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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Published
Publication Date
23-Aug-2012
Current Stage
PPUB - Publication issued
Start Date
24-Aug-2012
Completion Date
24-Aug-2012
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IEC 62697-1:2012 - 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)
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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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---------------------- Page: 2 ----------------------
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

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – 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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62697-1 © IEC:2012 – 3 –

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 white

mineral oil ............................................................................................................................. 23

Figure A.2 – GC-ECD chromatogram of 200 mg kg DBDS and DPDS (IS) in white

mineral 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 no

known DBDS contamination .................................................................................................. 25

Figure A.5 – GC-ECD chromatogram of commercial mineral insulating oil with known
DBDS contamination fortified with acommercial polychlorinated biphenyls (PCBs)

formulation............................................................................................................................ 25

Figure A.6 – Carbon and sulfur (C-S) oil finger prints of a commercial mineral

insulating 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 and
DBDS 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 and
DBDS 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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– 4 – 62697-1 © IEC:2012
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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62697-1 © IEC:2012 – 5 –
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
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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 correct

understanding 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 any
amendments) 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 oil
3 Terms, definitions and abbreviations

For the purposes of this document, the following terms, definitions and abbreviations apply.

3.1 Terms and definitions
3.1.1
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 characteristics

Note 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 column

Note 1 to entry: AED thus provides heteroatom profiles, i.e. “fingerprints” of complex samples such as insulating

liquids.
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– 10 – 62697-1 ©
...

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