Evaluation and qualification of electrical insulation systems

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.

Bewertung und Kennzeichnung von elektrischen Isoliersystemen

Evaluation et qualification des systèmes d'isolation électrique

La CEI 60505:2011 établit les bases de l'estimation du vieillissement des systèmes d'isolation électrique (SIE) dans des conditions de contraintes électriques, thermiques, mécaniques, environnementales ou de combinaisons de ces contraintes (contraintes multifactorielles). Elle spécifie les principes et les procédures qui doivent être suivis, au cours du développement d'essais fonctionnels ou de procédures d'évaluation des SIE, pour établir la durée de vie estimée d'un SIE spécifique. Il convient que tous les comités d'études de la CEI responsables de matériels ayant un SIE utilisent la présente norme. La principale modification par rapport à l'édition précédente est que l'Annexe A: Glossaire, est désormais disponible en version internet ainsi qu'en version imprimée. Cette version internet consiste en une version textuelle abrégée et un complément multimédia.

Vrednotenje in kvalificiranje električnih izolacijskih sistemov

Ta mednarodni standard vzpostavlja osnovo za ocenjevanje staranja električnih izolacijskih sistemov (EIA) pod pogoji električnega, toplotnega, mehanskega ali okoljskega stresa ali kombinacije navedenih (večfaktorski stresi) dejavnikov. Določa načela in postopke, ki se morajo upoštevati med razvojem postopkov funkcijskega preskušanja in vrednotenja EIS, da se oceni življenjska doba določenega EIS. Ta standard morajo uporabljati vsi tehnični odbori IEC, odgovorni za opremo, ki vsebuje EIS.

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6060 - National Implementation/Publication (Adopted Project)
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SIST EN 60505:2011
Evaluation and qualification of electrical insulation systems
Bewertung und Kennzeichnung von elektrischen Isoliersystemen
Evaluation et qualification des systèmes d'isolation électrique
Ta slovenski standard je istoveten z: EN 60505:2011
29.080.30 Izolacijski sistemi Insulation systems
SIST EN 60505:2011 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 60505:2011

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SIST EN 60505:2011

EN 60505

August 2011

ICS 29.080.30 Supersedes EN 60505:2004

English version

Evaluation and qualification of electrical insulation systems
(IEC 60505:2011)

Evaluation et qualification des systèmes Bewertung und Kennzeichnung von
d'isolation électrique elektrischen Isoliersystemen
(CEI 60505:2011) (IEC 60505:2011)

This European Standard was approved by CENELEC on 2011-08-15. 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 Central Secretariat 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 Central Secretariat 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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.

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

Management Centre: Avenue Marnix 17, B - 1000 Brussels

© 2011 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60505:2011 E

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SIST EN 60505:2011
EN 60505:2011 - 2 -
The text of document 112/174/FDIS, future edition 4 of IEC 60505, prepared by IEC TC 112, Evaluation
and qualification of electrical insulating materials and systems, was submitted to the IEC-CENELEC
parallel vote and approved by CENELEC as EN 60505:2011.
The following dates are fixed:
(dop) 2012-05-15
• latest date by which the document has
to be implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2014-08-15
standards conflicting with the
document have to be withdrawn

This document supersedes EN 60505:2004.

The main change with respect to EN 60505:2004 is that Annex A: Glossary is now available in an Internet
version (http://std.iec.ch/iec60505) as well as a hardcopy version. The internet version contains an
abridged text version and a multimedia supplement.

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

Endorsement notice
The text of the International Standard IEC 60505:2011 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:
IEC 60068-1 NOTE  Harmonized as EN 60068-1.
IEC 60068-2 series NOTE  Harmonized in EN 60068-2 series.
IEC 60068-2-1 NOTE  Harmonized as EN 60068-2-1.
IEC 60068-2-2 NOTE  Harmonized as EN 60068-2-2.
IEC 60068-2-10 NOTE  Harmonized as EN 60068-2-10.
IEC 60068-2-14 NOTE  Harmonized as EN 60068-2-14.
IEC 60068-2-27 NOTE  Harmonized as EN 60068-2-27.
IEC 60112 NOTE  Harmonized as EN 60112.
IEC 60212 NOTE  Harmonized as EN 60212.
IEC 60216 series NOTE  Harmonized in EN 60216 series.
IEC 60216-1 NOTE  Harmonized as EN 60216-1.
IEC 60243-1 NOTE  Harmonized as EN 60243-1.
IEC 60243-2 NOTE  Harmonized as EN 60243-2.
IEC 60243-3 NOTE  Harmonized as EN 60243-3.
IEC 60664-4 NOTE  Harmonized as EN 60664-4.
IEC 60270:2000 NOTE  Harmonized as EN 60270:2001 (not modified).

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SIST EN 60505:2011
- 3 - EN 60505:2011
IEC 60371-2 NOTE  Harmonized as EN 60371-2.
IEC 60587 NOTE  Harmonized as EN 60587.
IEC 60721 series NOTE  Harmonized in EN 60721 series.
IEC 60811-3-1 NOTE  Harmonized as EN 60811-3-1.
IEC 61033 NOTE  Harmonized as EN 61033.
IEC 61710 NOTE  Harmonized as EN 61710.
IEC 62231 NOTE  Harmonized as EN 62231.
IEC 62271-304 NOTE  Harmonized as CLC/TS 62271-304.
ISO 62 NOTE  Harmonized as EN ISO 62.
ISO 175 NOTE  Harmonized as EN ISO 175.
ISO 877-1 NOTE  Harmonized as EN ISO 877-1.
ISO 877-2 NOTE  Harmonized as EN ISO 877-2.
ISO 4611 NOTE  Harmonized as EN ISO 4611.

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SIST EN 60505:2011
EN 60505:2011 - 4 -
Annex ZA

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

Publication Year Title EN/HD Year

IEC 60216-2 - Electrical insulating materials - Thermal EN 60216-2 -
endurance properties -
Part 2: Determination of thermal endurance
properties of electrical insulating materials -
Choice of test criteria

IEC 60216-3 - Electrical insulating materials - Thermal EN 60216-3 -
endurance properties -
Part 3: Instructions for calculating thermal
endurance characteristics

IEC 60216-5 - Electrical insulating materials - Thermal EN 60216-5 -
endurance properties -
Part 5: Determination of relative thermal
endurance index (RTE) of an insulating

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 EN 60544-1 -
of the effects of ionizing radiation -
Part 1: Radiation interaction and dosimetry

IEC/TS 61251 - Electrical insulating materials - A.C. voltage - -
endurance evaluation - Introduction

IEC 62539 - Guide for the statistical analysis of electrical - -
insulation breakdown data

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SIST EN 60505:2011

IEC 60505

Edition 4.0 2011-07

Evaluation and qualification of electrical insulation systems

Évaluation et qualification des systèmes d'isolation électrique

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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SIST EN 60505:2011
– 2 – 60505 © IEC:2011
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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SIST EN 60505:2011
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 )
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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SIST EN 60505:2011
– 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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SIST EN 60505:2011
60505 © IEC:2011 – 5 –


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
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 that Annex A: Glossary is now
available in an Internet version (http://std.iec.ch/iec60505) as well as a hardcopy version. The
internet version contains an abridged text version and a multimedia supplement.
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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SIST EN 60505:2011
– 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.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.

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SIST EN 60505:2011
60505 © IEC:2011 – 7 –
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
– 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
SIST EN 60505:2011

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SIST EN 60505:2011
60505 © IEC:2011 – 9 –

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 follow

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