“Sulfur can be present in insulating liquids in various forms, including elemental sulfur, inorganic sulfur compounds and organic sulfur compounds…Certain sulfur compounds present in the insulating liquids exhibit antioxidant and metal deactivating properties without being corrosive, whereas other sulfur compounds have been known to react with metal surfaces. Specifically, sulfur compounds such as mercaptans are very corrosive to metallic components of electrical devices. Presence of these corrosive sulfur species has been linked to failures of electrical equipment used in generation, transmission and distribution of electrical energy for several decades. Therefore, the IEC standard for mineral insulating oils states that corrosive sulfur compounds shall not be present in unused and used insulating liquids (see IEC 60296). Recently, the serious detrimental impact of corrosive sulfur has been linked to the presence of a specific highly corrosive sulfur compound, DBDS. This compound has been found in certain mineral insulating oils; presence of this compound has been shown to result in copper sulfide formation on the surfaces of copper conductors under normal operating conditions of transformers.”(Quote from IEC 62697)
What method is used to analyze the sample?
How do you interpret the results?
What do the results indicate?
“[IEC 62697] describes the determination of DBDS in insulating liquids for analysis. DBDS is an aromatic organosulfur compound, which may be present in insulating liquids and impart oxidation stability to the liquids. However, DBDS can react with copper and other metal conductors in transformers, reactors and other similar devices to form copper and other metal sulfides. Therefore, this compound is classified as potentially corrosive sulfur. DBDS has been found in insulating mineral oils at concentrations ranging between 5 mg kg–1 and 600 mg kg–1, but it may be present at levels outside this range, in oils that have been blended, or oils in which DBDS have been consumed through its reaction with the copper or other metals. This method can be used for detecting and quantifying DBDS content in used and unused insulating liquids.” (Quote from IEC 62697)