The technical-scientific article describing the corrosive sulfur depolarization treatment (DBDS removal) on giant transformers that Sea Marconi is carrying out in Saudi Arabia has seen the publication (October 2022) in the main sector magazine, Transformer Magazine.
The article is entitled: “On-load integrated treatment of giant power transformers in a severe scenario“. The article, subjected to careful technical review by Transformer Magazine’s international consultants, was written in collaboration with GCC Lab and the Saudi national power grid.
Regarding the readers, this article is of absolute interest to owners of electrical transformers all over the world who are faced with the problem of corrosiveness of oils (contained in transformers).
The text does not exclusively describe the countermeasure adopted, but goes into detail on the decision-making process, supported by sector regulations, which guided the holder in choosing the correct asset management and “corrosiveness” risk management strategy. In particular, the actions recommended by the technical guides are described, starting from the CIGRE Technical Brochure 625 “Copper sulphide long term mitigation and risk assessment“, considered the most complete document in this area.
In a nutshell (I leave all the insights to reading the article), considering the operating conditions of the transformers, highly stressed by high loads and high ambient temperatures, the options suggested by the guide in case of corrosivity are: oil change or removal of the corrosive sulfur (oil treatment).
In light of the numerous advantages offered by oil treatment compared to its replacement (see CIGRE TB 625 – Table 12 – Mitigation techniques ranking), the customer then independently explored and tested some oil treatment techniques, obtaining unsatisfactory results. This consequently led to the choice of the solution by Sea Marconi: the selective depolarization treatment from DBDS called Chedcos.
This treatment, in addition to removing the DBDS, the main cause of the “pathology” Corrosive sulfur with DBDS (C1), is able to block the formation of copper sulphide, which typically determines the failures attributed to corrosive sulfur. Sea Marconi depolarization is also able to restore the other oil parameters, bringing them back to values similar to a new oil (unused). In addition to this, the main strength of our treatment is the guarantee of long-term results, in fact, as the article clearly shows, in this case Sea Marconi guaranteed the DBDS <10 mg/kg both at the end of the treatment (almost it always goes below 5 mg / kg) and one year after treatment.
About a year after the start of the treatment campaign, 8 transformers were successfully decontaminated (36% of the total), corresponding to approximately 809 tons of insulating oil (47% of the total).