SIST EN IEC 60156:2025

SLOVENSKI STANDARD
01-junij-2025
Nadomešča:
SIST EN 60156:1997
Izolacijske tekočine - Ugotavljanje prebojne napetosti pri mrežni frekvenci - Testna
metoda
Insulating liquids - Determination of the breakdown voltage at power frequency - Test
method
Isolierflüssigkeiten - Bestimmung der Durchschlagspannung bei Netzfrequenz -
Prüfverfahren
Isolants liquides - Détermination de la tension de claquage à
fréquence industrielle - Méthode d’essai
Ta slovenski standard je istoveten z: EN IEC 60156:2025
ICS:
29.040.01 Izolacijski fluidi na splošno Insulating fluids in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 60156

NORME EUROPÉENNE
EUROPÄISCHE NORM March 2025
ICS 29.040 Supersedes EN 60156:1995
English Version
Insulating liquids - Determination of the breakdown voltage at
power frequency - Test method
(IEC 60156:2025)
Isolants liquides - Détermination de la tension de claquage Isolierflüssigkeiten - Bestimmung der Durchschlagspannung
à fréquence industrielle - Méthode d'essai bei Netzfrequenz - Prüfverfahren
(IEC 60156:2025) (IEC 60156:2025)
This European Standard was approved by CENELEC on 2025-03-07. 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 CEN-CENELEC
Management Centre 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 CEN-CENELEC Management Centre 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, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 60156:2025 E
European foreword
The text of document 10/1241/FDIS, future edition 4 of IEC 60156, prepared by TC 10 "Fluids for
electrotechnical applications" was submitted to the IEC-CENELEC parallel vote and approved by
CENELEC as EN IEC 60156:2025.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2026-03-31
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2028-03-31
document have to be withdrawn
This document supersedes EN 60156:1995 and all of its amendments and corrigenda (if any).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 60156:2025 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 standard indicated:
IEC 60060-3 NOTE Approved as EN 60060-3
IEC 60052:2002 NOTE Approved as EN 60052:2002 (not modified)
IEC 60060-2:2010 NOTE Approved as EN 60060-2:2011 (not modified)
ISO 21920-2:2021 NOTE Approved as EN ISO 21920-2:2022 (not modified)
IEC 60296 NOTE Approved as EN IEC 60296
IEC 60422 NOTE Approved as EN IEC 60422
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 1  Where an International Publication has been modified by common modifications, indicated by (mod),
the relevant EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 60475 -  Method of sampling insulating liquids EN IEC 60475 -

IEC 60156 ®
Edition 4.0 2025-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Insulating liquids – Determination of the breakdown voltage at power

frequency – Test method
Isolants liquides – Détermination de la tension de claquage à fréquence

industrielle – Méthode d’essai

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.040  ISBN 978-2-8327-0140-9

– 2 – IEC 60156:2025 © IEC 2025
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Electrical apparatus . 6
4.1 General . 6
4.2 Voltage regulator . 6
4.3 Step-up transformer . 7
4.4 Switching system . 7
4.5 Current-limiting resistors . 7
4.6 Measuring system . 7
5 Test assembly . 7
5.1 General . 7
5.2 Test cell . 8
5.3 Electrodes . 9
5.4 Stirring device . 9
6 Preparation of electrodes. 9
7 Test assembly preparation . 9
8 Sampling . 10
9 Test procedure . 10
9.1 Sample preparation . 10
9.2 Filling of the cell . 10
9.3 Application of the voltage . 10
10 Report . 11
11 Test data dispersion and reproducibility . 11
11.1 Test data dispersion . 11
11.2 Reproducibility . 12
Annex A (informative) Improved test method . 13
A.1 Test procedure for improved test method . 13
A.2 Report. 14
Annex B (informative) Special test method for low volume samples . 15
Annex C (informative) Representative material for a performance test . 16
Bibliography . 17

Figure 1 – Example of test cell with spherical electrodes 12,5 mm to 13,0 mm diameter . 8
Figure 2 – Example of test cell with partially hemispherical electrodes with 25 mm
radius and 36 mm diameter . 8
Figure 3 – Graphical representation of coefficient of variation versus mean breakdown
voltage . 12
Figure A.1 – Example of a sequence of breakdown shots for determination of the
breakdown voltage . 14

IEC 60156:2025 © IEC 2025 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INSULATING LIQUIDS – DETERMINATION OF THE BREAKDOWN
VOLTAGE AT POWER FREQUENCY – TEST METHOD

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) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
may be required to implement this document. However, implementers are cautioned that this may not represent
the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC 60156 has been prepared by IEC technical committee 10: Fluids for electrotechnical
applications. It is an International Standard.
This fourth edition cancels and replaces the third edition published in 2018. This edition
constitutes a technical revision.
This edition constitutes a technical revision and, mainly, confirms the content of the previous
edition even if some advances are included. The test method has not been changed for practical
reasons, due to the very large number of instrumentations disseminated around the world.

– 4 – IEC 60156:2025 © IEC 2025
The text of this International Standard is based on the following documents:
Draft Report on voting
10/1241/FDIS 10/1256/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
IEC 60156:2025 © IEC 2025 – 5 –
INTRODUCTION
As normally applied, breakdown voltage of insulating liquids is not a basic material property but
an empirical test procedure intended to indicate the presence of contaminants such as water
and solid suspended matter and the advisability of carrying out drying and filtration treatment.
The AC breakdown voltage value of insulating liquids strongly depends on the particular set of
conditions used in its measurement. Therefore, standardized testing procedures and equipment
are essential for the unambiguous interpretation of test results.
The method described in this document applies to either acceptance tests on new deliveries of
insulating liquids or testing of treated liquids prior to or during filling into electrical equipment,
or to the monitoring and maintenance of insulating liquid-filled apparatus in service. It specifies
rigorous sample-handling procedures and temperature control that should be adhered to when
certified results are required. For routine tests, especially in the field, less stringent procedures
may be practicable, and it is the responsibility of the user to determine their effect on the results.
Annex A describes, for comparison, an alternative test method which could be introduced in the
future. Annex B describes special test methods, using cells which may include low volume
samples. Annex C describes a reference material for a performance test and check according
.
to IEC 60060-3 [1]
___________
Numbers in square brackets refer to the Bibliography.

– 6 – IEC 60156:2025 © IEC 2025
INSULATING LIQUIDS – DETERMINATION OF THE BREAKDOWN
VOLTAGE AT POWER FREQUENCY – TEST METHOD

1 Scope
This document specifies the method for determining the dielectric breakdown voltage of
insulating liquids at power frequency. The test procedure is performed in a specified apparatus,
where the oil sample is subjected to an increasing AC electrical field until breakdown occurs.
The method applies to all types of insulating liquids of nominal viscosity up to 350 mm /s at
40 °C. It is appropriate both for acceptance testing on unused liquids at the time of their delivery
and for establishing the condition of samples taken in monitoring and maintenance of
equipment.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 60475, Method of sampling insulating liquids
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https
...