Rotating electrical machines - Part 18-31: Functional evaluation of insulation systems - Test procedures for form-wound windings - Thermal evaluation and classification of insulation systems used in rotating machines

IEC 60034-18-31:2012 describes thermal endurance test procedures for classification of insulation systems used in a.c. or d.c. rotating electrical machines with indirect cooling and form-wound windings. These test procedures are intended to compare the thermal endurance performance of the mainwall insulation between conductor(s) and ground and, where required by the design of the coil or bar, the insulation between the turns. The main technical changes with regard to the previous edition include: - Definition of the test method and sub-cycles required to establish a consistent standardized platform for thermal ageing of insulation systems for form-wound windings. - Recommendations for establishing a thermal life curve based on confidence intervals. - Comparison of candidate and reference system performance for specific requirements of thermal class, within feasible limits. Keywords: rotating machinery, insulation systems

Drehende elektrische Maschinen - Teil 18-31: Funktionelle Bewertung von Isoliersystemen - Prüfverfahren für Wicklungen mit vorgeformten Elementen - Thermische Bewertung und Klassifizierung von Isoliersystemen für drehende Maschinen

Machines électriques tournantes - Partie 18-31: Evaluation fonctionnelle des systèmes d'isolation - Procédures d'essai pour enroulements préformés - Evaluation thermique et classification des systèmes d'isolation utilisés dans les machines tournantes

La CEI 60034-18-31:2012 décrit les procédures d'essai d'endurance thermique pour la classification des systèmes d'isolation utilisés dans les machines électriques tournantes à courant alternatif ou continu, à refroidissement indirect et à enroulements préformés. Ces procédures d'essai permettent de comparer les performances d'endurance thermique de l'isolation principale entre le (ou les) conducteur(s) et la terre, et si requis par la conception de la bobine ou de la barre, l'isolation entre spires. Les principales modifications techniques par rapport à l'édition précédente sont les suivantes: - Définition de la méthode d'essai et des sous-cycles requis pour établir une plate-forme normalisée et cohérente applicable au vieillissement thermique des systèmes d'isolation des enroulements préformés. - Recommandations pour établir une courbe de durée de vie thermique fondée sur des intervalles de confiance. - Comparaison des performances des systèmes candidats et de référence en fonction d'exigences spécifiques de classe thermique, dans des limites réalisables. Mots clefs: machines tournantes, systèmes d'isolation.

Električni rotacijski stroji - 18-31. del: Funkcionalno vrednotenje izolacijskih sistemov - Preskusni postopki za predhodno oblikovana navitja - Toplotno vrednotenje in klasificiranje izolacijskih sistemov, ki se uporabljajo pri rotacijskih strojih (IEC 60034-18-31:2012)

Ta del standarda IEC 60034 opisuje preskusne postopke v zvezi s toplotno vzdržljivostjo za klasificiranje izolacijskih sistemov, ki se uporabljajo pri električnih rotacijskih strojih z izmenično ali enosmerno napetostjo s posrednim hlajenjem in predhodno oblikovanimi navitji. Preskusno delovanje kandidatnega izolacijskega sistema se primerja s preskusnim delovanjem referenčnega izolacijskega sistema z dokazanimi izkušnjami pri uporabi. Preskusni postopki iz standarda IEC 60034-18-31 so namenjeni primerjavi delovanja toplotne vzdržljivosti izolacije glavne stene med vodniki in tlemi ter, kadar tako zahteva zasnova tuljave ali palice, izolacija med ovoji. Preskus ni namenjen simuliranju mehanskih obremenitev končnih opornih ali podpornih materialov med delovanjem. Ne zajema vrednotenja toplotno-mehanskega propadanja zaradi širjenja in krčenja izolacije med menjavanjem temperature. Standard IEC 60034-18-1 opisuje splošna preskusna načela, ki se uporabljajo za preskušanje toplotne vzdržljivosti izolacijskih sistemov, ki se uporabljajo pri električnih rotacijskih strojih. Upoštevajo se načela standarda IEC 60034-18-1, razen če v standardu IEC 60034-18-31 ni navedeno drugače. Toplotni razred izolacijskega sistema se nanaša na njegovo najvišjo dovoljeno temperaturo (»vroča točka«). Povprečna temperatura, izmerjena med delovanjem, naj ne bi presegla dovoljenega temperaturnega dviga iz standarda IEC 60034-1.

General Information

Status
Published
Publication Date
23-Aug-2012
Technical Committee
Drafting Committee
Current Stage
6060 - Document made available
Due Date
30-Oct-2012
Completion Date
24-Aug-2012

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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.RSORWQRMachines électriques tournantes - Partie 18-31: Evaluation fonctionnelle des systèmes d'isolation - Procédures d'essai pour enroulements préformés - Evaluation thermique et classification des systèmes d'isolation utilisés dans les machines tournantes (IEC 60034-18-31:2012)Machines électriques tournantes - Partie 18-31: Evaluation fonctionnelle des systèmes d'isolation - Procédures d'essai pour enroulements préformés - Evaluation thermique et classification des systèmes d'isolation utilisés dans les machines tournantes (CEI 60034-18-31:2012)Rotating electrical machines - Part 18-31: Functional evaluation of insulation systems - Test procedures for form-wound windings - Thermal evaluation and classification of insulation systems used in rotating machines (IEC 60034-18-31:2012)29.160.01Rotacijski stroji na splošnoRotating machinery in general29.080.30Izolacijski sistemiInsulation systemsICS:Ta slovenski standard je istoveten z:EN 60034-18-31:2012SIST EN 60034-18-31:2012en01-oktober-2012SIST EN 60034-18-31:2012SLOVENSKI

STANDARDSIST EN 60034-18-31:1999/A1:1999SIST EN 60034-18-31:19991DGRPHãþD
SIST EN 60034-18-31:2012
EUROPEAN STANDARD EN 60034-18-31 NORME EUROPÉENNE
EUROPÄISCHE NORM August 2012

CENELEC European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung

Management Centre: Avenue Marnix 17, B - 1000 Brussels
© 2012 CENELEC -

All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 60034-18-31:2012 E
ICS 29.160 Supersedes EN 60034-18-31:1994 + A1:1996
English version
Rotating electrical machines -
Part 18-31: Functional evaluation of insulation systems -
Test procedures for form-wound windings -

Thermal evaluation and classification of insulation systems used in rotating machines (IEC 60034-18-31:2012)

Machines électriques tournantes -
Partie 18-31: Evaluation fonctionnelle des systèmes d'isolation -
Procédures d'essai pour enroulements préformés -

Evaluation thermique et classification des systèmes d'isolation utilisés dans les machines tournantes (CEI 60034-18-31:2012)

Drehende elektrische Maschinen -
Teil 18-31: Funktionelle Bewertung von Isoliersystemen -
Prüfverfahren für Wicklungen mit vorgeformten Elementen -

Thermische Bewertung und Klassifizierung von Isoliersystemen für drehende Maschinen (IEC 60034-18-31:2012)

This European Standard was approved by CENELEC on 2012-07-30. 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 CEN-CENELEC Management Centre 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 CEN-CENELEC Management Centre has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

SIST EN 60034-18-31:2012
EN 60034-18-31:2012 - 2 -

Foreword The text of document 2/1662/FDIS, future edition 2 of IEC 60034-18-31, prepared by IEC/TC 2 "Rotating machinery" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as

EN 60034-18-31:2012.

The following dates are fixed: • latest date by which the document has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2013-04-30 • latest date by which the national standards conflicting with the document have to be withdrawn (dow) 2015-07-30

This document supersedes EN 60034-18-31:1994 + A1:1996. EN 60034-18-31:2012 includes the following significant technical changes with respect to

EN 60034-18-31:1994 + A1:1996:

- Definition of the test method and sub-cycles required to establish a consistent standardized platform for thermal ageing of insulation systems for form-wound windings. - Recommendations for establishing a thermal life curve based on confidence intervals. - Comparison of candidate and reference system performance for specific requirements of thermal class, within feasible limits.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such patent rights.

Endorsement notice The text of the International Standard IEC 60034-18-31:2012 was approved by CENELEC as a European Standard without any modification. In the official version, for Bibliography, the following note has to be added for the standard indicated: IEC 60034-1 NOTE

Harmonized as EN 60034-1.SIST EN 60034-18-31:2012
- 3 - EN 60034-18-31:2012 Annex ZA

(normative) Normative references to international publications with their corresponding European publications 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.

NOTE

When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD applies.

Publication Year Title EN/HD Year
IEC 60034-15 2009 Rotating electrical machines -

Part 15: Impulse voltage withstand levels of form-wound stator coils for rotating a.c. machines EN 60034-15 2009

IEC 60034-18-1 2010 Rotating electrical machines -

Part 18-1: Functional evaluation of insulation systems - General guidelines EN 60034-18-1 2010

IEC/TS 60034-18-42 - Rotating electrical machines -
Part 18-42: Qualification and acceptance

tests for partial discharge resistant electrical insulation systems (Type II) used in rotating electrical machines fed from voltage converters CLC/TS

60034-18-42 -
IEC 60060-1 - High-voltage test techniques -
Part 1: General definitions and test requirements EN 60060-1 -

IEC 60085 - Electrical insulation - Thermal evaluation and designation EN 60085 -

IEC 60216-1 - Electrical insulating materials - Thermal endurance properties -
Part 1: Ageing procedures and evaluation of test results EN 60216-1 -
IEC 60216-4-1 - Electrical insulating materials - Thermal endurance properties -
Part 4-1: Ageing ovens - Single-chamber ovens EN 60216-4-1 -
IEC 60216-5 - Electrical insulating materials - Thermal endurance properties -

Part 5: Determination of relative thermal endurance index (RTE) of an insulating material EN 60216-5 -

IEC 60505 - Evaluation and qualification of electrical insulation systems EN 60505 -

SIST EN 60034-18-31:2012
SIST EN 60034-18-31:2012

IEC 60034-18-31 Edition 2.0 2012-06 INTERNATIONAL STANDARD NORME INTERNATIONALE Rotating electrical machines –

Part 18-31: Functional evaluation of insulation systems – Test procedures for form-wound windings – Thermal evaluation and classification of insulation systems used in rotating machines

Machines électriques tournantes –

Partie 18-31: Evaluation fonctionnelle des systèmes d'isolation – Procédures d'essai pour enroulements préformés – Evaluation thermique et classification des systèmes d'isolation utilisés dans les machines tournantes

INTERNATIONAL ELECTROTECHNICAL COMMISSION COMMISSION ELECTROTECHNIQUE INTERNATIONALE U ICS 29.160 PRICE CODE CODE PRIX ISBN 978-2-83220-159-6

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale ®

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé. SIST EN 60034-18-31:2012

– 2 – 60034-18-31 © IEC:2012 CONTENTS

FOREWORD ........................................................................................................................... 4 INTRODUCTION ..................................................................................................................... 6 1 Scope ............................................................................................................................... 7 2 Normative references ....................................................................................................... 7 3 General considerations ..................................................................................................... 8 3.1 Reference insulation system .................................................................................... 8 3.2 Test procedures ...................................................................................................... 8 4 Test objects and test specimens ....................................................................................... 9 4.1 Construction of test objects ..................................................................................... 9 4.2 Verification of effects of minor changes in insulation systems .................................. 9 4.3 Number of test specimens ....................................................................................... 9 4.4 Quality control ......................................................................................................... 9 4.5 Initial diagnostic tests ............................................................................................ 10 5 Test procedures ............................................................................................................. 10 5.1 Thermal ageing sub-cycle ...................................................................................... 10 5.2 Ageing temperatures and sub-cycle lengths .......................................................... 10 5.3 Method of heating.................................................................................................. 11 5.4 Thermal ageing of test objects ............................................................................... 12 6 Diagnostic sub-cycle....................................................................................................... 12 6.1 Conditioning procedure ......................................................................................... 12 6.1.1 General ..................................................................................................... 12 6.1.2 Mechanical conditioning ............................................................................ 12 6.1.3 Moisture conditioning ................................................................................. 13 6.2 Diagnostic tests ..................................................................................................... 13 6.2.1 Voltage withstand test ............................................................................... 13 6.2.2 Method ...................................................................................................... 14 6.2.3 Mainwall insulation test.............................................................................. 14 6.2.4 Turn insulation test .................................................................................... 14 6.3 Informative tests .................................................................................................... 15 7 Reporting and functional evaluation of data from candidate and reference systems ........ 15 7.1 General ................................................................................................................. 15 7.2 Determining qualification ....................................................................................... 15 7.2.1 Overview ................................................................................................... 15 7.2.2 Case A: Qualification for the same class temperature and same expected service life .................................................................................. 16 7.2.3 Case B: Qualification for the same class temperature and a different expected service life .................................................................................. 17 7.2.4 Case C: Qualification for a different class temperature and same expected service life .................................................................................. 18 7.2.5 Case D: Qualification for a different class temperature and different expected service life .................................................................................. 19 7.2.6 Non-linearity of regression lines ................................................................ 20 7.2.7 Reduced evaluation ................................................................................... 20 Annex A (informative)

Example of test object (formette) construction ................................... 22 Bibliography .......................................................................................................................... 27 SIST EN 60034-18-31:2012

60034-18-31 © IEC:2012 – 3 –
Figure 1 – Candidate system qualified for the same

thermal class and the same expected service life ............................................................................................................. 17 Figure 2 – Candidate system qualified for the same

thermal class and different expected service life ............................................................................................................. 18 Figure 3 – Candidate system qualified for a different

class temperature and the same expected service life ............................................................................................................. 19 Figure 4 – Candidate system qualified for a different service life

and different thermal class from the reference ....................................................................................................... 20 Figure A.1 – Typical slot assembly ........................................................................................ 23 Figure A.2 – Typical slot assembly ........................................................................................ 24 Figure A.3 – Formette for testing DC armature coils .............................................................. 25 Figure A.4 – Test fixture for rotor slot section ....................................................................... 26

Table 1 – Thermal classes .................................................................................................... 10 Table 2 – Recommended temperatures and ageing sub-cycle exposure periods ................... 11 Table 3 – Conditions for qualification of candidate system .................................................... 16 SIST EN 60034-18-31:2012

– 4 – 60034-18-31 © IEC:2012 INTERNATIONAL ELECTROTECHNICAL COMMISSION ____________

ROTATING ELECTRICAL MACHINES –
Part 18-31: Functional evaluation of insulation systems –
Test procedures for form-wound windings –
Thermal evaluation and classification of insulation
systems used in rotating machines

FOREWORD 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). The 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 Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work. International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for Standardization (ISO) in accordance with conditions determined by agreement between the two organizations. 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international consensus of opinion on the relevant subjects since each technical committee has representation from all interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any misinterpretation by any end user. 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications transparently to the maximum extent possible in their national and regional publications. Any divergence between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter. 5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any services carried out by independent certification bodies. 6) All users should ensure that they have the latest edition of this publication. 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and members of its technical committees and IEC National Committees for any personal injury, property damage or other damage of any nature whatsoever, 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 publications is indispensable for the correct application of this publication. 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights. International Standard IEC 60034-18-31 has been prepared by IEC technical committee 2: Rotating machinery. This second edition cancels and replaces the first edition published in 1992, and its amendment 1 (1996), of which it constitutes a technical revision. The main technical changes with regard to the previous edition include: – Definition of the test method and sub-cycles required to establish a consistent standardized platform for thermal ageing of insulation systems for form-wound windings. – Recommendations for establishing a thermal life curve based on confidence intervals. – Comparison of candidate and reference system performance for specific requirements of thermal class, within feasible limits. SIST EN 60034-18-31:2012

60034-18-31 © IEC:2012 – 5 – The text of this standard is based on the following documents: FDIS Report on voting 2/1662/FDIS 2/1671/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/IEC Directives, Part 2. NOTE A table of cross-references of all IEC TC 2 publications can be found on the IEC TC 2 dashboard on the IEC website. The committee has decided that the contents of this publication will remain unchanged until the stability date indicated on the IEC 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.
SIST EN 60034-18-31:2012

– 6 – 60034-18-31 © IEC:2012 INTRODUCTION IEC 60034-18 comprises several parts, dealing with different types of functional evaluation and special kinds of test procedures for insulation systems of rotating electrial machines. IEC 60034-18-1 provides general guidelines for such procedures and qualification principles. The subsequent parts IEC 60034-18-21, IEC 60034-18-31, IEC 60034-18-32, IEC 60034-18-33, IEC 60034-18-34, IEC 60034-18-41 and IEC 60034-18-42 give detailed procedures for the various types of windings.

IEC 60034-18-31 describes thermal evaluation and classification of insulation systems for form-wound windings. It provides standard thermal ageing techniques and diagnostic test procedures. Parts relevant to this document are: – IEC 60034-18-1: General guidelines

– IEC 60034-18-21: Test procedures for wire-wound windings

– IEC 60034-18-41: Qualification and type tests for Type I electrical insulation systems used in rotating electrical machines fed from voltage converters – IEC 60034-18-42: Qualification and acceptance tests for partial discharge resistant electrical insulation systems (Type II) electrical insulation systems used in rotating electrical machines fed from voltage converters

SIST EN 60034-18-31:2012
60034-18-31 © IEC:2012 – 7 – ROTATING ELECTRICAL MACHINES –
Part 18-31: Functional evaluation of insulation systems –
Test procedures for form-wound windings –
Thermal evaluation and classification of insulation
systems used in rotating machines

1 Scope This part of IEC 60034 describes thermal endurance test procedures for classification of insulation systems used in a.c. or d.c. rotating electrical machines with indirect cooling and form-wound windings.

The test performance of a candidate insulation system is compared to the test performance of a reference insulation system with proven service experience. The test procedures described in IEC 60034-18-31 are intended to compare the thermal endurance performance of the mainwall insulation between conductor(s) and ground and, where required by the design of the coil or bar, the insulation between the turns.

The test is not intended to simulate the in-service mechanical stresses experienced by the endwinding bracing or support materials. It does not include the evaluation of thermo-mechanical deterioration by expansion and contraction of insulation during temperature cycling. IEC 60034-18-1 describes general testing principles applicable to thermal endurance testing of insulation systems used in rotating electrical machines. The principles of IEC 60034-18-1 are followed unless otherwise stated in IEC60034-18-31. The thermal class for the insulation system refers to its maximum allowed (“hot spot”) temperature. The average temperature measured in service should not exceed the allowed temperature rise according to IEC 60034-1. NOTE 1 Large machines, especially synchronous generators using bars, may require special thermal evaluation test procedures which are not included in this part.

NOTE 2 Recommended parameters for the diagnostic test may be applied according to IEC 60034-18-42 to form-wound coils designed with Type II insulation systems for use in converter applications. 2 Normative references 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. IEC 60034-15:2009, Rotating electrical machines – Part 15:

Impulse voltage withstand levels of form-wound stator coils for rotating a.c. machines IEC 60034-18-1:2010, Rotating electrical machines – Part 18-1: Functional evaluation of insulation systems – General guidelines SIST EN 60034-18-31:2012

– 8 – 60034-18-31 © IEC:2012 IEC 60034-18-42, Rotating electrical machines – Part 18-42: Qualification and acceptance tests for partial discharge resistant electrical insulation systems (Type II) used in rotating electrical machines fed from voltage converters IEC 60060-1, High-voltage test techniques – Part 1: General definitions and test requirements IEC 60085, Electrical Insulation – Thermal evaluation and designation IEC 60216-1, Electrical insulating materials – Properties of thermal endurance – Part 1: Ageing procedures and evaluation of test results

IEC 60216-4-1, Electrical insulating materials – Thermal endurance properties – Part 4-1: Ageing ovens – Single-chamber ovens IEC 60216-5, Electrical insulating materials – Thermal endurance properties – Part 5: Determination of relative thermal endurance index (RTE) of an insulating material IEC 60505, Evaluation and qualification of electrical insulation systems 3 General considerations 3.1 Reference insulation system A reference insulation system, as described in 4.3 of IEC 60034-18-1, shall be tested using the same procedure as that used for the candidate system. Acceptable service life of a low voltage system does not automatically qualify a high voltage (HV) system, especially since HV systems usually feature additional materials: for example corona suppression systems and enhanced turn insulation. These materials may affect the design and thermal endurance of the system.

A manufacturer may wish to qualify a new system with reduced mainwall thickness. It should be appropriate to compare the candidate to the reference by modifying the thickness or the rated voltage (UN) of the diagnostic test, provided the test sample designs include all the specified materials and processing. 3.2 Test procedures Each thermal endurance test consists of a series of cycles, where each cycle comprises a thermal ageing sub-cycle followed by a diagnostic sub-cycle, consisting of a conditioning procedure and a diagnostic test. The conditioning procedure shall include application of mechanical stress and moisture, in that order. The diagnostic tests are described in Clause 6. The mechanical conditioning requires shaking the test object on a table equipped to vibrate with specified amplitude. A condensation chamber is required for moisture conditioning of an unsealed insulation system. The condensation chamber and complete immersion are required for moisture conditioning of a sealed insulation system. For sealed systems, the diagnostic voltage withstand test is performed while the specimens are immersed. For unsealed systems, the diagnostic voltage test may be performed outside the condensation chamber, provided that the samples are still thoroughly wetted. The voltage withstand test in either case shall be applied across the mainwall insulation and between turns, where appropriate to the design of the coil or bar. Additional voltage withstand tests may be applied as appropriate to the design. SIST EN 60034-18-31:2012

60034-18-31 © IEC:2012 – 9 – In addition to the required tests, non-destructive informative diagnostic tests may be used to characterize the insulation system or obtain periodic measurements of its response to the thermal and diagnostic sub-cycles. 4 Test objects and test specimens 4.1 Construction of test objects The various insulating materials and components of an insulation system to be evaluated by these test procedures should be screened beforehand. The temperature indices (TI) of insulating materials may be used, but they provide only an indication of potential performance in the thermal functional tests and do not constitute qualification of insulation systems. Wherever feasible, test objects should closely represent the actual construction of the insulation system to be used in a rotating machine. Usually this requires coils of full cross-section with actual clearances and creepage distances, mounted in a fixture that simulates the arrangement of coils in the machine. The coils or bars are the test specimens, and the complete fixture with specimens in place is the test object. Where the test specimens are coils or bars, they should represent the full insulation design, including insulation thickness, coil-to-coil (or bar-to-bar) clearance, and any required corona suppression or grading materials. The specimens tested shall represent the design for the intended maximum rated voltage and equipment standards.

For large and high-voltage machines, test specimens representing a partial coil or bar may be used, provided that: a) representative factors of influence can be applied to the test specimens to investigate ageing processes specific to that part of the system, and

b) each material employed in the higher voltage design is represented in the test specimens, and arranged and processed on the specimens as it would be in service.

Test objects known as formettes simulate the geometry, clearance and placing of a series of form-wound coils in a winding. They have been used successfully for thermal evaluation testing. Examples of formettes are illustrated in Annex A. 4.2 Verification of effects of minor changes in insulation systems A minor change is described in IEC 60034-18-1. An example of a minor change in a form-wound insulation system may include purchasing a key component material from a new supplier without changing the material specification. If thermal ageing evaluation is appropriate to evaluate a minor change to a service-proven insulation system, it is acceptable to use one temperature to age one test object consisting of no fewer than the recommended number of test specimens.

This reduced evaluation should be performed using an ageing temperature cycle within the

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