Dielectric Properties of Insulated Vegetable Oil Under the Effect of Electric Field and Partial Discharges

Power transformers are critical equipment in electrical networks. Most have an insulation system made of cellulose paper and mineral oil. Current trends lead to replacing mineral oil with biodegradable vegetable oils from sustainable resources. Thus, electrical equipment manufacturers are currently turning towards the so-called “green power transformers” in which the dielectric fluid is made in natural esters with a high biodegradability rate. This study aims to investigate the changes in the electrical properties of a transformer vegetable oil subjected to the action of a high-strength electric field and partial discharges within a laboratory experimental procedure. Thus, the results presented in this paper indicate that under the action of the electric field and partial discharges produced in laboratory conditions, the real and imaginary parts of the complex relative permittivity, the dielectric loss factor, and the electrical conductivity increase with the aging duration. This indicates that possible degradation processes of vegetable oil occur.