Introduction: The long-term effects of passivation as a remedial strategy to keep transformers in operation are poorly understood and largely informed by experience over a limited number of years rather than laboratory studies that consider the potential chemical reactions. The effectiveness with which copper surfaces are coated with passivator following retrospective addition of Irgamet 39 TM to a transformer has not been studied.

In this study we will investigate, and gain a greater understanding of, the chemical effects of passivation through laboratory based experiments, and visits into the field. The proposed work will involve collaboration between the School of Chemistry at the University of Southampton and the Tony Davies High Voltage Laboratory, building upon a highly effective collaborative relationship developed during the recently completed, IFI-funded feasibility study on corrosion in the gas phase. Questions that are to be addressed during this study include:

• What is the long term stability of passivator on the surface of copper?

• Is it necessary to add more passivator when it is consumed in the oil? How might one analyse the surface of copper for the presence of passivator?

• Can this be used on scrapped transformers to investigate whether the passivator gets through all the paper insulation to where it is needed?

• If passivator works by coating the surface of copper, which has a fixed surface area, why have others reported that more is required when you have a higher concentration of DBDS?

Objectives:

The objective of this proposal is to reduce the risk of transformer failure and unreliability resulting from corrosive sulphur in oil.

This key objective will be met by:

• Better understanding of the mechanism by which copper sulphide failures occur and the effectiveness of passivation

• Fully understanding the effects, both chemical and electrical, of passivation on transformer insulation performance

• Investigating the reasons for silver corrosion in tap changers and to formulate monitoring/assessment strategies in order to provide a measure of asset health. 

Expected Benefits: This project will be successful if we understand and have an increased learning around the transformer oil passivation issue, specifically around silver corrosion on tapchangers.