Study on Conduction Mechanism in Corrosive Transformer Oil and its Reclamation Properties

• Published in: IEEE transactions on dielectrics and electrical insulation Vol. 30; no. 5; p. 1
• Main Authors: Amizhtan, S. K., Sarathi, R., Edin, Hans, Taylor, Nathaniel
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.10.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Aging; Contaminants; Corona; Current voltage characteristics; Dielectric response spectroscopy (DRS); DRS; Electric fields; Electrical resistivity; Fluids; Fluorescence; Fuller's earth (FE); fuller’s earth; Ionic mobility; Mineral oils; Oil insulation; oil reclamation; Oils; power transformer; Power transformer insulation; Reclamation; Sulfur compounds; Transformers; Voltage measurement
• ISSN: 1070-9878; 1558-4135; 1558-4135
• DOI: 10.1109/TDEI.2023.3304602

This work deals with the effect of oil reclamation on the conduction mechanism and dielectric aspects of accelerated thermally aged transformer mineral oil. The reclamation is a treatment with fuller's earth adsorbent to remove corrosive sulphur compounds and other contaminants formed during the thermal ageing. Properties of the oil are compared between different stages of the treatment. Corona (partial discharge) inception is identified by the optical fluorescent fiber technique. The results show an increased corona inception voltage after treatment. Dielectric response spectroscopy (DRS) showed lower loss factor and electrical conductivity after treatment. Conduction mechanism is measured under uniform and non-uniform electric field with variation in applied voltage magnitude. Conduction mechanism at a uniform electric field (low E ) is studied using the polarity reversal technique to estimate the respective ionic motilities in the fluid. The apparent mobility of ions, conductivity, ionic radius and concentration from the oil are found to reduce on reclamation. In addition, the conduction mechanism for a higher electric field is simulated by the current-voltage characteristic in non-uniform conditions and the slope determines the ionic mobility of the fluid.