Abstract. Transformer explosions caused by dielectric failure account for over 50% of the disasters. The aim of this thesis is to examine, compare and outline the differences, in function, as dielectric insulators, vegetables oil has, with respect to the mineral oil used in high-power transformers. We will first consider the vegetable oil which has less dielectric capabilities than the mineral oil used in power transformers. Later in the experiments, we will focus mainly to examine the breakdown voltage property, as we try to alter some properties of the respective oils used. Considering the fact that vegetable oil has low viscosity, with its chemical compounds constituting less molecular masses compared to mineral oil, we endorse, from our experimental findings, that mineral oil is indeed worthy and reasonable to be used as a dielectric in high power transformers. In this write-up, we have considered eleven transformer oil properties. In the experiment proper, we considered only the acidity, whose concentration in the transformer oil increases with aging if the transformer, moisture, and a ‘suitable’ impurity like NaOH(aq). At first glance, one would be tempted to think, as we were, that since the increase in acid content of the oil deteriorates its dielectric performance, an increase in alkaline content of the transformer oil, would increase its dielectric ability; reversing the acid effect. But as we see in the results from our experiments, this is false. We think that the visible degradation of the insulating property of the oil, with the introduction of NaOH(aq), is because it acts as an impurity to suitable dielectric function. From the experiments, the heating procedures resulted in the production of toxic gases. This indicated the actual loss of chemical structure and significant breakage of chemical bonds. The resulting chemical composition of the oil does not produce the same dielectric properties as the initial oil sample. Also, here has been considerable inconsistency in the addition of NaOH(aq) or HCl(aq) to both oils. We only added HCl(aq), before every measurement, in two of the experiments. The other experiments were either with moisture, or a single addition of 2cm3 of either HCl(aq) or NaOH(aq) before heating; after which several measurements were taken, at specific intervals, as the mixture cools. We did so, in the latter, in which we had only one addition of a 2cm3 chemical, because in real life, given the short time frame of the experiment, the total amount of acid in the oil has a negligible change. So, in a functioning heated transformer, within a short time frame, there is actually deterioration in oil insulation properties