SIST IEC 60905:1997

IEC 60505
®

Edition 4.0 2011-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside


Evaluation and qualification of electrical insulation systems

Évaluation et qualification des systèmes d'isolation électrique
IEC 60505:2011

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IEC 60505
®

Edition 4.0 2011-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside


Evaluation and qualification of electrical insulation systems

Évaluation et qualification des systèmes d'isolation électrique

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX XC
ICS 29.080.30 ISBN 978-2-88912-539-5

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

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– 2 – 60505 © IEC:2011
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 9
2 Normative references . 9
3 Terms and definitions . 9
3.1 General terms . 10
3.2 Terms related to service stresses and ageing . 10
3.3 Terms related to testing . 11
4 Ageing . 12
4.1 Ageing mechanism . 12
4.2 Assessment of ageing mechanisms . 14
4.3 Electrical ageing . 15
4.4 Thermal ageing . 17
4.5 Mechanical ageing . 19
4.6 Environmental ageing . 21
4.7 Accelerated ageing . 22
4.8 Multifactor ageing . 23
5 Basic evaluation considerations . 23
5.1 Elements for preparing an evaluation method . 23
5.1.1 Object . 23
5.1.2 Service conditions . 23
5.1.3 Life values . 24
5.2 Types of evaluation procedures . 24
5.3 Choice of the test object . 26
5.4 Experimental test procedures . 26
5.5 Conclusions for standardization practices . 27
6 Functional ageing tests. 27
6.1 Test objects. 27
6.1.1 Construction of test objects . 27
6.1.2 Number of test objects . 28
6.1.3 Quality assurance tests . 28
6.1.4 Preconditioning subcycle . 28
6.1.5 Initial diagnostic tests . 28
6.1.6 Reference EIS . 28
6.2 Test conditions . 28
6.2.1 Continuous and cyclic testing . 28
6.2.2 Levels of test stresses, ageing factors and diagnostic factors . 29
6.3 Determination of EIS service life . 29
6.3.1 Extrapolation of life test results . 29
6.3.2 Comparison of life test data . 29
6.4 Diagnostics . 30
6.4.1 Diagnostic tests – End point criteria. 30
6.4.2 Additional specific tests . 31
6.5 Analysing the data . 31
6.6 Test report . 31
Annex A (informative) Glossary . 32

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60505 © IEC:2011 – 3 –
Bibliography . 71

Figure 1 – Ageing of an EIS . 13
Figure 2 – Intrinsic/extrinsic electrical ageing of practical EIS . 15
Figure 3 – Intrinsic/extrinsic thermal ageing of practical EIS . 17
Figure 4 – Intrinsic/extrinsic mechanical ageing of practical EIS . 20
Figure 5 – Intrinsic/extrinsic environmental ageing of practical EIS . 22
Figure 6 – Elements of evaluation methods . 23
Figure 7 – Type of evaluation procedure . 25
Figure 8 – Selection of test object . 26
Figure 9 – Establishing the test method . 27
Figure A.1 – Surface abrasion damage . 32
Figure A.2 – Surface enamel peeling like string . 32
Figure A.3 – Scheme of the measurement set-up for the charging/discharging current . 33
Figure A.4 – Example of sample preparation . 33
Figure A.5 – Charging/discharging current on HDPE film . 34
Figure A.6 – Property versus time behaviour, detection of threshold (end point, p )
L
and maintenance time . 35
Figure A.7 – Correspondence between the ageing plots of the property p (in red),
obtained at different stress levels, and the resulting life line . 35
Figure A.8 – Example of charge injection of positive carriers (holes) from the anode
and of negative charge carriers (electrons) from the cathode in a PE flat specimen,
detected by space charge measurement performed by PEA method . 36
Figure A.9 – Stress-strain curve for a typical material . 37
Figure A.10 – Scheme of measurement set- up for charging/discharging current . 38
Figure A.11 – Example of sample preparation . 38
Figure A.12 – Charging/discharging current on HDPE film . 38
Figure A.13 – Charging current at 135 °C and different values of DC electrical field . 39
Figure A.14 – Charging current at 120 °C and different values of DC electrical field . 39
Figure A.15 – Corona at post insulator head . 40
Figure A.16 – Corona on top and arcing to ground . 40
Figure A.17 – Stages of mechanical ductile fracture (cracking) (Source unknown) . 41
Figure A.18 – Photo showing orderings in epoxy structure and void . 42
Figure A.19 – Discharge between conductors through air. 44
Figure A.20 – Paper insulation degraded by electrical surface discharges . 44
Figure A.21 – Example of electric strength test on XLPE sample 0,2 mm thick . 45
Figure A.22 – Two parameters Weibull plot electric strength results performed on
seven XLPE specimens, 0,2 mm thick . 45
Figure A.23 – Loss angle of a dielectric . 47
Figure A.24 – Loss factor for pre-treated and thermally aged (at 110 °C and 130 °C)
XLPE cables measured at 90 °C plotted vs. frequency . 47
Figure A.25 – Field lines from a positive charge above a plane conductor . 48
Figure A.26 – Electrical tree. 49
Figure A.27 – EPDM ashing and erosion on fitting . 50
Figure A.28 – Failing external insulation . 51

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– 4 – 60505 © IEC:2011
Figure A.29 – Failing external insulation . 51
Figure A.30 – Critical failure of solid cable insulation (XLPE) by electrical breakdown . 52
Figure A.31 – Example flashover . 53
Figure A.32 – Substation – Outdoor installation . 54
Figure A.34 – Internal interfaces in epoxy structure and void . 56
Figure A.35 – Example of craze and crack development in an inter-lamellar space
under mechanical tension T . 57
Figure A.36 – Water treeing . 58
Figure A.37 – After 11 years in service UV and moisture impact . 59
Figure A.38 – Random (amorphous) structure of a molecular chain . 59
Figure A.39 – Oriented structure (semi-crystalline) of a molecular chain . 59
Figure A.40 – Typical morphology of melt-grown polyethylene spherulites . 60
Figure A.41 – Areas in which PD generally occur . 61
Figure A.42 – Classes of defect – Internal, surface and corona PD . 61
Figure A.43 – Basic PD measurement circuit . 62
Figure A.44 – Examples of PD patterns relevant to internal, surface and corona PD . 62
Figure A.45 – GIS research – Metal conductor protrusion . 63
Figure A.46 – Internally strained epoxy – Frozen in strains in epoxy resin due to
thermal stress, measured by TMA curves . 64
Figure A.47 – Externally strained parts in an on-load tap changer (OLTC) . 64
Figure A.48 – A material being loaded in a) compression, b) tension, c) shear . 65
Figure A.49 – Effect of thermal-mechanical stresses leading to interfacial electrical
tracking . 66
Figure A.50 – Stress-strain curve for a typical material . 66
Figure A.51 – Over crimped rod; breaks during tensile test . 67
Figure A.52 – Typical installation fault . 68
Figure A.53 – Surface tracking on sheds and fitting end . 68
Figure A.54 – Vented trees – Initiate at interface . 69
Figure A.55 – Tape wrinkling . 70

Table 1 – Ageing temperatures . 19
Table 2 – Cyclical and continuous procedures . 30

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60505 © IEC:2011 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________

EVALUATION AND QUALIFICATION
OF ELECTRICAL INSULATION SYSTEMS

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
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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 60505 has been prepared by IEC technical committee 112:
Evaluation and qualification of electrical insulating materials and systems.
This fourth edition cancels and replaces the third edition, published in 2004, and constitutes a
technical revision.
The main change with respect to the previous edition is the addition of a Glossary in the form
of Annex A to this standard.
The text of this standard is based on the following documents:
FDIS Report on voting
112/174/FDIS 112/184/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.

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– 6 – 60505 © IEC:2011
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.
The contents of the corrigendum of March 2017 have been included in this copy.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
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60505 © IEC:2011 – 7 –
INTRODUCTION
The life of an electrical insulation system (EIS) or systems frequently determines the life of
electrical equipment which can be affected by electrical, thermal, mechanical or
environmental stresses acting either individually or in combination.
Intended, estimated or proven service life times are essential parameters for describing the
life of electrical insulation systems. In the early days of electrotechnical engineering, life
figures were rather vague. The limitation of the life of the insulation under thermal stress was
one of the first indicators of the effect of ageing in some equipment in service. As experience
in using EIS increased, it was appreciated that there was a need to select specific materials
having satisfactory life time at a given temperature, to enable the required service life to be
achieved and to allow for the calculation of the thermal capability of equipment.
The user of this standard may evaluate existing test methods and provide correlation with his
equipment. Therefore, the user of this standard is responsible for demonstrating the validity of
the existing test method in accordance with the principles of this standard.
The determination of the prospective life is a fundamental task when developing and
designing an EIS. Estimated service life of an EIS needs to be established for several
reasons:
– for type testing when introducing a new EIS into production;
– for quality assurance of production;
– for estimating the life expectancy of new equipment;
– for estimating the remaining life for maintenance purposes.
“Ageing” focuses on the mechanisms affecting the EIS performance. “Evaluation” links these
potential mechanisms by “Analysis” and “Diagnostics” to the design of a specific kind of
evaluation test procedure.
The keyword structure below meets such requirements and allows an easier choice of the
parts of interest.

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– 8 –                60505 © IEC:2011

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60505 © IEC:2011 – 9 –
EVALUATION AND QUALIFICATION
OF ELECTRICAL INSULATION SYSTEMS



1 Scope
This International Standard establishes the basis for estimating the ageing of electrical
insulation systems (EIS) under conditions of either electrical, thermal, mechanical,
environmental stresses or combinations of these (multifactor stresses).
It specifies the principles and procedures that shall be followed, during the development of
EIS functional test and evaluation procedures, to establish the estimated service life for a
specific EIS.
This standard should be used by all IEC technical committees responsible for equipment
having an EIS.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60216-2, Electrical insulating materials – Thermal endurance properties – Part 2:
Determination of thermal endurance properties of electrical insulating materials – Choice of
test criteria
IEC 60216-3, Electrical insulating materials – Thermal endurance properties – Part 3:
Instructions for calculating thermal endurance characteristics
IEC 60216-5, Electrical insulating materials – Thermal endurance properties – Part 5:
Determination of relative thermal endurance index (RTE) of an insulating material
IEC 60493-1, Guide for the statistical analysis of ageing test data – Part 1: Methods based on
mean values of normally distributed test results
IEC 60544-1, Electrical insulating materials – Determination of the effects of ionizing radiation
– Part 1: Radiation interaction and dosimetry
IEC/TS 61251, Electrical insulating materials – AC voltage endurance evaluation –
Introduction
IEC 62539, Guide for the statistical analysis of electrical insulation breakdown data
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

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– 10 – 60505 © IEC:2011
3.1 General terms
3.1.1
electrical insulation system
EIS
insulating structure containing one or more electrical insulating materials (EIM) together with
associated conducting parts employed in an electrotechnical device
3.1.2
electrical insulating material
EIM
material with negligibly low electric conductivity, used to separate conducting parts at different
electrical potentials
[IEC 60050-212:2010, 212-11-01, modified]
3.1.3
reference EIS
established EIS evaluated on the basis of either a known service experience record or a
known comparative functional evaluation
3.1.4
candidate EIS
EIS under evaluation to determine its service capability (with regard to electrical, thermal,
mechanical, environmental or multifactor stresses)
3.1.5
intended life
design life of an EIS under service conditions
3.1.6
estimated life
expected service life derived from either service experience or the results of tests performed
in accordance with appropriate evaluation procedures, or both, as established by the
responsible organization or technical committee
3.1.7
evaluation
establishment of rela
...