Oil-filled electrical equipment - Sampling of gases and analysis of free and dissolved gases - Guidance

IEC 60567:2011 deals with the techniques for sampling free gases from gas-collecting relays from power transformers. Three methods of sampling free gases are described. 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. Since the publication of the previous edition, CIGRE TF.D1.01.15 has made progress in several areas of dissolved gas analysis (DGA). These advances are included in this fourth edition.

Matériels électriques immergés - Echantillonnage de gaz et analyse des gaz libres et dissous - Lignes directrices

La CEI 60567:2011 traite des techniques d'échantillonnage de gaz libres au niveau des relais de protection des transformateurs de puissance. Trois méthodes d'échantillonnage des gaz libres sont décrites. Les techniques décrites tiennent compte, d'une part, des problèmes spéciaux d'analyse liés aux essais de réception en usine, pour lesquels les teneurs en gaz sont généralement très faibles et, d'autre part, des problèmes rencontrés dans la surveillance de l'équipement en service, pour lesquels il se peut que le transport des échantillons se fasse par fret aérien non pressurisé, ou que des différences importantes de températures puissent exister entre le site de prélèvement et le laboratoire d'analyse. Depuis la publication de l'édition précédente, CIGRE TF.D1.01.15 a fait des progrès dans plusieurs domaines de l'analyse AGD. Ces avancées sont incluses dans la quatrième édition.

General Information

Status
Published
Publication Date
19-Oct-2011
Current Stage
PPUB - Publication issued
Start Date
20-Oct-2011
Completion Date
20-Oct-2011
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IEC 60567
Edition 4.0 2011-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Oil-filled electrical equipment – Sampling of gases and analysis of free and
dissolved gases – Guidance
Matériels électriques immergés – Échantillonnage de gaz et analyse des gaz
libres et dissous – Lignes directrices
IEC 60567:2011
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60567
Edition 4.0 2011-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Oil-filled electrical equipment – Sampling of gases and analysis of free and
dissolved gases – Guidance
Matériels électriques immergés – Échantillonnage de gaz et analyse des gaz
libres et dissous – Lignes directrices
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX XA
ICS 29.040 ISBN 978-2-88912-768-9
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – 60567 © IEC:2011
CONTENTS

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

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

1 Scope ............................................................................................................................... 9

2 Normative references ....................................................................................................... 9

3 Sampling of gases from gas-collecting (Buchholz) relays ................................................ 10

3.1 General remarks.................................................................................................... 10

3.2 Sampling of free gases by syringe ......................................................................... 10

3.2.1 Sampling equipment .................................................................................. 10

3.2.2 Sampling procedure................................................................................... 11

3.3 Sampling of free gases by displacement of oil ....................................................... 12

3.4 Sampling of free gases by vacuum ........................................................................ 13

3.5 Sampling of oil from oil filled equipment ................................................................ 14

4 Labelling of gas samples ................................................................................................ 14

5 Sampling, labelling and transferring of oil from oil-filled equipment ................................. 14

5.1 Sampling and labelling of oil .................................................................................. 14

5.2 Transfer of oil for DGA analysis ............................................................................. 14

5.2.1 Transfer from oil syringes .......................................................................... 14

5.2.2 Transfer from ampoules ............................................................................. 15

5.2.3 Transfer from flexible metal bottles ............................................................ 15

5.2.4 Transfer from glass and rigid metal bottles ................................................ 15

6 Preparation of gas-in-oil standards ................................................................................. 15

6.1 General remark ..................................................................................................... 15

6.2 First method: preparation of a large volume of gas-in-oil standard ......................... 15

6.2.1 Equipment ................................................................................................. 15

6.2.2 Procedure .................................................................................................. 16

6.2.3 Calculation ................................................................................................ 18

6.3 Second method: preparation of gas-in-oil standards in a syringe or a vial .............. 18

6.3.1 Equipment ................................................................................................. 19

6.3.2 Procedure .................................................................................................. 20

7 Extraction of gases from oil ............................................................................................ 20

7.1 General remarks.................................................................................................... 20

7.2 Multi-cycle vacuum extraction using Toepler pump apparatus ............................... 21

7.2.1 Toepler pump extraction apparatus ............................................................ 21

7.2.2 Extraction procedure ................................................................................. 24

7.3 Vacuum extraction by partial degassing method .................................................... 25

7.3.1 General remark ......................................................................................... 25

7.3.2 Partial degassing apparatus ...................................................................... 25

7.3.3 Extraction procedure ................................................................................. 26

7.4 Stripping extraction method ................................................................................... 26

7.4.1 Stripping apparatus ................................................................................... 26

7.4.2 Outline of procedure .................................................................................. 29

7.5 Headspace method ............................................................................................... 30

7.5.1 Principle of the method .............................................................................. 30

7.5.2 Symbols and abbreviations ........................................................................ 30

7.5.3 Headspace extraction apparatus................................................................ 31

7.5.4 Headspace extraction procedure ............................................................... 35

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60567 © IEC:2011 – 3 –

7.5.5 Calibration of the headspace extractor ...................................................... 39

8 Gas analysis by gas-solid chromatography ..................................................................... 41

8.1 General remarks.................................................................................................... 41

8.2 Outline of suitable methods using Table 4 ............................................................. 42

8.3 Apparatus .............................................................................................................. 42

8.3.1 Gas chromatograph ................................................................................... 42

8.3.2 Columns .................................................................................................... 44

8.3.3 Carrier gas ................................................................................................ 44

8.3.4 Detectors ................................................................................................... 44

8.3.5 Methanator ................................................................................................ 44

8.3.6 Cold trap ................................................................................................... 44

8.3.7 Integrator and recorder .............................................................................. 44

8.4 Preparation of apparatus ....................................................................................... 45

8.5 Analysis ................................................................................................................ 45

8.6 Calibration of the chromatograph ........................................................................... 45

8.7 Calculations .......................................................................................................... 46

9 Quality control ................................................................................................................ 46

9.1 Verification of the entire analytical system ............................................................. 46

9.2 Limits of detection and quantification ..................................................................... 47

9.3 Repeatability, reproducibility and accuracy ............................................................ 47

9.3.1 General remark ......................................................................................... 47

9.3.2 Repeatability ............................................................................................. 48

9.3.3 Reproducibility ........................................................................................... 48

9.3.4 Accuracy ................................................................................................... 48

10 Report of results ............................................................................................................. 49

Annex A (informative) Correction for incomplete gas extraction in partial degassing

method by calculation ........................................................................................................... 51

Annex B (informative) Mercury-free and shake test versions of the standard extraction

methods ................................................................................................................................ 53

Annex C (informative) Preparation of air-saturated standards .............................................. 55

Annex D (informative) Correction for gas bubbles in syringes and air gap in rigid

bottles .................................................................................................................................. 56

Annex E (informative) Procedure for comparing gas monitor readings to laboratory

results .................................................................................................................................. 57

Bibliography .......................................................................................................................... 58

Figure 1 – Sampling of gas by syringe .................................................................................. 11

Figure 2 – Sampling of free gases by oil displacement .......................................................... 12

Figure 3 – Sampling of free gases by vacuum ....................................................................... 13

Figure 4 – First method of preparing gas-in-oil standards ..................................................... 17

Figure 5 – Second method for preparing gas-in-oil standards ................................................ 19

Figure 6 – Example of a Toepler pump extraction apparatus ................................................. 23

Figure 7 – Types of glass strippers ....................................................................................... 27

Figure 8 – Stainless steel stripper ......................................................................................... 28

Figure 9 – Schematic arrangement for connecting an oil stripper to a gas

chromatograph ...................................................................................................................... 29

Figure 10 – Schematic representation of headspace sampler ................................................ 30

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– 4 – 60567 © IEC:2011

Figure 11 – Vial filled with water ........................................................................................... 32

Figure 12 – Revolving table .................................................................................................. 34

Figure 13 – Schematic arrangement for gas chromatography ................................................ 43

Figure B.1 – Schematic representation of methods in Annex B ............................................. 54

Table 1 – Information required for gas samples .................................................................... 14

Table 2 – Examples of headspace operating conditions ........................................................ 35

Table 3 – Headspace partition coefficients at 70 °C in mineral insulating oil ......................... 40

Table 4 – Examples of gas chromatographic operating conditions ......................................... 41

Table 5 – Required limits of detection in oil ........................................................................... 47

Table 6 – Examples of accuracy of extraction methods ......................................................... 49

Table A.1 – Examples of solubility coefficients a (at 25 ºC) reported by CIGRE TF

D1.01.15 ............................................................................................................................... 51

Table C.1 – Examples of solubility values of air for different oil types ................................... 55

Table C.2 – Examples of temperature variations for oxygen and nitrogen solubility in

mineral oil ............................................................................................................................. 55

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60567 © IEC:2011 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OIL-FILLED ELECTRICAL EQUIPMENT –
SAMPLING OF GASES AND 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,

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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.

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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 itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

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 fourth edition cancels and replaces the third edition, published in 2005, and constitutes a

technical revision.
The main changes with respect to the previous edition are listed below:

Since the publication of the third edition, CIGRE TF.D1.01.15 has made progress in several

areas of dissolved gas analysis (DGA), notably
a) oil sampling,
b) laboratory analysis and solubility coefficients of gases in non-mineral oils,
c) calibration of the headspace gas extraction method,
---------------------- Page: 7 ----------------------
– 6 – 60567 © IEC:2011
d) more sensitive detectors for chromatography,
e) preparation of air-saturated standards and
f) evaluation of gas monitor readings.
These advances are included in this fourth edition.

Sampling of oil for DGA from oil-filled equipment has been moved from IEC 60567 to

IEC 60475 as reflected in the revised title of this standard.
The text of this standard is based on the following documents:
FDIS Report on voting
10/849/FDIS 10/872/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 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.
---------------------- Page: 8 ----------------------
60567 © IEC:2011 – 7 –
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 insulating oils, since experience to date has 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 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.

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.
---------------------- Page: 9 ----------------------
– 8 – 60567 © IEC:2011
Environment

This standard is applicable to insulating oils, chemicals and used sample containers.

Attention is drawn to the fact that, at the time of writing of this standard, many insulating oils

in service are known to be contaminated to some degree by PCBs. If this is the case, safety

countermeasures should 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 should be carried out strictly according to local regulations.

Every precaution should be taken to prevent release of insulating oil into the environment.

---------------------- Page: 10 ----------------------
60567 © IEC:2011 – 9 –
OIL-FILLED ELECTRICAL EQUIPMENT –
SAMPLING OF GASES AND ANALYSIS
OF FREE AND DISSOLVED GASES –
GUIDANCE
1 Scope

This International Standard deals with the techniques for sampling free gases from gas-

collecting relays from power transformers. Three methods of sampling free gases are

described.

The techniques for sampling oil from oil-filled equipment such as power and instrument

transformers, reactors, bushings, oil-filled cables and oil-filled tank-type capacitors are no

longer covered by this standard, but are instead described in 4.2 of IEC 60475:2011.

Before analysing the gases dissolved in oil, they are first 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 (headspace). 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 common 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
...

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