Effect of Accelerated Aging Under High Electric Field and Partial Discharges on Electric Conduction in Mineral Oil

The cellulose paper-mineral oil insulation system remains the most popular choice for power transformers due to its proven efficiency and stability over time. Although the primary aging mechanisms of oil and paper are well-known and can be evaluated by various methods, there is a permanent need to understand how different types of stress can affect the main isolation properties. This study presents an experimental analysis of the accelerated aging of mineral oil under high-strength electric fields and partial discharges. This article introduces an experimental method of accelerated electrical aging and describes the variations in the oil’s main dielectric properties with aging conditions. The findings highlight that accelerated electrical aging leads to significant changes in the spectra of both real and imaginary parts of complex relative permittivity and conductivity. Using a simplified model, the study also calculates the average values of charge carriers’ mobility. The results indicate that increasing the aging duration of oil samples leads to an increase in the average value of charge carriers’ mobility.