IEC 60243-1:2013

IEC 60243-1 ®
Edition 3.0 2013-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electric strength of insulating materials – Test methods –
Part 1: Tests at power frequencies

Rigidité diélectrique des matériaux isolants – Méthodes d'essai –
Partie 1: Essais aux fréquences industrielles

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester.
If you have any questions about IEC copyright or have an enquiry about obtaining additional rights to this publication,
please contact the address below or your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite ni
utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie et les
microfilms, sans l'accord écrit de la CEI ou du Comité national de la CEI du pays du demandeur.
Si vous avez des questions sur le copyright de la CEI ou si vous désirez obtenir des droits supplémentaires sur cette
publication, utilisez les coordonnées ci-après ou contactez le Comité national de la CEI de votre pays de résidence.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé Fax: +41 22 919 03 00
CH-1211 Geneva 20 info@iec.ch
Switzerland www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

Useful links:
IEC publications search - www.iec.ch/searchpub Electropedia - www.electropedia.org
The advanced search enables you to find IEC publications The world's leading online dictionary of electronic and
by a variety of criteria (reference number, text, technical electrical terms containing more than 30 000 terms and
committee,…). definitions in English and French, with equivalent terms in
It also gives information on projects, replaced and additional languages. Also known as the International
withdrawn publications. Electrotechnical Vocabulary (IEV) on-line.

IEC Just Published - webstore.iec.ch/justpublished Customer Service Centre - webstore.iec.ch/csc
Stay up to date on all new IEC publications. Just Published If you wish to give us your feedback on this publication
details all new publications released. Available on-line and or need further assistance, please contact the
also once a month by email. Customer Service Centre: csc@iec.ch.

A propos de la CEI
La Commission Electrotechnique Internationale (CEI) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications CEI
Le contenu technique des publications de la CEI est constamment revu. Veuillez vous assurer que vous possédez
l’édition la plus récente, un corrigendum ou amendement peut avoir été publié.

Liens utiles:
Recherche de publications CEI - www.iec.ch/searchpub Electropedia - www.electropedia.org
La recherche avancée vous permet de trouver des Le premier dictionnaire en ligne au monde de termes
publications CEI en utilisant différents critères (numéro de électroniques et électriques. Il contient plus de 30 000
référence, texte, comité d’études,…). termes et définitions en anglais et en français, ainsi que
Elle donne aussi des informations sur les projets et les les termes équivalents dans les langues additionnelles.
publications remplacées ou retirées. Egalement appelé Vocabulaire Electrotechnique
International (VEI) en ligne.
Just Published CEI - webstore.iec.ch/justpublished
Service Clients - webstore.iec.ch/csc
Restez informé sur les nouvelles publications de la CEI.
Just Published détaille les nouvelles publications parues. Si vous désirez nous donner des commentaires sur
Disponible en ligne et aussi une fois par mois par email. cette publication ou si vous avez des questions
contactez-nous: csc@iec.ch.
IEC 60243-1 ®
Edition 3.0 2013-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electric strength of insulating materials – Test methods –

Part 1: Tests at power frequencies

Rigidité diélectrique des matériaux isolants – Méthodes d'essai –

Partie 1: Essais aux fréquences industrielles

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX U
ICS 17.220.99; 29.035.01 ISBN 978-2-83220-696-6

– 2 – 60243-1 © IEC:2013
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Significance of the test . 7
5 Electrodes and specimens . 8
5.1 General . 8
5.2 Tests perpendicular to the surface of non-laminated materials and normal to
laminate of laminated materials . 8
5.2.1 Boards and sheet materials, including pressboards, papers, fabrics
and films . 8
5.2.2 Tapes, films and narrow strips . 9
5.2.3 Flexible tubing and sleeving . 9
5.2.4 Rigid tubes (having an internal diameter up to and including 100 mm) . 9
5.2.5 Tubes and hollow cylinders (having an internal diameter greater than
100 mm) . 10
5.2.6 Cast and moulded materials . 10
5.2.7 Shaped solid pieces . 11
5.2.8 Varnishes . 11
5.2.9 Filling compounds . 11
5.3 Tests parallel to the surface of non-laminated materials and parallel to the
laminate of laminated materials . 11
5.3.1 General . 11
5.3.2 Parallel plate electrodes . 11
5.3.3 Taper pin electrodes . 12
5.3.4 Parallel cylindrical electrodes . 12
5.4 Test specimens . 12
5.5 Distance between electrodes . 12
6 Conditioning before tests . 13
7 Surrounding medium . 13
7.1 General . 13
7.2 Tests in air at elevated temperature . 13
7.3 Tests in liquids . 13
7.4 Tests in solid materials . 14
8 Electrical apparatus . 14
8.1 Voltage source . 14
8.2 Voltage measurement . 14
9 Procedure. 15
10 Mode of increase of voltage . 15
10.1 Short-time (rapid-rise) test . 15
10.2 20 s step-by-step test . 16
10.3 Slow rate-of-rise test (120 s. 240 s) . 16
10.4 60 s step-by-step test . 17
10.5 Very slow rate-of-rise test (300 s. 600 s) . 17
10.6 Proof tests . 17
11 Criterion of breakdown . 17
12 Number of tests . 18

60243-1 © IEC:2013 – 3 –
13 Report . 18
Annex A (informative) Treatment of experimental data . 25
Bibliography . 26

Figure 1 – Electrode arrangements for tests on boards and sheets perpendicular to the
surface . 19
Figure 2 – Typical example of electrode arrangement for tests on tapes perpendicular
to the surface (see 5.2.2) . 20
Figure 3 – Electrode arrangement for tests perpendicular to the surface on tubes and
cylinders with internal diameter greater than 100 mm. 20
Figure 4 – Electrode arrangement for tests on casting and moulding materials
(diameter of the spherical electrodes: d = (20 ± 0,1) mm) . 21
Figure 5 – Electrode arrangement for test on shaped insulating parts (see 5.2.7) . 21
Figure 6 – Electrode arrangement for tests parallel to the surface (and along the
laminae, if present) . 22
Figure 7 – Electrode arrangement for tests parallel to the surface (and along the
laminae if present) . 23
Figure 8 – Arrangement for tests parallel to the laminae for boards more than 15 mm
thick with parallel cylindrical electrodes (see 5.3.4) . 24

Table 1 – Increments of voltage increase (kilovolts, peak / ) . 16
– 4 – 60243-1 © IEC:2013
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRIC STRENGTH OF INSULATING MATERIALS –
TEST METHODS –
Part 1: Tests at power frequencies

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60243-1 has been prepared by technical committee 112:
Evaluation and qualification of electrical insulating materials and systems.
This third edition cancels and replaces the second edition, published in 1998, and constitutes
a technical revision.
The significant technical change with respect to the previous edition is that the current version
now includes an option for testing elastomeric materials.
The text of this standard is based on the following documents:
FDIS Report on voting
112/237/FDIS 112/248/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.

60243-1 © IEC:2013 – 5 –
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 60243 series, published under the general title Electric
strength of insulating materials – Test methods, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – 60243-1 © IEC:2013
ELECTRIC STRENGTH OF INSULATING MATERIALS –
TEST METHODS –
Part 1: Tests at power frequencies

1 Scope
This part of IEC 60243 provides test methods for the determination of short-time electric
strength of solid insulating materials at power frequencies between 48 Hz and 62 Hz.
This standard does not cover the testing of liquids and gases, although these are specified
and used as impregnates or surrounding media for the solid insulating materials being tested.
NOTE Methods for the determination of breakdown voltages along the surfaces of solid insulating materials are
included.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60212, Standard conditions for use prior to and during the testing of solid electical
insulating materials
IEC 60296, Fluids for electrotechnical applications – Unused mineral insulating oils for
transformers and switchgear
IEC 60455-2, Specification for solventless polymerizable resinous compounds used for
electrical insulation – Part 2: Methods of test
IEC 60464-2, Varnishes used for electrical insulation – Part 2: Methods of test
IEC 60684-2, Flexible insulating sleeving – Part 2: Methods of test
IEC 60836, Specifications for unused silicone insulating liquids for electrotechnical purposes
IEC 61099, Insulating liquids – Specifications for unused synthetic organic esters for electrical
purposes
ISO 293, Plastics – Compression moulding of test specimens of thermoplastic materials
ISO 294-1, Plastics – Injection moulding of test specimens of thermoplastic materials – Part 1:
General principles, and moulding of multipurpose and bar test specimens
ISO 294-3, Plastics – Injection moulding of test specimens of thermoplastic materials – Part 3:
Small plates
ISO 295, Plastics – Compression moulding of test specimens of thermosetting materials

60243-1 © IEC:2013 – 7 –
ISO 10724 (all parts), Plastics – Injection moulding of test specimens of thermosetting powder
moulding compounds (PMCs)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
electric breakdown
severe loss of the insulating properties of test specimens while exposed to electric stress,
which causes the current in the test circuit to operate an appropriate circuit-breaker
Note 1 to entry: Breakdown is often caused by partial discharges in the gas or liquid medium surrounding the test
specimen and the electrodes which puncture the specimen beyond the periphery of the smaller electrode (or of
both electrodes, if of equal diameter).
3.2
flashover
loss of the insulating properties of the gas or liquid medium surrounding a test specimen and
electrodes while exposed to electric stress, which causes the current in the test circuit to
operate an appropriate circuit-breaker
Note 1 to entry: The presence of carbonized channels or punctures through the specimen distinguishes tests
where breakdown occurred, from others where flashover occurred.
3.3
breakdown voltage
3.3.1
< tests with continuously rising voltage > voltage at which a specimen suffers breakdown
under the prescribed test conditions
3.3.2
< step-by-step tests > highest voltage which a specimen withstands without breakdown for the
duration of the time at that voltage level
3.4
electric strength
quotient of the breakdown voltage and the distance between the electrodes between which
the voltage is applied under the prescribed test conditions
Note 1 to entry: The distance between the test electrodes is determined as specified in 5.5, unless otherwise
specified.
4 Significance of the test
Electric strength test results obtained in accordance with this standard are useful for detecting
changes or deviations from normal characteristics resulting from processing variables, ageing
conditions or other manufacturing or environmental situations. However, they are not intended for
use in evaluating the behaviour of insulating materials in an actual application.
Measured values of the electric strength of a material may be affected by many factors,
including:
a) Condition of test specimens
1) the thickness and homogeneity of the specimen and the presence of mechanical strain;
2) previous conditioning of the specimens, in particular drying and impregnation
procedures;
– 8 – 60243-1 © IEC:2013
3) the presence of gaseous inclusions, moisture or other contamination.
b) Test conditions
1) the frequency, waveform and rate of rise or time of application of the voltage;
2) the ambient temperature, pressure and humidity;
3) the configuration, the dimensions, and thermal conductivity of the test electrodes;
4) the electrical and thermal characteristics of the surrounding medium.
The effects of all these factors shall be considered when investigating materials for which no
experience exists. This standard defines particular conditions which give rapid discrimination
between materials and which can be used for quality control and similar purposes.
The results given by different methods are not directly comparable but each may provide
information on relative electric strengths of materials. The electric strength of most materials
decreases as the thickness of the specimen between the electrodes increases and as the time
of voltage application increases.
The measured electric strength of most materials is significantly affected by the intensity and
the duration of surface discharges prior to breakdown. For designs which are free from partial
discharges up to the test voltage, it is very important to know the electric strength without
discharges prior to breakdown. However, the methods in this standard are generally not
suitable for providing this information.
Materials with high electric strength will not necessarily resist long-term degradation
processes such as heat, erosion or chemical deterioration by partial discharges, or
electrochemical deterioration in the presence of moisture, all of which may cause failure in
service at much lower stress.
5 Electrodes and specimens
5.1 General
The metal electrodes shall be maintained smooth, clean and free from defects at all times.
Electrode arrangements for tests on boards and sheets perpendicular to the surface are
shown in Figure 1.
NOTE This maintenance becomes more important when thin specimens are being tested. Stainless steel
electrodes e.g. minimize electrode damage at breakdown.
The leads to the electrodes shall not tilt or otherwise move the electrodes, nor affect the
pressure on the specimen, nor appreciably affect the electric field configuration in the
neighbourhood of the specimen.
When very thin films (for example <5 μm thick) are to be tested, the standards for those
materials shall specify the electrodes and special procedures for handling and specimen
preparation.
5.2 Tests perpendicular to the surface of non-laminated materials and normal to
laminate of laminated materials
5.2.1 Boards and sheet materials, including pressboards, papers, fabrics and films
5.2.1.1 Unequal electrodes
The electrodes shall consist of two metal cylinders with the edges rounded to give a radius of
(3 ± 0,2) mm. One electrode shall be (25 ± 1) mm in diameter and approximately 25 mm high.
The other electrode shall be (75 ± 1) mm in diameter and approximately 15 mm high. These
two electrodes shall be arranged coaxially within 2 mm as in Figure 1a.

60243-1 © IEC:2013 – 9 –
NOTE Radii for surface not in contact with the electrode are not critical with respect to test results but should
avoid partial discharges in the surrounding medium.
5.2.1.2 Equal diameter electrodes
If a fixture is employed, which accurately aligns upper and lower electrodes within 1,0 mm,
the diameter of the lower electrode may be reduced to (25 ± 1) mm, the diameters of the two
electrodes differing by no more than 0,2 mm. The results obtained will not necessarily be the
same as those obtained with the unequal electrodes of 5.2.1.1.
5.2.1.3 Sphere and plate electrodes
The electrodes shall consist of a metal sphere and a metal plate (see Figure 1c). The upper
electrode shall be a sphere of (20 ± 1) mm in diameter and the lower one is a metal plate of
(25 ± 1) mm in diameter with the edge rounded to give a radius of 2.5 mm. The discrepancy of
the central axes between upper and lower electrodes shall be within 1 mm.
5.2.1.4 Tests on thick sample
When specified, boards and sheets over 3 mm thick shall be reduced by machining on one
side to (3 ± 0,2) mm and then tested with the high-potential electrode on the non-machined
surface.
When it is necessary in order to avoid flashover or because of limitations of available
equipment, specimens may be prepared by machining to smaller thicknesses as needed.
5.2.2 Tapes, films and narrow strips
The electrodes shall consist of two metal rods, each (6 ± 0,1) mm in diameter, mounted
vertically one above the other in a jig so that the specimen is held between the faces of the
ends of the rods.
The upper and lower electrodes shall be coaxial within 0,1 mm. The ends of the electrodes
shall form planes at right angles to their axes, with edge radii of (1 ± 0,2) mm. The upper
electrode shall have a mass of (50 ± 2) g and shall move freely in the vertical direction in
the jig.
Figure 2 shows an appropriate arrangement. If specimens are to be tested while extended,
they shall be clamped in a frame holding them in the required position relative to the
assembly shown in Figure 2. Wrapping one end of the specimen around a rotatable rod is one
convenient way of achieving the required extension.
To prevent flashover around the edges of narrow tapes, the test specimen may be clamped
using strips of film or other thin dielectric material overlapping the edges of the tape.
Alternatively, gaskets that surround the electrodes may be used, provided that there is an
annular space between electrode and gasket of 1 mm to 2 mm. The distance between the
bottom electrode and the specimen (before the top electrode comes in contact with the
specimen) shall be less than 0,1 mm.
NOTE For testing films see IEC 60674-2.
5.2.3 Flexible tubing and sleeving
To be tested according to IEC 60684-2.
5.2.4 Rigid tubes (having an internal diameter up to and including 100 mm)
The outer electrode shall consist of a band of metal foil (25 ± 1) mm wide. The inner electrode
is a closely fitting internal conductor, e.g. rod, tube, metal foil or a packing of metal spheres

– 10 – 60243-1 © IEC:2013
0,75 mm to 2 mm in diameter, making good contact with the inner surface. In each case, the
ends of the inner electrode shall extend for at least 25 mm beyond the ends of the outer
electrode.
Where no adverse effect will result, petroleum jelly may be used for attaching the foil to the
inner and outer surfaces.
5.2.5 Tubes and hollow cylinders (having an internal diameter greater than 100 mm)
The outer electrode shall be a band of metal foil (75 ± 1) mm wide and the inner electrode, a
disk of metal foil (25 ± 1) mm in diameter, flexible enough to conform with the curvature of the
cylinder. The arrangement is shown in Figure 3.
5.2.6 Cast and moulded materials
5.2.6.1 Cast materials
Make test pieces and test according to IEC 60455-2.
5.2.6.2 Moulded materials
5.2.6.2.1 General
Use a pair of spherical electrodes, each (20 ± 0,1) mm in diameter, arranged on a common
axis which is normal to the plane of the test specimen (see Figure 4) or, in case of
elastomers, unequal electrodes according to 5.2.1.3 (see Figure 1c) .
5.2.6.2.2 Thermosets
Use test specimens of (1,0 ± 0,1) mm thickness, compression moulded in accordance with
ISO 295; or injection moulded in accordance with the ISO 10724 series with lateral
dimensions which are sufficient to prevent flashover (see 5.4).
If it is not possible to use specimens of (1,0 ± 0,1) mm thickness, specimens with a thickness
of (2,0 ± 0,2) mm shall be used.
5.2.6.2.3 Thermoplastics
Use test specimens injection moulded in accordance with ISO 294-1 and ISO 294-3,
ISO mould type D1 60 mm × 60 mm × 1 mm. If these dimensions are insufficient to prevent
flashover (see 5.4) or if compression moulded test specimens are stipulated by the standard
for the relevant material, use plates at least 100 mm in diameter and (1,0 ± 0,1) mm thick,
compression moulded in accordance with ISO 293.
For the conditions of injection or compression moulding, see the standard for the relevant
material. If there is no applicable material standard, the conditions shall be agreed between
the interested parties.
5.2.6.2.4 Elastomers
Use test specimens of (1,0 ± 0,1) mm thickness with sufficient lateral dimensions to prevent
flashover (see 5.4), moulded under standard conditions. If there is no effective standard the
processing conditions shall be agreed between the interested parties.
As electrode arrangement, unequal electrodes according 5.2.1.3 (see Figure 1c) shall be
used. In the case of elastomers of low hardness, e.g. silicone rubbers, a suitable casting
material shall be used as embedding material or surrounding medium, respectively.

60243-1 © IEC:2013 – 11 –
5.2.7 Shaped solid pieces
For shaped insulating specimens which do not have sufficient contact with the electrode’s flat contact
surface, the opposing identical spherical electrodes shall be used (see Figure 5). Commonly used
electrodes for tests of this nature have diameters of 12,5 mm or 20 mm.
5.2.8 Varnishes
To be tested according to IEC 60464-2.
5.2.9 Filling compounds
The electrodes shall consist of two metal spheres, each 12,5 mm to 13 mm in diameter,
arranged horizontally along the same axis (1 ± 0,1) mm apart, unless otherwise specified, and
embedded in the compound. Care shall be taken to avoid cavities, particularly between the
electrodes. As values obtained with the different electrode spacing are not directly
comparable, the gap length shall be detailed in the specification for the compound and
mentioned in the test report.
5.3 Tests parallel to the surface of non-laminated materials and parallel to the
laminate of laminated materials
5.3.1 General
If it is not necessary to differentiate between failure by puncture of the specimen and failure
across its surface, the electrodes of 5.3.2 or 5.3.3 may be used, those of 5.3.2 being
preferred.
When the prevention of surface failure is required, the electrodes of 5.3.3 shall be used.
5.3.2 Parallel plate electrodes
5.3.2.1 Boards and sheets
For tests on boards and sheets, the test specimen shall be of the thickness of the material to
be tested and rectangular, (100 ± 2) mm long and (25 ± 0,2) mm wide. The long edges shall
be cut as parallel planes at right angles to the surface of the material. The test specimen is
placed with the 25 mm width between parallel metal plates, not less than 10 mm thick, forming
the electrodes between which the voltage shall be applied. For thin materials, two or three
test specimens are used suitably placed (i.e. with their long edges at a convenient angle) to
support the upper electrode. The electrodes shall be of sufficient size to overlap the edges of
the test specimens by not less than 15 mm and care shall be taken to ensure good contact
over the whole area of those edges. The edges of the electrodes shall be suitably rounded
(3 mm to 5 mm) to avoid breakdown from edge to edge of the electrodes (see Figure 6).
If breakdown cannot be obtained with available equipment, the width of the specimens may be
reduced to (15 ± 0,2) mm or (10 ± 0,2) mm. Such reduction of specimen width shall be
specifically recorded in the test report.
This type of electrode is suitable only for tests on rigid materials at least 1,5 mm thick.
5.3.2.2 Tubes and cylinders
For tests on tubes and cylinders, the test specimen shall be a complete ring or a 100 mm
circumferential portion of a ring of (25 ± 0,2)mm axial length. Both edges of the specimen
shall be finished as parallel planes at right angles to the axis of the tube or cylinder. The
specimen is tested between parallel plates as described in 5.3.2.1 for boards and sheets.
Where necessary to support the upper electrode, two or three specimens are used. The
electrodes shall be of sufficient size to overlap the edges of the specimens by not less than

– 12 – 60243-1 © IEC:2013
15 mm and care shall be taken to ensure good contact over the whole area of the edges of
the specimens.
5.3.3 Taper pin electrodes
Two parallel holes are drilled perpendicularly to the surface, with centres (25 ± 1) mm apart
and of such a diameter that, after reaming with a reamer having a taper of approximately 2 %,
the diameter of each hole at the larger end is not less than 4,5 mm and not greater than
5,5 mm.
The holes shall be drilled completely through the specimen or, in the case of large tubes,
through one wall only, and shall be reamed throughout their full length.
When the specimens are drilled and reamed, the material adjacent to the holes shall not be
damaged, e.g. split, broken or charred, in any way.
The taper pins used as electrodes shall have a taper of (2 ± 0,02) % and shall be pressed, not
hammered into the holes so that they fit tightly and extend on each side of the test specimen
by not less than 2 mm (see Figure 7, 7a and 7b).
This type of electrode is suitable only for tests on rigid materials at least 1,5 mm thick.
5.3.4 Parallel cylindrical electrodes
For tests on specimens of high electric strength and which are more than 15 mm thick,
specimens 100 mm × 50 mm shall be cut and two holes drilled as shown in Figure 8 so that
each is not more than 0,1 mm greater in diameter than each cylindrical electrode which shall
be (6 ± 0,1) mm in diameter and have hemispherical ends. The base of each hole is
hemispherical to mate with the end of the electrode, so that the gap between the end of the
electrode and the base of the hole will not exceed 0,05 mm at any point. If not otherwise
specified in the material specification, the holes shall be (10 ± 1) mm apart, edge-to-edge,
throughout their length and extend to within (2,25 ± 0,25) mm of the surface opposite that
through which they are drilled. Two alternative forms of vented electrodes are shown in
Figure 8. When electrodes with slots are used, these slots shall be diametrically opposed to
the gap between the electrodes.
5.4 Test specimens
In addition to the information concerning specimens given in the preceding subclauses, the
following general points shall be noted.
In the preparation of test specimens from solid materials, care shall be taken that the surfaces
in contact with the electrodes are parallel and as flat and smooth as the material allows.
For tests made perpendicularly to the surface of the material, test specimens need only be of
sufficient area to prevent flashover under the conditions of test.
In tests made perpendicularly to the surface of the material, the results on specimens of
different thicknesses are not directly comparable (see Clause 4).
5.5 Distance between electrodes
The value to be used in calculating the electric strength shall be one of the following, as
specified for the material under test:
a) nominal thickness or distance between electrodes (use this value unless otherwise
specified);
60243-1 © IEC:2013 – 13 –
b) average thickness of the test specimen or distance between electrodes for tests parallel to
the surface;
c) thickness or distance between electrodes measured immediately adjacent to the
breakdown on each test specimen.
6 Conditioning before tests
The electric strength of insulating materials varies with temperature and moisture content.
Where a specification is available for the material to be tested, this shall be followed.
Otherwise, specimens shall be conditioned for not less than 24 h at (23 ± 2) °C, (50 ± 5) %
relative humidity, that is, the standard ambient atmosphere of IEC 60212, unless other
conditions are agreed upon.
7 Surrounding medium
7.1 General
Materials shall be tested in a surrounding medium selected to prevent flashover. Suitable
materials may be transformer oil according to IEC 60296, silicone fluid according to
IEC 60836 or ester fluid according to IEC 61099 or appropriate casting material. The
surrounding medium shall not have significant interaction with the material under test, e.g. by
causing swelling, during the time of testing.
Specimens having relatively low breakdown values may be tested in air, particularly if the
tests are to be made at elevated temperature. Even at moderate test voltages, discharges at
the edges of the electrodes may have significant effects on the test values.
If it is intended that the tests evaluate the behaviour of a material in another medium, that
medium may be used.
Select a medium which has minimum deleterious effect on the material under test.
The effect of the ambient medium on the results may be great, particularly in the case of
absorbent materials such as paper and pressboard, and it is essential that procedures for
specimen preparation define fully all necessary steps (e.g. drying and impregnation), and the
condition of the ambient medium during test.
Sufficient time shall be allowed for the specimen and the electrodes to attain the required
temperature, but some materials may be affected by prolonged exposure to high
temperatures.
7.2 Tests in air at elevated temperature
Tests in air at elevated temperature may be made in any well-designed oven of sufficient size
to accommodate the test specimen and the electrodes without flashover occurring during the
tests. Some means of circulating the air within the oven shall be provided so that a
substantially uniform temperature within ±2 K of the specified temperature is maintained
around the test specimen, and with a thermometer, thermocouple or other means for
measuring the temperature as near the point of test as practicable.
7.3 Tests in liquids
When tests are conducted in an insulating liquid, it is necessary to ensure adequate electric
strength of the liquid to avoid flashover. Specimens tested in liquids which have a higher
relative permittivity than transformer oil may show a higher dielectric strength than when
tested in transformer oil. Contamination which reduces the electric strength of the oil or other
liquid may also increase the measured electric strength of test specimens.

– 14 – 60243-1 © IEC:2013
Tests at elevated temperature may be made either in a container of liquid in an oven (see 7.1)
or in a thermostatically controlled bath using the insulating liquid for heat transfer. In this
case, suitable means for circulating the liquid, so that the temperature is substantially uniform
and maintained within ±2 K of the specified temperature around the test specimen, shall be
provided.
7.4 Tests in solid materials
For plate-shaped specimens of soft elastomers, a suitable casting material shall be used,
which preferably cures at room temperature and has a permittivity similar to the tested
elastomer. During the casting, voids shall be avoided, particularly in the volume between the
cylindrical electrode and test plate by a vacuum treatment. The casting material shall have a
sufficient adhesion at the electrodes and the surface of the test plate.
For silicone elastomers this can be silicone rubber of low viscosity (room temperature
vulcanizing two components)
8 Electrical apparatus
8.1 Voltage source
The test voltage shall be obtained from a step-up transformer supplied from a variable
sinusoidal low-voltage source. The transformer, its voltage source and the associated controls
shall have the following properties.
The ratio of crest to root-mean-square (r.m.s.) test voltage shall be equal to ±5 %
(1,34.1,48), with the test specimen in the circuit, at all voltages up to and including the
breakdown voltage.
The power rating of the source shall be sufficient to meet the requirements above until electric
breakdown occurs. For most materials, using electrodes as recommended, an output current
capacity of 40 mA is usually adequate. The power rating for most tests will vary from 0,5 kVA,
for testing low-capacitance specimens at voltages up to 10 kV, to 5 kVA for voltages up to 100
kV.
The controls on the variable low-voltage source shall be capable of varying the test voltage
smoothly, uniformly and without overshoots. When applying voltage in accordance with
Clause 8, the incremental increase produced, e.g. by a variable autotransformer, shall not
exceed 2 % of the expected breakdown voltage.
Motor-driven controls are preferable for making short-time or rapid-rise tests.
To protect the voltage source from damage, it shall be equipped with a device which
disconnects the power supply within a few cycles on breakdown of the specimen. It may
consist of a current-sensitive element in the HV supply to the electrodes.
To restrict damage by current or voltage surges at breakdown, it is desirable to include a
resistor with a suitable value in series with the electrodes. The value of the resistor will
depend on the damage which can be tolerated on the electrodes.
The use of a very high valued resistor may result in breakdown voltages which are higher than
those obtained with a lower valued resistor.
8.2 Voltage measurement
The voltage values are recorded in equivalent r.m.s. values. It is preferable to use a peak-
reading voltmeter and divide the reading by . The overall error of the voltage-measuring
60243-1 © IEC:2013 – 15 –
circuit shall not exceed 5 % of the measured value, including the error due to the response
time of the voltmeter. The response-time induced error shall not b
...