The depletion of dibenzyl disulfide from a mineral transformer insulating oil

Abstract

This study examines the kinetics of the net depletion of dibenzyl disulfide (DBDS) from its solution in mineral insulating oil due to copper corrosion at elevated temperatures in power transformers. The concentration of DBDS is determined using liquid-liquid extraction followed by GC detection. Measurements, at 24 h intervals, up to 168 h, show that the depletion of DBDS from its solutions in mineral insulating oil at 150 C and initial concentrations of 3.00, 6.00, 9.00, 12.00 and 15.00 mg L −1 is very slight compared to identical measurements in the presence of copper strips in the mineral oil. The analysis of the kinetic data reflects the complexity of the corrosion process and its occurrence at a concentration as low as 1 mg L −1 which is much lower than what has been previously believed. Measurements on solutions at initial DBDS concentrations of 150 mg L −1 indicate that even when the insulation oil matrix is in contact with copper strips the corrosion does not occur to any measurable extent below 100 C and starts to speed up appreciably only beyond 125 C. From data at 100, 125 and 150 C an energy of activation equal to 123 kJ mol −1 is estimated.

Dibenzyl disulfide adsorption on Cu(111) surface: a DFT study

“…Under operation conditions, DBDS is known to further copper corrosion in electric equipment, by forming copper (I) sulfide Cu2S as the main product, with the subsequent production of other sulfur compounds such as benzyl sulfide and dibenzyl sulphide. In spite of successive studies about the chemical phenomenon, the mechanism remains unclear [39][40][41][42] . Since DBDS is related to the commonly used thiol molecules, in the well-known thiol self-assembled monolayers (SAM) on metal surfaces, 9,[43][44][45] , the analysis of the metal-sulfur bond is important to complete the already known information on the chemical properties of this type of systems.…”

Micro‐mechanism study on synergistic degradation of the oil‐paper insulation with dibenzyl disulfide, hexadecyl mercaptan and benzothiophene

“…They verified the aforementioned research results and found that DBDS can react completely in different oxygen concentration, as well as the reaction process does not need oxygen to participate. Regarding the concentration of sulphur corrosion, experiments also have shown that even the DBDS concentration as low as 1 mg/L will cause sulphur corrosion, and the content of most dissolved gases in the oil and the acid value in the oil would increase [8]. Scholars have also carried out a lot of research work on the influencing factors of corrosive sulfides [9][10][11], and find that the external conditions such as electric field [9], oxygen [10], temperature [11] and other factors also have an important influence on the formation of sulfides.…”

Study on Sulfide Distribution in the Operating Oil of Power Transformers and Its Effect on the Oil Quality

“…In the past few decades, the sulfide deposition phenomenon was discovered successively in transformer fault inspections of 220 kV and above voltage classes in areas within China Southern Power Grid, East China, and North China [5,6]. Studies and reports on corrosive sulfur faults were also conducted in other countries such as Japan, Europe and other countries [7,8]. The insulation fault caused by sulfur corrosion has become a major threat to the safe operation of oil-immersed power transformers.…”