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

IEC 60599:2022 describes how the concentrations of dissolved gases or free gases can be interpreted to diagnose the condition of oil-filled electrical equipment in service and suggest future action. This document 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 document can be applied, but only with caution, to other liquid-solid insulating systems. In any case, the indications obtained are given only as guidance with resulting action undertaken only with proper engineering judgment.

Matériels électriques remplis d'huile minérale en service - Recommandations relatives à l'interprétation de l'analyse des gaz dissous et des gaz libres

IEC 60599:2022 décrit la façon dont 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. Le présent document 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 fluide sont données, à titre informatif seulement, dans les notes d'application. Le présent document peut être appliqué, mais uniquement avec prudence, à d'autres systèmes d'isolation liquide-solide. Dans tous les cas, les indications obtenues sont données uniquement à titre de recommandations et toute action qui en résulte n'est à entreprendre qu'après une appréciation technique convenable.

General Information

Status
Published
Publication Date
24-May-2022
Current Stage
PPUB - Publication issued
Completion Date
25-May-2022
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IEC 60599
Edition 4.0 2022-05
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 – Recommandations
relatives à l'interprétation de l'analyse des gaz dissous et des gaz libres
IEC 60599:2022-05(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60599
Edition 4.0 2022-05
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 – Recommandations
relatives à 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 978-2-8322-3696-3

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 60599:2022 © IEC 2022
CONTENTS

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

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

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

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

3 Terms, definitions and abbreviated terms ........................................................................ 8

3.1 Terms and definitions .............................................................................................. 8

3.2 Abbreviated terms ................................................................................................. 10

3.2.1 Chemical names and formulae ....................................................................... 10

3.2.2 General abbreviated terms ............................................................................ 10

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 .................................................................................................... 12

5.1 General ................................................................................................................. 12

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

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

5.4 Basic gas ratios .................................................................................................... 13

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

5.6 O /N ratio ........................................................................................................... 15

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 ..................................................................................... 16

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 ........................................................................... 17

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 ............................................................................ 20

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

9 Recommended method of DGA interpretation ................................................................ 21

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

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

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

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

---------------------- Page: 4 ----------------------
IEC 60599:2022 © IEC 2022 – 3 –

A.2.1 Specific subtypes........................................................................................... 24

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 ....................................... 27

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

A.3.1 Specific subtypes........................................................................................... 27

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

A.3.3 Identification of faults by DGA ....................................................................... 28

A.3.4 Typical concentration values .......................................................................... 28

A.4 Instrument transformers ........................................................................................ 29

A.4.1 Specific subtypes........................................................................................... 29

A.4.2 Typical faults ................................................................................................. 29

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

A.4.4 Typical concentration values .......................................................................... 30

A.5 Oil-impregnated paper bushings ........................................................................... 30

A.5.1 Specific subtypes........................................................................................... 30

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

A.5.3 Identification of faults by DGA ....................................................................... 31

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

A.6 Oil-filled cables ..................................................................................................... 32

A.6.1 Typical faults ................................................................................................. 32

A.6.2 Identification of faults by DGA ....................................................................... 32

A.6.3 Typical concentration values .......................................................................... 32

A.7 Switching equipment ............................................................................................. 33

A.7.1 Specific subtypes........................................................................................... 33

A.7.2 Normal operation ........................................................................................... 33

A.7.3 Typical faults ................................................................................................. 33

A.7.4 Identification of faults by DGA ....................................................................... 33

A.8 Equipment filled with non-mineral fluids ................................................................ 34

Annex B (informative) Graphical representations of gas ratios ............................................. 35

Bibliography .......................................................................................................................... 39

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

Figure B.1 – Graphical representation 1 of gas ratios ............................................................ 35

Figure B.2 – Graphical representation 2 of gas ratios ............................................................ 36

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

transformers, bushings and cables ........................................................................................ 37

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

(see A.7.2) ............................................................................................................................ 38

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

Table 2 – Simplified scheme of interpretation ........................................................................ 14

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 ......................................................................................................................... 26

---------------------- Page: 5 ----------------------
– 4 – IEC 60599:2022 © IEC 2022
Table A.3 – Ranges of 90 % typical rates of gas increase observed in power

transformers (all types) ......................................................................................................... 26

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

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

Table A.5 – Ranges of 90 % typical concentration values observed in WTTs ........................ 28

Table A.6 – Typical faults in instrument transformers ............................................................ 29

Table A.7 – Ranges of 90 % typical concentration values observed in instrument

transformers ......................................................................................................................... 30

Table A.8 – Maximum admissible values for sealed instrument transformers......................... 30

Table A.9 – Typical faults in bushings ................................................................................... 31

Table A.10 – Simplified interpretation scheme for bushings .................................................. 31

Table A.11 – Ranges of 90 % typical concentration values in bushings ................................. 32

Table A.12 – Ranges of 95 % typical concentration values observed on cables .................... 33

Table A.13 – Typical faults in switching equipment ............................................................... 33

---------------------- Page: 6 ----------------------
IEC 60599:2022 © IEC 2022 – 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 international

co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and

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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

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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.

IEC 60599 has been prepared by IEC technical committee 10: Fluids for electrotechnical

applications. It is an International Standard.

This fourth edition cancels and replaces the third edition published in 2015. This edition

constitutes a technical revision.

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

edition:

a) revision of Clause A.5 on bushings, at the request of IEC subcommittee 36A, in order to

transfer to IEC 60599 the corresponding contents of IEC TR 61464 [1] relating to DGA in

bushings and include the new information on DGA in bushings available in CIGRE Technical

Brochure 771 (2019) [2];
___________
Numbers in square brackets refer to the Bibliography.
---------------------- Page: 7 ----------------------
– 6 – IEC 60599:2022 © IEC 2022

b) revision of Clause A.3 on wind turbine transformers, in order to include in IEC 60599 the

new information on DGA in wind turbine transformers available in CIGRE Technical
Brochure 771 (2019) [2].
The text of this International Standard is based on the following documents:
Draft Report on voting
10/1164/FDIS 10/1174/RVD

Full information on the voting for its approval can be found in the report on voting indicated in

the above table.
The language used for the development of this International Standard is English.

This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in

accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available

at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are

described in greater detail at www.iec.ch/publications.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under webstore.iec.ch in the data related to the

specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
---------------------- Page: 8 ----------------------
IEC 60599:2022 © IEC 2022 – 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 document 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 (2015) 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 60599:2022 © IEC 2022
MINERAL OIL-FILLED ELECTRICAL EQUIPMENT
IN SERVICE – GUIDANCE ON THE INTERPRETATION
OF DISSOLVED AND FREE GASES ANALYSIS
1 Scope

This document describes how the concentrations of dissolved gases or free gases can be

interpreted to diagnose the condition of oil-filled electrical equipment in service and suggest

future action.

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

In any case, the indications obtained are given only as guidance with resulting action

undertaken only with proper engineering judgment.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies.

For undated references, the latest edition of the referenced document (including any

amendments) applies.
IEC 60475, Method of sampling insulating liquids

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
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminology databases for use in standardization at the following

addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
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
---------------------- Page: 10 ----------------------
IEC 60599:2022 © IEC 2022 – 9 –
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.
3.1.3
damage fault
fault that involves repair or replacement action at the point of the fault
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 this document "incidents" are related to internal faults.

Note 2 to entry: For the purposes of this document typical examples of "incidents" are gas alarms, equipment

tripping or equipment leakage.
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.

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.

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 result of local

dielectric breakdowns of high ionization density, or small arcs, according to the conventions of physics.

Note 3 to entry: For the purposes of this document the following consideration can also be added:

– Corona is a form of partial discharge that occurs in gaseous media around conductors that are remote from solid

or liquid insulation. This term shall not be used as a general term for all forms of partial discharges.

– As a result of corona discharges, X-wax, a solid material consisting of polymerized fragments of the molecules

of the original liquid, can be formed.
3.1.8
disruptive discharge
passage of an arc following the breakdown

Note 1 to entry: The term "sparkover" (in French: "amorçage") is used when a disruptive discharge occurs in a

gaseous or liquid dielectric.

The term "flashover" (in French: "contournement") is used when a disruptive discharge occurs over the surface of a

solid dielectric surrounded by a gaseous or l
...

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