EN 60599:1999

SLOVENSKI STANDARD
01-december-1999
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Mineral oil-impregnated electrical equipment in service - Guide to the interpretation of
dissolved and free gases analysis
In Betrieb befindliche, mit Mineralöl imprägnierte elektrische Geräte - Leitfaden zur
Interpretation der Analyse gelöster und freier Gase
Matériels électriques imprégnés d'huile minérale en service - Guide pour l'interprétation
de l'analyse des gaz dissous et des gaz libres
Ta slovenski standard je istoveten z: EN 60599:1999
ICS:
29.040.10 Izolacijska olja Insulating oils
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

NORME
CEI
INTERNATIONALE
IEC
INTERNATIONAL
Deuxième édition
STANDARD
Second edition
1999-03
Matériels électriques imprégnés d’huile minérale
en service –
Guide pour l’interprétation de l’analyse des gaz
dissous et des gaz libres
Mineral oil-impregnated electrical equipment
in service –
Guide to the interpretation of dissolved
and free gases analysis
 IEC 1999 Droits de reproduction réservés  Copyright - all rights reserved
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60599 © IEC:1999 – 3 –
CONTENTS
Page
FOREWORD . 5
INTRODUCTION . 7
Clause
1 Scope .9
2 Normative references . 9
3 Definitions and abbreviations. 9
4 Mechanisms of gas formation. 15
5 Identification of faults . 17
6 Conditions for calculating ratios. 27
7 Application to free gases in gas relays. 29
8 Gas concentration levels in service. 31
9 Recommended method of DGA interpretation (figure 1) . 37
10 Report of results . 37
Annex A (informative) Equipment application notes . 43
Annex B (informative) Graphical representation of gas ratios . 63
Annex C (informative) Bibliography . 69
Figure 1 – Flow chart . 41
Figure B.1 – Graphical representation 1 of gas ratios . 63
Figure B.2 – Graphical representation 2 of gas ratios . 65
Figure B.3 – Graphical representation 3 of gas ratios – Duval's triangle. 67

60599 © IEC:1999 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
_________
MINERAL OIL-IMPREGNATED ELECTRICAL EQUIPMENT IN SERVICE –
GUIDE TO THE INTERPRETATION OF DISSOLVED AND
FREE GASES ANALYSIS
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The 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 the 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 National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical reports or guides and they are accepted by the National Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60599 has been prepared by IEC technical committee 10: Fluids for
electrotechnical applications.
This second edition cancels and replaces the first edition published in 1978. This second
edition constitutes a technical revision.
The text of this standard is based on the following documents:
FDIS Report on voting
10/450/FDIS 10/460/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.
Annexes A, B and C are for information only.

60599 © IEC:1999 – 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. However, interpretation of DGA results
is often complex and should always be done with care, involving experienced insulation
maintenance personnel.
This guide 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. This second edition attempts to address some of
these shortcomings. Interpretation schemes are 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.

60599 © IEC:1999 – 9 –
MINERAL OIL-IMPREGNATED ELECTRICAL EQUIPMENT IN SERVICE –
GUIDE TO THE INTERPRETATION OF DISSOLVED AND
FREE GASES ANALYSIS
1 Scope
This International Standard is a guide describing 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 guide 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).
The Guide may be applied 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 normative documents contain provisions which, through reference in this text,
constitute provisions of this International Standard. At the time of publication, the editions
indicated were valid. All normative documents are subject to revision, and parties to
agreements based on this International Standard are encouraged to investigate the possibility
of applying the most recent editions of the normative documents indicated below. Members of
IEC and ISO maintain registers of currently valid International Standards.
IEC 60050(191):1990, International Electrotechnical Vocabulary (IEV) – Chapter 191: Depen-
dability and quality of service
IEC 60050(212):1990, International Electrotechnical Vocabulary (IEV) – Chapter 212: Insulating
solids, liquids and gases
IEC 60050(604):1987, International Electrotechnical Vocabulary (IEV) – Chapter 604: Generation,
transmission and distribution of electricity – Operation
IEC 60567:1992, Guide for the sampling of gases and of oil from oil-filled electrical equipment
and for the analysis of free and dissolved gases
IEC 61198:1993, Mineral insulating oils – Methods for the determination of 2-furfural and
related compounds
3 Definitions and abbreviations
3.1 Definitions
For the purpose of this International Standard, the following definitions, some of them based on
IEC 60050(191), IEC 60050(212) and IEC 60050(604) apply:
3.1.1
fault
an unplanned occurrence or defect in an item which may result in one or more failures of the
item itself or of other associated equipment [IEV 604-02-01]
NOTE – In electrical equipment, a fault may or may not result in damage to the insulation and failure of the
equipment.
60599 © IEC:1999 – 11 –
3.1.2
non-damage fault
a fault which does not involve repair or replacement action at the point of the fault
[IEV 604-02-09]
NOTE – Typical examples are self-extinguishing arcs in switching equipment or general overheating without paper
carbonization.
3.1.3
damage fault
a fault which involves repair or replacement action at the point of the fault
[IEV 604-02-08, modified]
3.1.4
incident
an event related to an internal fault which temporarily or permanently disturbs the normal
operation of an equipment [IEV 604-02-03, modified]
NOTE – Typical examples are gas alarms, equipment tripping or equipment leakage.
3.1.5
failure
the termination of the ability of an item to perform a required function [IEV 191-04-01]
NOTE – In the 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
a partial or disruptive discharge through the insulation
3.1.7
partial discharge
a discharge which only partially bridges the insulation between conductors. It may occur inside
the insulation or adjacent to a conductor [IEV 212-01-34, modified]
NOTE 1 – Corona is a form of partial discharge that occurs in gazeous media around conductors which are remote
from solid or liquid insulation. This term is not to be used as a general term for all forms of partial discharges.
NOTE 2 – X-wax is a solid material which is formed from mineral insulating oil as a result of electrical discharges
and which consists of polymerized fragments of the molecules of the original liquid [IEV 212-07-24, modified].
Comparable products may be formed from other liquids under similar conditions.
NOTE 3 – Sparking of low energy, for example because of metals or floating potentials, is sometimes described as
partial discharge but should rather be considered as a discharge of low energy.
3.1.8
discharge (disruptive)
the passage of an arc following the breakdown of the insulation [IEV 604-03-38, modified]
NOTE 1 – Discharges are often described as arcing, breakdown or short circuits. The more specific following terms
are also used:
– sparkover (discharge through the oil);
– puncture (discharge through the solid insulation);
– flashover (discharge at the surface of the solid insulation);
– tracking (the progressive degradation of the surface of solid insulation by local discharges to form conducting or
partially conducting paths);
– sparking discharges which, in the conventions of physics, are local dielectric breakdowns of high ionization
density or small arcs.
NOTE 2 – Depending on the amount of energy contained in the discharge, it will be described as a discharge of low
or high energy, based on the extent of damage observed on the equipment (see 5.2).

60599 © IEC:1999 – 13 –
3.1.9
thermal fault
excessive temperature rise in the insulation
NOTE – Typical causes are
– insufficient cooling,
– excessive currents circulating in adjacent metal parts (as a result of bad contacts, eddy currents, stray losses or
leakage flux),
– excessive currents circulating through the insulation (as a result of high dielectric losses), leading to a thermal
runaway,
– overheating of internal winding or bushing connection lead.
3.1.10
typical values of gas concentrations
gas concentrations normally found in the equipment in service which have no symptoms of
failure, and which are overpassed by only an arbitary percentage of higher gas contents, for
example 10 % (see 8.2.1)
NOTE 1 – Typical values will differ in different types of equipment and in different networks, depending on operating
practices (load levels, climate,
...