Removal of Dibenzyl Disulfide (DBDS) by Polyethylene Glycol Sodium and Its Effects on Mineral Insulating Oil

Dibenzyl disulfide (DBDS) is the major corrosive sulfur compound in mineral insulating oils, which will corrode the copper wires of windings in the oil-immersed power transformers and reactors and eventually cause operation failures. This paper studies the method to eliminate DBDS in insulation oils using the Polyethylene Glycol Sodium (Na-PEG) reagent. The preparation method of the Na-PEG reagent from NaOH and polyethylene glycol 400 is studied in the laboratory. The effect of the Na-PEG reagent dosage and reaction temperature on eliminating DBDS in insulating oils is studied, and a treatment process is recommended. An automatic processing device to remove DBDS from the transformer oil is developed, and the short-term electrical properties and long-term thermal stability of the insulating oil after the Na-PEG reagent treatment are tested. The results show that the Na-PEG reagent can efficiently eliminate DBDS in the insulating oil (the DBDS concentration decreases from 448 mg/kg to less than 5 mg/kg (undetectable) within 1 hour) and will not significantly negatively affect the oil properties such as the breakdown strength at the power frequency, dissipation factor or acidity. A preliminary exploration of the reaction mechanism is explored.