Mineral oil-filled electrical equipment in service - Guidance on the interpretation of dissolved and free gases analysis

IEC 60599:2015 is available as IEC 60599:2015 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.
IEC 60599:2015 describes how the concentrations of dissolved gases or free gases may be interpreted to diagnose the condition of oil-filled electrical equipment in service and suggest future action. This standard is applicable to electrical equipment filled with mineral insulating oil and insulated with cellulosic paper or pressboard-based solid insulation. Information about specific types of equipment such as transformers (power, instrument, industrial, railways, distribution), reactors, bushings, switchgear and oil-filled cables is given only as an indication in the application notes. This standard may be applied, but only with caution, to other liquid-solid insulating systems. This third edition cancels and replaces the second edition published in 1999 and Amendment 1:2007. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) revision of 5.5, 6.1, 7, 8, 9, 10, A.2.6, A.3, A.7;
b) addition of new sub-clause 4.3;
c) expansion of the Bibliography;
d) revision of Figure 1;
e) addition of Figure B.4.

Matériels électriques remplis d'huile minérale en service - Lignes directrices pour l'interprétation de l'analyse des gaz dissous et des gaz libres

IEC 60599:2015 est disponible sous forme de IEC 60599:2015 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.
IEC 60599:2015 décrit comment les concentrations de gaz dissous ou de gaz libres peuvent être interprétées pour diagnostiquer l'état des matériels électriques remplis d'huile en service et pour proposer une intervention ultérieure. La présente norme s'applique aux matériels électriques remplis d'huile minérale isolante et isolés par des isolants solides constitués de papier ou de carton cellulosiques. Des informations relatives aux types spécifiques de matériels tels que les transformateurs (de puissance, de mesure, industriels, ferroviaires, de distribution), les réactances, les traversées, les appareillages de connexion et les câbles à huile sont données, à titre informatif seulement, dans les notes d'application (voir Annexe A). La présente norme peut être appliquée, mais uniquement avec prudence, à d'autres systèmes d'isolation liquide-solide. Cette troisième édition annule et remplace la deuxième édition parue en 1999 et l'Amendement 1:2007. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) révision de 5.5, 6.1, 7, 8, 9, 10, A.2.6, A.3, A.7 ;
b) ajout d'un nouveau paragraphe 4.3;
c) enrichissement de la Bibliographie;
d) révision de la Figure 1;
e) ajout de la Figure B.4.

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Status
Published
Publication Date
15-Sep-2015
Current Stage
DELPUB - Deleted Publication
Completion Date
25-May-2022
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IEC 60599
Edition 3.0 2015-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE

Mineral oil-filled electrical equipment in service – Guidance on the interpretation

of dissolved and free gases analysis
Matériels électriques remplis d'huile minérale en service – Lignes directrices
pour l'interprétation de l'analyse des gaz dissous et des gaz libres
IEC 60599:2015-09(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60599
Edition 3.0 2015-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE

Mineral oil-filled electrical equipment in service – Guidance on the interpretation

of dissolved and free gases analysis
Matériels électriques remplis d'huile minérale en service – Lignes directrices
pour l'interprétation de l'analyse des gaz dissous et des gaz libres
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.99; 29.040.10; 29.180 ISBN 978-2-8322-2899-9

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 60599:2015 © IEC 2015
CONTENTS

FOREWORD ........................................................................................................................... 5

INTRODUCTION ..................................................................................................................... 7

1 Scope .............................................................................................................................. 8

2 Normative references ...................................................................................................... 8

3 Terms, definitions and abbreviations ............................................................................... 9

3.1 Terms and definitions .............................................................................................. 9

3.2 Abbreviations ........................................................................................................ 11

3.2.1 Chemical names and formulae ....................................................................... 11

3.2.2 General abbreviations .................................................................................... 11

4 Mechanisms of gas formation ........................................................................................ 11

4.1 Decomposition of oil ............................................................................................. 11

4.2 Decomposition of cellulosic insulation ................................................................... 12

4.3 Stray gassing of oil ............................................................................................... 12

4.4 Other sources of gas ............................................................................................. 12

5 Identification of faults .................................................................................................... 13

5.1 General ................................................................................................................. 13

5.2 Dissolved gas compositions .................................................................................. 13

5.3 Types of faults ...................................................................................................... 13

5.4 Basic gas ratios .................................................................................................... 14

5.5 CO /CO ratio ........................................................................................................ 15

5.6 O /N ratio ........................................................................................................... 16

2 2

5.7 C H /H ratio ....................................................................................................... 16

2 2 2

5.8 C hydrocarbons ................................................................................................... 16

5.9 Evolution of faults ................................................................................................. 16

5.10 Graphical representations ..................................................................................... 17

6 Conditions for calculating ratios ..................................................................................... 17

6.1 Examination of DGA values .................................................................................. 17

6.2 Uncertainty on gas ratios ...................................................................................... 17

7 Application to free gases in gas relays ........................................................................... 18

8 Gas concentration levels in service ................................................................................ 19

8.1 Probability of failure in service .............................................................................. 19

8.1.1 General ......................................................................................................... 19

8.1.2 Calculation methods ...................................................................................... 20

8.2 Typical concentration values ................................................................................. 20

8.2.1 General ......................................................................................................... 20

8.2.2 Calculation methods ...................................................................................... 20

8.2.3 Choice of normality percentages .................................................................... 20

8.2.4 Alarm concentration values ............................................................................ 21

8.3 Rates of gas increase ........................................................................................... 21

9 Recommended method of DGA interpretation (see Figure 1) ......................................... 21

10 Report of results ............................................................................................................ 22

Annex A (informative) Equipment application notes .............................................................. 24

A.1 General warning ................................................................................................... 24

A.2 Power transformers ............................................................................................... 24

A.2.1 Specific sub-types ......................................................................................... 24

---------------------- Page: 4 ----------------------
IEC 60599:2015 © IEC 2015 – 3 –

A.2.2 Typical faults ................................................................................................. 24

A.2.3 Identification of faults by DGA ....................................................................... 25

A.2.4 Typical concentration values .......................................................................... 25

A.2.5 Typical rates of gas increase ......................................................................... 26

A.2.6 Specific information to be added to the DGA report (see Clause 10) .............. 27

A.3 Industrial and special transformers ....................................................................... 27

A.3.1 Specific sub-types ......................................................................................... 27

A.3.2 Typical faults ................................................................................................. 27

A.3.3 Identification of faults by DGA. ...................................................................... 27

A.3.4 Typical concentration values .......................................................................... 27

A.4 Instrument transformers ........................................................................................ 28

A.4.1 Specific sub-types ......................................................................................... 28

A.4.2 Typical faults ................................................................................................. 28

A.4.3 Identification of faults by DGA ....................................................................... 29

A.4.4 Typical concentration values .......................................................................... 29

A.5 Bushings ............................................................................................................... 30

A.5.1 Specific sub-types ......................................................................................... 30

A.5.2 Typical faults ................................................................................................. 30

A.5.3 Identification of faults by DGA ....................................................................... 30

A.5.4 Typical concentration values .......................................................................... 31

A.6 Oil-filled cables ..................................................................................................... 31

A.6.1 Typical faults ................................................................................................. 31

A.6.2 Identification of faults by DGA ....................................................................... 31

A.6.3 Typical concentration values .......................................................................... 31

A.7 Switching equipment ............................................................................................. 32

A.7.1 Specific sub-types ......................................................................................... 32

A.7.2 Normal operation ........................................................................................... 32

A.7.3 Typical faults ................................................................................................. 32

A.7.4 Identification of faults by DGA ....................................................................... 32

A.8 Equipment filled with non-mineral fluids ................................................................ 33

Annex B (informative) Graphical representations of gas ratios (see 5.10) ............................ 34

Bibliography .......................................................................................................................... 38

Figure 1 – Flow chart ............................................................................................................ 23

Figure B.1 – Graphical representation 1 of gas ratios (see [3]) .............................................. 34

Figure B.2 – Graphical representation 2 of gas ratios ............................................................ 35

Figure B.3 – Graphical representation 3 of gas ratios – Duval's triangle 1 for

transformers, bushings and cables(see [4]) ........................................................................... 36

Figure B.4 – Graphical representation 4 of gas ratios – Duval's triangle 2 for OLTCs

(see A.7.2) ............................................................................................................................ 37

Table 1 – DGA interpretation table ........................................................................................ 14

Table 2 – Simplified scheme of interpretation ........................................................................ 15

Table 3 – Ostwald solubility coefficients for various gases in mineral insulating oils ............. 19

Table A.1 – Typical faults in power transformers ................................................................... 25

Table A.2 – Ranges of 90 % typical gas concentration values observed in power

transformers, in µl/l ............................................................................................................... 26

---------------------- Page: 5 ----------------------
– 4 – IEC 60599:2015 © IEC 2015
Table A.3 – Ranges of 90 % typical rates of gas increase observed in power

transformers (all types), in µl/l/year ....................................................................................... 26

Table A.4 – Examples of 90 % typical concentration values observed on individual

networks ............................................................................................................................... 28

Table A.5 – Typical faults in instrument transformers ............................................................ 29

Table A.6 – Ranges of 90 % typical concentration values observed in instrument

transformers ......................................................................................................................... 29

Table A.7 – Maximum admissible values for sealed instrument transformers......................... 30

Table A.8 – Typical faults in bushings ................................................................................... 30

Table A.9 – Simplified interpretation scheme for bushings .................................................... 31

Table A.10 – 95 % typical concentration values in bushings .................................................. 31

Table A.11 – Ranges of 95 % typical concentration values observed on cables .................... 32

Table A.12 – Typical faults in switching equipment ............................................................... 32

---------------------- Page: 6 ----------------------
IEC 60599:2015 © IEC 2015 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MINERAL OIL-FILLED ELECTRICAL EQUIPMENT
IN SERVICE – GUIDANCE ON THE INTERPRETATION
OF DISSOLVED AND FREE GASES ANALYSIS
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

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International Standard IEC 60599 has been prepared by IEC technical committee 10: Fluids

for electrotechnical applications.
This third edition cancels and replaces the second edition published in 1999 and
Amendment 1:2007. This edition constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:
a) revision of 5.5, 6.1, 7, 8, 9, 10, A.2.6, A.3, A.7;
b) addition of new sub-clause 4.3;
c) expansion of the Bibliography;
d) revision of Figure 1;
e) addition of Figure B.4.
---------------------- Page: 7 ----------------------
– 6 – IEC 60599:2015 © IEC 2015
The text of this standard is based on the following documents:
FDIS Report on voting
10/967/FDIS 10/973/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

the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
---------------------- Page: 8 ----------------------
IEC 60599:2015 © IEC 2015 – 7 –
INTRODUCTION

Dissolved and free gas analysis (DGA) is one of the most widely used diagnostic tools for

detecting and evaluating faults in electrical equipment filled with insulating liquid. However,

interpretation of DGA results is often complex and should always be done with care, involving

experienced insulation maintenance personnel.

This International Standard gives information for facilitating this interpretation. The first

edition, published in 1978, has served the industry well, but had its limitations, such as the

absence of a diagnosis in some cases, the absence of concentration levels and the fact that it

was based mainly on experience gained from power transformers. The second edition

attempted to address some of these shortcomings. Interpretation schemes were based on

observations made after inspection of a large number of faulty oil-filled equipment in service

and concentrations levels deduced from analyses collected worldwide.
---------------------- Page: 9 ----------------------
– 8 – IEC 60599:2015 © IEC 2015
MINERAL OIL-FILLED ELECTRICAL EQUIPMENT
IN SERVICE – GUIDANCE ON THE INTERPRETATION
OF DISSOLVED AND FREE GASES ANALYSIS
1 Scope

This International Standard describes how the concentrations of dissolved gases or free

gases may be interpreted to diagnose the condition of oil-filled electrical equipment in service

and suggest future action.

This standard is applicable to electrical equipment filled with mineral insulating oil and

insulated with cellulosic paper or pressboard-based solid insulation. Information about

specific types of equipment such as transformers (power, instrument, industrial, railways,

distribution), reactors, bushings, switchgear and oil-filled cables is given only as an indication

in the application notes (see Annex A).

This standard may be applied, but only with caution, to other liquid-solid insulating systems.

In any case, the indications obtained should be viewed only as guidance and any resulting

action should be undertaken only with proper engineering judgment.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and

are indispensable for its application. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any
amendments) applies.

IEC 60050-191:1990, International Electrotechnical Vocabulary – Chapter 191: Dependability

and quality of service (available at http://www.electropedia.org)

IEC 60050-192:2015, International Electrotechnical Vocabulary – Part 192: Dependability

(available at http://www.electropedia.org)

IEC 60050-212:2010, International Electrotechnical Vocabulary – Part 212: Electrical

insulating solids, liquids and gases (available at http://www.electropedia.org)

IEC 60050-604:1987, International Electrotechnical Vocabulary – Chapter 604: Generation,

transmission and distribution of electricity – Operation (available at
http://www.electropedia.org)
IEC 60475, Method of sampling insulating liquids

IEC 60567:2011, Oil-filled electrical equipment – Sampling of gases and analysis of free and

dissolved gases – Guidance

IEC 61198, Mineral insulating oils – Methods for the determination of 2-furfural and related

compounds
---------------------- Page: 10 ----------------------
IEC 60599:2015 © IEC 2015 – 9 –
3 Terms, definitions and abbreviations
3.1 Terms and definitions

For the purposes of this document, the following terms and definitions, some of which are

based on IEC 60050-191, IEC 60050-192, IEC 60050-212 and IEC 60050-604, apply.
3.1.1
fault

unplanned occurrence or defect in an item which may result in one or more failures of the item

itself or of other associated equipment
[SOURCE: IEC 60050-604:1987, 604-02-01]
3.1.2
non-damage fault

fault which does not involve repair or replacement action at the point of the fault

Note 1 to entry: Typical examples are self-extinguishing arcs in switching equipment or general overheating

without paper carbonization or stray gassing of oil.
[SOURCE: IEC 60050-604:1987, 604-02-09]
3.1.3
damage fault
fault that involves repair or replacement action at the point of the fault
[SOURCE: IEC 60050-604:1987, 604-02-08]
3.1.4
incident

event of external or internal origin, affecting equipment or the supply system and which

disturbs its normal operation

Note 1 to entry: For the purposes of the present standard “incidents” are related to internal faults.

Note 2 to entry: For the purposes of the present standard typical examples of “incidents” are gas alarms,

equipment tripping or equipment leakage.
[SOURCE: IEC 60050-604:1987, 604-02-03]
3.1.5
failure
loss of ability to perform as required

Note 1 to entry: In electrical equipment, failure will result from a damage fault or incident necessitating outage,

repair or replacement of the equipment, such as internal breakdown, rupture of tank, fire or explosion.

[SOURCE: IEC 60050-192:2015, 192-03-01]
3.1.6
electrical fault
partial or disruptive discharge through the insulation
3.1.7
partial discharge
electric discharge that only partially bridges the insulation between conductors

Note 1 to entry: A partial discharge may occur inside the insulation or adjacent to a conductor.

---------------------- Page: 11 ----------------------
– 10 – IEC 60599:2015 © IEC 2015

Note 2 to entry: Scintillations of low energy on the surface of insulating materials are often described as partial

discharges but should rather be considered as disruptive discharges of low energy, since they are the

...

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