SIST-TP CLC/TR 60034-18-33:2005
(Main)Rotating electrical machines - Part 18-33: Functional evaluation of insulation systems - Test procedures for form-wound windings - Multifactor functional evaluation - Endurance under combined thermal and electrical stresses of insulation systems used in machines up to and including 50 MVA and 15 kV (IEC/TR 60034-18-33:1995)
Rotating electrical machines - Part 18-33: Functional evaluation of insulation systems - Test procedures for form-wound windings - Multifactor functional evaluation - Endurance under combined thermal and electrical stresses of insulation systems used in machines up to and including 50 MVA and 15 kV (IEC/TR 60034-18-33:1995)
This publication has the status of a technical report - type 2.
Drehende elektrische Maschinen - Teil 18-33: Funktionelle Bewertung von Isoliersystemen - Prüfverfahren für Wicklungen mit vorgeformten Elementen - Funktionelle Bewertung bei mehreren Einflussgrößen - Lebensdauer von Isoliersystemen für Maschinen bis 50 MVA und 15 kV bei kombinierter thermischer und elektrischer Beanspruchung (IEC/TR 60034-18-33:1995)
Machines électriques tournantes - Partie 18-33: Evaluation fonctionnelle des systèmes d'isolation - Procédures d'essai pour enroulements préformés - Evaluation fonctionnelle à plusieurs facteurs - Endurance sous contrainte thermique et électrique combinée des systèmes d'isolation utilisés dans les machines jusqu'à et y compris 50 MVA et 15 kV (CEI/TR 60034-18-33:1995)
Cette publication a le statut d'un rapport technique - type 2.
Električni rotacijski stroji - 18-33. del: Funkcionalno vrednotenje izolacijskih sistemov - Preskusni postopki za predhodno oblikovana navitja - Funkcionalno vrednotenje z več faktorji - Vzdržljivost izolacijskih sistemov, ki se uporabljajo za stroje do vključno 50 MVA in 15 kV, pri kombiniranih toplotnih in električnih obremenitvah (IEC/TR 60034-18-33:1995)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST-TP CLC/TR 60034-18-33:2005
01-junij-2005
(OHNWULþQLURWDFLMVNLVWURMLGHO )XQNFLRQDOQRYUHGQRWHQMHL]RODFLMVNLK
VLVWHPRY3UHVNXVQLSRVWRSNL]DSUHGKRGQRREOLNRYDQDQDYLWMD)XQNFLRQDOQR
YUHGQRWHQMH]YHþIDNWRUML9]GUåOMLYRVWL]RODFLMVNLKVLVWHPRYNLVHXSRUDEOMDMR]D
VWURMHGRYNOMXþQR09$LQN9SULNRPELQLUDQLKWRSORWQLKLQHOHNWULþQLK
REUHPHQLWYDK ,(&75
Rotating electrical machines - Part 18-33: Functional evaluation of insulation systems -
Test procedures for form-wound windings - Multifactor functional evaluation - Endurance
under combined thermal and electrical stresses of insulation systems used in machines
up to and including 50 MVA and 15 kV (IEC/TR 60034-18-33:1995)
Drehende elektrische Maschinen - Teil 18-33: Funktionelle Bewertung von
Isoliersystemen - Prüfverfahren für Wicklungen mit vorgeformten Elementen -
Funktionelle Bewertung bei mehreren Einflussgrößen - Lebensdauer von Isoliersystemen
für Maschinen bis 50 MVA und 15 kV bei kombinierter thermischer und elektrischer
Beanspruchung (IEC/TR 60034-18-33:1995)
Machines électriques tournantes - Partie 18-33: Evaluation fonctionnelle des systèmes
d'isolation - Procédures d'essai pour enroulements préformés - Evaluation fonctionnelle
à plusieurs facteurs - Endurance sous contrainte thermique et électrique combinée des
systèmes d'isolation utilisés dans les machines jusqu'à et y compris 50 MVA et 15 kV
(CEI/TR 60034-18-33:1995)
Ta slovenski standard je istoveten z: CLC/TR 60034-18-33:2004
ICS:
29.080.30 Izolacijski sistemi Insulation systems
29.160.01 Rotacijski stroji na splošno Rotating machinery in
general
SIST-TP CLC/TR 60034-18-33:2005 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST-TP CLC/TR 60034-18-33:2005
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SIST-TP CLC/TR 60034-18-33:2005
TECHNICAL REPORT CLC/TR 60034-18-33
RAPPORT TECHNIQUE
TECHNISCHER BERICHT September 2004
ICS 29.080; 29.160
English version
Rotating electrical machines
Part 18-33: Functional evaluation of insulation systems -
Test procedures for form-wound windings -
Multifactor functional evaluation -
Endurance under combined thermal and electrical stresses of insulation
systems used in machines up to and including 50 MVA and 15 kV
(IEC/TR 60034-18-33:1995)
Machines électriques tournantes Drehende elektrische Maschinen
Partie 18-33: Evaluation fonctionnelle Teil 18-33: Funktionelle Bewertung
des systèmes d'isolation - von Isoliersystemen -
Procédures d'essai Prüfverfahren für Wicklungen
pour enroulements préformés - mit vorgeformten Elementen -
Evaluation fonctionnelle Funktionelle Bewertung
à plusieurs facteurs - bei mehreren Einflussgrößen -
Endurance sous contrainte thermique Lebensdauer von Isoliersystemen
et électrique combinée des systèmes für Maschinen bis 50 MVA und 15 kV
d'isolation utilisés dans les machines bei kombinierter thermischer
jusqu'à et y compris 50 MVA et 15 kV und elektrischer Beanspruchung
(CEI/TR 60034-18-33:1995) (IEC 60034-18-33:1995)
This Technical Report was approved by CENELEC on 2004-07-03.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,
Switzerland and 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 - 1050 Brussels
© 2004 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. CLC/TR 60034-18-33:2004 E
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SIST-TP CLC/TR 60034-18-33:2005
CLC/TR 60034-18-33:2004 - 2 -
Foreword
The text of the Technical Report IEC/TR 60034-18-33:1995, prepared by IEC TC 2, Rotating machinery,
was submitted to the formal vote and was approved by CENELEC as CLC/TR 60034-18-33 on
2004-07-03 without any modification.
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the Technical Report IEC/TR 60034-18-33:1995 was approved by CENELEC as a Technical
Report without any modification.
__________
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SIST-TP CLC/TR 60034-18-33:2005
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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 Year Title EN/HD Year
1)
IEC 60034-1 (mod) 1994 Rotating electrical machines EN 60034-1 1995
+ corr. December 1994 Part 1: Rating and performance + corr. April 1995
IEC 60034-15 1995 Part 15: Impulse voltage withstand EN 60034-15 1996
levels of rotating a.c. machines with
form-wound stator coils
IEC 60034-18-1 1992 Part 18: Functional evaluation of EN 60034-18-1 1994
+ corr. August 1992 insulation systems
Section 1: General guidelines
IEC/TR 60034-18-32 1995 Part 18-32: Functional evaluation of CLC/TR 60034-18-32 2004
insulation systems - Test procedures for
form-wound windings - Electrical
evaluation of insulation systems used in
machines up to and including 50 MVA
and 15 kV
IEC 60727-1 1982 Evaluation of electrical endurance of - -
electrical insulation systems
Part 1: General considerations and
evaluation procedures based on normal
distributions
IEC 60727-2 1993 Part 2: Evaluation procedures based on - -
extreme-value distributions
1)
EN 60034-1:1995 is replaced by EN 60034-1:2004, which is based on IEC 60034-1:2004.
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SIST-TP CLC/TR 60034-18-33:2005
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SIST-TP CLC/TR 60034-18-33:2005
CEI
RAPPORT
TECHNIQUE - TYPE 2 IEC
34-18-
33
TECHNICAL
Première édition
REPORT - TYPE 2
First edition
1995-03
Machines électriques tournantes –
Partie 18:
Evaluation fonctionnelle des systèmes d'isolation –
Section 33: Procédures d'essai pour enroulements
préformés – Evaluation fonctionnelle à plusieurs
facteurs – Endurance sous contrainte thermique
et électrique combinée des systèmes d'isolation
utilisés dans les machines jusqu'à et y compris
50 MVA et 15 kV
Rotating electrical machines –
Part 18:
Functional evaluation of insulation systems –
Section 33: Test procedures for form-wound windings –
Multifactor functional evaluation – Endurance under
combined thermal and electrical stresses of insulation
systems used in machines up to and including
50 MVA and 15 kV
© CEI 1995 Droits de reproduction réservés — Copyright — all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in
utilisée sous quelque forme que ce soit et par aucun pro- any form or by any means, electronic or mechanical,
cédé, électronique ou mécanique, y compris la photocopie et including photocopying and microfilm, without permission
les microfilms, sans l'accord écrit de l'éditeur. in writing from the publisher.
Bureau Central de la Commission Electrotechnique Internationale 3, rue de Varembé Genève, Suisse
Commission Electrotechnique Internationale CODE PRIX
International Electrotechnical Commission
PRICE CODE
IEC MewtyHapoAHaa 3nerapoTeXHH4ecnata HOMHCc ln
voir catalogue en vigueur
Pour prix,
• •
For price, see current catalogue
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SIST-TP CLC/TR 60034-18-33:2005
– 3 –
34-18-33 ©IEC:1995
CONTENTS
Page
FOREWORD 5
INTRODUCTION 9
Clause
11
1 Scope
2 Normative references 11
3 General 13
13 3.1 Relationship to section 1
13
3.2 Designation of test procedures
13
3.3 Reference insulation system
13 3.4 Verification of diagnostic tests
13 3.5 Characteristics of test procedures
15
3.6 Means of heating and definition of thermal stress level
17 3.7 Means of electrical ageing
19
3.8 Definition of ageing sub-cycle duration
19
3.9 Reference operating conditions
21
4 Test objects
21
4.1 Construction of test objects
21
4.2 Number of test specimens
21
4.3 Quality assurance tests
4.4 Initial diagnostic tests 23
23 5 Ageing sub-cycle
5.1 Ageing stress levels 23
27 5.2 Duration and number of ageing sub-cycles
29
5.3 Procedure 1: ageing sub-cycle with ageing stresses applied simultaneously
5.4 Procedure 2: ageing sub-cycle with sequentially applied thermal and
electrical stresses 29
5.5 Procedure 3: ageing sub-cycle when single-point procedure is applicable 29
6 Diagnostic sub-cycle 31
31 6.1 Mechanical tests
31
6.2 Moisture tests
33
6.3 Voltage tests
35
6.4 Other diagnostic tests
37
7 Analyzing the data, reporting and evaluation
7.1 Analyzing the data 37
37
7.2 Reporting
37
7.3 Evaluation
39
Annex A
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SIST-TP CLC/TR 60034-18-33:2005
34-18-33 ©IEC:1995 - 5 -
INTERNATIONAL ELECTROTECHNICAL COMMISSION
ROTATING ELECTRICAL MACHINES –
Part 18: Functional evaluation of insulation systems –
Section 33: Test procedures for form-wound windings –
Multifactor functional evaluation –
Endurance under combined thermal and electrical stresses
of insulation systems used in machines
up to and including 50 MVA and 15 kV
FOREWORD
The IEC (International Electrotechnical Commission) is a worldwide organization for standardization
1)
comprising all national electrotechnical committees (IEC National Committees). The object of the IEC is to
promote international cooperation on all questions concerning standardization in the electrical and
electronic fields. To this end and in addition to other activities, the IEC publishes International Standards.
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. The 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 the IEC on technical matters, prepared by technical committees on
which all the National Committees having a special interest therein are represented, express, as nearly as
possible, an international consensus of opinion on the subjects dealt with.
They have the form of recommendations for international use published in the form of standards, technical
3)
reports or guides and they are accepted by the National Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
The main task of IEC technical committees is to prepare International Standards. In excep-
tional circumstances, a technical committee may propose the publication of a technical
report of one of the following types:
type 1, when the required support cannot be obtained for the publication of an Inter-
•
national Standard, despite repeated efforts;
type 2, when the subject is still under technical development or where for any other
•
reason there is the future but not immediate possibility of an agreement on an Inter-
national Standard;
type 3, when a technical committee has collected data of a different kind from that
•
which is normally published as an International Standard, for example "state of the art".
Technical reports of types 1 and 2 are subject to review within three years of publication to
decide whether they can be transformed into International Standards. Technical reports of
type 3 do not necessarily have to be reviewed until the data they provide are considered
to be no longer valid or useful.
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SIST-TP CLC/TR 60034-18-33:2005
34-18-33 © IEC:1 995 - 7 -
IEC 34-18-33, which is a technical report of type 2, has been prepared by sub-
committee 2J: Classification of insulation systems for rotating machinery, of IEC technical
committee 2: Rotating machinery.
The text of this technical report is based on the following documents:
Committee draft Report on voting
2J(SEC)38
2J(SEC)29
Full information on the voting for the approval of this technical report can be found in the
report on voting indicated in the above table.
series of
This document is issued in the type 2 technical repo rt
publications (according to G.4.2.2 of part 1 of the IEC/ISO Directives) as
on" in the field of the
a "prospective standard for provisional applica ti
evaluation of insulating systems for rotating electrical machines because
field
there is an urgent requirement for guidance on how standards in this
should be used to meet an identified need.
This document is not to be regarded as an "International Standard". It is
proposed for provisional application so that information and experience
of its use in practice may be gathered. Comments on the content of this
document should be sent to the IEC Central Office.
rt will be carried out not later than
A review of this type 2 technical repo
three years after its publication, with the options of either extension for a
further three years or conversion to an International Standard or
withdrawal.
Annex A forms an integral part of this technical report.
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SIST-TP CLC/TR 60034-18-33:2005
34-18-33 © IEC:1995 — 9 —
INTRODUCTION
Section 1 of IEC 34-18 presents general guidelines for the evaluation and classification of
insulation systems used in rotating machines.
Section 33 deals exclusively with insulation systems for form-wound windings, and con-
centrates on multifactor functional evaluation limited to thermal and electrical ageing. It is
intended to be a basic technical report, from which the test standard will be developed.
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34-18-33 ©IEC:1995
ROTATING ELECTRICAL MACHINES –
Part 18: Functional evaluation of insulation systems –
Section 33: Test procedures for form-wound windings –
Multifactor functional evaluation –
Endurance under combined thermal and electrical stresses
of insulation systems used in machines
up to and including 50 MVA and 15 kV
1 Scope
This section of IEC 34-18 is a technical repo rt that describes test procedures for
evaluation of multifactor endurance of insulation systems in those cases where both
thermal and electrical ageing factors are significant. The procedures are intended for
insulation systems used, or proposed to be used, in a.c. electrical machines using
form-wound windings up to and including 50 MVA and 15 kV. The test procedures are
ormance of a candidate insulation system is
comparative in nature, so that the pe rf
compared to that of a reference insulation system with proven se rvice experience. The
does not include stress grading.
evaluation described in this technical repo rt
2 Normative references
The following normative documents contain provisions which, through reference in this
. At the time of publication, the editions
text, constitute provisions of this technical repo rt
indicated are valid. All normative documents are subject to revision, and pa rties to agree-
are encouraged to investigate the possibility of
ments based on this technical repo rt
applying the most recent editions of the normative documents indicated below. Members
of IEC and ISO maintain registers of currently valid International Standards.
Rotating electrical machines - Part 1: Rating and pe rformance
IEC 34-1: 1994,
IEC 34-15: 1995, Rotating electrical machines - Part 15: Impulse voltage withstand levels
of rotating a.c. machines with form-wound stator coils
Rotating electrical machines - Part 18: Functional evaluation of
IEC 34-18-1: 1992,
insulation systems - Section 1: General guidelines
Rotating electrical machines - Part 18: Functional evaluation of insu-
IEC 34-18-32: 1995,
lation systems - Section 32: Test procedures for form-wound windings - Electrical evalu-
ation of insulation systems used in machines up to and including 50 MVA and 15 kV
Evaluation of electrical endurance of electrical insulation systems -
IEC 727-1: 1982,
Part 1: General considerations and evaluation procedures based on normal distributions
The multi-factor functional testing of electrical insulation systems -
IEC 792-1: 1985,
Part 1: Test procedures
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34-18-33 © IEC:1995
3 General
3.1 Relationship to section 1
The principles of IEC 34-18-1 shall be followed, unless the recommendations or proposals
of this section indicate otherwise.
3.2 Designation of test procedures
It is proposed, when describing the test procedure in short form, that the designation of
procedures from table 1 are used. Designation of a multifactor test procedure described in
this technical report will then be 34-18-33 Procedure N, where N is the number of the
selected procedure from table 1.
Reference insulation system
3.3
A reference insulation system is to be tested using a test procedure equivalent to that
used for the candidate system in the same laboratory, using the same test equipment. The
performance of the reference insulation system shall be established by service experience
under typical operating conditions in the range of the reference operating conditions
(see 3.9). If the reference system has been tested previously, then a single-point test on
the reference system is adequate to confirm the test procedure.
Since the values of accelerations are not known in the multifactor testing conditions, this
requirement can be fulfilled only by using virtually identical levels of ageing factors for
both systems.
NOTE - It is possible that the actual values of accelerations in the multifactor testing of the reference
and candidate systems are not identical, even when the levels of both the electrical and thermal ageing
factors are identical for the two systems.
3.4 Verification of diagnostic tests
Preliminary thermal ageing tests that follow the principles given in 5.3.4 of IEC 34-18-1, to
check the suitability of the diagnostic sub-cycle, may be performed, when appropriate.
Characteristics of test procedures
3.5
3.5.1 General characteristics
In general the tests according to this technical report are performed in cycles, each cycle
consisting of an ageing sub-cycle and a diagnostic sub-cycle.
3.5.2 Ageing sub-cycle
The ageing sub-cycle includes both thermal and electrical ageing, performed either simul-
taneously or sequentially.
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34-18-33 © IEC:1995
The multifactor ageing tests can be complicated by the effects of interactions. When inter-
action is present between two factors of influence, the ageing caused by an ageing factor
can change, due to the presence of the other factor (this is direct interaction); or due to
the ageing caused by the other factor (this is indirect interaction). Procedure 3 is simplified
and shorter when compared to the other two. However, its applicability is limited to minor
or no intended changes in the insulation system.
Direct interaction can be reproduced only in a simultaneous multifactor ageing test.
Indirect interaction can be reproduced in both simultaneous and sequential type tests.
In 5.1.3, guidelines are given for testing procedures when interaction occurs. In annex A,
more information is given about interactions.
Three different procedures for ageing sub-cycles are presented in table 1 and described in
detail in clause 5. Procedures 1 and 2 provide a comprehensive comparison of the test life
expectancy under several combinations of thermal and electrical stresses.
Table 1 - Designation of ageing sub -cycles
Number N
Sub-
of the
Description
Ageing sub-cycle
clause
test
procedure
Ageing stresses are applied simultaneously during
5.3
Ageing sub-cycle with ageing
the ageing sub-cycle.
1 stresses applied simultaneously
5.4 This procedure may be used, particularly in those
Ageing sub-cycle with sequentially
cases, where it seems likely that direct inter-
applied ageing stresses
2 actions between thermal and electrical ageing
factors do not affect the test results appreciably.
See annex.
This procedure provides the comparison at only
5.5
Single-point procedure similar
one combination of thermal and electrical stress.
to 5.3.2.2 in IEC 34-18-1.
This shorter test procedure results in less infor-
3
mation, but which sometimes may be sufficient,
on the performance of the candidate system.
Diagnostic sub-cycle
3.5.3
The diagnostic sub-cycle may consist of mechanical tests, moisture tests, voltage tests
and other diagnostic tests, as appropriate. When selecting these tests, the set of refer-
ence operating conditions (see 3.9) should be used as guidance. The diagnostic tests are
usually applied in the order listed above.
Means of heating and definition of thermal stress level
3.6
3.6.1 Methods of heating
All appropriate means of heating',for example those presented in IEC 34-18-1, may be
used. The specimens should be heated up at a rate typical of normal service.
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34-18-33 © IEC:1995
3.6.2 Thermal stress level
Where practicable, the thermal stress level is defined as the average conductor tempera-
ture in the centre section of the slot section. Where it is considered impracticable to make
an accurate assessment of this temperature, the temperature of the outer su rface of the
main insulation in the middle section of the slot section may be used.
The method used for the measurement of thermal stress level shall be the same for the
candidate and the reference systems. Where oven heating is applied, the oven tempera-
ture may provide an acceptable value of thermal stress, but only when it has been
validated by the procedure given in 3.6.3.
Where thermal stress is provided by current heating, the conductor temperature as
obtained from resistance measurements is an acceptable value of thermal stress if pre-
±5
K between specimens and
cautions are taken to maintain constant temperature with
within them.
3.6.3 Thermal stress measuring techniques
It is recommended that the temperature measurement be made in two steps in cases when
the electrical and thermal ageing stresses are applied simultaneously:
first, at equilibrium with only the thermal stress applied;
a)
a second time, again at equilibrium, but after the additional application of the elec-
b)
trical stress.
Both temperatures are recorded for information, with the higher temperature denoting the
thermal stress level.
NOTES
Measurement of the temperature in the second phase is most safely carried out using the extrapolated
1
cooling curve technique, immediately after the removal of the electrical stress; or by fibre-optic sensors.
2 Higher local temperatures can occur (for example at the stress grading area). These temperatures may
be determined, for example, by using an IR detector. If failures occur systematically at these points then
the ageing stresses possibly can be too high for the used version of stress grading. This problem may be
solved by a reduction in ageing stress, or an improvement of the stress grading.
3.7 Means of electrical ageing
It is recommended that power frequency voltage be used to produce electrical ageing. The
a.c. ageing voltage is applied between the stator core, or the outer conductive layer on the
surface of the test specimen and the conductors.
To reduce the duration of the test, an increased frequency up to 10 times the power
frequency may be used. However, care should be taken that the dielectric losses do not
increase the temperature of the insulation so much that the results are affected. The same
frequency shall be used for the candidate and reference system.
NOTE — As stated in IEC 34-18-1 and in IEC 34-18-32, the real acceleration achieved by increasing the
frequency can deviate from the expected value in an unpredictable manner.
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3.8 Definition of ageing sub-cycle duration
3.8.1 Simultaneous ageing
The ageing sub-cycle will be considered to start at the time when the ageing factors are
applied, and to end when the ageing factors cease to be applied.
3.8.2 Sequential ageing
When ageing factors are applied sequentially, the definition above applies separately to
the thermal and electrical ageing sections of the sub-cycle.
The duration of the sub-cycle is the duration of either the thermal or electrical ageing
section of the sub-cycle.
The duration of the thermal and electrical sections of the sub-cycle shall be identical,
unless the relative operating times for thermal and electrical ageing in service are clearly
different. In that case, the duration of both the thermal and electrical sections of the sub-
cycle shall be reported.
3.9 Reference operating conditions
Reference operating conditions consist of the most severe levels of all the ageing and
diagnostic factors for which the insulation system is designed. The reference operating
conditions shall be defined. In the thermal-electrical multifactor evaluation procedures, the
levels and types of diagnostic factors and the levels of ageing factors shall depend on the
reference operating conditions.
3.9.1 Reference ageing factors
As stated in the scope of this technical report, thermal and electrical ageing factors are
assumed to be the most significant ageing factors. Their levels are dependent on class
temperature and maximum intended rated voltage of the insulation system. See 5.1.1 for
their values.
3.9.2 Reference diagnostic factors
The reference diagnostic factors may include:
a) maximum expected exposure to moisture in se rv ice;
maximum mechanical stress, which can act upon that section of winding which the
b)
test object simulates, for example stresses due to transient currents at start;
c) maximum expected transient overvoltage, from which the maximum interturn
transient overvoltages can be estimated.
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34-18-33 g IEC:1995 -21 -
4 Test objects
4.1 Construction of test objects
4.1.1 General aspects
Test objects shall be constructed to represent adequately the configuration of the finished
winding component to be evaluated, and shall be subjected to the full normal or intended
manufacturing processes as far as possible. If the mechanical attachment of the insulation
during service, that is the way of fixing the coil sides or bars in the slots, or overhang
support structure, is considered to influence the ageing processes, it should be simulated
in the test objects.
When using separate coils or bars as models, creepage distances and voltage grading
means, where required, are to be appropriate to the stresses applied during testing. An
electrode should extend the full slot length of the model and encircle the entire circum-
ference of the coil cross-section. The details given in IEC 727-1 should be observed.
Considerations on turns and strands in test objects
4.1.2
Where turn insulation is diagnostically tested, it is generally necessary to use complete
coils in order to include possible effects of shaping and conductor reinforcement.
Where an impulse voltage diagnostic test is applied, the number of turns in the coil should
be the smallest appropriate for the insulation system, in order to have the highest stress
over the turn-to-turn insulation.
Where it is required to apply a power-frequency voltage between the turns, then the coil
preferably should be wound with two parallel conductors (bifilar), or the coil has to be cut
in the endwindings. When using vacuum pressure impregnation (VPI) coils, the
cut-through and separation of the conductors in that area shall be made before
impregnation.
4.2 Number of test specimens
An adequate number of test specimens should be aged at each of the combinations of
ageing temperatures and voltages that are being used, to obtain a statistical confidence.
This number shall not be less than five.
NOTE – If bars or half-coils are used, the minimum number is five bars or half-coils. If full coils are used,
the minimum number is five full coils.
4.3 Quality assurance tests
Before starting the first ageing sub-cycle, the following quality assurance tests shall be
performed:
visual inspection of the test specimens;
a)
b) voltage tests, according to IEC 34-1.
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SIST-TP CLC/TR 60034-18-33:2005
34-18-33 ©
IEC:1995 - 23 -
4.4 Initial diagnostic tests
Each completed test object shall be subjected to all the diagnostic tests selected for the
test procedure before starting the first ageing sub-cycle.
5 Ageing sub-cycle
5.1 Ageing s
...
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