I E C 60 455-2 ® Edition 3.0 201 5-06 I N TE RN ATI ON AL S TAN D ARD Res i n bas ed reacti ve com pou n d s u s ed for el ectri cal i n s u l ati on – IEC 60455-2:201 5-06(en) Part : M eth od s of tes t TH I S P U B L I C ATI O N I S C O P YRI G H T P RO TE C T E D C o p yri g h t © I E C , G e n e va , S w i tze rl a n d All rights reserved Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either IEC or IEC's member National Committee in the country of the requester If you have any questions about IEC copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or your local IEC member National Committee for further information IEC Central Office 3, rue de Varembé CH-1 21 Geneva 20 Switzerland Tel.: +41 22 91 02 1 Fax: +41 22 91 03 00 info@iec.ch www.iec.ch Abou t th e I E C The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes International Standards for all electrical, electronic and related technologies Ab o u t I E C p u b l i c a ti o n s The technical content of IEC publications is kept under constant review by the IEC Please make sure that you have the latest edition, a corrigenda or an amendment might have been published I E C C atal og u e - webs tore i ec ch /catal og u e E l ectroped i a - www el ectroped i a org The stand-alone application for consulting the entire bibliographical information on IEC International Standards, Technical Specifications, Technical Reports and other documents Available for PC, Mac OS, Android Tablets and iPad The world's leading online dictionary of electronic and electrical terms containing more than 30 000 terms and definitions in English and French, with equivalent terms in additional languages Also known as the International Electrotechnical Vocabulary (IEV) online I E C pu bl i cati on s s earch - www i ec ch /s earch pu b I E C G l os s ary - s td i ec ch /g l os s ary The advanced search enables to find IEC publications by a variety of criteria (reference number, text, technical committee,…) It also gives information on projects, replaced and withdrawn publications More than 60 000 electrotechnical terminology entries in English and French extracted from the Terms and Definitions clause of IEC publications issued since 2002 Some entries have been collected from earlier publications of IEC TC 37, 77, 86 and CISPR I E C J u st P u bl i s h ed - webs tore i ec ch /j u s u bl i s h ed Stay up to date on all new IEC publications Just Published details all new publications released Available online and also once a month by email I E C C u s to m er S ervi ce C en tre - webs tore i ec ch /cs c If you wish to give us your feedback on this publication or need further assistance, please contact the Customer Service Centre: csc@iec.ch I E C 60 455-2 ® Edition 3.0 201 5-06 I N TE RN ATI ON AL S TAN D ARD Res i n bas ed reacti ve com pou n d s u s ed for el ectri cal i n s u l ati on – Part : M eth od s of tes t INTERNATIONAL ELECTROTECHNICAL COMMISSION ICS 7.220.99; 29.035.01 ISBN 978-2-8322-2748-0 Warn i n g ! M ake s u re th at you obtai n ed th i s pu bl i cati on from an au th ori zed d i s tri bu tor ® Registered trademark of the International Electrotechnical Commission –2– I EC 60455-2: 201 © I EC 201 CONTENTS FOREWORD I NTRODUCTI ON Scope Normative references Terms and definitions 1 General notes on methods of test 1 Preparation and conditioning 1 Sequence of tests Test report Methods of test for reactive compounds and their components Flash point Density Viscosity Viscosity after storing at elevated temperature 5 Content of volatile organic components I sothermal increase of viscosity (processing time) Shelf life Colour Softening temperature Ash content 1 Filler content Chlorine content 2.1 Total chlorine content of unsaturated polyesters and epoxide resins 2.2 I norganic chlorine content of epoxide resins and glycidyl esters 2.3 Easily saponifiable chlorine content of epoxide resins and related materials Tendency of cristallisation Epoxide equivalent of epoxide resins 5 Content of isocyanate Water content (Karl Fischer method) H ydroxyl value 5 7.1 Polyester resins 5 7.2 Resins other than polyester 5 Acid value of polyester resins 5 Amount of double bonds of unsaturated polyester and acrylate resins 5 20 Acid and acid-anhydride content of acid-anhydride hardeners 5 21 Amine value 5 22 Pot life 5 22.1 General 5 22.2 Resinous compounds for cable accessories 5 23 Gel time 23.1 Unsaturated polyester based compounds 23.2 Phenolic resin based compounds 23.3 Other compounds 24 Exothermic temperature rise 24.1 Unsaturated polyester based compounds 24.2 Resinous compounds for cable accessories I EC 60455-2: 201 © I EC 201 –3– Other compounds 24.3 25 Total volume shrinkage of epoxide and unsaturated polyester based compounds 26 Curing in presence of water 26.1 General 26.2 Apparatus and materials 26.3 Pouring device 26.4 Procedure 26.5 Test report 27 Determination of the degree of curing 28 Curing in thick layer and emissions during curing 28.1 General 28.2 Equipment 28.3 Test specimen 28.4 Procedure Methods of test for cured reactive compounds 20 General 20 Test specimens 20 2.1 General 20 2.2 Preparation of the reactive compound 20 2.3 Preparation of test specimens 21 2.4 Type and number of test specimens 21 Density 21 Mechanical properties 21 4.1 Tensile properties 21 4.2 Compressive properties 21 4.3 Flexural properties 22 4.4 I mpact strength 22 4.5 Hardness 22 Thermal properties 22 5.1 Bond strength at elevated temperature 22 5.2 Linear thermal expansion 22 5.3 Thermal conductivity 22 5.4 Glass transition 23 5.5 Flammability 23 5.6 Thermal shock 23 5.7 Dry heat resistance of resins for cable accessories – Method of test 23 5.8 Wet heat resistance of resins for cable accessories 24 5.9 Loss of mass 26 5.1 Temperature index 27 6 Chemical properties 27 6.1 Water absorption 27 6.2 Effect of liquid chemicals 28 6.3 Resistance to mould growth 28 6.4 Water vapour permeability 28 Electrical properties 28 7.1 Effect of water immersion on volume resistivity 28 7.2 Dielectric dissipation factor (tan δ ) and relative permittivity ( ε r) 29 7.3 Breakdown voltage and electric strength 30 –4– I EC 60455-2: 201 © I EC 201 Proof tracking index (PTI) 31 7.5 Electrolytic corrosion 31 Annex A (informative) Health and safety 36 Bibliography 37 Figure Figure Figure Figure – Test apparatus for curing in presence of water test 32 – Test set-up for volume resistivity 33 – Example of electrode arrangement for flexible cured compound 34 – Example of electrode arrangement for rigid cured compound 35 Table – Condition of the top side Table – Condition of the bottom side Table – Condition of the interior 20 I EC 60455-2: 201 © I EC 201 –5– I NTERNATIONAL ELECTROTECHNI CAL COMMI SSI ON RE S I N B AS E D RE AC T I VE C O M P O U N D S U S E D F O R E L E C T RI C AL I N S U L AT I O N P a rt : – M e th o d s o f te s t FOREWORD ) The I ntern ati onal El ectrotechnical Commi ssi on (I EC) is a worl d wid e org anizati on for standard izati on comprisi ng all nati onal electrotech nical committees (I EC N ational Comm ittees) Th e object of I EC i s to promote i nternati on al co-operati on on al l q u esti ons concerni ng standard izati on in the el ectrical and el ectronic fi el ds To this end an d in ad di ti on to other acti vi ti es, I EC pu blish es I nternati onal Stan d ards, Technical Speci fi cati ons, Technical Reports, Pu blicl y Availabl e Specificati ons (PAS) an d Gu id es (hereafter referred to as “I EC Pu blicati on(s)”) Their preparati on is entru sted to technical committees; any I EC N ati onal Committee i nterested i n the subject d eal t wi th may parti ci pate i n thi s preparatory work I nternati onal , governmental and n ongovernm ental organizations l iaisi ng wi th the I EC al so participate i n this preparati on I EC coll aborates cl osely wi th th e I n ternational Organizati on for Stand ard izati on (I SO) i n accordan ce wi th cond i ti ons d etermined by agreement between th e two org anizati ons 2) Th e form al d ecision s or ag reements of I EC on technical m atters express, as n earl y as possibl e, an i nternati onal consensus of opi ni on on the rel evan t su bjects si nce each technical committee has representati on from all i nterested I EC N ati onal Commi ttees 3) I EC Pu blications have th e form of recommend ati ons for internati onal u se and are accepted by I EC N ati onal Comm ittees i n th at sense While all reasonabl e efforts are mad e to ensu re that the technical content of I EC Pu blicati ons is accu rate, I EC cann ot be hel d responsi bl e for the way in wh i ch they are used or for an y misin terpretati on by any end u ser 4) I n ord er to promote i nternational u ni formi ty, I EC N ati onal Commi ttees u nd ertake to appl y I EC Publicati on s transparen tl y to the maximum extent possibl e i n thei r nati onal and regi onal pu blicati ons Any d i vergence between an y I EC Pu bl icati on and the correspond i ng nati onal or region al publi cation shal l be cl earl y i ndi cated in the l atter 5) I EC i tsel f d oes not provi d e any attestation of conformity I nd epend ent certificati on bodies provi d e conform ity assessment services an d , in some areas, access to I EC marks of conformi ty I EC i s not responsi bl e for an y services carried ou t by i nd epend en t certi fication bodi es 6) All users sh ould ensu re that they h ave the l atest edi ti on of this pu blicati on 7) N o li abili ty shal l attach to I EC or i ts di rectors, empl oyees, servan ts or agents in clu di ng i nd ivi du al experts and members of i ts technical commi ttees and I EC N ati onal Comm ittees for any personal i nju ry, property d amage or other d amage of any natu re whatsoever, wh eth er di rect or i nd i rect, or for costs (i nclud i ng l egal fees) and expenses arising ou t of the pu bli cati on, use of, or rel iance u pon, this I EC Pu bl ication or any oth er I EC Pu blicati ons 8) Attention is d rawn to the N orm ative references ci ted in this pu bl icati on U se of the referenced pu blicati ons is i ndi spensabl e for the correct appli cati on of this publicati on 9) Attention is d rawn to th e possibili ty that som e of the el ements of thi s I EC Pu bl icati on may be th e su bj ect of patent ri ghts I EC sh al l not be held responsi bl e for i d en ti fyi ng any or all su ch patent ri ghts I nternational Standard I EC 60455-2 has been prepared by IEC technical committee 5: Solid electrical insulating materials This third edition cancels and replaces the second edition published in 998 This edition constitutes a technical revision This edition includes the following significant technical changes with respect to the previous edition: a) I ntroduction of test methods related to I EC 60455-3-8; b) Additional and updated test methods for resins –6– I EC 60455-2: 201 © I EC 201 The text of this standard is based on the following documents: FDI S Report on voti ng 5/751 /FDI S 5/757/RVD Full information on the voting for the approval of this standard can be found in the report on voting indicated in the above table This publication has been drafted in accordance with the ISO/I EC Directives, Part A list of all parts in the I EC 60455 series, published under the general title Resin based reactive compounds used for electrical insulation , can be found on the IEC website The committee has decided that the contents of this publication will remain unchanged until the stability date indicated on the I EC 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 revised edition, or amended A bilingual version of this publication may be issued at a later date I EC 60455-2: 201 © I EC 201 –7– I NTRODUCTION This part of I EC 60455 is one of a series which deals with solvent-free resin based reactive compounds and their components used for electrical insulation The series consists of three parts: – Part : Definitions and general requirements (IEC 60455-1 ); – Part 2: Methods of test (IEC 60455-2); – Part 3: Specifications for individual materials (I EC 60455-3) –8– RE S I N I EC 60455-2: 201 © I EC 201 B AS E D RE AC T I VE C O M P O U N D S U S E D F O R E L E C T RI C AL I N S U L AT I O N P a rt : – M e th o d s o f te s t Scope This part of I EC 60455 specifies methods of test to be used for testing resin based reactive compounds, their components and cured compounds used for electrical insulation N o rm a t i v e re fe re n c e s The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application For dated references, only the edition cited applies For undated references, the latest edition of the referenced document (including any amendments) applies I EC 60050 (all parts), International http: //www electropedia.org) Electrotechnical Vocabulary (available at I EC 60068-2-1 0:2005, Environmental testing – Part 2-10: Tests – Test J and guidance: Mould growth I EC 60093: 980, Methods of test for volume resistivity and surface resistivity of solid electrical insulating materials I EC 601 2: 2003, Method for the determination of the proof and the comparative tracking indices of solid insulating materials I EC 6021 (all parts), Electrical insulating materials – Thermal endurance properties I EC 60243-1 : 998, Electrical strength of insulating materials – Test methods – Part 1: Tests at power frequencies IEC 60250:1 969, Recommended methods for the determination of the permittivity and dielectric dissipation factor of electrical insulating materials at power, audio and radio frequencies including metre wavelengths IEC 60296:201 2, Fluids for electrotechnical applications – Unused mineral insulating oils for transformers and switchgear IEC 60426:2007, Electrical insulating materials – Determination of electrolytic corrosion caused by insulating materials – Test methods IEC 60455-1 : 998, Resin based reactive compounds used for electrical insulation – Part 1: Definitions and general require ments IEC 60455-3 (all parts), Resin based reactive compounds used for electrical insulation – Part 3: Specifications for individual materials IEC 60455-3-8: 201 3, Resin based reactive compounds used for electrical insulation – Part 3: Specifications for individual materials – Sheet 8: Resins for cable accessories – 26 – 6.5.8.7 I EC 60455-2: 201 © I EC 201 Conditioning and assessment The test specimens shall be conditioned before the hardness, the tensile/elongation and the electric strength tests for 24 h in accordance with I SO 291 using an atmosphere 23/50 The mechanical test specimens (reference and wet aged) shall be subjected to hardness measurement, followed by tensile/elongation measurement The hardness test shall be carried out in accordance with I SO 868 on ends of the mechanical test specimens outside their clamping length and in the centre of their surfaces The tensile and elongation test shall be carried out in accordance with I SO 527, with a jaw speed of 50 mm/min up to Shore D hardness 70 A jaw speed of mm/min shall be applied if the Shore hardness is ≥ 70 The electrical test specimens shall be subjected to electric strength measurement in accordance with I EC 60093 For mechanical tests the following arithmetic mean for each property shall be calculated: E1 : E2 : value on the reference test specimens; value on the aged test specimens The retained percentage of the values for these properties after the temperature/water exposure shall be calculated using the following equation: E = ( E2 / E1 ) × 00 For the electric strength test, the arithmetic mean of the test specimens shall be calculated and compared to the values in I EC 60455-3-8: 201 3, Table 6.5.8.8 Test report The test report shall include the following information: • • • • retained percent of Shore hardness; retained percent of tensile strength; retained percent of elongation at break; value of dielectric strength 6.5.9 Loss of mass 6.5.9.1 General This method applies to resinous compounds for cable accessories 6.5.9.2 Apparatus and materials Equipment to be used: – analytic balance with accuracy ± mg; – constant temperature oven with ventilation; – desiccator with calcium dichloride as a drying agent I EC 60455-2: 201 © I EC 201 6.5.9.3 – 27 – Specimen Three specimens with the dimension of 80 mm × 40 mm × mm shall be conditioned for 24 h at standard atmosphere 23/50 in accordance with I SO 291 and individually identified 6.5.9.4 Procedure The three conditioned test specimens shall be weighed individually to the nearest mg (= mass m ) and stored for one week at (1 20 ± 2) °C in the vented oven They shall then be cooled in a desiccator I mmediately after removal from the desiccator, the test specimens shall be weighed individually to the nearest mg (= mass m ) 6.5.9.5 Results The percent loss of mass, M, shall be calculated for each individual sample, in accordance with the following equation: M = m1 − m × 00 m1 The average value of the three measurements shall be reported 6.5.1 Temperature index N OTE Th e temperatu re i nd ex d epen ds on th e choice of test cri teri on and of the en d -point criterion Therefore, for one and the same material, resul ts for the temperatu re ind ex can vary by 80 K or more 6.5.1 0.1 Procedure The method given in I EC 6021 shall be used The test and end-point criteria shall be in accordance with the relevant specification sheet of I EC 60455-3, or shall be agreed upon between supplier and purchaser Two test criteria shall be used For each test criterion at least three exposure temperatures shall be applied The difference between two subsequent exposure temperatures shall not exceed 20 K I f the correlation coefficient is less than 0,95, one more set of specimens shall be tested at an exposure temperature different from the temperature originally chosen N OTE I SO 2578 is based on the pri nci pl es lai d down i n I EC 6021 By d el eti ng all i nformati on that is not req ui red for pl anni ng and ru nn i ng a temperatu re i n d ex experi ment an d for cal cul ation of resul ts, I SO 2578 has become a practical short versi on as req ui red for use i n a l aboratory 6.5.1 0.2 Result For each test criterion, the kind of preparation and the type and dimensions of the specimen, the number of specimens for each test, the exposure temperatures, and the results shall be reported along with reference to the standards applied The results for each test set shall contain the specimen end-point times, the time to end-point for each exposure temperature, a graph showing the property values as a function of the logarithm of the times to end-point, the thermal endurance graph (first order regression line) on thermal endurance graph paper, the temperature index, and the correlation coefficient 6.6 Chemical properties 6.6.1 Water absorption Method (water at 23 °C) and method (boiling water) given in I SO 62 shall be used For each method three specimens shall be tested The kind of preparation and the dimensions of the specimen, and the three results of water absorption obtained with each of method and method shall be reported One untreated specimen shall be kept for reference – 28 – 6.6.2 I EC 60455-2: 201 © I EC 201 Effect of liquid chemicals The method given in I SO 75 shall be used U nless otherwise specified, the temperature of the test liquid shall be (23 ± 2) °C and the immersion time shall be (1 68 ± ) h (seven days) For each test liquid three specimens shall be tested The kind of preparation and the dimensions of the specimen, the type of test liquid and the three results for each of the test liquids shall be reported For each test liquid the result shall contain the change of appearance, dimensions and mass for each of the three specimens One untreated specimen shall be kept for reference 6.6.3 Resistance to mould growth The method given in I EC 60068-2-1 shall be used Three specimens according to shall be tested, and the three results of resistance to mould growth shall be reported One untreated specimen shall be kept for reference 6.6.4 Water vapour permeability To be agreed between supplier and purchaser 6.7 Electrical properties 6.7.1 6.7.1 Effect of water immersion on volume resistivity General The method given in I EC 60093 shall be used I f I EC 60093 is not applicable for the material under test, then the following method may be used N OTE I EC 60093 wi l l be repl aced by I EC 62631 i n the fu tu re U sers are en cou raged to i nvestigate th e status of stand ardi sation of I EC 62631 and the possi bili ty of appl yin g th e stan d ard M embers of I SO and I EC mai ntai n registers of cu rren tl y vali d I nternati onal Stan dard s 6.7.1 Equipment The following equipment shall be used: • • • • • any commercially available tera-ohmmeter with an accuracy of ± %; a metal cylinder to be used as voltage electrode (top electrode) of at least 60 mm diameter having a mass to provide a pressure on the specimen of about 0, 01 MPa; two conducting rubber disks having the same diameter as the top electrode and of mm to mm thickness with a maximum resistance of 000 Ω , and with a Shore A hardness of 65 to 85; a metal cylinder having the same diameter as the top electrode and of about 70 mm height; (a bottom electrode) 6.7.1 Test specimen The specimen shall be in the form of a disk or a square with a diameter or an edge length exceeding the diameter of the top electrode by at least mm The thickness shall not exceed mm and the flat surfaces shall be in parallel Three specimens shall be prepared N OTE Th e specim en can be cast between pl ates, wi th a wou n d piece of enamel led rou nd wi nd i ng wi re u sed as a spacer 6.7.1 Procedure The test set-up shall consist of the specimen placed between the two metal cylinders with the rubber disks as intervening layers For an example of the complete test arrangement, see Figure The d.c test voltage shall be adjusted to provide an electrical field strength of not I EC 60455-2: 201 © I EC 201 – 29 – more than 000 V/mm The specimen shall be tested before and after immersion in demineralized water Unless otherwise specified, the temperature of the water shall be (23 ± 2) °C and the time of immersion shall be (1 68 ± ) h (seven days) After immersion in water the test set-up shall be made immediately after removing the specimen from the water and blotting it between filter papers to remove excessive water The resistance measurement shall be taken (1 ± ) after the test set-up is made The reading shall be taken (60 ± 5) s after electrification In the case where, for example, the diameter of the top electrode is 60 mm, resistivity shall be calculated as: ρ = (2,83 ⋅ R )/d where ρ is the resistivity ( Ω m); d is the specimen thickness (mm); R is the measured resistance ( Ω ) For a different diameter D of the top electrode, replace the factor 2,83 by: 2, 83 D / 600 with D in millimetres 6.7.1 Result Three specimens shall be tested and the kind of preparation, the diameter of the electrodes, the dimensions of the test specimen, the test voltage used, and the three results before and after immersion in water shall be reported, along with reference to the standard applied The results shall contain volume resistance and volume resistivity 6.7.2 6.7.2.1 Dielectric dissipation factor (tan δ ) and relative permittivity ( ε r) General The method given in I EC 60250 shall be used I f I EC 60250 is not applicable for the material under test, then the following method may be used N OTE I EC 60250 wi l l be repl aced by I EC 62631 i n the fu tu re U sers are en cou raged to i nvestigate th e status of stand ardi sation of I EC 62631 and the possi bi lity of appl yi ng the stan d ard M embers of I SO and I EC mai ntai n registers of cu rrentl y vali d I ntern ati on al Standard s 6.7.2.2 Equipment Any commercially available and adequate impedance-meter may be used, indicating the dielectric dissipation factor (tan δ ) and the relative permittivity ( ε r) 6.7.2.3 Test specimen A test specimen in accordance with 7.1 shall be used 6.7.2.4 Procedure The top electrode shall have a diameter of at least 40 mm and may or may not be surrounded by a shield electrode The bottom electrode shall have a diameter exceeding the diameter of the top electrode by at least 20 mm and shall be applied concentrically to the upper electrode The electrodes shall be provided by brushing a conductive dispersion such as graphite or silver, or by applying a metal foil of a thickness of not more than 0, 005 mm, made to adhere with a drop of oil, or by any other equally suitable procedure U nless otherwise specified, the test shall be carried out at (23 ± 2) °C with a sinusoidal test voltage at a frequency of kHz The connections to the specimen shall be in accordance with the instruction manual of the testing device – 30 – 6.7.2.5 I EC 60455-2: 201 © I EC 201 Result Two specimens shall be tested The kind of preparation and the dimensions of the test specimen, the test temperature, the electrodes employed, the test voltage and frequency used, and the two results shall be reported along with reference to the standard applied The report shall contain the dielectric dissipation factor and the relative permittivity 6.7.3 6.7.3.1 Breakdown voltage and electric strength General Breakdown voltage shall be measured by using IEC 60243-1 I f I EC 60243-1 is not applicable to the material under test, Clauses and may be amended as below 6.7.3.2 Electrodes The electrode arrangement shall be the ball-to-plate type The high-voltage electrode shall consist of a polished steel ball with a radius of (3 ± 0, 000 5) mm for rigid material, and (1 ± 0, 000 5) mm for flexible material Polished steel balls with a surface roughness of less than 0,001 mm as used in ball bearings (class II I ) are easily available and have been found adequate for the purpose The earth electrode shall be a plate with a diameter of (75 ± ) mm and with rounded edge of a radius of (3 ± 0, ) mm For the complete test arrangement for flexible material, see Figure In the case of rigid material, the upper electrode and the specimen shall be as shown in Figure N OTE The ball -to-pl ate electrode arrangem ent gives, compared to a pl ate-to-pl ate set, a slig htl y i ncreased fi eld strength depend in g on th e radi us of the bal l el ectrod e an d the thi ckn ess of the speci men EXAMPLE For a rad i us of mm an d a thi ckn ess of 0, mm, the increase i n fi el d strength compared to that of pl ate-to-pl ate arran gement i s abou t % N OTE I f a rou nd cyl ind rical glass tai ner of su ffici en t size i s used to accommod ate the test set-u p an d the fl ui d wi th th e earth electrod e at th e bottom of i t, such a contai ner makes i t possible to observe visu all y the process when the voltage i s appli ed I t al so permi ts the earth connecti on and the fl ui d su ppl y throu gh the bottom el ectrod e, wi th a flu i d overfl ow at th e top of the contai ner, see Fi gu re I f an el evated test temperatu re is requ i red , such an arran gement allows the fl ui d to be used for heating pu rposes 6.7.3.3 6.7.3.3.1 Test specimen General The thickness of that part of the specimen which is subject to breakdown shall not exceed mm The thickness of any two of the specimens of one set shall not vary by more than % N OTE I t is generall y fou nd th at the electric strength for cu red reacti ve compou nds wi th a gl ass transi ti on temperatu re above 80 °C is from 50 kV/mm to 00 kV/m m and can be even more, for instance, for hot cu ri ng cycl oali phatic epoxi d e based compounds Consequ entl y, testi ng speci mens of a thickness of si gnifican tl y more than mm an d wi th an el ectrod e arrangement of, for i nstance, 25/75 mm as speci fi ed i n I EC 60243-1 , can req u i re vol tage l evel s above 200 kV Thi s can l ead to condi tions where fl ashover or parti al fl ashover wi th subseq uent breakdown ou tsid e the el ectrod e area cannot be avoi d ed 6.7.3.3.2 Rigid material The specimen shall form a cylindrical rod of cast compound with a diameter of about 30 mm and with a length, in millimetres, twice the assumed numerical value of breakdown voltage in kilovolts This rod shall contain a central lead wire with a steel ball attached to it at one end and apart from the other end completely embedded in the casting compound After the mould is removed, that end of the specimen which is close to the ball electrode shall be ground to the specified thickness, then polished and coated with a conductive layer, for instance a dispersion of graphite or silver, which serves as the earth electrode During grinding the thickness shall be controlled by means of a permeameter type device calibrated I EC 60455-2: 201 © I EC 201 – 31 – in thickness For an example of the specimen set-up, see Figure This set-up can be accommodated in a glass container as in Figure N OTE For casti ng, a gl ass tu be can serve as a moul d wi th th e lead wi re and th e bal l electrode properly cen tred by ad eq u ate means A pi ece of wel di n g wire of, for i nstance, mm d iam eter can serve as a lead wi re, wi th one end sol d ered to the ball el ectrod e After testing, the cured compound is removed at the point of breakdown to allow measurement of the space between the polished surface and the ball electrode The space shall be measured by means of a micrometer probe, and reported as thickness 3 F l e x i b l e m a t e ri a l A specimen in accordance with 6.7.1 shall be used P ro c e d u re The rate of increase of the voltage shall be not more than 500 V/s U nless otherwise specified, the test temperature shall be (23 ± 2) °C The test shall be carried out with the specimen and the electrodes in a dielectric fluid, which is circulated and maintained at the specified test temperature U nless otherwise specified, unused mineral insulating oil according to I EC 60296, or unused synthetic organic ester according to I EC 61 099, shall be employed Re s u l t Five specimens shall be tested The type and method of preparation of the specimen and its dimensions, the test temperature, the radius of the ball electrode, the type of dielectric fluid used and the five results shall be reported, along with reference to the standards applied The results shall contain the thickness of the specimen at the point of breakdown, the breakdown voltage and the electric strength P ro o f t c k i n g i n d e x ( P T I ) The method given in Clause of I EC 601 2:2003 shall be used Three specimens shall be tested with a proof voltage as specified in the relevant specification sheet, or as agreed upon between supplier and purchaser The kind of preparation and the dimensions of the specimen, as well as the three results of PTI, shall be reported The results shall contain the proof voltage applied and the number of drops obtained E l e c t ro l yt i c c o rro s i o n The visual method given in I EC 60426 shall be used Three specimens shall be tested The three results of electrolytic corrosion shall be reported – 32 – I EC 60455-2: 201 © I EC 201 mm IEC spray bottl e d emineral ized water fl exi ble tube fi xtu re water basi n tap water measu ri ng cylind er stand Figure – Test apparatus for curing in presence of water test Di mensi ons i n mil limetres I EC 60455-2: 201 © I EC 201 – 33 – Top cylinder Teraohmeter Conducting rubber layer Bottom cylind er About 70 Test specimen ≥ ∅ 60 IEC F i g u re – Te s t s e t-u p fo r vo l u m e re s i s ti vi ty – 34 – I EC 60455-2: 201 © I EC 201 Spherical top for high-voltage connection Fluid level Fluid overflow Metal tube Ball electrode Specimen Plate electrode N ut Gaskets Fluid inflow IEC Figure – Example of electrode arrangement for flexible cured compound I EC 60455-2: 201 © I EC 201 – 35 – Leadwire Spherical cap for high-voltage connection Ball electrode Thickness Cured compound Conductive coating IEC Figure – Example of electrode arrangement for rigid cured compound – 36 – I EC 60455-2: 201 © I EC 201 Annex A (informative) Health and safety The manufacturer shall make available on request the MSDS for each component, in order to enable the purchaser to transport, use and dispose of the components and their packaging in a safe manner, in relevant languages Further relevant information concerning health and safety linked to installation conditions shall be made available on request I EC 60455-2: 201 © I EC 201 – 37 – Bibliography [1 ] I SO 558:1 980, Conditioning and testing – Standard atmospheres – Definitions [2] I SO 2578: 993, Plastics – Determination of time-temperature limits after prolonged exposure to heat _ I N TE RN ATI O N AL E LE CTRO TE CH N I CAL CO M M I S S I O N 3, ru e d e Va re m bé P O B ox CH -1 1 G e n e va S wi tze rl a n d Te l : + 41 F a x: + 22 91 02 1 22 91 03 00 i n fo @i e c ch www i e c ch