A new class of colloidal insulating transformer oil is formulated by dispersing CNT nanomaterials with mineral oil in purpose to enhance the breakdown strength performanc existing transformer oil. This paper represents the experimental studied dealing with the influence of CNT nanomaterials mix with transformer mineral oil in term of AC breakdown voltage at various gap distances. The concentrations of CNT nanomaterials were measured in range 0.01g/L to 0.2g/L. The impact of three gap distances (1.5mm, 2.5mm and 3.5mm) for mushroom-mushroom electrode configuration is studied in order to observe and trend between conventional mineral oil and CNT nanofluids. To employ CNTs as effective reinforcement in mineral oil, proper dispersion methods need to be applied.

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Oil-based nanofluids have been indicated to enhance the breakdown strength and dielectric behavior of mineral oil. However, partial discharge (PD) development in these new materials has not yet been clarified. This study aims to deeply investigate PD development in nanofluids considering the role of the electrical double layer (EDL) around nanoparticles. Two types of nanoparticles (TiO2 and Al2O3) with different EDL thicknesses were used. Nanofluids were prepared using the two-step method, and their proper composition was adopted after considering their stability and avoiding the drawbacks that are present when surfactants are used. The prepared nanofluids together with the base oil were tested for PD development. First, the PD inception voltage was evaluated and analyzed using the Weibull distribution. Then, PD parameters including the PD magnitude and repetition rate were obtained for both types of nanofluids; these values were compared with the corresponding results of the base oil. Finally, the PD time transition was acquired over ten minutes of applied voltage using the segmented memory mode of the oscilloscope. Based on obtained results, physical mechanisms behind PD activity are proposed and discussed. It was found that nanoparticles with a large EDL thickness could more effectively suppress PD activity.

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