brackets refer to th e bi bl i ography I ntern ati on al Cou nci l on Larg e H i gh Vol tag e El ectri c System s: Worki n g Grou p B2 03 BS EN 61 09:200 61 09 ? I EC: 2008 –7– I N S U L AT O RS F O R O VE RH E AD L I N E S – C O M P O S I T E S U S P E N S I O N AN D T E N S I O N I N S U L AT O RS F O R A C S YS T E M S WI T H A N O M I N AL VO L T AG E G RE AT E R T H AN 000 V – D E F I N I T I O N S , T E S T M E T H O D S AN D AC C E P T AN C E C RI T E RI A S co p e an d ob j e ct This I nternational Standard applies to com posite suspension/tension insulators consisting of a load-bearing cylindrical insulating solid core consisting of fibres – usually glass – in a resinbased m atrix, a housing (outside the insulating core) m ad e of polym eric m aterial and end fittings perm anently attached to the insulating core Com posite insulators covered by this standard are intend ed for use as suspension/tension line insulators, but it should be noted that these insulators can occasionally be subj ected to com pression or bending, for exam ple when used as phase-spacers This standard can be applied in part to hybrid com posite insulators where the core is m ade of a hom ogeneous m aterial (porcelain, resin), see Clause The obj ect of this stand ard is to – – – define the term s used, prescribe test m ethods, prescribe acceptance criteria This standard does not include requirem ents dealing with the choice of insulators for specific operating conditions N o rm a t i ve re fe re n c e s The following referenced docum ents are indispensable for the application of this docum ent For dated references, only the edition cited applies For undated references, the latest edition of the referenced docum ent (includ ing any am end m ents) applies I EC 60383-1 , In sula tors for overh ea d lines with a nomina l volta ge a b ove 000 V – Pa rt : Ce mic or gla ss insula tor units for a c syste ms – De finitions, te st meth ods a n d a cce pta nce criteria I EC 60383-2, In sula tor Insula tors for overh ea d lines with a nomina l volta ge a b ove 000 V – Pa rt 2: strings and insula tor se ts for a c syste ms – Defin ition s, te st meth ods and a ccepta nce crite ria I EC 61 466-1 , Composite string insula tor units for overh ea d lines with a nomina l volta ge a nomin a l volta ge grea ter th a n 000 V – Pa rt : Sta nda rd stre ngth cla sses a nd end fittings I EC 6221 7: 2005, Polymeric insula tors for indoor a nd outdoor use > 000 V – Ge nera l definition s, test me th ods a nd a ccepta nce criteria I SO 3452 (all parts), Non-destructive testing – Pen etra nt testing with BS EN 61 09:200 –8– 61 09 ? I EC: 2008 Terms, definitions and abbreviations For the purposes of this d ocum ent, the following term s, definitions and abbreviations apply N OTE Certai n term s from I EC 6221 are reprod u ced here for ease of reference Ad d i ti onal d efi ni ti on s appl i cabl e to i n su l ators can be fou nd i n I EC 60050-471 [6] 3.1 Terms and definitions 3.1 polymeric insulator insulator whose insulating body consists of at least one organic based m aterial N OTE Pol ym eri c i n su l ators are al so known as n on -ceram i c i nsul ators N OTE Coupl i ng d evi ces m ay be attach ed to the end s of the i n su l ati ng bod y [I EV 471 -01 -1 3] 3.1 composite insulator insulator m ade of at least two insulating parts, nam ely a core and a housing equipped with m etal fittings N OTE Com posi te i nsu l ators, for exam pl e, can si st ei ther of i nd i vi d ual shed s m oun ted on th e core, wi th or wi thou t an i n term ed i ate sh eath , or al ternati vel y, of a h ousi ng d i rectl y m ou l d ed or cast i n on e or several pi eces on to th e core [I EV 471 -01 -02] 3.1 core of a composite insulator internal insulating part of a com posite insulator which is designed to ensure the m echanical characteristics N OTE Th e core usual l y consi sts of ei th er fi bres (e g g l ass) whi ch are posi ti on ed i n a resi n-based m atri x or a hom og en eous i n sul ati n g m ateri al (e g porcel n or resi n ) [I EV 471 -01 -03, m odified ] 3.1 insulator trunk central insulating part of an insulator from which the sheds proj ect N OTE Al so known as sh ank on sm al l er insul ators [I EV 471 -01 -1 ] 3.1 housing external insulating part of a com posite insulator providing the necessary creepage distance and protecting core from the environm ent N OTE An i n term ed i ate sheath m ad e of i n sul ati ng m ateri al m ay be part of the h ou si n g [I EV 471 -01 -09] BS EN 61 09:200 – 18 – 61 09 ? I EC: 2008 2.2 Verification of dimensions (E1 + E2) The dim ensions given in the drawings shall be verified The tolerances given in the drawings are valid I f no tolerances are given in the drawings the values m entioned in Clause shall be used 2.3 Verification of the end fittings (E2) The dim ensions and gauges for end fittings are given in I EC 61 466-1 The appropriate verification shall be m ade for the types of fitting used including, if applicable, verification of the locking system in accordance with I EC 60383-1 2.4 Verification of tightness of the interface between end fittings and insulator housing (E2) and of the specified mechanical load, SM L (E1 ) a) One insulator, selected rand om ly from the sam ple E2, shall be subj ected to crack indication by dye penetration, in accordance with I SO 3452, on the housing in the zone em bracing the com plete length of the interface between the housing and m etal fitting and including an ad ditional area, sufficiently extended , beyond the end of the m etal part The indication shall be perform ed in the following way: – the surface shall be properly pre-cleaned with the cleaner; – the penetrant, which shall act during 20 m in, shall be applied on the cleaned surface; – within m in after the application of the penetrant, the insulator shall be subjected, at the am bient tem perature, to a tensile load of 70 % of the SML, applied between the m etal fittings; the tensile load shall be increased rapidly but sm oothly from zero up to 70 % of the SML, and then m aintained at this value for m in; – the surface shall be cleaned with the excess penetrant rem oved , and dried; – the developer shall be applied, if necessary; – the surface shall be inspected Som e housing m aterials m ay be penetrated by the penetrant I n such cases, evidence shall be provided to validate the interpretation of the results After the m in test at 70 % of the SML, if any cracks occur, the housing and, if necessary, the m etal fittings and the core shall be cut perpendicular to the crack in the m iddle of the widest of the indicated cracks, into two halves The surface of the two halves shall then be investigated to m easure the depth of the cracks b) The insulators of the sam ple E1 shall be subjected at am bient tem perature to a tensile load, applied between the couplings The tensile load shall be increased rapidly but sm oothly from zero to approxim ately 75 % of the SML and then gradually increased to the SML in a tim e between 30 s to 90 s I f 00 % of the SML is reached in less than 90 s, the load (1 00 % of the SML) shall be m aintained for the rem ainder of the 90 s (this test is considered to be equivalent to a m in withstand test at the SML) I n order to obtain m ore inform ation from the test, unless special reasons apply (for instance the m axim um tensile load of the test m achine), the load m ay be increased until the failing load is reached, and its value recorded The insulators have passed this test if – – – no failure (breakage or com plete pull-out of the core, or fracture of the m etal fitting) occurs either during the m in 70 % withstand test (a)) or d uring the m in 00 % withstand test (b)), no cracks are ind icated after the d ye penetration m ethod described in a), the investigation of the halves described in a) shows clearly that the cracks not reach the core BS EN 61 09:200 61 09 ? I EC: 2008 – 19 – 2.5 Galvanizing test (E2) This test shall be perform ed on all galvanized parts in accordance with I EC 60383-1 2.6 Re-testing procedure I f only one insulator or end fitting fails to com ply with the sam pling tests, re-testing shall be perform ed using a new sam ple size equal to twice the quantity originally subm itted to the tests The re-testing shall com prise the test in which failure occurred I f two or m ore insulators or m etal parts fail to com ply with any of the sam pling tests, or if any failure occurs during the re-testing, the com plete lot is considered as not com plying with this standard and shall be withdrawn by the m anufacturer Provid ed the cause of the failure can be clearly identified, the m anufacturer m ay sort the lot to elim inate all the insulators with this defect The sorted lot m ay then be re-subm itted for testing The num ber then selected shall be three tim es the first quantity chosen for tests I f any insulator fails during this re-testing, the com plete lot is consid ered as not com plying with this standard and shall be withdrawn by the m anufacturer Routine tests 3.1 Mechanical routine test Every insulator shall withstand , at am bient tem perature, a tensile load at RTL corresponding to 0, × SML ( +1 ) % for at least s 3.2 Visual examination Each insulator shall be exam ined The m ounting of the end fittings on the insulating parts shall be in accordance with the drawings The colour of the insulator shall be approxim ately as specified in the drawings The m arkings shall be in conform ance with the requirem ents of this standard (see Clause 4) The following defects are not perm itted: a) b) c) d) e) superficial defects of an area greater than 25 m m (the total d efective area not to exceed 0, % of the total insulator surface) or of depth greater than m m ; cracks at the root of the shed, notably next to the m etal fittings; separation or lack of bond ing at the housing to m etal fitting joint (if applicable); separation or bonding d efects at the shed to sheath interface, m oulding flashes protruding m ore than m m above the housing surface BS EN 61 09:200 – 20 – 61 09 ? I EC: 2008 88 96 Time h Load RTL (≥0,5 SML) 16 24 32 40 48 56 64 72 80 Air temperature °C +50 ± 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 Time h –35 ± Thermal cycles IEC Figure − Thermal-mechanical test 807/08 BS EN 61 09:200 61 09 ? I EC: 2008 – 21 – An n e x A (informative) P ri n c i p l e s o f th e d a m a g e l i m i t , l o a d c o o rd i n a ti o n a n d t e s t i n g fo r c o m p o s i t e s u s p e n s i o n a n d te n s i o n i n s u l a t o rs A I n t ro d u c t o ry re m a rk This annex is intended to explain the long-term behaviour of com posite suspension and tension insulators under m echanical load, to show typical coordination between SML and service load s and to explain the m echanical testing philosophy A L o a d -t i m e b e h a vi o u r a n d t h e d a m a g e l i m i t An essential part of the m echanical behaviour of resin bonded fibre cores, typically used for com posite insulators, is their load-tim e behaviour, which deserves som e explanation The vast experience gained with com posite insulators load ed with tension load s, both in the laboratory and confirm ed in service, has shown that the load-tim e curve is indeed a curve, and not a straight line as was presented in the first version of I EC 61 09 This straight line had often been m isinterpreted , leading to the d eduction that a com posite insulator would only retain a sm all fraction of its original m echanical strength after a period of 50 years, whatever the applied load I t is now known that the tim e to failure of com posite insulators under static tensile loads follows a curve such as that presented in Figure A To take into account the dispersion in the tensile characteristic of the insulator, the withstand curve is positioned, as shown in Figure A , below the failure curve Being asym ptotic, it shows that for a given insulator, there is a load below which the insulator will not fail no m atter how long the load is applied since there is no d am age to the core This load level is known as the dam age lim it Typically the dam age lim it lays around 60 % to 70 % of the ultim ate strength of the core when assem bled with fittings The d am age lim it depends on the kind of core m aterial, on the type of end fitting and on the design of the connection zone The dam age lim it represents the load value which causes inception of m icroscopic m echanical dam age within the core m aterial BS EN 61 09:200 – 22 – 61 09 ? I EC: 2008 Load Average failing load curve Withstand load curve Damage limit of the assembled core Log(time) IEC 808/08 Figure A.1 − Load-time strength and damage limit of a core assembled with fittings A.3 Service load coordination For both short- and long-term m echanical loading of the entire com posite insulator, the m echanical properties of the individ ual end fitting types also have to be considered The m axim um adm issible working load value for the m etal end fittings is lim ited by the elastic lim it of the m etal m aterial and the design (m echanically stressed cross-section) of the weakest end fitting part The m axim um adm issible load for the entire insulator is therefore given either by the elastic lim it of the end fittings or by the dam age lim it of the assem bled core (und er norm al environm ental conditions as given in I EC 6221 7) Figure A shows a graphical representation of the typical relationship of the dam age lim it to the m echanical characteristics of an insulator with a m m d iam eter core for typical service loads BS EN 61 09:200 61 09 ? I EC: 2008 – 23 – % SML I n s u l ator Core kN 70 30 % 00 % 80 % 70 % 60 % 50 % 40 % 20 % SML P l asti c p h ase 33 Dam ag e l i m i t Elastic limit of fittings Typical EML* RTL 80 E l asti c p h ase Ran g e of typi cal e veryd a y l oad s 0% * EML Extraordinary mechanical working load (1 week/50 years) IEC 809/08 F i g u re A – G p h i c a l re p re s e n t a t i o n o f t h e re l a t i o n s h i p o f t h e d a m a g e l i m i t t o t h e m e c h a n i c a l c h a c t e ri s t i c s a n d s e rv i c e l o a d s o f a n i n s u l a t o r w i t h a m m d i a m e t e r c o re I n all cases, the m axim um working load (static and d ynam ic) shall be below the dam age lim it of the insulator I t is norm al practice to adopt a safety factor of at least between the SML and the m axim um working load; this generally ensures that there is also a sufficient m argin between the dam age lim it of the insulator and all service loads I EC 60826 [8] gives guidance for calculation of loads and application of proper safety factors A Ve ri fi c a t i o n t e s t s Two tests are prescribed in this standard to check m echanical strength and dam age: – – a design test “96 h withstand load test” (load/tim e pairs D1 and D2 in Figure A 3) to check the position of the strength/tim e curve of the insulator (see 2); a type test ”dam age lim it proof test” (load/tim e pairs T1 and T2 in Figure A 3) to check the dam age lim it after loading with a constant load of 0, SML for 96 h (see 1 2) BS EN 61 09:200 – 24 – 61 09 ? I EC: 2008 Load MAV Type test load (SML withstand check) D1 T2 SML 60 % Average failing load curve D2 MAV 70 % SML Design test load T1 Type test load (96 h) 96 h Damage limit of the assembled core Log(time) IEC 81 0/08 Figure A.3 – Test loads The design test verifies the starting point of the actual initial load tim e curve by using MAV (average failing load of the assem bled core) and the m inim um position of the dam age lim it by a withstand test for 96 h at 0, MAV The choice of the SM L with respect to MAV is m ade by the m anufacturer as a function of statistical data, design and process There is no sim ple rule governing this relation I n order to check the coherence of the chosen SML with respect to the dam age lim it of the assem bled insulator, the type test requires the insulator to withstand 70 % of the SML during 96 h followed by the SML for one m in I f the strength coordination is correct then the insulator will not suffer any d am age during the 96 h and will still be able to withstand the SML N OTE I n som e cases, d epend i n g on the chosen SML l evel , i t i s possi bl e for the 96 h l oad for the type test to be hi gher th an the 96 h l oad for the d esi g n test Thi s d oes not precl ud e th e need for th e d esi gn test BS EN 61 09:200 61 09 ? I EC: 2008 – 25 – Annex B (informative) Example of two possible devices for sudden release of load B.1 Device (Figure B.1 ) The d evice consists of a hook A, a release lever B and a m ounting plate C H ook A can rotate on its pivot which is attached to the m ounting plate Tension is applied to the insulator by m eans of a suitable bolt or shackle, D During the tim e the insulator is und er load, the release lever is retained in the position shown by the unbroken lines Due to the length of the release lever B, a sm all force is sufficient to m ove it to the position shown by a broken line, rotating it on its pivot and m oving the pivot in the direction X This operation of the release lever causes the hook to rotate on its pivot, hence releasing the bolt or shackle, D B D X A C IEC 81 /08 Figure B.1 − Example of possible device for sudden release of load B.2 Device (Figure B.2) The device consists of a breakage piece E screwed into two m etallic extrem ities F and G which link the insulator to the tensile m achine The breakage piece E is in the form of a dum b bell whose diam eter is calibrated as a function of the steel used and of the desired breaking load The steel utilized for the piece E shall have a yield stress close to the ultim ate tensile stress BS EN 61 09:200 – 26 – F E Diameter 61 09 ? I EC: 2008 G IEC Figure B.2 − Example of possible device for sudden release of load 81 2/08 BS EN 61 09:200 61 09 ? I EC: 2008 – 27 – An n e x C (informative) G u i d a n c e o n n o n -s ta n d a rd m e c h a n i c a l s t re s s e s a n d d yn a m i c m e c h a n i c a l l o a d i n g o f c o m p o s i te t e n s i o n /s u s p e n s i o n i n s u l a to rs C.1 I n t ro d u c t o ry re m a rk This annex provides guidance on service conditions where non-standard m echanical loads are introd uced to the com posite suspension/tension insulator Exam ples of such non-standard m echanical loads are torsion, com pression (buckling) and bending stress loads Reference is m ad e, based on insulator field experience to date, on the expected m echanical perform ance of com posite insulators subjected to in-service dynam ic m echanical loads Com posite suspension/tension insulators are prim arily designed to operate under m echanical tensile loads/stresses H owever, in certain operations/applications, additional non-standard loads can be applied to the insulator Avoidance of subj ecting tension/suspension insulators to these non-stand ard loads should be m ade where possible Guidance on m inim izing the introd uction of such load conditions is given in the CI GRE Com posite I nsulator H andling Guide [7] C To rs i o n l o a d s I n line stringing operations, if twisting of the cond uctor bund le occurs and it is attem pted to be corrected by rotation of the com posite insulator, then a torsion stress can be introduced to the com posite insulator Furtherm ore, the probability of dam age to the insulator is increased if a single strain insulator is used to support a twin conductor bundle I n such cases, the use of two insulators, either with or without inter-connecting yoke plates, is preferred The introduction of torsion stresses should be avoided as m uch as possible during conductor stringing Subj ecting the insulators to excess torsion load s can lead to a red uction in the m echanical integrity of the com posite insulator C C o m p re s s i ve ( b u c kl i n g ) l o a d s Special conditions arise in the case of insulator V-string applications where the suspension insulator m ay be subj ected to com pressive loads (if the wind load is greater than the m ass supported, then the leeward insulator carries no load and the unit goes into com pression) As a result of critical buckling loads being introduced to the insulator, significant dam age m ay occur C Ben d i n g l oad s Long rod insulators m ay be subjected to critical bending loads during stringing operations The introduction of such bending stresses should be avoid ed as m uch as possible Subj ecting the insulator to critical bend ing stresses can cause large deflection of the insulator, which can cause dam age and loss of m echanical integrity of the insulator C D yn a m i c m e c h a n i c a l l o a d s Service experience to date indicates that dynam ic loads are unlikely to be of am plitude or duration to be detrim ental to the m echanical perform ance of com posite suspension/tension insulators BS EN 61 09:200 – 28 – C.6 61 09 ? I EC: 2008 Limits I t is difficult to give general lim iting values for non-standard stresses due to the varied designs and m aterials used for com posite suspension insulators The intrinsic m axim um stress for com m on core m aterials, before dam age occurs, is of the ord er of 400 MPa in bend ing and 60 MPa in torsion – where the strength of the end fitting assem bly onto the rod also com es into play H owever, the often large displacem ents caused by non-standard loads can ind uce stress in the housing m aterials and their interfaces with the core or fittings, leading to their d am age For exam ple, at a stress of 400 MPa, a m long insulator with a m m diam eter core would have a deflection of , m For this reason it is recom m end ed that the purchaser bring to the attention of the m anufacturer, whenever possible, any anticipated non-standard loads or displacem ents in order to determ ine if they are critical for the product I n this way, working loads/displacem ents, the need for a test, the test procedure and the test loads/displacem ents can then be determ ined by agreem ent BS EN 61 09:200 61 09 ? I EC: 2008 – 29 – Bibliography [1 ] I EC 61 467, Insula tors for overh ea d lines with a nomin a l volta ge a b ove 000 V – A C power a rc te sts on insula tor sets [2] CI GRE 22 03, N o 21 4, 2004 – Electra Brittle fra cture of composite insula tors – Field e xpe rience, occurrence a nd risk a ssessmen t [3] CI GRE 22 03, mode Ele ctra ch e mistry, N o 21 5, 2004 – in fluence of resin Brittle fra ctures of composite insula tors – Fa ilure va ria tions and sea rch for a simple in sula tor core eva lua tion te st meth od [4] CI GRE D1 4, Technical Brochure 255 – Ma teria l propertie s for non-cera mic outdoor in sula tion, A ugust 2004 [5] I EC Guide 1 , Electrica l h igh -volta ge e quipmen t in h igh -volta ge sub sta tions – Common re commenda tions for product sta nda rds [6] I EC 60050-471 , [7] CI GRE 22 03, [8] I EC 60826, Intern a tiona l Electrotech nica l Voca b ula ry – Pa rt 471 : Insula tors Tech nica l Broch ure 84 – Composite Insula tor Ha ndling Guide A pril 2001 Design 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