New issue identified (pathology): C5 – Corrosion of silver contacts from total sulfur compounds

Monday August 28th, 2023

Sea Marconi is one of the world’s leading experts on corrosion phenomena, having discovered DBDS in 2005 as the main cause of failures related to corrosive sulfur (C1).

In the last 2 years Sea Marconi has assisted, and has been directly involved, on several cases of failure related to corrosion phenomena on the silver contacts of the selectors, with very significant consequences in terms of damage and lack of production (losses). Sea Marconi has identified and defined a new pathology: “C5 – Corrosion of silver contacts from total sulfur compounds“.

Here are the facts we are aware of. Last year in Italy Sea Marconi learned of a catastrophic failure on a 440 MVA, 400 KV GSU step-up transformer, with evidence of silver sulfide on the selector contacts. The same evidence was found in Brazil, Colombia and Argentina on highly strategic 500 KV HVDC equipment during 2021 and 2022. These events add up to the failure cases cited in a 2021 IEEE article that says “In Australia, most of the transformer that are failed due to silver sulphide corrosion were originally filled…”*

The My Transfo 2023 meeting conference (Turin, 3-4 October 2023) will be an opportunity to share and deepen this significant criticality, identifying new risk assessment strategies. Precisely for this purpose Dr. Sameera Samarasinghe, the author of the article on the cases in Australia cited above: *”A Risk Assessment for Utilities to Prevent Transformer OLTC Failures Caused by Silver Sulphide Corrosion,” in IEEE Transactions on Power Delivery, 2022.

The corrosion phenomena, more than 30 years after the first cases of corrosion of 500 KV shunt reactors in Colombia (type C1 – from DBDS), require technical and regulatory updating. At My Transfo will also be present prof. Shubhen Kapila, convenor of the working group that led to the publication of the 3 parts of IEC 62697 “Test methods for quantitative determination of corrosive sulfur compounds in unused and used insulating liquids”.

Click here to see the agenda of My Transfo 2023 – Sustainability, Asset, Risk, Solutions

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