EN 60567:2005

SLOVENSKI SIST EN 60567:2006
STANDARD
januar 2006
Z oljem polnjena električna oprema – Vzorčenje plinov in olja ter analiziranje
prostih in raztopljenih plinov – Napotek (IEC 60567:2005)
(istoveten EN 60567:2005)
Oil-filled electrical equipment – Sampling of gases and of oil for analysis of free
and dissolved gases – Guidance (IEC 60567:2005)
ICS 29.040.10 Referenčna številka
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

EUROPEAN STANDARD EN 60567
NORME EUROPÉENNE
EUROPÄISCHE NORM October 2005

ICS 17.220.99; 29.040.10; 29.035.99 Supersedes EN 60567:1992

English version
Oil-filled electrical equipment –
Sampling of gases and of oil for analysis of
free and dissolved gases –
Guidance
(IEC 60567:2005)
Matériels électriques immergés – Ölgefüllte elektrische Betriebsmittel –
Echantillonnage de gaz et d'huile pour Probennahme von Gasen und von Öl
analyse des gaz libres et dissous – für die Analyse freier und gelöster Gase –
Lignes directrices Anleitung
(CEI 60567:2005) (IEC 60567:2005)

This European Standard was approved by CENELEC on 2005-09-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,
Switzerland and United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 60567:2005 E
Foreword
The text of document 10/621/FDIS, future edition 3 of IEC 60567, prepared by IEC TC 10, Fluids for
electrotechnical applications, was submitted to the IEC-CENELEC parallel vote and was approved by
CENELEC as EN 60567 on 2005-09-01.
This European Standard supersedes EN 60567:1992.
The main changes with respect to EN 60567:1992 are listed below.
Since the publication of EN 60567:1992, a number of new gas extraction methods have been
developed and are commercially available, such as mercury-free versions of the standard Toepler and
partial degassing methods, which are referenced to in Annex C of this new edition. The head space
method, based on a new concept for the extraction of gases from oil is introduced as a full method,
and reference is made to a simplified version of it also in Annex C (shake test method). More sensitive
chromatographic techniques have also been developed and are presented in this new edition of the
standard.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2006-06-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2008-09-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60567:2005 was approved by CENELEC as a European
Standard without any modification.
__________
- 3 - EN 60567:2005
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE Where an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
1) 2)
IEC 60296 - Fluids for electrotechnical applications - EN 60296 2004
Unused mineral insulating oils for + corr. September 2004
transformers and switchgear
1) 2)
IEC 60599 - Mineral oil-impregnated electrical EN 60599 1999
equipment in service - Guide to the
interpretation of dissolved and free gases
analysis
1) 2)
ISO/IEC 17025 - General requirements for the competence EN ISO/IEC 2005
of testing and calibration laboratories 17025

ISO 5725 Series Accuracy (trueness and precision) of - -
measurement methods and results

1)
Undated reference.
2)
Valid edition at date of issue.

NORME CEI
INTERNATIONALE
IEC
INTERNATIONAL
Troisième édition
STANDARD
Third edition
2005-06
Matériels électriques immergés –
Echantillonnage de gaz et d'huile
pour analyse des gaz libres et dissous –
Lignes directrices
Oil-filled electrical equipment –
Sampling of gases and of oil for analysis
of free and dissolved gases – Guidance

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60567  IEC:2005 – 3 –
CONTENTS
FOREWORD.7
INTRODUCTION.11

1 Scope.15
2 Normative references .15
3 Sampling of gases from gas-collecting (Buchholz) relays.17
3.1 General remarks.17
3.2 Sampling of free gases by syringe.17
3.3 Sampling of free gases by displacement of oil .19
3.4 Sampling of free gases by vacuum .21
4 Sampling of oil from oil-filled equipment .21
4.1 General remarks.21
4.2 Sampling of oil by syringe .23
4.3 Sampling of oil by sampling tube .25
4.4 Sampling of oil by bottles .27
4.5 Disposal of waste oil .29
5 Labelling of samples.29
6 Preparation of gas-in-oil standards .31
6.1 First method: preparation of a large volume of gas-in-oil standard.31
6.2 Second method: preparation of gas-in-oil standards in a syringe or a vial.35
7 Extraction of gases from oil .37
7.1 General remarks.37
7.2 Multi-cycle vacuum extraction using Toepler pump apparatus .39
7.3 Vacuum extraction by partial degassing method .43
7.4 Stripping extraction method.47
7.5 Head-space method .49
8 Gas analysis by gas-solid chromatography.69
8.1 General remarks.69
8.2 Outline of suitable methods using Table 3 .71
8.3 Apparatus.71
8.4 Preparation of apparatus .75
8.5 Analysis .77
8.6 Calibration of the chromatograph.77
8.7 Calculations .79
9 Quality control .79
9.1 Verification of the entire analytical system.79
9.2 Limits of detection and quantification.81
9.3 Repeatability, reproducibility and accuracy.83
10 Report of results.87

60567  IEC:2005 – 5 –
Annex A (informative) Procedure for testing the integrity of the syringes before filling
with oil (see Figure 4) .121
Annex B (informative) Correction for incomplete gas extraction in partial degassing
method by calculation .123
Annex C (informative) Mercury-free and shake test versions of the standard
extraction methods .125
Annex D (informative) Preparation of air-saturated standards .127

60567  IEC:2005 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
OIL-FILLED ELECTRICAL EQUIPMENT –
SAMPLING OF GASES AND OF OIL FOR ANALYSIS
OF FREE AND DISSOLVED GASES – GUIDANCE

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 60567 has been prepared by IEC technical committee 10: Fluids
for electrotechnical applications.
This third edition cancels and replaces the second edition published in 1992. This edition
constitutes a technical revision.
The main changes with respect to the previous edition are listed below.
Since the publication of the second edition of this standard, a number of new gas extraction
methods have been developed and are commercially available, such as mercury-free versions
of the standard Toepler and partial degassing methods, which are referenced to in Annex C of
the present edition. The head space method, based on a new concept for the extraction of
gases from oil is introduced as a full method in this third edition, and reference is made to a
simplified version of it also in Annex C (shake test method). More sensitive chromatographic
techniques have also been developed since the last edition, and are presented in this third
edition.
60567  IEC:2005 – 9 –
The text of this standard is based on the following documents:
FDIS Report on voting
10/621/FDIS 10/630/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 maintenance result date indicated on the IEC web site 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.
60567  IEC:2005 – 11 –
INTRODUCTION
Gases may be formed in oil-filled electrical equipment due to natural ageing but also, to a
much greater extent, as a result of faults.
Operation with a fault may seriously damage the equipment, and it is valuable to be able to
detect the fault at an early stage of development.
Where a fault is not severe, the gases formed will normally dissolve in the oil, with a small
proportion eventually diffusing from the liquid into any gas phase above it. Extracting
dissolved gas from a sample of the oil and determining the amount and composition of this
gas is a means of detecting such faults, and the type and severity of any fault may often be
inferred from the composition of the gas and the rate at which it is formed.
In the case of a sufficiently severe fault, free gas will pass through the oil and collect in the
gas-collecting (Buchholz) relay if fitted; if necessary, this gas may be analysed to assist in
determining the type of fault that has generated it. The composition of gases within the
bubbles changes as they move through the oil towards the gas-collecting relay.
This can be put to good use, as information on the rate of gas production may often be
inferred by comparing the composition of the free gases collected with the concentrations
remaining dissolved in the liquid.
The interpretation of the gas analyses is the subject of IEC 60599.
These techniques are valuable at all stages in the life of oil-filled equipment. During
acceptance tests on transformers in the factory, comparison of gas-in-oil analyses before,
during and after a heat run test can show if any hot-spots are present, and similarly analysis
after dielectric testing can add to information regarding the presence of partial discharges or
sparking. During operation in the field, the periodic removal of an oil sample and analysis of
the gas content serve to monitor the condition of transformers and other oil-filled equipment.
The importance of these techniques has led to the preparation of this standard to the
procedures to be used for the sampling, from oil-filled electrical equipment, of gases and oils
containing gases, and for subsequent analysis.
NOTE Methods described in this standard apply to mineral insulating oils, since experience to date bas been
almost entirely with such oils. The methods may also be applied to other insulating liquids, in some cases with
modifications.
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.
60567  IEC:2005 – 13 –
Mercury presents an environmental and health hazard. Any spillage should immediately be
removed and be properly disposed of. Consult local regulations for mercury use and handling.
Mercury-free methods may be requested in some countries.
Environment
This standard is applicable to mineral oils, chemicals and used sample containers.
Attention is drawn to the fact that, at the time of writing of this standard, many mineral oils in
service are known to be contaminated to some degree by PCBs. As this is the case, safety
countermeasures must be taken to avoid risks to workers, the public and the environment
during the life of the equipment, by strictly controlling spills and emissions. Disposal or
decontamination of these oils must be carried out strictly according to local regulations. Every
precaution should be taken to prevent release of mineral oil into the environment.

60567  IEC:2005 – 15 –
OIL-FILLED ELECTRICAL EQUIPMENT –
SAMPLING OF GASES AND OF OIL FOR ANALYSIS
OF FREE AND DISSOLVED GASES – GUIDANCE

1 Scope
This International Standard deals with the techniques for sampling free gases from gas-
collecting relays and for sampling oil from oil-filled equipment such as power and instrument
transformers, reactors, bushings, oil-filled cables and oil-filled tank-type capacitors. Three
methods of sampling free gases and three methods of sampling oil are described; the choice
between the methods often depends on the apparatus available and on the quantity of oil
needed for analysis.
Before analysing the gases dissolved in oil, they must first be extracted from the oil. Three
basic methods are described, one using extraction by vacuum (Toepler and partial
degassing), another by displacement of the dissolved gases by bubbling the carrier gas
through the oil sample (stripping), and the last one by partition of gases between the oil
sample and a small volume of the carrier gas (head space). The gases are analysed
quantitatively after extraction by gas chromatography; a method of analysis is described. Free
gases from gas-collecting relays are analysed without preliminary treatment.
The preferred method for assuring the performance of the gas extraction and analysis
equipment, considered together as a single system, is to degas samples of oil prepared in the
laboratory and containing known concentrations of gases (“gas-in-oil standards”) and
quantitatively analyse the gases extracted. Two methods of preparing gas-in-oil standards are
described.
For daily calibration checks of the chromatograph, it is convenient to use a standard gas
mixture containing a suitable known amount of each of the gas components to be in a similar
ratio to the commons ratios of the gases extracted from transformer oils.
The techniques described take account, on the one hand, of the problems peculiar to
analyses associated with acceptance testing in the factory, where gas contents of oil are
generally very low and, on the other hand, of the problems imposed by monitoring equipment
in the field, where transport of samples may be by un-pressurized air freight and where
considerable differences in ambient temperature may exist between the plant and the
examining laboratory.
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 60296, Fluids for electrotechnical applications – Unused mineral insulating oils for
transformers and switchgear
IEC 60599, Mineral oil-impregnated electrical equipment in service – Guide to the inter-
pretation of dissolved and free gases analysis

60567  IEC:2005 – 17 –
ISO/IEC 17025, General requirements for the competence of testing and calibration
laboratories
ISO 5725 (all parts), Accuracy, trueness and precision of measurement methods and results
3 Sampling of gases from gas-collecting (Buchholz) relays
3.1 General remarks
It is important to bear in mind that receiving a qualitative and a representative sample is
crucial for obtaining a reliable diagnosis of the electrical equipment. Even the most
sophisticated extraction or diagnosis methods cannot overcome faulty samples.
Gas samples from relays should be taken from the equipment with the minimum delay after
gas accumulation has been signalled. Changes in composition caused by the selective re-
absorption of components may occur if free gases are left in contact with oil.
Certain precautions are necessary when taking gas samples. The connection between the
sampling device and the sampling vessel must avoid the ingress of air. Temporary
connections should be as short as possible. Any rubber or plastic tubing used should have
been proved to be impermeable to gases.
Gas samples should be properly labelled (see Clause 5) and analysed without undue delay to
minimize hydrogen loss (for example, within a maximum period of one week).
Oxygen, if present in the gas, may react with any oil drawn out with the sample. Reaction is
delayed by excluding light from the sample, for example, by wrapping the vessel in aluminium
foil or suitable opaque material.
Of the three methods described below, the syringe method is recommended. The other two
methods are alternatives to be used exclusively in case of serious hindrance.
Sampling into a sampling tube by liquid displacement using transformer oil as a sealing liquid
is simple, but the different solubilities of the gas components may need to be taken into
account if the gas quantity is such that some oil remains in the tube.
The vacuum method requires skill to avoid contaminating the sample by leakage of air into the
system. It is particularly true where the gas to be sampled may be at less than atmospheric
pressure (for example, some sealed transformers).
3.2 Sampling of free gases by syringe
3.2.1 Sampling equipment
See Figure 1.
a) Impermeable oil-resistant plastic or rubber tubing (3) provided with a connecter to fit onto
a suitable sampling connection of the gas-collecting relay. To avoid cross-contamination,
the tubing should be used only once.

60567  IEC:2005 – 19 –
b) Gas-tight syringes of suitable volume (1) (25 ml to 250 ml). Medical or veterinary quality
glass syringes with ground-in plungers may be suitable; alternatively, syringes with oil-
proof seals may be used. The syringe should be fitted with a cock enabling it to be sealed.
It is often convenient to use the same syringes for both gas sampling and for oil sampling
(see item b) of 4.2.1). The gas tightness of a syringe may be tested by storing an oil
sample containing a measurable quantity of hydrogen for at least two weeks and analysing
aliquots for hydrogen at the beginning and end of the period. An acceptable syringe will
permit losses of hydrogen of less than 2,5 % per week. General experience suggests that
all-glass syringes leak less than those using plastic seals. Improvement of the gas
tightness may be obtained by the use of a lubricant such as a light grease or transformer
oil.
It is a good practice to test the integrity of syringes and stopcock system before the
sampling. A recommended procedure appears in Annex A.
c) Transport containers which should be designed to hold the syringe firmly in place during
transport but allow the syringe plunger freedom to move, and prevent its tip from
contacting the container whatever its position during transportation.
3.2.2 Sampling procedure
The apparatus is connected as shown in Figure 1. The connections should be as short as
possible and filled with oil at the start of sampling.
Sampling valve (5) is opened. If sampling from a gas-collecting relay on a transformer fitted
with a conservator, a positive pressure will exist; the three-way cock (4) is carefully turned to
position A and the oil in the connecting tubing (3) allowed to flow to waste (7). When gas
reaches the three-way cock (4), the latter is turned to position B to connect the pre-lubricated
syringe (1). Cock (2) is then opened and the syringe allowed to fill under the hydrostatic
pressure, taking care that its plunger is not expelled. When a sufficient sample has been
taken, cock (2) and sampling valve (5) are closed and the apparatus is disconnected.
The oil in the syringe is expelled by inverting the syringe and applying gentle pressure to the
plunger.
Label carefully the sample (see Clause 5).
3.3 Sampling of free gases by displacement of oil
This method is reliable only where the gas sample is at or above atmospheric pressure. The
apparatus is shown in Figure 2.
The sampling tube (28), typically of 100 ml capacity, is preferably of glass since the operator
can then see how much oil remains in it during gas sampling. The sampling tube is filled with
oil from the transformer on site. Before being used as described below, the connecting tube
(3) should also be filled with oil.
The open end of the connecting tube (3) is fitted onto the gas sampling valve (5). The
sampling valve and inlet cock of the sampling tube are opened. The sampling tube is inclined
so that its closed end is the lowest point. The outlet cock on the sampling tube is then
opened, allowing oil to run out to waste (7), drawing first any oil from the connection between
relay and sampling valve, and the gas from the relay, into the sampling tube.

60567  IEC:2005 – 21 –
Sampling is complete when the gas collecting relay is completely filled with oil or when nearly
all oil has gone from the sampling tube.
Both cocks (2) on the sampling tube and the sampling valve (5) are closed and then the
connections removed.
3.4 Sampling of free gases by vacuum
The apparatus is connected as shown in Figure 3. With the equipment sampling valve closed,
cocks (1), (2) and (10) open, and the three-way cock (4) turned to position A, the vacuum
pump (12) is allowed to evacuate the connecting tubing, the trap and the sampling vessel.
A satisfactory vacuum will be below 100 Pa. The system should be checked for leaks by
closing the pump suction cock (10) and observing that no appreciable change in vacuum
occurs. Over a time equal to that which will be taken for sampling, the pressure should not
increase by more than 100 Pa. Similarly, the stopcock (1) on the sampling tube should be
vacuum tight to the same degree over several weeks.
If the connecting tubing between the equipment sampling valve (5) and the gas-collecting
relay is filled with oil, the three-way cock (4) is turned to position (B). The equipment sampling
valve (5) is carefully opened and oil allowed to flow into the trap (9). When the end of the oil
stream is observed to reach the three-way cock (4), it is turned to position D to evacuate the
oil from it. Thereafter, cock (4) is turned to position C. When sampling is complete, cock (1) is
closed first, then the equipment sampling valve (5) closed and the apparatus disconnected.
If the connecting tubing between the equipment and the sampling valve is empty of oil, the
procedure for draining oil is omitted and the three-way cock (4) used in position C after
evacuating and testing that the apparatus is leak tight.
4 Sampling of oil from oil-filled equipment
4.1 General remarks
It is important to bear in mind that receiving a qualitative and a representative sample is
crucial for obtaining a reliable diagnosis of the electrical equipment. Even the most
sophisticated extraction or diagnosis methods cannot overcome faulty samples.
Warning: When sampling oil, precautions should be taken to deal with any sudden release of
oil and avoid oil spillage.
Of the three methods described below, the method of sampling by syringe is recommended.
The other two methods are alternatives to be used in case of difficulties.
Sampling into glass sampling tubes is also suitable provided they are fitted with sufficient
lengths of rubber tubing acting as expansion devices.
Stainless steel sampling tubes fitted with valves are very robust and are not affected by large
temperature changes and can be used without expansion devices.

60567  IEC:2005 – 23 –
Sampling in glass bottles is also adequate provided the bottles are fitted with a suitable cap
which allows oil expansion. Sampling into bottles is simple, requires little skill, and is
adequate for many purposes such as routine sampling on a large scale from equipment on
site. The use of bottles (0,5 l to 2,5 l capacity) may be preferred where comparatively large
samples of oil are required. When using the glass bottle sampling method, care should be
taken to minimize air contact with the sample.
The methods described are suitable for large oil-volume equipment such as power
transformers. With small oil-volume equipment, it is essential to ensure that the total volume
of oil drawn off does not endanger the operation of the equipment.
The selection of points from which samples are drawn should be made with care. Normally,
the sample should be taken from a point where it is representative of the bulk of the oil in the
equipment. It will sometimes be necessary, however, to draw samples deliberately where they
are not expected to be representative (for example, in trying to locate the site of a fault).
Samples should be taken with the equipment in its normal condition. This will be important in
assessing the rate of gas production.
Some of the dissolved oxygen present in the oil sample may be consumed by oxidation. The
reaction can be delayed by exclusion of light (for example, by wrapping a clear glass sampling
vessel in an opaque material) but, in any case, the analysis should be carried out as soon as
possible after sampling.
NOTE 1 When sampling from bushings, the manufacturer’s instructions should be followed carefully. Failure to do
so may lead to serious damage and bushing failure. The oil sampling should be carried out on de-energized
bushings. When sampling, precautions should be taken to deal with any sudden release of oil. Samples should be
taken with the off-load equipment in its normal position in order to assess correctly the bushing condition.
NOTE 2 For transformers with two sampling valves, the following procedure should be used: open the outer valve
first, followed by the second one. This is particularly important to avoid entrance of air into the transformers.
4.2 Sampling of oil by syringe
4.2.1 Sampling equipment
a) Impermeable oil-proof plastic or rubber tubing to connect the equipment to the syringe.
This should be as short as possible. A three-way cock should be inserted in the tubing.
The connection between the tubing and the equipment will depend upon the equipment. If
a sampling valve suitable for fitting to a tubing has not been provided, it may be necessary
to use a drilled flange or a bored oil-proof rubber bung on a drain or filling connection.
NOTE Sampling by syringe is the procedure recommended for bushings by IEC SC36A. In the case of
bushings fitted with a sampling point at the mounting flange, the described procedure applies.
In the case of bushings not fitted with a sampling point at mounting flange, it may be
possible to take a sample from the top of the bushing. The manufacturer’s instructions
should be consulted to determine a suitable position. Insert one end of the sampling tube
into the bushing, from the top, and connect the other end to the three-way stopcock on the
syringe, using plastic coupling, then follow the same procedure.
In the case of bushings pressurized at ambient temperature, the procedure is not
applicable, and reference should be made to the instructions of the equipment
manufacturer.
60567  IEC:2005 – 25 –
b) Graduated gas-tight syringes of a size suitable for containing an adequate oil sample
volume (20 ml to 250 ml) fitted with a cock or an obturator so that it may be sealed. See
item b) of 3.2.1 for checking the gas-tightness of the syringe. The size of sample required
depends on the likely concentration of gas in the sample, the analytical techniques and
the sensitivity required.
c) Transport containers which should be designed to hold the syringe firmly in place during
transport but allow the syringe plunger freedom to move and prevent its tip from
contacting the container whatever its position during transportation.
4.2.2 Sampling procedure
See Figure 4.
a) The blank flange or cover (11) of the sampling valve is removed and the outlet cleaned
with a lint-free cloth to remove all visible dirt. The apparatus is then connected as shown
in Figure 4a, and the equipment sampling valve (5) opened.
b) The three-way cock (4) is adjusted (position A) to allow 1 l to 2 l of oil to flow to waste (7)
(or less, see note).
c) The three-way cock (4) is then turned (position B) to allow oil to enter the syringe slowly
(Figure 4b). The plunger should not be withdrawn but allowed to move back under the
pressure of the oil.
d) The three-way cock (4) is then turned (position C) to allow the oil in the syringe to flow to
waste (7) and the plunger pushed to empty the syringe. To ensure that all air is expelled
from the syringe, it should be approximately vertical, nozzle upwards, as shown in Figure
4c. Confirm that the inner surfaces of the syringe and plunger are completely oiled.
e) The procedure described in steps 3) and 4) of this subclause is then repeated until no gas
bubble is present. Then the three-way stopcock (4) is turned to position B and the syringe
filled with oil (Figure 4d).
f) The cock (2) on the syringe and the sampling valve (5) are then closed.
g) The three-way stop-cock (4) is turned to position C and the syringe disconnected (Figure
4).
Label carefully the sample (see Clause 5).
NOTE 1 In the case of small oil-volume equipment, the procedure described in step b) of this subclause is not
applicable, and lower volumes should be removed. Reference should be made to the instructions of the equipment
manufacturer.
NOTE 2 It is good practice to avoid contamination of the outer surface of the plunger and inner surfaces of the
syringe by dust or sand. Those particles can affect the sealing properties of the syringe. This kind of contamination
can be originated by dusty winds or from the handling of the syringe.
NOTE 3 In the case of sealed transformers, if a bubble appears in the syringe directly after sampling, it is
recommended to resample.
4.3 Sampling of oil by sampling tube
4.3.1 Sampling equipment
a) Impermeable oil-proof plastic or rubber tubing to connect the equipment to the sampling
tube. This should be as short as possible.
The connection between the tubing and the equipment will depend upon the equipment. If
a sampling valve suitable for fitting to a tubing has not been provided, it may be necessary
to improvise by using a drilled flange, or a bored oil-proof rubber bung on a drain or filling
connections.
60567  IEC:2005 – 27 –
b) Glass or metal sampling tube, typically of volume 250 ml to 1 l. It may be closed either by
cocks or pinch cocks on impermeable oil-resistant tubing or by valves.
A sampling tube and its seal design is acceptable if the loss of hydrogen of the sample
contained is less than 2,5 % each week.
The size of sample required depends on the likely concentration of gas in the sample, the
analytical technique and the sensitivity required.
c) Transport containers, which should be designed to hold the sampling tubes firmly in place
during transport.
4.3.2 Sampling procedure
See Figure 5.
a) The blank flange or cover (11) of the sampling valve is removed and the outlet cleaned
with a lint-free cloth to remove all visible dirt. The device is then connected as shown in
Figure 5.
b) The cocks (2) on the sampling tube (28) are opened and the equipment sampling valve (5)
is carefully opened so that oil flows through the sampling tube to waste (7).
c) After the sampling tube (28) has been completely filled with oil, about 1 l to 2 l are allowed
to flow to waste (7) (see Note 2).
d) The oil flow is then closed by shutting off firstly the outer cock (2), then the inner one (2)
and finally the sampling valve (5).
e) The sampling tube (28) is then disconnected and the sample carefully labelled (see
Clause 5).
NOTE 1 If a glass sampling tube with integral glass cocks is used, it is preferable to drain 1 ml or 2 ml of oil from
it prior to transporting it back to the laboratory in order to avoid breaking the tube in the event of it being exposed
to a rise in ambient temperature. Record on the label that this has been done.
NOTE 2 In the case of small oil-volume equipment, the procedure described in step c) of this subclause is not
applicable. Reference should be made to the instructions of the equipment manufacturer.
4.4 Sampling of oil by bottles
4.4.1 Sampling equipment
a) Impermeable oil-proof plastic or rubber tubing to connect the equipment to the bottle. This
should be as short as possible.
The connection between the tubing and the equipment will depend upon the equipment. If
a sampling valve suitable for fitting to a tubing has not been provided, it may be necessary
to improvise by using a drilled flange, or a bored oil-proof rubber bung on a drain or filling
connections.
b) Glass or metal bottles capable of being sealed gas-tight, typically of volume 0,5 l to 2,5 l.
Suitable bottles have, for example, screwed plastic caps holding a conical polyethylene
seal (see Figure 6b). A bottle and seal design is acceptable if it permits losses of
hydrogen of less than 2,5 % each week.
c) Transport containers, designed to protect the bottle during transport.
4.4.2 Sampling procedure
See Figure 6a.
a) The blank flange or cover (11) of the equipment sampling valve is removed and the outlet
cleaned with a lint-free cloth to remove all visible dirt.

60567  IEC:2005 – 29 –
b) Connect the oil-proof plastic or rubber tubing (3) to the equipment.
c) The sampling valve (5) is carefully opened and about 1 l to 2 l of oil allowed to flow to
waste (7) through the tubing (3) ensuring that all gas bubbles are eliminated before the oil
sample is collected (see the note at the end of this subclause).
d) Place the end of the tubing (3), with the oil still flowing, at the bottom of the sampling
bottle and allow the bottle to fill slowly.
e) Allow about one bottle volume to overflow to waste (7), then withdraw the tubing (3) slowly
with the oil still flowing.
f) Close the sampling valve (5) and disconnect the tubing.
g) Tilt the bottle to allow the oil level to fall a few millimetres from the rim so as to leave a
small expansion volume. Place the bottle cap securely in position and label the sample
(see Clause 5).
NOTE In the case of small oil-volume equipment, the procedure described in steps c) and e) of this subclause is
not applicable. Reference should be made to the instructions of the equipment manufacturer.
4.5 Disposal of waste oil
Waste oil shall be disposed of according to local regulations.
5 Labelling of samples
Oil and gas samples should be properly labelled before dispatch to the laboratory.
The following information is necessary (whenever it is known).
Transformer Sampling
- customer - sampling date
- location - sampling point
- transformer number - sampling person
- manufacturer - reason for analysis (routine or other)
- general type (power, instrument or - transforme
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