IEC 60156:2025
(Main)Insulating liquids - Determination of the breakdown voltage at power frequency - Test method
Insulating liquids - Determination of the breakdown voltage at power frequency - Test method
IEC 60156:2025 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 mm2/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.
Isolants liquides - Détermination de la tension de claquage à fréquence industrielle - Méthode d’essai
L'IEC 60156:2025 spécifie la méthode de détermination de la tension de claquage diélectrique des isolants liquides à fréquence industrielle. La procédure d’essai est réalisée dans un appareil spécifié dans lequel l’échantillon d’huile est soumis à un champ électrique alternatif croissant jusqu’à l’obtention du claquage. La méthode est applicable à tous les types d’isolants liquides de viscosité nominale allant jusqu’à 350 mm2/s à 40 °C. Elle convient aussi bien pour les essais de réception de liquides neufs à la livraison que pour définir l’état des échantillons prélevés lors de la surveillance et de la maintenance des matériels.
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IEC 60156 ®
Edition 4.0 2025-01
REDLINE VERSION
INTERNATIONAL
STANDARD
Insulating liquids – Determination of the breakdown voltage at power
frequency – Test method
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IEC 60156 ®
Edition 4.0 2025-01
REDLINE VERSION
INTERNATIONAL
STANDARD
Insulating liquids – Determination of the breakdown voltage at power
frequency – Test method
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.040 ISBN 978-2-8327-0194-2
– 2 – IEC 60156:2025 RLV © IEC 2025
CONTENTS
FOREWORD . 4
INTRODUCTION . 2
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Electrical apparatus . 7
4.1 General . 7
4.2 Voltage regulator . 7
4.3 Step-up transformer . 8
4.4 Switching system . 8
4.5 Current-limiting resistors . 8
4.6 Measuring system . 8
5 Test assembly . 8
5.1 General . 8
5.2 Test cell . 9
5.3 Electrodes . 9
5.4 Stirring device . 10
6 Preparation of electrodes. 11
7 Test assembly preparation . 11
8 Sampling . 11
9 Test procedure . 11
9.1 Sample preparation . 11
9.2 Filling of the cell . 12
9.3 Application of the voltage . 12
10 Report . 12
11 Test data dispersion and reproducibility . 13
11.1 Test data dispersion . 13
11.2 Reproducibility . 13
Annex A (informative) Improved test method . 14
A.1 Test procedure for improved test method . 14
A.2 Report. 15
Annex B (informative) Special test method for low volume samples . 16
Annex C (informative) Representative material for a performance test . 18
Bibliography . 19
Figure 1 – Example of test cell with spherical electrodes 12,5 mm to 13,0 mm diameter . 9
Figure 2 – Example of test cell with partially hemispherical electrodes with 25 mm
radius and 36 mm diameter . 10
Figure 3 – Graphical representation of coefficient of variation versus mean breakdown
voltage . 13
Figure A.1 – Example of a sequence of breakdown shots for determination of the
breakdown voltage . 15
Figure B.1 – Example of low volume test cell, fixed electrode distance of 2 mm with
2 ml active volume under dielectric stress .
Figure B.2 – Example of low volume test cell, fixed electrode distance of 2,5 mm
(150 ml to 200 ml) .
– 4 – IEC 60156:2025 RLV © IEC 2025
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INSULATING LIQUIDS – DETERMINATION OF THE BREAKDOWN
VOLTAGE AT POWER FREQUENCY – TEST METHOD
FOREWORD
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This redline version of the official IEC Standard allows the user to identify the changes
made to the previous edition IEC 60156:2018. A vertical bar appears in the margin
wherever a change has been made. Additions are in green text, deletions are in
strikethrough red text.
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.
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
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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.
– 6 – IEC 60156:2025 RLV © IEC 2025
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 ou
...
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