1、 IEC/TR 62662 Edition 1.0 2010-08 TECHNICAL REPORT Guidance for production, testing and diagnostics of polymer insulators with respect to brittle fracture of core materials IEC/TR 62662:2010(E) colour inside THIS PUBLICATION IS COPYRIGHT PROTECTED Copyright 2010 IEC, Geneva, Switzerland All rights r
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10、 IEC/TR 62662 Edition 1.0 2010-08 TECHNICAL REPORT Guidance for production, testing and diagnostics of polymer insulators with respect to brittle fracture of core materials INTERNATIONAL ELECTROTECHNICAL COMMISSION Q ICS 29.080.10 PRICE CODE ISBN 978-2-88912-172-4 Registered trademark of the Interna
11、tional Electrotechnical Commission colour inside 2 TR 62662 IEC:2010(E) CONTENTS FOREWORD.3 INTRODUCTION.5 1 Scope.6 2 Normative references .6 3 Terms and definitions .6 4 Description of brittle fracture 7 5 Identification of brittle fracture 8 6 Failure mechanisms .8 6.1 Description of identified f
12、ailure mechanisms8 6.2 Mechanism M1 Acid generated by electrical activity .8 6.3 Mechanism M2 Acid ingress from environment .9 6.4 Mechanism M3 Acid generated inside the core.10 7 Risk assessment 10 7.1 FMEA approach 10 7.2 Results11 7.3 Discussions.13 8 Guidance for material selection and productio
13、n 13 8.1 Rod materials and production process.13 8.1.1 Fibreglass .13 8.1.2 Resins.14 8.1.3 Rod production14 8.2 Housing and sealing14 9 Preventive methods15 9.1 Sealing15 9.2 Corona rings .15 9.3 Material selection 16 9.4 Housing quality .16 9.5 Handling, transportation and storage.16 Bibliography1
14、7 Figure 1 Typical brittle fracture 7 Table 1 Risk potential number (RPN) and standardized risk potential of brittle fracture failure modes .11 Table 2 Risk assessment of the identified brittle fracture failure modes11 TR 62662 IEC:2010(E) 3 INTERNATIONAL ELECTROTECHNICAL COMMISSION _ GUIDANCE FOR P
15、RODUCTION, TESTING AND DIAGNOSTICS OF POLYMER INSULATORS WITH RESPECT TO BRITTLE FRACTURE OF CORE MATERIALS FOREWORD 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). T
16、he object of IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports, Publicly Available Speci
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24、oever, whether direct or indirect, or for costs (including legal fees) and expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC Publications. 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publica
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26、C technical committees is to prepare International Standards. However, a technical committee may propose the publication of a technical report when it has collected data of a different kind from that which is normally published as an International Standard, for example “state of the art“. IEC 62662,
27、 which is a technical report, has been prepared by IEC technical committee 36: Insulators. The text of this technical report is based on the following documents: Enquiry draft Report on voting 36/294/DTR 36/297/RVC Full information on the voting for the approval of this technical report can be found
28、 in the report on voting indicated in the above table. 4 TR 62662 IEC:2010(E) This publication has been drafted in accordance with the ISO/IEC Directives, Part 2. The committee has decided that the contents of this publication will remain unchanged until the stability date indicated on the IEC web s
29、ite 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. IMPORTANT The colour inside logo on the c
30、over page of this publication indicates that it contains colours which are considered to be useful for the correct understanding of its contents. Users should therefore print this document using a colour printer. TR 62662 IEC:2010(E) 5 INTRODUCTION There is an urgent need within utilities and indust
31、ry for material standards, which define the physical properties of the polymers applied for outdoor insulation. As a first step, a state-of- the-art report was issued by CIGRE which led to the publication of IEC 62039. This IEC technical report presents as a conclusion of the CIGRE-report the import
32、ant material properties for polymeric materials used in outdoor insulation and, where applicable, lists the standardized test methods including the minimum requirements. The acid (brittle fracture) resistance of FRP core materials (see 3.7) was recognized as an important property for suspension/tens
33、ion composite insulators. This technical report presents more detailed guidance on this subject taking into account different insulator designs and production techniques. The risk of occurrence and the influencing parameters were evaluated by failure mode effect analysis (FMEA). Brittle fracture is
34、not the only failure mechanism for insulators in service and is generally less frequently observed than other modes, such as failure due to tracking and erosion. However, this subject is not yet covered by any IEC test procedures specifically designed to detect or prevent brittle fracture. 6 TR 6266
35、2 IEC:2010(E) GUIDANCE FOR PRODUCTION, TESTING AND DIAGNOSTICS OF POLYMER INSULATORS WITH RESPECT TO BRITTLE FRACTURE OF CORE MATERIALS 1 Scope This technical report presents an analysis of the risk of influencing factors for brittle fracture of composite insulators that are mostly loaded in the ten
36、sile mode (suspension and tension insulators). Guidance is given to reduce the risk of in-service brittle fractures. This phenomenon is limited to tension and suspension insulators. However, the general information given concerning the importance of various parameters can be used as a guideline for
37、the design and production of any kind of composite insulator. 2 Normative references 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
38、(including any amendments) applies: IEC 61109, Insulators for overhead lines Composite suspension and tension insulators for a.c. systems with a nominal voltage greater than 1 000 V Definitions, test methods and acceptance criteria. IEC/TR 62039, Selection guide for polymeric materials for outdoor u
39、se under HV stress 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 fibre reinforced plastic material FRP composite material consisting of reinforcing components e.g. glass or synthetic fibres that are embedded in a polymer matrix e.g. epoxy o
40、r polyester. The FRP core is the integral load- carrying part of a composite insulator 3.2 stress corrosion cracking SCC failure of material subjected to a constant tensile stress in a corrosive environment 3.3 brittle fracture abnormal and sudden breakage of FRP core materials with well-defined cha
41、racteristic fracture patterns NOTE Before brittle fracture, no apparent plastic deformation takes place. In the case of FRP core materials, brittle fracture is caused by SCC. 3.4 failure mechanism principal and fundamental process that leads to a characteristic failure, e.g. brittle fracture TR 6266
42、2 IEC:2010(E) 7 NOTE A failure mechanism may have several modes of final failure. 3.5 failure mode specific failure scenario or optional path of a failure mechanism 3.6 sealing system technical arrangement to prevent the ingress of moisture, gases, etc., at a material transition point exposed to the
43、 environment 3.7 failure mode effect analysis FMEA standardized risk assessment tool generally used for failure prevention 3.8 damage degradation of a component leading to penetration by acid or moisture 4 Description of brittle fracture Brittle fracture is the commonly used term for stress corrosio
44、n-induced failure of insulator core rods manufactured from resin bonded glass fibre material (RBGF, commonly known as fibre reinforced plastic FRP). This failure mechanism results in a complete mechanical separation of the core (normally near the energized end fitting), and can occur at tensile load
45、s well below the rated mechanical strength of the insulators. In addition to a (minimum) tensile stress of approximately 50 MPa, the brittle fracture mechanism requires the presence of acid from either external or internal sources. The chemical process of stress corrosion is an ion exchange mechanis
46、m whereby ions in the glass fibres are replaced by hydrogen ions from the acid (see IEC/TR 62039). Figure 1 Typical brittle fracture IEC 2042/10 8 TR 62662 IEC:2010(E) 5 Identification of brittle fracture The macroscopic features associated with the brittle fracture of an FRP core rod have been desc
47、ribed by CIGRE 21 . A typical brittle fracture is shown in Figure 1. The fracture surfaces typically have the following characteristics: a smooth, clean, planar surface perpendicular to the core axis, comprising a portion of the rod cross-section. Multiple failure planes separated by axial delaminat
48、ion may be present; normal tensile fracture (fibrous) in the remaining rod cross-section. In addition to these macroscopic features, confirmation of the brittle fracture mechanism is possible through the identification of several distinctive features of the fracture surface of the individual glass f
49、ibres using scanning electron microscopy 3. The mirror zone is a smooth region perpendicular to the fibre axis that includes the stress corrosion initiation site for the individual fibre and may cover from 90% of the fibre cross-section. The hackle zone is a rough region on the fibre fracture surface that failed mainly due to mechanical stresses. The mist zone is a transition zone between the mirror and hackle zones and is intermediate in roughness. C
