IEC TR 62697-2:2018

Test methods for quantitative determination of corrosive sulfur compounds in unused and used insulating liquids - Part 2: Test method for quantitative determination of total corrosive sulfur (TCS)

IEC TR 62697-2:2018(E) specifies a test method for the quantitative determination of total corrosive sulfur (TCS) in unused and used insulating liquids and solid matrices through the conversion of corrosive sulfur species to metal (copper, silver etc.) sulfides. The sulfides formed are quantitatively converted to sulfates; sulfates are determined through turbidity measurement or with ion chromatography.
The method is applicable with the following matrices:
a) Unused and used insulating liquids, for example mineral insulating oils and natural esters, which allow the determination of corrosive sulfur compounds over concentrations ranging between 2,5 mg kg-1 to 80 mg kg-1 TCS.
b) Solid matrices that come in contact with the insulating liquid, for example insulating papers in electrical equipment. The quantification limits for these matrices depend on the amount of matrix used during the determination. The method can be used for the quantitative or semi-quantitative determination of copper sulfide on paper after the test according to IEC 62535. The method can provide unambiguous quantitative assessment of copper sulfide present on paper rather than qualitative results obtained with the SEM-EDX examination stipulated in case of doubts in the interpretation of results obtained from the inspection of paper according to IEC 62535:2008, 6.3.
c) Paper and other solid insulating material/s obtained from failed transformers, reactors and other electrical equipment to assist in failure diagnostics.
d) Metal deactivator or passivators additives present in insulating liquids (qualitative assessment).
However, the method is not applicable for assessing corrosion phenomena for example the dissolution of copper in insulating liquids and deposition on solid matrices, which do not lead to sulfide formation.

General Information

• Status: Published
• Publication Date: 13-Feb-2018
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 29.040.10 - Insulating oils
• Technical Committee: TC 10 - Fluids for electrotechnical applications
• Current Stage: PPUB - Publication issued
• Start Date: 12-Mar-2018
• Completion Date: 14-Feb-2018

Standards Content (Sample)

IEC TR 62697-2 ®
Edition 1.0 2018-02
TECHNICAL
REPORT
Test methods for quantitative determination of corrosive sulfur compounds in
unused and used insulating liquids –
Part 2: Test method for quantitative determination of total corrosive sulfur (TCS)
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IEC TR 62697-2 ®
Edition1.0 2018-02
TECHNICAL
REPORT
Test methods for quantitative determination of corrosive sulfur compounds in

unused and used insulating liquids –

Part 2: Test method for quantitative determination of total corrosive sulfur (TCS)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.040.10 ISBN 978-2-8322-5362-5

– 2 – IEC TR 62697-2:2018 © IEC 2018
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 8
4 Sampling . 9
5 Procedure . 9
5.1 Principle . 9
5.2 Significance and use . 9
5.3 Interferences. 9
5.3.1 General . 9
5.3.2 Interferences in turbidity measurements . 10
5.3.3 Interferences in ion chromatography measurements . 10
5.4 Apparatus . 10
5.4.1 Balance . 10
5.4.2 Hot plate with stirrer . 10
5.4.3 Heating block . 10
5.4.4 Turbidity monitor . 10
5.4.5 Ion chromatograph . 10
5.4.6 Data system . 10
5.5 Reagents and materials . 10
5.5.1 Purity of reagents . 10
5.5.2 Gases . 10
5.5.3 Solvents . 10
5.6 Standard materials . 11
5.6.1 Dibenzyl disulfide (DBDS) . 11
5.6.2 Blank oil . 11
5.6.3 Copper powder . 11
5.6.4 Potassium nitrate . 11
5.6.5 Hydrochloric acid . 11
5.6.6 Barium chloride . 11
5.7 Standard solutions . 11
5.7.1 Stock solution . 11
5.7.2 Internal standard (IS) solution . 11
6 Instrument set-up . 12
6.1 Turbidity monitor . 12
6.2 Ion chromatograph . 12
6.2.1 General . 12
6.2.2 Column . 12
6.2.3 Mobile phase . 12
6.2.4 Injector . 12
6.2.5 Suppressor . 12
6.2.6 Conductivity detector . 12
6.3 Corrosive chemistry . 13
6.3.1 Reaction of corrosive sulfur compounds with copper – formation of
Cu S . 13
6.3.2 Conversion of cuprous sulfide into cupric sulfate . 13
6.3.3 Quantification of cupric sulfate in solution . 14
6.3.4 Turbidity measurement . 14
6.3.5 Ion chromatography measurement . 14
6.4 Calibration . 14
6.4.1 General . 14
6.4.2 Calibration procedure . 14
6.4.3 Quantification of total corrosive sulfur (TCS) . 15
6.4.4 Quantification of total corrosive sulfur and DBDS equivalents (DBDS ) . 15
eq
6.5 Results . 15
7 Precision data . 15
7.1 Detection limit . 15
7.2 Repeatability . 16
7.3 Reproducibility . 16
8 Report . 16
Annex A (informative) Figures with typical chromatograms and results . 17
Annex B (informative) RRT results for quantitative determination of corrosive sulfur . 18
Bibliography . 18

Figure A.1 – Ion exchange chromatography detection DBDS as sulfate . 17
Figure A.2 – Photograph of turbidity meter cuvette containing BaSO suspension . 17
Table 1 – Repeatability limit . 16
Table 2 – Reproducibility limit . 16
Table B.1 – Turbidity and ion chromatography . 18
Table B.2 – RRT results for quantitative determination of DBDS (GC-ECD or GC-AED)
– Sample number 1 to 7 . 19
Table B.3 – RRT results for potentially corrosive sulfur according to IEC 62535 –
Sample number 1 to 7 . 19

– 4 – IEC TR 62697-2:2018 © IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
TEST METHODS FOR QUANTITATIVE DETERMINATION OF CORROSIVE
SULFUR COMPOUNDS IN UNUSED AND USED INSULATING LIQUIDS –

Part 2: Test method for quantitative determination
of total corrosive sulfur (TCS)

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