IEC 60296:2003

Fluids for electrotechnical applications - Unused mineral insulating oils for transformers and switchgear

Covers specifications and test methods for unused mineral insulating oils. It applies to oil delivered to the agreed point and time of delivery, intended for use in transformers, switchgear and similar electrical equipment in which oil is required as an insulant and for heat transfer. These oils are obtained by distillation and refining of crude petroleum. Oils with and without additives are both within the scope of this standard. This standard is applicable only to unused mineral insulating oils. Reclaimed oils are beyond the scope of this standard. This standard does not apply to mineral oils used as impregnants in cables or capacitors. NOTE Mineral insulating oils complying with the requirements of this standard, of the same class and containing no additives (see 3.4), are considered to be compatible with one another and can be mixed in any proportion. This does not apply to oils containing additives. Where the user wishes to mix such oils, a check is recommended to be made to ensure that the mixture meets the requirements of this standard. Main changes with regard to previous edition include: the three classes of previous edition have been replaced by only two: transformer oil and low temperature switchgear oil, but a new concept, the lowest cold start energizing temperature, has been included; new properties have been added (i.e. charging tendency); values for properties have been revised.

Fluides pour applications électrotechniques - Huiles minérales isolantes neuves pour transformateurs et appareillages de connexion

Concerne les spécifications et méthodes d'essais des huiles minérales isolantes neuves. Elle s'applique à l'huile livrée en lieu et temps convenus, destinée à l'utilisation dans les transformateurs, interrupteurs et matériels électriques semblables où l'huile est nécessaire comme fluide isolant et caloporteur. Ces huiles proviennent de la distillation et du raffinage de pétrole brut. Cette norme s'applique aux huiles avec ou sans additifs. Cette norme ne s'applique qu'aux huiles minérales isolantes neuves. Les huiles régénérées sont hors du champ de cette norme. Cette norme ne concerne pas les huiles minérales utilisées pour imprégner les câbles ou les condensateurs. NOTE Les huiles minérales isolantes satisfaisant aux exigences de cette norme, de même classe et sans additifs (voir 3.4), sont considérées comme mutuellement compatibles et miscibles en toute proportion. Cela ne s'applique pas aux huiles additivées. Lorsque l'utilisateur souhaite mélanger de telles huiles, une vérification est recommandée pour s'assurer de la conformité du mélange à cette norme. Les principales modifications par rapport à l'édition précédente concernent les trois classes qui ont été remplacées par deux classes seulement: huile pour transformateur et huile pour appareillage de connexion basse température. Un nouveau concept, la température minimale de démarrage en puissance, a été introduit; de nouvelles propriétés ont été ajoutées (par exemple la tendance à la charge); et les valeurs concernant les propriétés ont été révisées.

General Information

• Status: Published
• Publication Date: 03-Nov-2003
• ICS: 29.040.10 - Insulating oils
• ICS: 29.130.01 - Switchgear and controlgear in general
• ICS: 29.180 - Transformers. Reactors
• Technical Committee: TC 10 - Fluids for electrotechnical applications
• Drafting Committee: WG 21 - TC 10/WG 21
• Current Stage: DELPUB - Deleted Publication
• Start Date: 20-Feb-2012
• Completion Date: 26-Oct-2025

Relations

• Revised: IEC 60296:2012 - Fluids for electrotechnical applications - Unused mineral insulating oils for transformers and switchgear
• Effective Date: 05-Sep-2023

Overview

IEC 60296:2003 - "Fluids for electrotechnical applications – Unused mineral insulating oils for transformers and switchgear" specifies requirements and test methods for unused mineral insulating oil intended as an insulant and heat-transfer fluid in transformers, switchgear and similar electrical equipment. The standard covers oils produced by distillation and refining of crude petroleum, with or without additives, delivered to the agreed point and time. It applies only to unused oils (reclaimed oils, cable/capacitor impregnants are excluded).

Key updates in the 2003 edition include consolidation from three classes to two (transformer oil and low temperature switchgear oil), the introduction of the lowest cold start energizing temperature, and the addition/revision of properties (for example, electrostatic charging tendency).

Key Topics and Requirements

• Classification & mixability
  • Two classes: transformer oil and low temperature switchgear oil.
  • Oils of the same class without additives are considered compatible and may be mixed. Oils with additives require compatibility checks.
• Properties & test methods (selected)
  • Viscosity (incl. very low temperature methods), pour point, water content
  • Breakdown voltage, dielectric dissipation factor (DDF), density
  • Oxidation stability, antioxidant additive content
  • Electrostatic charging tendency (ECT), gassing under electrical stress
  • Flash point, appearance, acidity, interfacial tension, sulfur/corrosive sulfur
  • Contaminant limits and detection for PCB, polycyclic aromatics (PCA), 2‑furfural (2‑FAL)
• Sampling, identification and delivery requirements to ensure conformity at point of delivery.
• Health, safety & environment (HSE) guidance: handling, testing hazards and disposal should follow local regulations.

Applications - Who Uses This Standard

• Transformer and switchgear manufacturers (OEMs) for specifying acceptable insulating oils.
• Utilities and grid operators for procurement, commissioning and maintenance specifications.
• Oil suppliers and refiners to certify product compliance and class designation.
• Testing laboratories for oil quality control, acceptance testing and compatibility checks.
• Asset owners and field engineers selecting oils for cold climates (low temperature switchgear oil) or checking oil mixing and dielectric performance.

Related Standards

Relevant normative references commonly used with IEC 60296 include:

• IEC 60156 (breakdown voltage), IEC 60247/61620/62021 (dielectric and acidity tests)
• IEC 60422 (maintenance of mineral insulating oils)
• IEC 61125 / IEC 61868 (oxidation stability, viscosity at low temperatures)
• ISO methods for pour point, flash point and density

Keywords: IEC 60296, mineral insulating oil, transformer oil, switchgear oil, insulating liquids standard, oil test methods, oil specification, electrostatic charging tendency.

Standards Content (Sample)

INTERNATIONAL IEC
STANDARD 60296
Third edition
2003-11
Fluids for electrotechnical applications –
Unused mineral insulating oils
for transformers and switchgear

This English-language version is derived from the original
bilingual publication by leaving out all French-language
pages. Missing page numbers correspond to the French-
language pages.
Reference number
Publication numbering
As from 1 January 1997 all IEC publications are issued with a designation in the

60000 series. For example, IEC 34-1 is now referred to as IEC 60034-1.

Consolidated editions
The IEC is now publishing consolidated versions of its publications. For example,

edition numbers 1.0, 1.1 and 1.2 refer, respectively, to the base publication, the

base publication incorporating amendment 1 and the base publication incorporating

amendments 1 and 2.
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INTERNATIONAL IEC
STANDARD 60296
Third edition
2003-11
Fluids for electrotechnical applications –
Unused mineral insulating oils
for transformers and switchgear

 IEC 2003 Copyright - all rights reserved
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 the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: [phone] Telefax: [phone] E-mail: [e-mail] Web: www.iec.ch
PRICE CODE
Commission Electrotechnique Internationale P
International Electrotechnical Commission
Международная Электротехническая Комиссия
For price, see current catalogue

60296  IEC:2003 – 3 –
CONTENTS
FOREWORD . 5

INTRODUCTION .9

1 Scope .11

2 Normative references.11

3 Terms and definitions .13

4 Properties of oil .15

4.1 Functional properties .15
4.2 Refining and stability .17
4.3 Performance.17
4.4 Health, safety and environment (HSE) properties.17
5 Classification, identification, general delivery requirements and sampling.17
5.1 Classification .17
5.2 Requirements .19
5.3 Mixability .19
5.4 Identification and general delivery requirements .19
5.5 Sampling .19
6 Properties, their significance and test methods .19
6.1 Viscosity.19
6.2 Pour point.21
6.3 Water content .21
6.4 Breakdown voltage .21
6.5 Dielectric dissipation factor (DDF) .21
6.6 Appearance .23
6.7 Acidity .23
6.8 Interfacial tension (IFT) .23
6.9 Sulfur content .23
6.10 Corrosive sulfur .23
6.11 Antioxidant additive content.23
6.12 Oxidation stability .23
6.13 Gassing .25
6.14 Electrostatic charging tendency (ECT) .25
6.15 Flash point.25
6.16 Density .25
6.17 Polycyclic aromatics (PCA).25
6.18 Polychlorinated biphenyls (PCB).25
6.19 2-Furfural and related compounds (2-FAL).25
7 Specific requirements for special applications.29
7.1 Higher oxidation stability and low sulfur content.29
7.2 Electrostatic charging tendency (ECT) .29
7.3 Gassing .29
Bibliography.31

60296  IEC:2003 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
FLUIDS FOR ELECTROTECHNICAL APPLICATIONS –

UNUSED MINERAL INSULATING OILS

FOR TRANSFORMERS AND SWITCHGEAR

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
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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 60296 has been prepared by IEC technical committee 10: Fluids
for electrotechnical applications.
This third edition cancels and replaces the second edition, published in 1982 and its amend-
ment 1 (1986), and constitutes a technical revision.
Main changes with regard to previous edition include: the three classes of previous edition
have been replaced by only two: transformer oil and low temperature switchgear oil, but a
new concept, the lowest cold start energizing temperature, has been included; new properties
have been added (i.e. charging tendency); values for properties have been revised.

60296  IEC:2003 – 7 –
The text of this standard is based on the following documents:

FDIS Report on voting
10/566/FDIS 10/569/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.

The committee has decided that the contents of this publication will remain unchanged until
2008. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
60296  IEC:2003 – 9 –
INTRODUCTION
General caution – Health, safety and environmental protection

This International Standard does not purport to address all the safety problems associated
with its use. It is the responsibility of the user of the standard to establish appropriate health

and safety practices and determine the applicability of regulatory limitations prior to use.

The mineral insulating oils which are the subject of this standard should be handled with due

regard to personal hygiene. Direct contact with the eyes may cause irritation. In the case of

eye contact, irrigation with copious quantities of clean running water should be carried out

and medical advice sought. Some of the tests specified in this standard involve the use of
processes that could lead to a hazardous situation. Attention is drawn to the relevant standard
for guidance.
This standard gives rise to mineral insulating oils, chemicals and used sample containers. The
disposal of these items shall be carried out according to the local regulations with regard to
the impact on the environment. Every precaution should be taken to prevent release of
mineral insulating oil into the environment.

60296  IEC:2003 – 11 –
FLUIDS FOR ELECTROTECHNICAL APPLICATIONS –

UNUSED MINERAL INSULATING OILS

FOR TRANSFORMERS AND SWITCHGEAR

1 Scope
This International Standard covers specifications and test methods for unused mineral
insulating oils. It applies to oil delivered to the agreed point and time of delivery, intended for
use in transformers, switchgear and similar electrical equipment in which oil is required as an
insulant and for heat transfer. These oils are obtained by distillation and refining of crude
petroleum.
Oils with and without additives are both within the scope of this standard.
This standard is applicable only to unused mineral insulating oils.
Reclaimed oils are beyond the scope of this standard.
This standard does not apply to mineral oils used as impregnants in cables or capacitors.
NOTE Mineral insulating oils complying with the requirements of this standard, of the same class and containing
no additives (see 3.4), are considered to be compatible with one another and can be mixed in any proportion. This
does not apply to oils containing additives. Where the user wishes to mix such oils, a check is recommended to be
made to ensure that the mixture meets the requirements of this standard.
2 Normative references
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.
IEC 60076-2, Power transformers – Part 2: Temperature rise
IEC 60156, Insulating liquids – Determination of the breakdown voltage at power frequency –
Test method
IEC 60247, Measurement of relative permittivity, dielectric dissipation factor and d.c.
resistivity of insulating liquids
IEC 60422, Supervision and maintenance guide for mineral insulating oils in electrical
equipment
IEC 60475, Method of sampling liquid dielectrics
IEC 60628, Gassing of insulating liquids under electrical stress and ionization
IEC 60666, Detection and determination of specified anti-oxidant additives in insulating oils
IEC 60814, Insulating liquids – Oil-impregnated paper and pressboard – Determination of
water by automatic coulometric Karl Fischer titration

60296  IEC:2003 – 13 –
IEC 61125, Unused hydrocarbon based insulating liquids – Test methods for evaluating the
oxidation stability
IEC 61198, Mineral insulating oils – Methods for the determination of 2-furfural and related
compounds
IEC 61619, Insulating liquids – Contamination by polychlorinated biphenyls (PCBs) – Method
of determination by capillary column gas chromatography

IEC 61620, Insulating liquids – Determination of the dielectric dissipation factor by
measurement of the conductance and capacitance – Test method

IEC 61868, Mineral insulating oils – Determination of kinematic viscosity at very low
temperatures
IEC 62021-1, Insulating liquids – Determination of acidity – Part 1: Automatic potentiometric
titration
ISO 2719, Determination of flash point – Pensky-Martens closed cup method
ISO 3016, Petroleum products – Determination of pour point
ISO 3104, Petroleum products – Transparent and opaque liquids – Determination of kinematic
viscosity and calculation of dynamic viscosity
ISO 3675, Crude petroleum and liquid petroleum products – Laboratory determination of
density – Hydrometer method
ISO 6295, Petroleum products – Mineral oils – Determination of interfacial tension of oil
against water – Ring method
ISO 12185, Crude petroleum and petroleum products – Determination of density – Oscillating
U-tube method
ISO 14596, Petroleum products – Determination of sulfur content – Wavelength-dispersive X-ray
fluorescence spectrometry
3 Terms and definitions
For the purposes of this document, the following definitions apply:
3.1
transformer oil
mineral insulating oil for transformers and similar electrical equipment where normal oxidation
resistance is required
3.2
low temperature switchgear oil
mineral insulating oil for oil-filled switchgear for outdoor application in very cold climatic
conditions
60296  IEC:2003 – 15 –
3.3
additive
suitable chemical substance which is deliberately added to a mineral insulating oil in order to

improve certain characteristics

NOTE Examples include antioxidants, pour point depressants, electrostatic charging tendency depressants such
as benzotriazole (BTA), anti-foam agents, refining process improvers, etc.

3.4
antioxidant additive
additive incorporated in an insulating oil to improve oxidation stability

NOTE A large number of antioxidant additives are available. For this standard, these are limited to those

identified in IEC 60666.
3.5
uninhibited oil
mineral insulating oil, containing no antioxidant additives, but which may contain other
additives
3.6
trace inhibited oil
mineral insulating oil containing up to 0,08 % antioxidant additive together with other additives
as mentioned in 3.4
3.7
inhibited oil
mineral insulating oil containing a minimum of 0,08 % and a maximum of 0,40 % antioxidant
additive together with other additives as mentioned in 3.3
3.8
unused mineral insulating oil
mineral insulating oil as delivered by the supplier
NOTE Such an oil has not been used in, nor been in contact with electrical equipment or other equipment not
required for manufacture, storage or transport. The manufacturer and supplier of unused oil will have taken all
reasonable precautions to ensure that there is no contamination with polychlorinated biphenyls or terphenyls (PCB,
PCT), used, reclaimed or dechlorinated oil or other contaminants.
3.9
reclaimed oil
mineral insulating oil used in electrical equipment which has been subjected to chemical
and/or physical processing to eliminate soluble and insoluble conta
...

NORME CEI
INTERNATIONALE 60296
Troisième édition
2003-11
Fluides pour applications électrotechniques –
Huiles minérales isolantes neuves
pour transformateurs et appareillages
de connexion
Cette version française découle de la publication d’origine
bilingue dont les pages anglaises ont été supprimées.
Les numéros de page manquants sont ceux des pages
supprimées.
Numéro de référence
CEI 60296:2003(F)
Numérotation des publications
Depuis le 1er janvier 1997, les publications de la CEI sont numérotées à partir de

60000. Ainsi, la CEI 34-1 devient la CEI 60034-1.

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indiquent respectivement la publication de base, la publication de base incorporant

l’amendement 1, et la publication de base incorporant les amendements 1 et 2

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NORME CEI
INTERNATIONALE 60296
Troisième édition
2003-11
Fluides pour applications électrotechniques –
Huiles minérales isolantes neuves
pour transformateurs et appareillages
de connexion
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Telephone: [phone] Telefax: [phone] E-mail: [e-mail] Web: www.iec.ch
CODE PRIX
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International Electrotechnical Commission
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Pour prix, voir catalogue en vigueur

– 2 – 60296  CEI:2003
SOMMAIRE
AVANT-PROPOS . 4

INTRODUCTION .8

1 Domaine d'application.10

2 Références normatives .10

3 Termes et définitions .12

4 Propriétés de l’huile .14

4.1 Propriétés fonctionnelles .14
4.2 Raffinage et stabilité.16
4.3 Performance.16
4.4 Propriétés liées à l'hygiène, à la sécurité et à l'environnement (HSE) .16
5 Classification, identification, exigences générales de livraison et d'échantillonnage.16
5.1 Classification .16
5.2 Exigences spécifiques .18
5.3 Miscibilité .18
5.4 Identification et exigences générales à la livraison .18
5.5 Echantillonnage .18
6 Propriétés, leur signification et méthodes d’essai.18
6.1 Viscosité.18
6.2 Point d'écoulement .20
6.3 Teneur en eau .20
6.4 Tension de claquage .20
6.5 Facteur de dissipation diélectrique (FDD) .20
6.6 Aspect .22
6.7 Acidité .22
6.8 Tension interfaciale (TIF).22
6.9 Teneur en soufre .22
6.10 Soufre corrosif .22
6.11 Teneur en additif antioxydant.22
6.12 Stabilité à l'oxydation.22
6.13 Gassing .24
6.14 Tendance à la charge électrostatique (TCE) .24

6.15 Point d'éclair.24
6.16 Densité.24
6.17 Hydrocarbures aromatiques polycycliques (HAP).24
6.18 Polychlorobiphényles (PCB) .24
6.19 2-Furfural et composés proches (2-FAL).24
7 Exigences spécifiques à des applications particulières .28
7.1 Stabilité à l'oxydation accrue et faible teneur en soufre .28
7.2 Tendance à la charge électrostatique (TCE) .28
7.3 Gassing .28
Bibliographie .30

– 4 – 60296  CEI:2003
COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE

____________
FLUIDES POUR APPLICATIONS ÉLECTROTECHNIQUES –

HUILES MINÉRALES ISOLANTES NEUVES

POUR TRANSFORMATEURS ET APPAREILLAGES DE CONNEXION

AVANT-PROPOS
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de justice) et les dépenses découlant de la publication ou de l'utilisation de cette Publication de la CEI ou de
toute autre Publication de la CEI, ou au crédit qui lui est accordé.
8) L'attention est attirée sur les références normatives citées dans cette publication. L'utilisation de publications
référencées est obligatoire pour une application correcte de la présente publication.
9) L’attention est attirée sur le fait que certains des éléments de la présente Publication de la CEI peuvent faire
l’objet de droits de propriété intellectuelle ou de droits analogues. La CEI ne saurait être tenue pour
responsable de ne pas avoir identifié de tels droits de propriété et de ne pas avoir signalé leur existence.

La Norme internationale CEI 60296 a été établie par le comité d'études 10 de la CEI: Fluides
pour applications électrotechniques.
Cette troisième édition annule et remplace la deuxième édition parue en 1982, et son amen-
dement 1 (1986) et constitue une révision technique.
Les principales modifications par rapport à l'édition précédente concernent les trois classes
qui ont été remplacées par deux classes seulement: huile pour transformateur et huile pour
appareillage de connexion basse température. Un nouveau concept, la température minimale
de démarrage en puissance, a été introduit; de nouvelles propriétés ont été ajoutées (par
exemple la tendance à la charge); et les valeurs concernant les propriétés ont été révisées.

– 6 – 60296  CEI:2003
Le texte de cette norme est issu des documents suivants:

FDIS Rapport de vote
10/566/FDIS 10/569/RVD
Le rapport de vote indiqué dans le tableau ci-dessus donne toute information sur le vote ayant

abouti à l'approbation de cette norme.

Cette publication a été rédigée selon les Directives ISO/CEI, Partie 2.

Le comité a décidé que le contenu de cette publication ne sera pas modifié avant 2008.
A cette date, la publication sera:
• reconduite;
• supprimée;
• remplacée par une révision révisée, ou
• amendée.
– 8 – 60296  CEI:2003
INTRODUCTION
Précautions générales – Protection de la santé, de la sécurité et de l'environnement

Cette Norme Internationale ne vise pas à répondre à tous les problèmes de sécurité liés à
son utilisation. L'utilisateur de cette norme a la responsabilité de mettre en place les

pratiques d'hygiène et de sécurité adéquates, et de vérifier avant utilisation si des contraintes

réglementaires s'appliquent.
Il convient que les huiles minérales isolantes dont traite cette norme soient manipulées en

respectant l'hygiène personnelle. Le contact direct avec les yeux peut provoquer une

irritation. En cas de contact oculaire, il est recommandé d’appliquer un copieux lavage à l'eau
courante propre, et de demander un avis médical. Certains des essais spécifiés dans cette
norme impliquent des opérations pouvant conduire à une situation dangereuse. Les
recommandations des normes correspondantes seront prises en compte.
Ces dispositions concernent les huiles minérales isolantes, les produits chimiques et les
récipients d'échantillons usagés. Leur élimination doit se faire selon les réglementations
locales en fonction de leur effet sur l'environnement. Il convient de prendre toutes les
précautions afin d’empêcher un déversement d’huile minérale isolante dans l’environnement.

– 10 – 60296  CEI:2003
FLUIDES POUR APPLICATIONS ÉLECTROTECHNIQUES –

HUILES MINÉRALES ISOLANTES NEUVES

POUR TRANSFORMATEURS ET APPAREILLAGES DE CONNEXION

1 Domaine d'application
La présente Norme internationale concerne les spécifications et méthodes d'essais des huiles
minérales isolantes neuves. Elle s'applique à l'huile livrée en lieu et temps convenus, destinée
à l'utilisation dans les transformateurs, interrupteurs et matériels électriques semblables où
l'huile est nécessaire comme fluide isolant et caloporteur. Ces huiles proviennent de la
distillation et du raffinage de pétrole brut.
Cette norme s'applique aux huiles avec ou sans additifs.
Cette norme ne s'applique qu'aux huiles minérales isolantes neuves.
Les huiles régénérées sont hors du champ de cette norme.
Cette norme ne concerne pas les huiles minérales utilisées pour imprégner les câbles ou les
condensateurs.
NOTE Les huiles minérales isolantes satisfaisant aux exigences de cette norme, de même classe et sans additifs
(voir 3.4), sont considérées comme mutuellement compatibles et miscibles en toute proportion. Cela ne s'applique
pas aux huiles additivées. Lorsque l'utilisateur souhaite mélanger de telles huiles, une vérification est
recommandée pour s'assurer de la conformité du mélange à cette norme.
2 Références normatives
Les documents de référence suivants sont indispensables pour l'application du présent
document. Pour les références datées, seule l'édition citée s'applique. Pour les références
non datées, la dernière édition du document de référence s'applique (y compris les éventuels
amendements).
CEI 60076-2, Transformateurs de puissance – Partie 2: Echauffement
CEI 60156, Isolants liquides – Détermination de la tension de claquage à fréquence
industrielle – Méthode d'essai

CEI 60247, Mesure de la permittivité relative, du facteur de dissipation diélectrique et de la
résistivité (en courant continu) des liquides isolants
CEI 60422, Guide de maintenance et de surveillance des huiles minérales isolantes en
service dans les matériels électriques
CEI 60475, Méthode d'échantillonnage des diélectriques liquides
CEI 60628, Gassing des isolants liquides sous contrainte électrique et ionisation
CEI 60666, Détection et dosage d'additifs antioxydants spécifiques présents dans les huiles
isolantes
CEI 60814, Isolants liquides – Cartons et papiers imprégnés d'huile – Détermination de la
teneur en eau par titrage coulométrique de Karl Fischer automatique

– 12 – 60296  CEI:2003
CEI 61125, Isolants liquides neufs à base d'hydrocarbures – Méthodes d'essai pour évaluer la
stabilité à l'oxydation
CEI 61198, Huiles minérales isolantes – Méthodes pour la détermination du 2-furfural et ses
dérivés
CEI 61619, Isolants liquides – Contamination par les polychlorobiphényles (PCB) – Méthode
de détermination par chromatographie en phase gazeuse sur colonne capillaire

CEI 61620, Isolants liquides – Détermination du facteur de dissipation diélectrique par mesure
de la conductance et de la capacité – Méthode d'essai

CEI 61868, Huiles minérales isolantes – Détermination de la viscosité cinématique à très
basse température
CEI 62021-1, Liquides isolants – Détermination de l'acidité – Partie 1: Titrage
potentiométrique automatique
ISO 2719, Détermination du point d'éclair – Méthode Pensky-Martens en vase clos
ISO 3016, Produits pétroliers – Détermination du point d'écoulement (disponible en anglais
seulement)
ISO 3104, Produits pétroliers – Liquides opaques et transparents – Détermination de la
viscosité cinématique et calcul de la viscosité dynamique
ISO 3675, Pétrole brut et produits pétroliers liquides – Détermination en laboratoire de la
masse volumique – Méthode à l'aréomètre
ISO 6295, Produits pétroliers – Huiles minérales – Détermination de la tension interfaciale
entre huile et eau – Méthode de l'anneau
ISO 12185, Pétroles bruts et produits pétroliers – Détermination de la masse volumique –
Méthode du type en U oscillant
ISO 14596, Produits pétroliers – Dosage du soufre – Spectrométrie de fluorescence X
dispersive en longueur d'onde
3 Termes et définitions
Pour les besoins du présent document, les définitions suivantes s'appliquent:
3.1
huile pour transformateur
huile minérale isolante pour transformateurs et appareillages électriques semblables pour
lesquels une stabilité à l'oxydation normale est requise
3.2
huile pour appareillages de connexion basse température
huile minérale isolante pour appareillages de connexion immergés en service extérieur et
climat très froid
– 14 – 60296  CEI:2003
3.3
additif
produit chimique adapté délibérément ajouté à une huile minérale isolante pour en améliorer

certaines propriétés
NOTE Des exemples comprennent des antioxydants, des abaisseurs de point de congélation, des modérateurs de
tendance à la charge statique comme le benzotriazole (BTA), des agents anti-mousse, des adjuvants de raffinage,
etc.
3.4
additif antioxydant
additif ajouté dans une huile isolante pour améliorer sa stabilité à l'oxydation

NOTE Un grand nombre d'additifs antioxydants est disponible. Pour cette norme, seuls sont retenus ceux
identifiables conformément à la CEI 60666.
3.5
huile non inhibée
huile minérale isolante ne contenant pas d'additif antioxydant, mais pouvant contenir d'autres
additifs
3.6
huile faiblement inhibée
huile minérale isolante contenant jusqu'à 0,08 % d'additif antioxydant ainsi que d’autres
additifs tels que mentionnés au Paragraphe 3.4
3.7
huile inhibée
huile minérale isolante contenant au minimum 0,08 % et au maximum 0,40 % d'additif
antioxydant ainsi que d’autres additifs tels que mentionnés au Paragraphe 3.3
3.8
huile minérale isolante neuve
huile minérale isolante en l'état de livraison par le fournisseur
NOTE Une telle huile n'a été ni utilisée dans des appareillages électriques, ni mise à leur contact ou au contact
de tout autre appareil non nécessaire à la fabrication, au stockage ou au transport. Le fabricant et le fournisseur
d'une huile neuve auront pris toutes les précautions utiles pour prévenir une contamination par des polychloro-
biphényles ou terphényles (PCB, PCT), des huiles usées, régénérées ou déchlorées, ou par d'autres contaminants.
3.9
huiles régénérées
huiles minérales isolantes ayant été utilisées dans des appareillages électriques, et ayant
subi un traitement physique et/ou chimique pour éliminer les contaminants solubles et
insolubles
NOTE Un mélange d'huiles neuves et régénérées est considéré comme régénéré.
4 Propriétés de l’huile
Les propriétés sont signalées dans les Tableaux 1 et 2 ainsi que dans l’Article 7.
4.1 Propriétés fonctionnelles
Les propriétés fonctionnelles de l'huile sont liées à son rôle de liquide isolant et caloporteur.
NOTE Les propriétés fonctionnelles comprennent la viscosité
...

IEC 60296
Edition 3.0 2003-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Fluids for electrotechnical applications – Unused mineral insulating oils for
transformers and switchgear
Fluides pour applications électrotechniques – Huiles minérales isolantes neuves
pour transformateurs et appareillages de connexion
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IEC 60296
Edition 3.0 2003-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Fluids for electrotechnical applications – Unused mineral insulating oils for
transformers and switchgear
Fluides pour applications électrotechniques – Huiles minérales isolantes
neuves pour transformateurs et appareillages de connexion

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
P
CODE PRIX
ICS 29.180; 29.040.0; 29.130 ISBN 2-8318-7272-3

– 2 – 60296 © IEC:2003
CONTENTS
FOREWORD.3
INTRODUCTION.5

1 Scope.6
2 Normative references.6
3 Terms and definitions .7
4 Properties of oil.8
4.1 Functional properties.8
4.2 Refining and stability.9
4.3 Performance.9
4.4 Health, safety and environment (HSE) properties .9
5 Classification, identification, general delivery requirements and sampling.9
5.1 Classification.9
5.2 Requirements.10
5.3 Mixability.10
5.4 Identification and general delivery requirements.10
5.5 Sampling.10
6 Properties, their significance and test methods.10
6.1 Viscosity.10
6.2 Pour point.11
6.3 Water content.11
6.4 Breakdown voltage.11
6.5 Dielectric dissipation factor (DDF) .11
6.6 Appearance.12
6.7 Acidity .12
6.8 Interfacial tension (IFT).12
6.9 Sulfur content.12
6.10 Corrosive sulfur.12
6.11 Antioxidant additive content.12
6.12 Oxidation stability.12
6.13 Gassing.13
6.14 Electrostatic charging tendency (ECT).13
6.15 Flash point.13
6.16 Density.13
6.17 Polycyclic aromatics (PCA).13
6.18 Polychlorinated biphenyls (PCB).13
6.19 2-Furfural and related compounds (2-FAL) .13
7 Specific requirements for special applications .15
7.1 Higher oxidation stability and low sulfur content .15
7.2 Electrostatic charging tendency (ECT).15
7.3 Gassing.15

Bibliography.16

60296 © IEC:2003 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FLUIDS FOR ELECTROTECHNICAL APPLICATIONS –
UNUSED MINERAL INSULATING OILS
FOR TRANSFORMERS AND SWITCHGEAR

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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
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 60296 has been prepared by IEC technical committee 10: Fluids
for electrotechnical applications.
This third edition cancels and replaces the second edition, published in 1982 and its amend-
ment 1 (1986), and constitutes a technical revision.
Main changes with regard to previous edition include: the three classes of previous edition
have been replaced by only two: transformer oil and low temperature switchgear oil, but a
new concept, the lowest cold start energizing temperature, has been included; new properties
have been added (i.e. charging tendency); values for properties have been revised.

– 4 – 60296 © IEC:2003
The text of this standard is based on the following documents:
FDIS Report on voting
10/566/FDIS 10/569/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.
The committee has decided that the contents of this publication will remain unchanged until
2008. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
60296 © IEC:2003 – 5 –
INTRODUCTION
General caution – Health, safety and environmental protection
This International Standard does not purport to address all the safety problems associated
with its use. It is the responsibility of the user of the standard to establish appropriate health
and safety practices and determine the applicability of regulatory limitations prior to use.
The mineral insulating oils which are the subject of this standard should be handled with due
regard to personal hygiene. Direct contact with the eyes may cause irritation. In the case of
eye contact, irrigation with copious quantities of clean running water should be carried out
and medical advice sought. Some of the tests specified in this standard involve the use of
processes that could lead to a hazardous situation. Attention is drawn to the relevant standard
for guidance.
This standard gives rise to mineral insulating oils, chemicals and used sample containers. The
disposal of these items shall be carried out according to the local regulations with regard to
the impact on the environment. Every precaution should be taken to prevent release of
mineral insulating oil into the environment.

– 6 – 60296 © IEC:2003
FLUIDS FOR ELECTROTECHNICAL APPLICATIONS –
UNUSED MINERAL INSULATING OILS
FOR TRANSFORMERS AND SWITCHGEAR

1 Scope
This International Standard covers specifications and test methods for unused mineral
insulating oils. It applies to oil delivered to the agreed point and time of delivery, intended for
use in transformers, switchgear and similar electrical equipment in which oil is required as an
insulant and for heat transfer. These oils are obtained by distillation and refining of crude
petroleum.
Oils with and without additives are both within the scope of this standard.
This standard is applicable only to unused mineral insulating oils.
Reclaimed oils are beyond the scope of this standard.
This standard does not apply to mineral oils used as impregnants in cables or capacitors.
NOTE Mineral insulating oils complying with the requirements of this standard, of the same class and containing
no additives (see 3.4), are considered to be compatible with one another and can be mixed in any proportion. This
does not apply to oils containing additives. Where the user wishes to mix such oils, a check is recommended to be
made to ensure that the mixture meets the requirements of this standard.
2 Normative references
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.
IEC 60076-2, Power transformers – Part 2: Temperature rise
IEC 60156, Insulating liquids – Determination of the breakdown voltage at power frequency –
Test method
IEC 60247, Measurement of relative permittivity, dielectric dissipation factor and d.c.
resistivity of insulating liquids
IEC 60422, Supervision and maintenance guide for mineral insulating oils in electrical
equipment
IEC 60475, Method of sampling liquid dielectrics
IEC 60628, Gassing of insulating liquids under electrical stress and ionization
IEC 60666, Detection and determination of specified anti-oxidant additives in insulating oils
IEC 60814, Insulating liquids – Oil-impregnated paper and pressboard – Determination of
water by automatic coulometric Karl Fischer titration

60296 © IEC:2003 – 7 –
IEC 61125, Unused hydrocarbon based insulating liquids – Test methods for evaluating the
oxidation stability
IEC 61198, Mineral insulating oils – Methods for the determination of 2-furfural and related
compounds
IEC 61619, Insulating liquids – Contamination by polychlorinated biphenyls (PCBs) – Method
of determination by capillary column gas chromatography
IEC 61620, Insulating liquids – Determination of the dielectric dissipation factor by
measurement of the conductance and capacitance – Test method
IEC 61868, Mineral insulating oils – Determination of kinematic viscosity at very low
temperatures
IEC 62021-1, Insulating liquids – Determination of acidity – Part 1: Automatic potentiometric
titration
ISO 2719, Determination of flash point – Pensky-Martens closed cup method
ISO 3016, Petroleum products – Determination of pour point
ISO 3104, Petroleum products – Transparent and opaque liquids – Determination of kinematic
viscosity and calculation of dynamic viscosity
ISO 3675, Crude petroleum and liquid petroleum products – Laboratory determination of
density – Hydrometer method
ISO 6295, Petroleum products – Mineral oils – Determination of interfacial tension of oil
against water – Ring method
ISO 12185, Crude petroleum and petroleum products – Determination of density – Oscillating
U-tube method
ISO 14596, Petroleum products – Determination of sulfur content – Wavelength-dispersive X-ray
fluorescence spectrometry
3 Terms and definitions
For the purposes of this document, the following definitions apply:
3.1
transformer oil
mineral insulating oil for transformers and similar electrical equipment where normal oxidation
resistance is required
3.2
low temperature switchgear oil
mineral insulating oil for oil-filled switchgear for outdoor application in very cold climatic
conditions
– 8 – 60296 © IEC:2003
3.3
additive
suitable chemical substance which is deliberately added to a mineral insulating oil in order to
improve certain characteristics
NOTE Examples include antioxidants, pour point depressants, electrostatic charging tendency depressants such
as benzotriazole (BTA), anti-foam agents, refining process improvers, etc.
3.4
antioxidant additive
additive incorporated in an insulating oil to improve oxidation stability
NOTE A large number of antioxidant additives are available. For this standard, these are limited to those
identified in IEC 60666.
3.5
uninhibited oil
mineral insulating oil, containing no antioxidant additives, but which may contain other
additives
3.6
trace inhibited oil
mineral insulating oil containing up to 0,08 % antioxidant additive together with other additives
as mentioned in 3.4
3.7
inhibited oil
mineral insulating oil containing a minimum of 0,08 % and a maximum of 0,40 % antioxidant
additive together with other additives as mentioned in 3.3
3.8
unused mineral insulating oil
mineral insulating oil as delivered by the supplier
NOTE Such an oil has not been used in, nor been in contact with electrical equipment or other equipment not
required for manufacture, storage or transport. The manufacturer and supplier of unused oil will have taken all
reasonable precautions to ensure that there is no contamination with polychlorinated biphenyls or terphenyls (PCB,
PCT), used, reclaimed or dechlorinated oil or other contaminants.
3.9
reclaimed oil
mineral insulating oil used in electrical equipment which has been subjected to chemical
and/or physical processing to eliminate soluble and insoluble contaminants
NOTE A blend of unused and reclaimed oil in any proportion is regarded as being reclaimed.
4 Properties of oil
Characteristics are listed in Tables 1 and 2 and in Clause 7.
4.1 Functional properties
Properties of oil which have impact on its function as an insulating and cooling liquid.
NOTE Functional properties include viscosity, density, pour point, water content, breakdown voltage and dielectric
dissipation factor.
60296 © IEC:2003 – 9 –
4.2 Refining and stability
Properties of oil that are influenced by quality and type of refining and additives.
NOTE This can include appearance, interfacial tension, sulfur content, acidity, corrosive sulfur, 2-furfural content.
4.3 Performance
Properties that are related to the long-term behaviour of oil in service and/or its reaction to
high electric stress and temperature.
NOTE Examples include oxidation stability, gassing tendency and electrostatic charging tendency (ECT).
4.4 Health, safety and environment (HSE) properties
Oil properties related to safe handling and environment protection.
NOTE Examples can include flash point, density, PCA (polycyclic aromatics), PCB/PCT (polychlorinated
biphenyls/terphenyls).
5 Classification, identification, general delivery requirements and sampling
5.1 Classification
5.1.1 Classes
For the purpose of this standard, mineral insulating oils are classified into two classes:
– transformer oils;
– low temperature switchgear oil.
5.1.2 Antioxidant additive (inhibitor) content
Transformer oils are classified into three groups, according to their content of antioxidant
additive:
– uninhibited transformer oils: marked with U;
– trace inhibited transformer oils: marked with T;
– inhibited transformer oils: marked with I.
5.1.3 Lowest cold start energizing temperature (LCSET)
After the inhibitor marking, the LCSET shall be indicated.
Standard LCSET in this standard is –30 °C; optionally other LCSET can be selected according
to Table 1.
Example: Transformer oil I –40 °C, transformer oil T –30 °C, transformer oil U 0 °C.

– 10 – 60296 © IEC:2003
5.2 Requirements
General requirements of this standard are given in Table 2.
Specific requirements are defined under Clause 7.
5.3 Mixability
Unused insulating oils of the same class, the same group and the same LCSET are
considered to be mixable and compatible with each other (see as well IEC 60422).
5.4 Identification and general delivery requirements
a) Oil is normally delivered in bulk, rail tank cars, tank containers or packed in drums or IBC
(intermediate bulk containers). These shall be clean and suitable for this purpose to avoid
any contamination.
b) Oil drums and sample containers shall carry at least the following markings:
– supplier's designation;
– classification;
– oil quantity.
c) Each oil delivery shall be accompanied by a document from the supplier specifying at
least: suppliers designation, oil classification and compliance certificate. At purchaser’s
request, the supplier has to indicate the presence (type, concentration) of any additive.
5.5 Sampling
Sampling shall be carried out in accordance with the procedure described in IEC 60475.
6 Properties, their significance and test methods
6.1 Viscosity
Viscosity influences heat transfer and therefore the temperature rise of the equipment.
The lower the viscosity, the easier the oil circulates leading to improved heat transfer. At low
temperatures the resulting higher viscosity of oil is a critical factor for the cold start of trans-
formers with ON cooling (no circulation and therefore possible overheating at the hot spots) and
negatively influences the speed of moving parts, such as in power circuit breakers,
switchgear, on-load tap changer mechanisms, pumps and regulators. The viscosity at the lowest
2 2
cold start energizing temperature (LCSET) shall not exceed 1 800 mm /s (resp. 2 500 mm /s
at –40 °C, see Table 1). This lowest cold start energizing temperature (LCSET) for trans-
former oils is defined in this standard as being –30 °C (this is 5 K lower than indicated in IEC
60076-2). Other LCSET (see Table 1) can be agreed between supplier and purchaser.
Low temperature switchgear oil should have a lower viscosity at LCSET: max. 400 mm /s.
Standard LCSET of low temperature switchgear oil is defined with –40 °C but other LCSET
may be agreed between supplier and purchaser.
NOTE 1 For more details concerning ON cooling (natural oil circulation without pump), refer to IEC 60076-2.

60296 © IEC:2003 – 11 –
Table 1 – Maximum viscosity and pour point of transformer oil at lowest cold start
energizing temperature (LCSET)
LCSET Maximum viscosity Maximum pour point
°C mm /s °C
0 1 800 –10*
–20 1 800 –30*
–30 1 800 –40
–40 2 500 –50*
* Optional.
NOTE 2 There is no lower viscosity limit set in this standard, but under certain conditions oils with a viscosity less
than 7 mm /s /40 °C can be considered to be a potential aspiration hazard.
Viscosity shall be measured according to ISO 3104, viscosity at very low temperatures
according to IEC 61868.
6.2 Pour point
Pour point of mineral insulating oil is the lowest temperature at which the oil will just flow. It is
recommended that the pour point should be minimum 10 K below the lowest cold start
energizing temperature (LCSET). If a pour point depressant additive is used, this should be
mentioned by the supplier to the user. Pour point shall be measured in accordance with
ISO 3016.
6.3 Water content
A low water content of mineral insulating oil is necessary to achieve adequate electrical
strength and low dissipation losses. To avoid separation of free water, unused insulating oil
should have a limited water content. Before filling the electrical equipment, the oil should be
treated to meet the requirements of IEC 60422. Where requested by the purchaser, the
supplier of oil shall demonstrate that after treatment to remove solid particles, humidity and
dissolved air by a vacuum procedure (see note), the oil shall have a high dielectric strength of
minimum 70 kV breakdown voltage. Water content shall be measured in accordance with
IEC 60814.
NOTE This laboratory treatment referred to consists of filtration of the oil at 60 °C by vacuum (pressure below
2,5 kPa) through a sintered glass filter (porosity 4).
6.4 Breakdown voltage
Breakdown voltage of transformer oil indicates its ability to resist electrical stress in electrical
equipment. Breakdown voltage shall be measured in accordance with IEC 60156.
6.5 Dielectric dissipation factor (DDF)
DDF is a measure for dielectric losses caused by the oil. Increased DDF can indicate
contamination of the oil by moisture, particles or soluble polar contaminants or poor refining
quality. DDF shall be measured in accordance with IEC 60247 or IEC 61620 at 90 °C. In case
of dispute, IEC 60247 at 90 °C should be used.
NOTE By agreement between parties, DDF may be measured at temperatures other than 90 °C. In such cases the
temperature of measurement should be stated in the report.

– 12 – 60296 © IEC:2003
6.6 Appearance
A visual inspection of insulating oil (oil sample in transmitted light under a thickness of
approximately 10 cm and at ambient temperature) indicates the presence of visible
contaminants, free water or suspended matter.
6.7 Acidity
Unused mineral insulating oil should be neutral and free from any acidic compound. Acidity
should be measured following IEC 62021-1.
6.8 Interfacial tension (IFT)
Low IFT sometimes indicates the presence of undesirable contaminants. IFT shall be
measured in accordance with ISO 6295.
6.9 Sulfur content
Different organo-sulfur compounds are present in transformer oils, dependent on the crude oil
origin and the degree and type of refining. Refining treats sulfur and aromatic hydrocarbons.
As some sulfur compounds have an affinity to metals, they may act as copper passivators or
they may promote corrosion.
Sulfur content should be measured following BS 2000 Part 373 or ISO 14596.
6.10 Corrosive sulfur
Some sulfur compounds, e.g. mercaptans, are very corrosive to metal surfaces, i.e. steel,
copper and silver (switchgear contacts) and shall not be present in new oil. Corrosive sulfur
should be measured following DIN 51353.
6.11 Antioxidant additive content
Antioxidant additive (inhibitor) slows down the oxidation of oil and therefore the formation of
oil sludge and acidity. It is important to know whether and in what proportion antioxidant
additive has been added in order to monitor additive depletion during service. 2,6-di-tert-butyl-
p-cresol (DBPC) is the most commonly used antioxidant, but others are also used. Detection
and measurement of defined antioxidant additives shall be determined in accordance with
IEC 60666. The type and quantity of each antioxidant additive present in the oil shall be
stated in the quality certificate. If co-stabilizers are used during the refining process, their
presence shall be agreed between the supplier and the purchaser.
6.12 Oxidation stability
Oxidation of oil gives rise to acidity and sludge formation and can be minimized as a result of
high oxidation stability leading to longer service life time by minimizing sludge deposition,
electrical losses, metal corrosion, electrical faults and maximizing insulation life. Oxidation
stability is measured in accordance with method C of IEC 61125. There is an option for
stricter limits for special applications. In some countries more stringent limits and/or additional
requirements and tests may be requested.

60296 © IEC:2003 – 13 –
6.13 Gassing
Gassing tendency of mineral insulating oil, i.e. the gas absorbing property of an oil under
electrical stress, is only necessary and important for special transformers like HV (high
voltage) transformers and is a measure of the rate of absorption or evolution of hydrogen into
oil under prescribed laboratory conditions. Gas absorption properties are related to oil
aromaticity which is subject to indirect control by the oil's oxidation requirements. Gassing
tendency is measured using method A of IEC 60628. Gassing tendency is a specific
requirement.
6.14 Electrostatic charging tendency (ECT)
ECT of oil is an important property for certain designs of HV and EHV transformers which
have oil pumping rates that can give rise to the build-up of electrostatic charge. This charge
can result in energy discharge causing transformer failure. A method to measure ECT is
proposed by CIGRE SC12 (see Bibliography).
ECT is a specific requirement.
6.15 Flash point
The safe operation of electrical equipment requires an adequately high flash point that is
measured in accordance with ISO 2719 (Pensky-Martens closed cup procedure).
6.16 Density
Density of oil shall be low enough to avoid, in cold climates, that ice resulting from the
freezing of free water is floating on the oil surface and possibly leading to fault conditions
developing in flashover of conductors. Density shall be measured in accordance with
ISO 3675 (reference method) but ISO 12185 as well is accepted.
6.17 Polycyclic aromatics (PCA)
Some PCAs are classified to be carcinogens and therefore need to be controlled to an
acceptable level in mineral insulating oil. PCAs are defined so as to be detectable by
extraction with DMSO (Dimethylsulfoxide) under the conditions of BS 2000 Part 346.
6.18 Polychlorinated biphenyls (PCB)
Unused mineral insulating oil shall be free from PCB. The reference method is IEC 61619.
The detection limit for a single peak is 0,1 mg/kg.
NOTE The total limits are given by national regulations.
6.19 2-Furfural and related compounds (2-FAL)
2-FAL and related compounds in unused mineral insulating oils can result either from
improper redistillation after solvent extraction during refining or from contamination with used
oil.
Unused insulating oils should have a low level of 2-FAL and related compounds;
measurement should be done according to IEC 61198.

– 14 – 60296 © IEC:2003
Table 2 – General specifications
Limits
Property Test method
Low temperature
Transformer oil
switchgear oil
1 – Function
2 2
Viscosity at 40 °C ISO 3104 Max. 12 mm /s Max. 3,5 mm /s
a 2
Viscosity at –30 °C ISO 3104 Max. 1 800 mm /s --
b 2
Viscosity at –40 °C IEC 61868 -- Max. 400 mm /s
a
ISO 3016 Max. –40 °C Max. –60 °C
Pour point
c d
Water content IEC 60814
Max. 30 mg/kg / 40 mg/kg
e
Breakdown voltage IEC 60156 Min. 30 kV / 70 kV
Density at 20 °C ISO 3675 or ISO 12185 Max. 0,895 g/ml
DDF at 90°C IEC 60247 or IEC 61620 Max. 0,005
2 – Refining/stability
Appearance -- Clear, free from sediment and suspended matter
Acidity IEC 62021-1 Max. 0,01 mg KOH/g
f
Interfacial tension ISO 6295 No general requirement
Total sulfur content BS 2000 Part 373 or No general requirement
ISO 14596
Corrosive sulfur DIN 51353 Not corrosive
Antioxidant additive IEC 60666 (U) uninhibited oil: not detectable
(T) trace inhibited oil: max. 0,08 %
(I) inhibited oils: 0,08 – 0,40 %
2-Furfural content IEC 61198 Max. 0,1 mg/kg
3 – Performance
IEC 61125 (method C)
Oxidation stability
Test duration:
(U) Uninhibited oil: 164 h
(T) Trace inhibited oil:332 h
(I) Inhibited oil: 500 h
- Total acidity Max. 1,2 mg KOH/g
- Sludge
Max. 0,8 %
DDF at 90 °C IEC 60247 Max. 0,500
Gassing IEC 60628, A No general requirement
4 – Health, safety and environment (HSE)
Flash point ISO 2719 Min. 135 °C Min. 100 °C
PCA content BS 2000 Part 346 max. 3 %
PCB content IEC 61619 Not detectable
a
This is the standard LCSET for an transformer oil (see 5.1) and can be modified depending on the climatic
condition of each country. Pour point should be minimum 10 K below LCSET.
b
Standard LCSET for low temperature switch gear oil.
c
For bulk supply.
d
For delivery in drums and IBC.
e
After laboratory treatment (see 6.4).
f
Where it is used as a general requirement, a limit of minimum 40 mN/m is recommended.

___________
In some countries more stringent limits and/or additional requirements may be requested.

60296 © IEC:2003 – 15 –
7 Specific requirements for special applications
7.1 Higher oxidation stability and low sulfur content
For transformers with higher operating temperatures or designed for extended service life,
there may exist restricted limits after oxidation test (see IEC 61125, method C). Mostly, such
,
2 3
oil is inhibited (I) .
– Total acidity: max. 0,3 mg KOH/g;
– Sludge: max. 0,05 %;
– DDF at 90 °C: max. 0,050;
– Total sulfur content: max. 0,15 %.
7.2 Electrostatic charging tendency (ECT)
For OF- or OD-cooled power transformers (IEC 60076-2) with high oil circulation speed, as
e.g. HV/DC transformers, a limit may be agreed between purchaser and manufacturer.
7.3 Gassing
For equipment with high electrical field stress or special design, gas which may be formed
under special stress conditions must be absorbed by the oil. Therefore the gassing tendency
according to IEC 60628 must be agreed between the oil manufacturer and the user of the oil.

___________
In some countries more stringent limits and/or additional requirements may be requested.
In some countries a DDF of max. 0,020 after 2 h of oxidation (see IEC 61125, method C) is considered as
acceptable for application in EHV instrument transformers and bushings.
In some countries limits are available.

– 16 – 60296 © IEC:2003
Bibliography
DIN 51353: Detection of corrosive sulfur – Silver strip
BS 2000, Part 346: Determination of polycyclic aromatics in lubricant base oil and asphaltene
free petroleum fractions – Dimethylsulfoxide refractive method
BS 2000, Part 373: Determination of the sulfur content of light and middle distillates –
Oxidative microcoulometry
CIGRE SC12: Static electrification in power transformers (CIGRE SC12 – Technical Brochure,
Product Id 170 [2000])
___________
– 18 – 60296 © CEI:2003
SOMMAIRE
AVANT-PROPOS.19
INTRODUCTION.21

1 Domaine d'application.22
2 Références normatives.22
3 Termes et définitions .23
4 Propriétés de l’huile.24
4.1 Propriétés fonctionnelles.24
4.2 Raffinage et stabilité.25
4.3 Performance.25
4.4 Propriétés liées à l'hygiène, à la sécurité et à l'environnement (HSE).25
5 Classification, identification, exigences générales de livraison et d'échantillonnage .25
5.1 Classification.25
5.2 Exigences spécifiques .26
5.3 Miscibilité.26
5.4 Identification et exigences générales à la livraison .26
5.5 Echantillonnage.26
6 Propriétés, leur signification et méthodes d’essai .26
6.1 Viscosité.26
6.2 Point d'écoulement.27
6.3 Teneur en eau.27
6.4 Tension de claquage.27
6.5 Facteur de dissipation diélectrique (FDD).27
6.6 Aspect.28
6.7 Acidité.28
6.8 Tension interfaciale (TIF).28
6.9 Teneur en soufre.28
6.10 Soufre corrosif.28
6.11 Teneur en additif antioxydant .28
6.12 Stabilité à l'oxydation .28
6.13 Gassing.29
6.14 Tendance à la charge électrostatique (TCE).29
6.15 Point d'éclair .29
6.16 Densité.29
6.17 Hydrocarbures aromatiques polycycliques (HAP) .29
6.18 Polychlorobiphényles (PCB).29
6.19 2-Furfural et composés proches (2-FAL) .29
7 Exigences spécifiques à des applications particulières .31
7.1 Stabilité à l'oxydation accrue et faible teneur en soufre .31
7.2 Tendance à la charge électrostatique (TCE).31
7.3 Gassing.31

Bibliographie.32

60296 © CEI:2003 – 19 –
COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
____________
FLUIDES POUR APPLICATIONS ÉLECTROTECHNIQUES –

HUILES MINÉRALES ISOLANTES NEUVES
POUR TRANSFORMATEURS ET APPAREILLAGES DE CONNEXION

AVANT-PROPOS
1) La Commission Electrotechnique Internationale (CEI) est une organisation mondiale de normalisation
composée de l'ensemble des comités électrotechniques nationaux (Comités nationaux de la CEI). La CEI a
pour objet de favoriser la coopération internationale pour toutes les questions de normalisation dans les
domaines de l'électricité et de l'électronique. A cet effet, la CEI – entre autres activités – publie des Normes
internationales, des Spécifications techniques, des Rapports techniques, des Spécifications accessibles au
public (PAS) et des Guides (ci-après dénommés "Publication(s) de la CEI"). Leur élaboration est confiée à des
comités d'études, aux travaux desquels tout Comité national intéressé par le sujet traité peut participer.
...