Theoretical Justification of Transformer Oil Bubbling Treatment Using Sf6 Gas

Abstract

This paper examines the feasibility of using SF6 gas bubble bubbling in transformer oil as a promising method for removing moisture and mechanical impurities without draining the oil from the transformer tank. The aim of the research work is to theoretically substantiate the proposed method using mathematical modeling of the hydrodynamic and mass transfer processes accompanying the gas bubbles movement in mineral transformer oil. To achieve this goal, mathematical modeling of bubbling hydrodynamics, analytical relationships of mass transfer between the gas and liquid phases and the theoretical analysis of flotation extraction processes for mechanical impurities were used. The influence of bubble diameter, SF6 gas flow rate and processing time on the moisture and solid contaminant removal efficiency was assessed. Based on the calculation results, the ranges of process parameters that can ensure the highest process efficiency were determined. The obtained estimates demonstrate the possibility of reducing oil moisture content, increasing its electrical strength and removing a significant portion of mechanical impurities while maintaining the oil chemical stability by using a chemically inert working gas. It is shown that bubbling treatment can be considered as an independent oil treatment method for specific operating conditions or as a preliminary stage in a comprehensive regeneration technology that includes vacuum degassing, filtration or adsorption purification. The obtained results are theoretical in nature and can be used in the development of pilot industrial bubbling units, as well as in planning subsequent experimental studies aimed at verifying calculated dependencies and refining process parameters.