SIST EN IEC 61039:2025

Classification of insulating liquids

IEC 61039:2025 establishes the detailed classification of the N family (insulating liquids) that belongs to class L (lubricants, industrial oils and related products) in accordance with ISO 8681 and ISO 6743-99, affecting product categories that include products derived from petroleum processing, synthetic chemical products and synthetic and natural esters.

Klassifizierung der Isolierflüssigkeiten

Classification des liquides isolants

L'IEC 61039:2025 établit la classification détaillée de la famille N (liquides isolants) qui appartient à la classe L (lubrifiants, huiles industrielles et produits connexes) conformément aux normes ISO 8681 et ISO 6743-99, concernant les catégories de produit qui incluent des produits dérivés du traitement du pétrole, les produits chimiques synthétiques et les esters naturels et synthétiques. Ce document s’applique aux liquides neufs. Pour les liquides en service, des essais complémentaires peuvent être exigés pour assurer la conformité à la présente norme.

Splošna klasifikacija izolacijskih tekočin

Ta dokument določa podrobno klasifikacijo družine N (izolacijske tekočine), ki spada v razred L (maziva, industrijska olja in sorodni proizvodi) v skladu s standardoma ISO 8681 in ISO 6743-99, kar vključuje kategorije proizvodov, kot so proizvodi iz predelave nafte, sintetični kemični proizvodi ter sintetični in naravni estri.
Ta dokument se uporablja za neuporabljene tekočine. Pri tekočinah v uporabi bodo morda potrebni dodatni preskusi, da se zagotovi skladnost s tem dokumentom.

General Information

• Status: Published
• Public Enquiry End Date: 23-Nov-2023
• Publication Date: 13-May-2025
• ICS: 29.040.10 - Insulating oils
• Technical Committee: TPD - Fluids for electrotechnical applications
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 15-Apr-2025
• Due Date: 20-Jun-2025
• Completion Date: 14-May-2025
• Ref Project: EN IEC 61039:2025 - Classification of insulating liquids

Relations

• Replaces: SIST EN 61039:2008 - Classification of insulating liquids (IEC 61039:2008)
• Effective Date: 01-Jul-2025
• Revised: SIST EN 61039:2008 - Classification of insulating liquids (IEC 61039:2008)
• Effective Date: 03-Aug-2021

Overview

EN IEC 61039:2025 (IEC 61039:2025) specifies the detailed classification of insulating liquids (the N family) within class L - lubricants, industrial oils and related products, aligned with ISO 8681 and ISO 6743-99. This third edition (2025) updates and expands the classification to cover a broad range of unused insulating liquids, including products derived from petroleum processing, synthetic chemical products, and synthetic and natural esters. The European adoption was approved by CENELEC and supersedes EN 61039:2008.

Key topics and requirements

• Scope: Classification rules apply to unused electrical insulating liquids; in-service liquids may require additional testing to confirm continued compliance.
• ISO-based coding system: The standard uses the ISO classification format (e.g., ISO – CLASS – CATEGORY – NUMBERS), with a short form of CLASS – CATEGORY – NUMBERS. Categories are indicated by a group of four letters (the first identifying the family); insulating liquids receive a seven‑digit identification code as part of their nomination.
• Class L focus: Emphasizes lubricants/industrial oils and related insulating liquids used in electrical equipment.
• Technical considerations referenced: The document integrates normative references for testing and assessment such as IEC 60296 (mineral insulating oils), ISO 2592 (flash/fire point determination), OECD 301 (ready biodegradability) and ASTM D240 (heat of combustion).
• Health, safety and environment: Warnings on handling, eye contact, testing hazards and environmental impact (e.g., floating liquids as water hazards) are included; disposal and spill prevention are highlighted.

Practical applications

• Standardizes how insulating liquids are named and categorized for:
  • Manufacturers developing mineral, synthetic or ester-based insulating fluids.
  • Testing laboratories classifying samples and reporting identification codes.
  • Transformer and electrical equipment specifiers/engineers selecting fluids that meet classification-based procurement criteria.
  • Regulatory and compliance teams harmonizing national standards and environmental testing requirements.
• Useful for product datasheets, procurement specifications, conformity assessment and compatibility studies for insulating fluids used in transformers, switchgear and other electrical apparatus.

Who should use this standard

• Oil and fluid manufacturers, electrical equipment OEMs, utilities, independent test houses, standards committees and compliance officers responsible for fluid selection, labeling and environmental/safety compliance.

Related standards

• ISO 8681, ISO 6743-99, IEC 60296, ISO 2592, OECD 301, ASTM D240 - all referenced for classification principles and supporting test methods.

Keywords: EN IEC 61039:2025, classification of insulating liquids, insulating oils, IEC 61039, ISO 8681, ISO 6743-99, transformer oil, mineral oil, synthetic ester, biodegradability, CENELEC.

Standards Content (Sample)

SLOVENSKI STANDARD
01-junij-2025
Nadomešča:
SIST EN 61039:2008
Splošna klasifikacija izolacijskih tekočin
Classification of insulating liquids
Klassifizierung der Isolierflüssigkeiten
Classification des liquides isolants
Ta slovenski standard je istoveten z: EN IEC 61039:2025
ICS:
29.040.10 Izolacijska olja Insulating oils
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 61039

NORME EUROPÉENNE
EUROPÄISCHE NORM April 2025
ICS 29.040.10 Supersedes EN 61039:2008
English Version
Classification of insulating liquids
(IEC 61039:2025)
Classification des liquides isolants Klassifizierung der Isolierflüssigkeiten
(IEC 61039:2025) (IEC 61039:2025)
This European Standard was approved by CENELEC on 2025-03-24. 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 61039:2025 E
European foreword
The text of document 10/1249/FDIS, future edition 3 of IEC 61039, prepared by TC 10 "Fluids for
electrotechnical applications" was submitted to the IEC-CENELEC parallel vote and approved by
CENELEC as EN IEC 61039:2025.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2026-04-30
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2028-04-30
document have to be withdrawn
This document supersedes EN 61039:2008 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 61039:2025 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 60836 NOTE Approved as EN 60836
IEC 60867 NOTE Approved as EN IEC 60867
IEC 61099 NOTE Approved as EN 61099
IEC 62770 NOTE Approved as EN IEC 62770
IEC 63012 NOTE Approved as EN IEC 63012
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 60296 - Fluids for electrotechnical applications - Mineral EN IEC 60296 -
insulating oils for electrical equipment
ISO 2592 - Petroleum and related products - Determination of EN ISO 2592 -
flash and fire points - Cleveland open cup method
ISO 8681 - Petroleum products and lubricants -- Method of - -
classification -- Definition of classes
OECD 301 1992 OECD guidelines for the testing of chemicals - - -
Ready Biodegradability
ASTM D240 - Standard test method for heat of combustion of - -
liquid hydrocarbon fuels by bomb calorimeter

IEC 61039 ®
Edition 3.0 2025-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Classification of insulating liquids
Classification des liquides isolants
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.040.10 ISBN 978-2-8327-0162-1
– 2 – IEC 61039:2025 © IEC 2025
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 ISO classification system . 6
5 Classification of electrical insulating liquids . 7
5.1 General . 7
5.2 Class classification . 7
5.3 Category classification . 8
5.4 Identifying code . 8
6 Summarizing outline . 11
Bibliography . 12

Figure 1 – Meaning of all the letters and digits present in the classification of
insulating liquids . 11

Table 1 – Class classification of petroleum products or related products . 7
Table 2 – Examples of classification for different insulating liquids . 10

IEC 61039:2025 © IEC 2025 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CLASSIFICATION OF INSULATING LIQUIDS

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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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 61039 has been prepared by IEC technical committee 10: Fluids for electrotechnical
applications. It is an International Standard.
This third edition cancels and replaces the second edition published in 2008. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) updating of the classification of insulating liquids, taking into account the largest number
possible of substances that have, or may have, a possible application in electrical
components.
– 4 – IEC 61039:2025 © IEC 2025
The text of this International Standard is based on the following documents:
Draft Report on voting
10/1249/FDIS 10/1258/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
sta
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