IEC 62697-1:2012
(Main)Test methods for quantitative determination of corrosive sulfur compounds in unused and used insulating liquids - Part 1: Test method for quantitative determination of dibenzyldisulfide (DBDS)
Test methods for quantitative determination of corrosive sulfur compounds in unused and used insulating liquids - Part 1: Test method for quantitative determination of dibenzyldisulfide (DBDS)
IEC 62697-1:2012 specifies a test method for the quantitative determination of corrosive sulfur compounds-dibenzyl disulfide (DBDS) in used and unused insulating liquids over a 5 to 600 mg kg-1 concentration range.
Méthodes d'essai pour la détermination quantitative des composés de soufre corrosif dans les liquides isolants usagés et neufs - Partie 1: Méthode d'essai pour la détermination quantitative du disulfure de dibenzyle (DBDS)
La CEI 62697-1:2012 spécifie une méthode d essai pour la détermination quantitative des composés de soufre corrosif disulfure de dibenzyle (DBDS) dans les liquides isolants usagés et neufs sur une plage de concentration comprise entre 5 mg kg-1 et 600 mg kg-1.
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IEC 62697-1
Edition 1.0 2012-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Test methods for quantitative determination of corrosive sulfur compounds in
unused and used insulating liquids –
Part 1: Test method for quantitative determination of dibenzyldisulfide (DBDS)
Méthodes d’essai pour la détermination quantitative des composés de soufre
corrosif dans les liquides isolants usagés et neufs –
Partie 1: Méthode d’essai pour la détermination quantitative du disulfure de
dibenzyle (DBDS)
IEC 62697-1:2012
---------------------- Page: 1 ----------------------
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IEC 62697-1
Edition 1.0 2012-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Test methods for quantitative determination of corrosive sulfur compounds in
unused and used insulating liquids –
Part 1: Test method for quantitative determination of dibenzyldisulfide (DBDS)
Méthodes d’essai pour la détermination quantitative des composés de soufre
corrosif dans les liquides isolants usagés et neufs –
Partie 1: Méthode d’essai pour la détermination quantitative du disulfure de
dibenzyle (DBDS)
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX V
ICS 29.040 ISBN 978-2-83220-305-7
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® Registered trademark of the International Electrotechnical CommissionMarque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – 62697-1 © IEC:2012
CONTENTS
FOREWORD ........................................................................................................................... 5
INTRODUCTION ..................................................................................................................... 7
1 Scope ............................................................................................................................... 9
2 Normative references ....................................................................................................... 9
3 Terms, definitions and abbreviations ................................................................................ 9
3.1 Terms and definitions .............................................................................................. 9
3.2 Abbreviations ........................................................................................................ 13
4 Sampling ........................................................................................................................ 13
5 Procedure ...................................................................................................................... 13
5.1 Principle ................................................................................................................ 13
5.2 Significance and use ............................................................................................. 13
5.3 Interferences ......................................................................................................... 14
5.3.1 Co-eluting compounds ............................................................................... 14
5.3.2 Electron capture detector (ECD) ................................................................ 14
5.3.3 Atomic emission detector (AED) ................................................................ 14
5.3.4 Mass spectrometer (MS) ............................................................................ 14
5.3.5 MS/MS ...................................................................................................... 14
5.3.6 Interference from the matrix ....................................................................... 14
5.4 Apparatus .............................................................................................................. 15
5.4.1 Balance ..................................................................................................... 15
5.4.2 Gas chromatography system ..................................................................... 15
5.4.3 Data system .............................................................................................. 16
5.5 Reagents and materials ......................................................................................... 16
5.5.1 Purity of reagents ...................................................................................... 16
5.5.2 Gases ........................................................................................................ 16
5.5.3 Solvents .................................................................................................... 16
5.6 Standard materials ................................................................................................ 16
5.6.1 Dibenzyl disulfide (DBDS) ......................................................................... 16
5.6.2 Diphenyl disulfide (DPDS) ......................................................................... 16
5.6.3 Blank oil .................................................................................................... 16
5.7 Standard solutions ................................................................................................ 17
5.7.1 Stock solution ............................................................................................ 17
5.7.2 Internal standard (IS) solution.................................................................... 17
6 Instrument set-up ........................................................................................................... 17
6.1 Gas chromatograph ............................................................................................... 17
6.1.1 General ..................................................................................................... 17
6.1.2 Carrier gas ................................................................................................ 17
6.1.3 Injector ...................................................................................................... 17
6.1.4 Separation parameters .............................................................................. 17
6.1.5 ECD detection ........................................................................................... 18
6.1.6 AED detection ........................................................................................... 18
6.1.7 MS detection ............................................................................................. 18
6.1.8 MS/MS detection ....................................................................................... 18
6.2 Calibration ............................................................................................................. 19
6.2.1 General ..................................................................................................... 19
6.2.2 Calibration procedure ................................................................................ 19
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6.2.3 Response factor determination (ECD and AED) ......................................... 19
6.2.4 Response factor determination (MS) .......................................................... 19
6.2.5 Response factor determination (MS/MS) .................................................... 20
6.3 Analysis ................................................................................................................ 20
6.3.1 Sample pre-treatment ................................................................................ 20
6.3.2 Sample injection ........................................................................................ 20
6.3.3 Chromatographic run ................................................................................. 20
6.3.4 Peak integration ........................................................................................ 20
6.4 Calculations .......................................................................................................... 21
6.4.1 ECD and AED ............................................................................................ 21
6.4.2 Mass spectrometer (MS) ............................................................................ 21
6.4.3 MS/MS ...................................................................................................... 21
6.5 Results .................................................................................................................. 21
7 Precision data ................................................................................................................ 21
7.1 Detection limit ....................................................................................................... 21
7.2 Repeatability ......................................................................................................... 22
7.3 Reproducibility ...................................................................................................... 22
8 Report ............................................................................................................................ 22
Annex A (informative) Figures with typical chromatograms and results ................................ 23
Annex B (informative) Operating parameters for other suitable detectors ............................. 30
Bibliography .......................................................................................................................... 31
Figure A.1 – GC-ECD chromatogram of 2 mg kg DBDS and DPDS (IS) in whitemineral oil ............................................................................................................................. 23
Figure A.2 – GC-ECD chromatogram of 200 mg kg DBDS and DPDS (IS) in whitemineral oil ............................................................................................................................. 24
Figure A.3 – GC-ECD chromatogram of commercial mineral insulating oil with a known
DBDS contamination ............................................................................................................. 24
Figure A.4 – GC-ECD chromatogram of commercial mineral insulating oil with noknown DBDS contamination .................................................................................................. 25
Figure A.5 – GC-ECD chromatogram of commercial mineral insulating oil with knownDBDS contamination fortified with acommercial polychlorinated biphenyls (PCBs)
formulation............................................................................................................................ 25
Figure A.6 – Carbon and sulfur (C-S) oil finger prints of a commercial mineralinsulating oil with known DBDS contamination obtained with GC-AED .................................. 26
Figure A.7 – C-S oil fingerprints of a commercial mineral insulating oil with no known
DBDS contamination obtained with GC-AED ......................................................................... 26
Figure A.8 – C-S oil fingerprints of a commercial mineral insulating oil with known
DBDS contamination obtained with GC-AED ......................................................................... 27
Figure A.9 – Extracted ion chromatograms of DPDS (IS) molecular ion m/z 218 andDBDS molecular ion m/z 246 in white mineral fortified with DBDS, concentration
4 mg kg ............................................................................................................................. 27
Figure A.10 – Extracted ion chromatograms DPDS (IS) molecular ion m/z 218 andDBDS molecular ion m/z 246 in commercial mineral insulating oil with known DBDS
contamination ....................................................................................................................... 28
Figure A.11 – Extracted ion chromatograms m/z 109 derived from CID of DPDS (IS)molecular ion m/z 218 and m/z 91 derived from CID of DBDS molecular ion m/z 246 in
white mineral fortified with DBDS (4 mg/kg) .......................................................................... 28
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Figure A.12 – Extracted ion chromatograms m/z 109 derived from CID of DPDS (IS)
molecular ion m/z 218 and m/z 91 derived from CID of DBDS molecular ion m/z 246 in
a commercial mineral oil with known DBDS contamination .................................................... 29
Table 1 – Column oven temperature programming parameters ............................................. 18
Table 2 – Mass spectrometer parameters ............................................................................. 18
Table 3 – Repeatability limit .................................................................................................. 22
Table 4 – Reproducibility limit ............................................................................................... 22
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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
TEST METHODS FOR QUANTITATIVE DETERMINATION
OF CORROSIVE SULFUR COMPOUNDS IN UNUSED
AND USED INSULATING LIQUIDS –
Part 1: Test method for quantitative determination
of dibenzyldisulfide (DBDS)
FOREWORD
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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 62697-1 has been prepared by IEC technical committee 10: Fluids
for electrotechnical applications.The text of this standard is based on the following documents:
FDIS Report on voting
10/887/FDIS 10/891/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.
---------------------- Page: 7 ----------------------– 6 – 62697-1 © IEC:2012
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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correctunderstanding of its contents. Users should therefore print this document using a
colour printer.---------------------- Page: 8 ----------------------
62697-1 © IEC:2012 – 7 –
INTRODUCTION
Sulfur can be present in insulating liquids in various forms, including elemental sulfur,
inorganic sulfur compounds and organic sulfur compounds. The number of diverse sulfur
species comprised of different isomers and homologous can run into hundreds. The total
sulfur(TS) concentration in insulating liquids depends on the origin of the liquid, refining
processes and the degree of refining and formulation including addition of additives to the
base oils. Base oils include mineral based paraffinic and naphthenic oils, synthetic iso-
paraffins obtained through gas to liquid conversion process (GTL-Fischer-Tropsch), esters,
poly alpha olefins, poly alkylene glycols, etc. Additives can be comprised of electrostatic
discharge depressants, metal deactivators, metal passivators, phenolic and sulfur containing
antioxidants such as the polysulfides, disulfides, dibenzyl disulfide (DBDS), etc.
Certain sulfur compounds present in the insulating liquids exhibit antioxidant and metal
deactivating properties without being corrosive, whereas other sulfur compounds have been
known to react with metal surfaces. Specifically, sulfur compounds such as mercaptans are
very corrosive to metallic components of electrical devices. Presence of these corrosive sulfur
species has been linked to failures of electrical equipment used in generation, transmission
and distribution of electrical energy for several decades. Therefore, the IEC standard for
mineral insulating oils states that corrosive sulfur compounds shall not be present in unused
and used insulating liquids (see IEC 60296) [5] .Recently, the serious detrimental impact of corrosive sulfur has been linked to the presence of
a specific highly corrosive sulfur compound, DBDS. This compound has been found in certain
mineral insulating oils [1, 14, 15, 16]; presence of this compound has been shown to result in
copper sulfide formation on the surfaces of copper conductors under normal operating
conditions of transformers [2].Current standard test methods for detection of corrosive sulfur (ASTM D1275, methods A and
B, and DIN 51353) and potentially corrosive sulfur in used and unused insulating oil
(IEC 62535) are empirical and qualitative. These methods rely on visual and subjective
perception of colour profiles. The methods do not yield quantitative results in regard to the
concentration of DBDS or other corrosive sulfur compounds present in insulating liquids.
Furthermore, methods for corrosive sulfur and potentially corrosive sulfur in insulating liquids
(ASTM D1275, method B and IEC 62535) are applicable only to mineral insulating oils that do
not contain a metal passivator additive, the methods otherwise can yield negative results even
when corrosive sulfur compounds are present in the insulating liquids – thus providing a false
negative test result. On the other hand, the test method when used with aged insulating oils
(e.g. those with relative high acidity), may give ambiguous results and lead to a false positive
test result. Further analysis of insulating liquids is stipulated, e.g. IEC 62535 specifies that if
there are any doubts in the interpretation of the results of inspection of paper, the composition
of precipitate should be analyzed by other methods (for example by SEM-EDX).For this reason, IEC TC 10 WG 37 was set up to prepare test methods for the unambiguous
quantitative determination of corrosive sulfur compounds in unused and used insulating
liquids. Because of the complexity of such determinations, the test methods are divided into
three parts:Part 1 – Test method for quantitative determination of dibenzyldisulfide (DBDS).
Part 2 – Test methods for quantitative determination of total corrosive sulfur (TCS).
Part 3 – Test methods for quantitative determination of total mercaptans and disulfides (TMD)
and other targeted corrosive sulfur species.___________
Figures in square brackets refer to the bibliography.
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– 8 – 62697-1 © IEC:2012
Health and safety
This part of IEC 62697 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 liquids which are the subject of this standard should be handled with due
regard to personal hygiene. Direct contact with eyes may cause slight 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.Environment
This standard involves mineral insulating oils, natural ester insulating liquids, chemicals and
used sample containers. The disposal of these items should be carried out in accordance with
current national legislation with regard to the impact on the environment. Every precaution
should be taken to prevent the release of chemicals used during the test into the environment.
---------------------- Page: 10 ----------------------62697-1 © IEC:2012 – 9 –
TEST METHODS FOR QUANTITATIVE DETERMINATION
OF CORROSIVE SULFUR COMPOUNDS IN UNUSED
AND USED INSULATING LIQUIDS –
Part 1: Test method for quantitative determination
of dibenzyldisulfide (DBDS)
1 Scope
This part of IEC 62697 specifies a test method for the quantitative determination of corrosive
sulfur compounds-dibenzyl disulfide (DBDS) in used and unused insulating liquids over a 5 –
600 mg kg concentration range.2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including anyamendments) applies.
IEC 60475, Method of sampling liquid dielectrics
IEC 62535:2008, Insulating liquids – Test method for detection of potentially corrosive sulfur
in used and unused insulating oil3 Terms, definitions and abbreviations
For the purposes of this document, the following terms, definitions and abbreviations apply.
3.1 Terms and definitions3.1.1
accuracy
closeness of agreement between test result and the accepted reference value
3.1.2
additive
a suitable chemical substance that is deliberately added to insulating liquid in order to
improve certain characteristicsNote 1 to entry: Examples include antioxidants, pour-point depressants, electrostatic charging tendency
depressant such as benzotriazol (BTA) metal passivator or deactivators, antifoam agent, refining process improver,
etc.3.1.3
atomic emission detector
AED
simultaneously monitors emissions of radiation resulting from atomic species excited in a
microwave-induced plasma and permits quantitative determination of selected heteroatoms in
compounds that elute from a GC columnNote 1 to entry: AED thus provides heteroatom profiles, i.e. “fingerprints” of complex samples such as insulating
liquids.---------------------- Page: 11 ----------------------
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