Ageing Assessment of a Gas to Liquid Hydrocarbon Transformer Oil Compared with an Inhibited Mineral Oil

Mineral oils extracted from crude oil have been used as an insulating liquid in power transformers for over a century. However, in recent years Gas-to-liquid (GTL) technology has been introduced to produce iso-paraffinic transformer oil that are purer and hence could provide better performance over the conventional mineral oils. This paper investigates the ageing performance of a GTL based transformer oil and its effect on paper ageing compared with a conventional inhibited mineral oil through an accelerated laboratory ageing experiment. The experiment was conducted with oil paper systems in a sealed condition at 120 °C for up to 40 weeks. During the experiment, ageing state of oil and paper was assessed through different measurements including moisture, acidity, tensile strength and…