Impact of Aging on Dielectric Properties of Oil-Paper Insulation System using Gas-to-Liquid Oil and Mineral Oil

Lately, gas-to-liquid (GTL) oil usage has a great trend as cooling and dielectric medium in power transformers due to their good properties, represented by its purity, chemical uniformity, and better performance than conventional oils. By the way, the study of GTL oil effect in comparison to conventional mineral oil (MO) on the electrical properties of the insulation paper under thermal aging is presented in this paper. Thermal aging samples were obtained based on an accelerated thermal aging test in the laboratory, that simulates the thermal stress in the service. Two different aging durations (i.e., 3 and 6 days) are applied to the two different oil types. Pure oils and aged oil samples were tested for dielectric losses and dielectric constant for a range of frequencies from 20 Hz to 2 MHz. In addition, insulation papers were impregnated in the same samples to check their effect by thermal aging. The results indicated that aging has a lower impact on the properties of GTL oil and GTL oil-paper insulation under aging conditions compared to that of MO.