Detection of sulfur corrosion in transformer insulation oils using an interdigitated capacitive sensor based on printed circuit board technology

Monitoring sulfur corrosion in insulation oils is essential since sulfur corrosion can result in catastrophic transformer failure when left unchecked. The objective of this study is to analyze the performance of an interdigitated capacitive sensor (IDC) utilizing printed circuit board technology as a potential tool to detect and monitor the progression of sulfur corrosion in mineral insulation oils. The sulfur corrosion is simulated by adding dibenzyl disulfide into 20 ml vials containing 15 ml of vacuum dried and degassed insulation oils at three concentrations: (1) 100, (2) 200, and (3) 300 ppm. Bare copper samples are then added into the oil samples and aged in a forced convection laboratory oven at 150°C for three days. The IDC sensor developed in this study is used to determine the variation in the oil capacitance due to the presence of dibenzyl disulfide. The surface of the bare copper samples is analyzed using scanning electron microscopy-energy dispersive spectroscopy equipped with AZtecEnergy software in order to quantify the variations of the copper and sulfur content. Based on the results, there is a strong positive correlation between the electrical capacitance of the insulation oil and DBDS concentration, whereby the coefficient of determination is within a range of 0.9643–0.9868. In conclusion, the IDC sensor is a simple and inexpensive way of characterizing the quality of insulation oils due to sulfur corrosion and therefore, it has great potential for industrial applications.