Marcel Rybensky-Our President along with Dr.Ed G. Tenyenhuis of Hitachi Energy-Canada had the pleasure of presenting the poster about DBDS and corrosive sulphur in Transformer oil at the ICTRAM 2023 in Croatia.
Transformer Corrosive Sulphur Removal by Oil Reclaiming for Life Extension: Using ECOIL Regeneration system of Filtervac
Abstract—Six large generator transformers had corrosive sulphur & DBDS in oil removed by oil reclamation process. This process extended the transformer life and allowed the transformer oil to be reused for a significant environmental benefit. Index Terms—Transformer oil, copper sulphide, DBDS, reclamation.
I. INTRODUCTION There have been documented failures of transformers due to the presence of corrosive sulphur compounds in oil, which is related to corrosive reaction with metal surfaces and formation of copper sulphide and deposits in the winding insulating paper [1, 2]. Transformers with content of corrosive sulphur compounds and dibenzyl disulphide (DBDS), have a much higher risk of failure depending on the winding design, loading and ambient temperature [3]. While metal passivator additions (such as Irgamet 39) to the oil can stabilize the effect of corrosive sulphur temporarily, any earlier copper sulphide penetration cannot be undone. Six transformers at a generating station had high corrosive sulphur level 4b (ASTM 1275B) and DBDS content up to 76ppm – see Table 1 below. The transformers were all 420kV generator transformers with ratings of 300 to 350 MVA. Three mitigation options as counter/preventive measures to reduce the corrosive sulphur and DBDS were given which included replacement of the transformer oil, passivation of the oil and online reclamation of the oil (while the transformer is energized and in service). The transformers had already received the addition of metal passivator additives, but the oil had remained corrosive. If performing only passivation without reducing corrosive sulphur to non-corrosive and DBDS to < 5ppm, then all added additives (2,6-ditertiarybutyl para-cresol [DBPC] & Irgamet 39) will deplete faster due to residual polar oil contaminants, corrosive sulphur & DBDS mercaptans (organic components of hydrocarbons with sulphur) present in the transformer oil. It was decided to proceed with the online reclamation process on 4 of the 6 units with the main reason to avoid production loss at the power plant. The remaining 2 units had the offline process reclamation process performed. The results were overwhelmingly great and after one year of testing, the DBDS and corrosive sulphur levels have not changed.
Kudos to our team in Canada and in the Middle East.
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