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The Tony Davies High Voltage Laboratory

Seminars

Speaker(s): Dr Jelena Lukic
Organiser: Richard Brown
Time: 17/12/2015 14:00-15:00
Location: B85/2207

Abstract

Dr Jelena Lukic presents a seminar on sulphur corrosion in power transformers as part of the seminar series within chemistry.

Phenomena of sulphur corrosion and problems encountered following formation of metallic (copper and silver) sulphides in transformer active part emerged in the transformer industry in recent decade. Power transformers failures (estimated more then 200) were related to deposition of metallic sulphides in transformer active part. This emerging problem was a driving wheel for revision of standards and specifications and investigations of the phenomena in transformer industry and scientific community. CIGRE working group A2.40: “Copper sulphide Long-term Mitigation and Risk Assessment” of study committee SC A2 – Transformers was founded in 2009 with a task to improve understanding of sulphur corrosion phenomena, provide mechanism of copper sulphide formation, guidelines for risk assessment and investigate long-term effects of applied mitigation techniques. Background of sulphur corrosion problem in recent decade is provided in introduction.

Further on mechanism of metallic sulphides formation, i.e. copper sulphide deposition in the paper insulation, based on copper in oil dissolved intermediates and growth of copper sulphide in the paper is presented. Oxygen content in the oil, oil composition and additives in the oil were found to have significant impact on copper sulphide deposition in the paper insulation. Postulated mechanism was analyzed in relation to the findings of post-mortem investigations of failed units in order to provide risk assessment guidelines. Brief description of mitigation techniques: metal passivator addition for suppressing copper sulphide formation and oil treatment process for removal of reactive sulphur compounds is provided, as these are nowadays most frequently applied mitigation techniques. Interactions of metal passivator with paper insulation and other side effects (interferences with oil compounds used in transformer oil diagnostics) are shown. In recent years problems encountered with oil reclamation process with adsorbent reactivation used for removal of reactive sulphur compounds was found to be correlated to silver sulphide formation and consequential transformers faults and failures. Differences between silver and copper corrosion were observed, beginning from the differences in sulphur species reactivity, to the risk assessment and mitigation guidelines. Monitoring procedure for detection of “target sulphur compounds”, stringent control of oil treatment processes and introduction of oil treatment process efficient in removal of sulphur species highly reactive to silver are need to counteract silver corrosion.

Speaker Biography

Dr Jelena Lukic

Dr Jelena Lukic, Electrical Engineering Institute Nikola Tesla Koste Glavinica 8A, Serbia. Jelena Lukić, was born on April 28 in Belgrade in 1970. She is PhD in Chemical Engineering, being employed in Electrical Engineering Institute Nikola Tesla since 1996. She is head of the Laboratory for Insulating Oil and Paper Testing, Department of Electrical Measurements. Her main fields of expertise are oil analysis, diagnostics, degradation phenomena of paper/oil insulation, corrosion phenomena induced by corrosive sulphur and oil treatment processes used for removal of oil ageing products, PCB and corrosive sulphur compounds. She is the author of 40 articles, 19 published at international conferences, three of them published in leading scientific papers. Jelena Lukić is Serbian National Committee representative in IEC TC 10, and co-liaison of IEC TC 10 in CIGRE SC A2. She is engaged in various IEC TC 10 working groups and CIGRE SC A2 and D1 working groups (currently in: WG A2.40, WG A2.45, WG A2/D1.46, WG A2/D1 47, AG.D1.01). Jelena Lukić is convenor of CIGRE WG A2.40: “Copper sulphide long-term Mitigation and Risk Assessment”.

Speaker(s): Dr Jelena Lukic
Organiser: Richard Brown
Time: 17/12/2015 14:00-15:00
Location: B85/2207

Abstract

Dr Jelena Lukic presents a seminar on sulphur corrosion in power transformers as part of the seminar series within chemistry.

Phenomena of sulphur corrosion and problems encountered following formation of metallic (copper and silver) sulphides in transformer active part emerged in the transformer industry in recent decade. Power transformers failures (estimated more then 200) were related to deposition of metallic sulphides in transformer active part. This emerging problem was a driving wheel for revision of standards and specifications and investigations of the phenomena in transformer industry and scientific community. CIGRE working group A2.40: “Copper sulphide Long-term Mitigation and Risk Assessment” of study committee SC A2 – Transformers was founded in 2009 with a task to improve understanding of sulphur corrosion phenomena, provide mechanism of copper sulphide formation, guidelines for risk assessment and investigate long-term effects of applied mitigation techniques. Background of sulphur corrosion problem in recent decade is provided in introduction.

Further on mechanism of metallic sulphides formation, i.e. copper sulphide deposition in the paper insulation, based on copper in oil dissolved intermediates and growth of copper sulphide in the paper is presented. Oxygen content in the oil, oil composition and additives in the oil were found to have significant impact on copper sulphide deposition in the paper insulation. Postulated mechanism was analyzed in relation to the findings of post-mortem investigations of failed units in order to provide risk assessment guidelines. Brief description of mitigation techniques: metal passivator addition for suppressing copper sulphide formation and oil treatment process for removal of reactive sulphur compounds is provided, as these are nowadays most frequently applied mitigation techniques. Interactions of metal passivator with paper insulation and other side effects (interferences with oil compounds used in transformer oil diagnostics) are shown. In recent years problems encountered with oil reclamation process with adsorbent reactivation used for removal of reactive sulphur compounds was found to be correlated to silver sulphide formation and consequential transformers faults and failures. Differences between silver and copper corrosion were observed, beginning from the differences in sulphur species reactivity, to the risk assessment and mitigation guidelines. Monitoring procedure for detection of “target sulphur compounds”, stringent control of oil treatment processes and introduction of oil treatment process efficient in removal of sulphur species highly reactive to silver are need to counteract silver corrosion.

Speaker Biography

Dr Jelena Lukic

Dr Jelena Lukic, Electrical Engineering Institute Nikola Tesla Koste Glavinica 8A, Serbia. Jelena Lukić, was born on April 28 in Belgrade in 1970. She is PhD in Chemical Engineering, being employed in Electrical Engineering Institute Nikola Tesla since 1996. She is head of the Laboratory for Insulating Oil and Paper Testing, Department of Electrical Measurements. Her main fields of expertise are oil analysis, diagnostics, degradation phenomena of paper/oil insulation, corrosion phenomena induced by corrosive sulphur and oil treatment processes used for removal of oil ageing products, PCB and corrosive sulphur compounds. She is the author of 40 articles, 19 published at international conferences, three of them published in leading scientific papers. Jelena Lukić is Serbian National Committee representative in IEC TC 10, and co-liaison of IEC TC 10 in CIGRE SC A2. She is engaged in various IEC TC 10 working groups and CIGRE SC A2 and D1 working groups (currently in: WG A2.40, WG A2.45, WG A2/D1.46, WG A2/D1 47, AG.D1.01). Jelena Lukić is convenor of CIGRE WG A2.40: “Copper sulphide long-term Mitigation and Risk Assessment”.

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