SIST EN 60034-18-1:1999
(Main)Rotating electrical machines -- Part 18: Functional evaluation of insulation systems -- Section 1: General guidelines
Rotating electrical machines -- Part 18: Functional evaluation of insulation systems -- Section 1: General guidelines
Provides test procedures and classification principles of insulation systems for rotating electrical machines. Tests are of comparative type between a reference system and a candidate system and apply to alternating or direct current machines.
Drehende elektrische Maschinen -- Teil 18: Funktionelle Bewertung von Isoliersystemen -- Hauptabschnitt 1: Allgemeine Richtlinien
Machines électriques tournantes -- Partie 18: Evaluation fonctionnelle des systèmes d'isolation -- Section 1: Principes directeurs généraux
Donne les principes directeurs généraux des procédures d'essai et de la classification des systèmes d'isolation des machines électriques tournantes. Les essais sont du type comparatif entre un système de référence et un système candidat et s'appliquent aux machines à courant alternatif ou continu.
Rotating electrical machines - Part 18: Functional evaluation of insulation systems - Section 1: General guidelines (IEC 60034-18-1:1992 + corrigendum Aug. 1992)
General Information
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Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 60034-18-1:1999
01-april-1999
Rotating electrical machines - Part 18: Functional evaluation of insulation systems
- Section 1: General guidelines (IEC 60034-18-1:1992 + corrigendum Aug. 1992)
Rotating electrical machines -- Part 18: Functional evaluation of insulation systems --
Section 1: General guidelines
Drehende elektrische Maschinen -- Teil 18: Funktionelle Bewertung von Isoliersystemen
-- Hauptabschnitt 1: Allgemeine Richtlinien
Machines électriques tournantes -- Partie 18: Evaluation fonctionnelle des systèmes
d'isolation -- Section 1: Principes directeurs généraux
Ta slovenski standard je istoveten z: EN 60034-18-1:1994
ICS:
29.080.30 Izolacijski sistemi Insulation systems
29.160.01 Rotacijski stroji na splošno Rotating machinery in
general
SIST EN 60034-18-1:1999 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 60034-18-1:1999
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SIST EN 60034-18-1:1999
34-18-1 © IEC - 3 -
CONTENTS
Page
FOREWORD . 5
INTRODUCTION . 7
Clause
1 Scope . 9
2 Normative references . 9
3 Definitions . 11
3.1 General terms . 11
3.2 Terms relating to the objects being tested . 13
3.3 Terms relating to factors of influence . 13
3.4 Terms relating to testing and evaluation . 15
4 General aspects of functional evaluation . 15
4.1 Effects of ageing factors . 15
4.2 Reference insulation system . 17
4.3 Functional tests . 17
5 Thermal functional tests . 19
5.1 General aspects of thermal functional tests . 19
5.2 Test objects and test specimens . 19
5.3 Thermal functional test procedures . 21
5.4 Thermal ageing sub-cycle . 27
5.5 Diagnostic sub-cycle . 27
5.6 Analyzing, reporting, and classification . 31
6 Electrical functional tests . 35
6.1 General aspects of electrical functional tests . 35
6.2 Test objects . 35
6.3 Electrical functional test procedures . 35
6.4 Analyzing and reporting . 37
7 Mechanical functional tests . 37
8 Environmental functional tests . 39
9 Multifactor functional tests . 39
Figure . 42
Annex A - Bibliographic references . 45
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SIST EN 60034-18-1:1999
34-18-1 © IEC - 5 -
INTERNATIONAL ELECTROTECHNICAL COMMISSION
FUNCTIONAL EVALUATION OF INSULATION SYSTEMS FOR
ROTATING ELECTRICAL MACHINES
Part 1: General guidelines
FOREWORD
1) 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.
2) They have the form of recommendations for international use and they are accepted by the National Committees in that
sense.
3) In order to promote international unification, the IEC expresses the wish that all National Committees should adopt the
text of the IEC recommendation for their national rules in so far as national conditions will permit. Any divergence
between the IEC recommendation and the corresponding national rules should, as far as possible, be clearly indicated
in the latter.
This part of International Standard IEC 34-18 has been prepared by Sub-Committee 2J:
Classification of insulation systems for rotating machinery, of IEC Technical Committee No. 2:
Rotating machinery.
The text of this part is based on the following documents:
Six Months’ Rule Report on Voting
2J(CO)4 2J(CO)8
Full information on the voting for the approval of this part can be found in the Voting Report
indicated in the above table.
Annex A is for information only.
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INTRODUCTION
IEC 34-18 comprises several parts:
Part 1: General guidelines
Part 2: Test procedures for wire-wound windings
Part 3: Test procedures for form-wound windings
Parts 2 and 3 are further divided into sub-parts, dealing with different types of functional
evaluation.
IEC 505 recognizes and defines all of the factors which might influence the time to end of life of
electrical equipment insulation. Those factors of influence causing ageing of the insulation are
considered to be thermal, electrical, environmental (ambient), and mechanical.
IEC 85 deals with thermal evaluation of insulating materials and insulation systems used
in electrical equipment. In particular, the thermal classes of insulation systems used in
rotating machines such as A, E, B, F and H, as well as the temperatures usually associated with
these thermal classes, are established in IEC 85. In the past, materials for insulation systems were
often selected solely on the basis of thermal endurance of individual materials.
However, the second edition of IEC 85 recognizes that such selection can be used only for
screening materials prior to further functional evaluation of a new insulation system which is not
service-proven. This evaluation is linked with earlier service experience through the use of a
service-proven reference insulation system as the basis for comparative evaluation. Service
experience is the preferred basis for assessing the thermal endurance of an insulation system.
IEC 611 describes the methodology based on the linear Arrhenius relationship (log life versus
reciprocal absolute temperature), to be used as a guide in the preparation of test procedures for
specific types of electromechanical products where the thermal ageing factor is considered to be
dominant.
IEC 727 deals with evaluation of electrical endurance of insulation systems.
IEC 791 gives instructions for evaluation of data from service experience and from functional tests.
IEC 792 describes general principles for multi-factor functional testing of insulation systems.
In the winding of an electrical machine, different factors of influence may be dominant in different
parts (e.g. turn insulation and end winding insulation). Therefore, different criteria may be
necessary to assess those parts of the insulation. It may also be appropriate to apply different
procedures of functional evaluation to these parts.
The large differences found in the rotating electrical machine windings, in terms of size, voltage
and operating conditions, necessitate the use of different procedures of functional evaluation to
evaluate various types of windings. These procedures may also be of different complexity, the
simplest being based on a single ageing mechanism (e.g. thermal or electrical). In the present
state of the art only thermal and electrical endurance testing procedures can be specified in some
detail. Principles of mechanical, environmental and multifactor functional testing are briefly
described to provide a basis for procedures to be developed later where appropriate.
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FUNCTIONAL EVALUATION OF INSULATION SYSTEMS FOR
ROTATING ELECTRICAL MACHINES
Part 1: General guidelines
1 Scope
This part of IEC 34-18 describes procedures for functional evaluation of electrical insulation
systems used or proposed to be used in rotating electrical machines within the scope of IEC 34-1,
and the classification of those insulation systems. This part (Part 1) provides general guidelines for
such procedures and classification principles, whereas the subsequent parts give detailed
procedures for the various types of windings.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute
provisions of this part of IEC 34-18. At the time of publication, the editions indicated were valid. All
standards are subject to revision, and parties to agreements based on this part of IEC 34-18 are
encouraged to investigate the possibility of applying the most recent editions of the standards
indicated below. Members of IEC and ISO maintain registers of currently valid International
Standards.
IEC 34-1: 1983, Rotating electrical machines - Part 1: Rating and performance.
IEC 60-2: 1973, High-voltage test techniques - Part 2: Test procedures.
IEC 85: 1984, Thermal evaluation and classification of electrical insulation.
IEC 216-1: 1987, Guide for the determination of thermal endurance properties of electrical
insulating materials - Part 1: General guidelines for ageing and evaluation of test results.
IEC 216-2: 1974, Guide for the determination of thermal endurance properties of electrical
insulating materials - Part 2: List of materials and available tests.
IEC 216-3: 1980, Guide for the determination of thermal endurance properties of electrical
insulating materials - Part 3: Statistical methods.
IEC 216-4: 1980, Guide for the determination of thermal endurance properties of electrical
insulating materials - Part 4: Instructions for calculating the thermal endurance profile.
IEC 493-1: 1974, Guide for the statistical analysis of ageing test data - Part 1: Methods based on
mean values of normally distributed test results.
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IEC 505: 1975, Guide for the evaluation and identification of insulation systems of electrical
equipment.
IEC 544-1: 1977, Guide for determining the effects of ionizing radiation on insulating materials -
Part 1: Radiation interaction.
IEC 544-2: 1979, Guide for determining the effects of ionizing radiation on insulating materials -
Part 2: Procedures for irradiation.
IEC 544-3: 1979, Guide for determining the effects of ionizing radiation on insulating materials -
Part 3: Test procedures for permanent effects.
IEC 544-4: 1985, Guide for determining the effects of ionizing radiation on insulating materials -
Part 4: Classification system for service in radiation environments.
IEC 610: 1978, Principal aspects of functional evaluation of electrical insulation systems: Ageing
mechanisms and diagnostic procedures.
IEC 611: 1978, Guide for the preparation of test procedures for evaluating the thermal endurance
of electrical insulation systems.
IEC 727-1: 1982, Evaluation of electrical endurance of electrical insulation systems - Part 1:
General considerations and evaluation procedures based on normal distributions.
IEC 792-1: 1985, The multi-factor functional testing of electrical insulation systems - Part 1: Test
procedures.
3 Definitions
For the purposes of this International Standard, the following definitions apply.
3.1 General terms
3.1.1 class temperature: The temperature for which the insulation system is suitable, as defined
by the thermal class in IEC 85.
3.1.2 insulation system: An insulating material, or an assembly of insulating materials, to be
considered in relation with associated conducting parts, as applied to a particular type or size or
part of electrical equipment (according to IEC 505).
NOTES
1 There may be several insulation components within the windings, each being designed for different stresses in
service, viz. turn insulation, slot insulation and end-winding insulation. Different criteria may be applied to the various
components within the overall system.
2 There may be more than one insulation system in a particular type of machine. These insulation systems may
have different thermal classes (e.g. stator and rotor windings).
3.1.3 candidate insulation system: The insulation system being tested to determine its capability
with respect to ageing factors (e.g. its thermal class).
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3.1.4 reference insulation system: An insulation system whose performance has been
established by satisfactory service experience.
3.1.5 coil: One or more turns of insulated conductors connected in series and surrounded by
common insulation, arranged to link or produce magnetic flux.
3.1.6 bar: One half of a form-wound coil (see 3.1.8), the two halves being joined after they have
been placed in their slots.
NOTE - Large a.c. machines commonly use bars, and usually, though not always, they form single-turn coils in a
two-layer winding.
3.1.7 wire-wound winding: A winding consisting of coils which are wound with one or several
insulated conductors. The coil is formed and insulated when it is wound and inserted into its final
place. It is usually random-wound with round conductors.
3.1.8 form-wound winding: A winding consisting of form-wound coils or bars which are
preformed to shape, insulated and substantially completed before they are inserted into their final
places. They are usually wound with rectangular conductors.
3.2 Terms relating to the objects being tested
3.2.1 test object: The unit being tested. It may be an actual machine, a machine component or a
test model (see 3.2.3, 3.2.4 and 3.2.5), which can be subjected to functional tests (see 3.4.2).
A test object may contain more than one test specimen (see 3.2.2).
3.2.2 test specimen: An individual component within a test object which can be used to
generate one piece of test data (e.g. time to failure). A test specimen may contain more than one
insulation component (e.g., turn insulation and conductor to earth insulation), any one of which
may provide that piece of data.
3.2.3 test model: A model representative of the actual machine or part thereof intended for use
in a functional test (see 3.4.2), according to IEC 505.
3.2.4 formette: A special test model used for the evaluation of the insulation systems for
form-wound windings.
3.2.5 motorette: A special test model used for the evaluation of the insulation systems for
wire-wound (random-wound) windings.
3.3 Terms relating to factors of influence
3.3.1 factor of influence: A stress or environmental influence which may affect the performance
of insulation in the machine during service.
3.3.2 ageing factor: A factor of influence which may produce ageing.
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3.4 Terms relating to testing and evaluation
3.4.1 diagnostic factor: A factor of influence applied to an insulation component of a test
specimen in order to establish its condition without significantly adding to the ageing.
3.4.2 functional test: A test in which the insulation system of a test object is exposed to ageing
factors and diagnostic factors simulating service conditions, in order to obtain information about
serviceability, including evaluation of test results.
3.4.3 endurance test: A test where changes in specific properties, produced by action of one or
several ageing factors, are determined, either through measurements or through proof tests, as
functions of time.
3.4.4 diagnostic test: A test in which a diagnostic factor is applied to a test specimen in order to
discern its condition and usually to aid in determining the end of its test life.
3.4.5 end-point criterion: A selected value of a characteristic of a test specimen indicating the
end of its test life, or arbitrarily chosen for the purpose of the comparison of insulation systems.
3.4.6 end-point: The end of a test as defined by the end-point criterion.
3.4.7 classification:
a) set of actions leading to determination of the class of an insulation system (e.g., thermal
class);
b) set of defined classes (e.g., thermal classes according to IEC 85).
4 General aspects of functional evaluation
All functional tests given in this standard are comparative. The performance of a candidate system
(an insulation system without proven service experience) is compared with that of a reference
system (a known system with proven service experience) when both are subjected to equivalent
test conditions with respect to test objects, methods of ageing and diagnostic tests.
4.1 Effects of ageing factors
All ageing factors, i.e. thermal, electrical, environmental, and mechanical, affect the life of all types
of machines, but the significance of each factor varies with the type of machine and the
expected duty.
In general, insulation of small machines is degraded primarily by temperature and environment,
with electrical and mechanical stresses being of less importance.
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Medium to large machines, using form-wound windings, are also affected by temperature and
environment but in addition the electrical and mechanical stresses may also be important ageing
factors.
Very large machines, which usually utilize bar-type windings and which may operate in an inert
environment such as hydrogen, are normally most affected by mechanical stresses or electrical
stresses or both. Temperature and environment may be less significant ageing factors.
4.2 Reference insulation system
As stated at the beginning of clause 4, functional testing is performed on a comparative basis.
Therefore, test results from a candidate system will be compared with results derived in the same
way from a reference system.
An insulation system qualifies to be used as a reference insulation system if:
- it has shown successful operation over suitably long periods of time at operating conditions
characteristic of the rating (or class) and in typical applications of that insulation system;
- its service experience is based on a statistically sufficient number of machines.
4.3 Functional tests
In clauses 5 to 8, general guidelines are given for thermal, electrical, mechanical, and
environmental functional tests. When more than one ageing factor is important, special tests
appropriate to the design and characteristics of the machine type in question may be devised.
General guidelines for such multifactor functional tests are given in clause 9.
Generally, the functional tests are performed in cycles, each cycle consisting of an ageing
sub-cycle and a diagnostic sub-cycle. In the ageing sub-cycle, the test specimens are exposed to
the specified ageing factor, intensified appropriately to accelerate ageing. In the diagnostic
sub-cycle, the test specimens are subjected to appropriate diagnostic tests to determine the end of
test life or to measure relevant properties of the insulation system at that time. In some cases, the
ageing factor itself may act as the diagnostic factor and produce the end-point.
If the design values for the candidate and reference systems differ, then, when technically justified,
appropriate different levels may be used for ageing factors or in the diagnostic tests or both.
Not all diagnostic tests indicated need be applied in all cases. Special considerations may
preclude or render inapplicable some diagnostic tests.
Suitable tests for specific applications may be agreed between manufacturer and user.
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5 Thermal functional tests
5.1 General aspects of thermal functional tests
The purpose of the thermal functional tests of this standard is to provide data which may be used
to establish the thermal class of a new insulation system before it is service-proven.
These guidelines are used in conjunction with other parts of this standard for the specific type
of winding being considered.
The concepts implemented herein are based on IEC 85, 505, 610 and 611.
The procedures will permit comparisons but cannot completely determine the merits of any
particular insulation system. Such information can be obtained only from extended service
experience.
The thermal ageing processes in rotating electrical machines may be complex in nature. Since
also the insulation systems of rotating machines are generally complicated in varying degrees,
simple systems referred to in IEC 85 may not exist in rotating machines.
5.1.1 Reference insulation system
A reference system (see 4.2) will be tested using the same test procedure as for the candidate
system.
All test procedures shall be equivalent, allowing for the fact that when the design values of the two
systems are different, then appropriate differences in temperatures, ageing sub-cycle lengths and
diagnostic tests may be necessary, when technically justified (see table 2).
5.2 Test objects and test specimens
5.2.1 Construction of test objects
It is expected that the various insulating materials or components making up any insulation system
to be evaluated by these test procedures will first be screened properly. Temperature indices for
insulating materials may be obtained by following the procedures outlined in IEC 216. However,
temperature indices of insulating materials cannot be used to classify insulation systems but are to
be considered only as indicators for the thermal functional tests for systems.
Wherever economics or the size of the machine, or both, warrant it, an actual machine or machine
component should be used as the test object. Usually this means that coils of full cross section,
with actual clearances and creepage distances are needed, though a reduced slot length may
be adequate.
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Test models, when used, shall contain all the essential elements employed in the windings they
simulate and shall be considered only as close approximations. Insulation thicknesses, creepage
distances and, where necessary, discharge protection, appropriate for the intended rated voltage
and equipment standards or practices, shall be used.
For large and high-voltage machines, test models representing a part of a coil or bar may be used,
when ageing specific for that part is investigated, provided that representative factors of influence
can be applied to the test specimens.
5.2.2 Number of test specimens
An adequate number of test specimens to obtain a good statistical average, shall be subjected to
the functional test procedure until failure occurs, for each chosen ageing temperature (see Parts 2
and 3).
5.2.3 Quality assurance tests
Each insulating material intended to be used in preparation of test objects should be subjected to
separate tests to establish uniformity and normality before it is used in assembly.
Each test specimen shall be subjected to the quality control tests of the normal or intended
production process.
5.2.4 Initial diagnostic tests
Each completed test object shall be subjected to all of the diagnostic tests selected to be used in
the thermal functional test (see 5.5) before starting the first thermal ageing sub-cycle, to establish
that each test specimen is capable of passing the selected diagnostic tests.
5.3 Thermal functional test procedures
5.3.1 General principles
Appropriate exposures to heat in repeated thermal ageing sub-cycles, which will impose thermal
degradation effects similar to those in service on insulation systems, on an accelerated basis are
specified in 5.3 and 5.4. The application of diagnostic tests such as mechanical, moisture and
voltage tests, to be applied after each thermal ageing sub-cycle to check the condition of the
insulation system is described in 5.5.
The evaluation of the deterioration of the insulation system due to thermal ageing may vary
depending on the size of the machine or the part of the winding of interest (e.g., end winding
or embedded slot section).
In many cases, experience has indicated that the best diagnostic evaluation of a thermally
degraded and thus usually brittle insulation system is obtained by exposure to mechanical stress,
thus producing cracks in the mechanically stressed parts, then exposure to moisture and finally
application of the test voltage.
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In other cases, mechanical stress, moisture exposure and application of voltage may not be the
best diagnostic tests. It may be appropriate to replace them by selected dielectric tests (e.g.,
measurement of partial discharge or loss tangent) to check the condition of the insulation after
each thermal ageing sub-cycle.
It should be realized that greater mechanical stress and higher concentration of the products of
decomposition may occur during ageing tests at higher than normal temperature. Also, it is
recognized that failures from abnormally high mechanical stress or voltage are generally of a
different character from those failures which are produced in long service.
If it is necessary to verify results in another laboratory it may be found that the actual numerical
test-life values differ unless the conditions in the original test are duplicated in extreme detail.
However, a comparison of results between qualified laboratories should show the same relative
performance differences between candidate and reference systems.
5.3.2 Ageing temperatures and sub-cycle lengths
5.3.2.1 Normal procedure
It is recommended that the tests be carried out on the number of specimens indicated
in subsequent parts of this standard for at least three different ageing temperatures.
The intended thermal class of the candidate insulation system as well as the known class of the
reference system shall be selected from table 1.
Table 2 lists the suggested ageing temperatures and corresponding periods of exposure in each
thermal ageing sub-cycle for insulation systems of the various thermal classes. Either time or
temperature may be adjusted to make the best use of facilities and staff but comparisons shall
take such variations into consideration. See 5.6.
The lowest ageing temperature selected should be such as to produce a log mean test life of about
5 000 h or more. In addition, at least two higher ageing temperatures should be selected,
separated by intervals of 20 K or more. Intervals of 10 K may be suitable when tests are made at
more than three ageing temperatures.
It is recommended that the lengths of ageing sub-cycles for the intended class temperature be
selected so as to give a mean life of about 10 cycles for each ageing temperature. (Table 2 is
constructed, based on experience, so that at each ageing temperature the mean test life will be
approximately 10 cycles of testing.)
5.3.2.2 Verification of effects of minor changes in insulation systems
It is recognized that from time to time in the manufacture of rotating machines, it will be necessary
to make minor changes in materials or the manufacturing process either for technological or
comm
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