Polymer nanocomposites have recently been attracting attention among researchers in electrical insulating applications from energy storage to power delivery. However, partial discharge has always been a predecessor to major faults and problems in this field. In addition, there is a lot more to explore, as neither the partial discharge characteristic in nanocomposites nor their electrical properties are clearly understood. By adding a small amount of weight percentage (wt%) of nanofillers, the physical, mechanical, and electrical properties of polymers can be greatly enhanced. For instance, nanofillers in nanocomposites such as silica (SiO2), alumina (Al2O3) and titania (TiO2) play a big role in providing a good approach to increasing the dielectric breakdown strength and partial discharge resistance of nanocomposites. Such polymer nanocomposites will be reviewed thoroughly in this paper, with the different experimental and analytical techniques used in previous studies. This paper also provides an academic review about partial discharge in polymer nanocomposites used as electrical insulating material from previous research, covering aspects of preparation, characteristics of the nanocomposite based on experimental works, application in power systems, methods and techniques of experiment and analysis, and future trends.

For use as insulating liquids in power transformers, palm based oils are gaining worldwide attention as biodegradable alternatives and competitors to the petroleum based oils. However, moisture ingress into insulation oils and its effect on the oil breakdown voltage (BDV) must be studied because moisture in oil can alter the physicochemical property of oil and drastically affects the breakdown voltage. This paper presents a comparative study on effect of increasing moisture content on physical structure and BDV of three palm based insulation oils (Red Palm Oil, Refined Bleached Deodorized Palm Oil (RBDPO) and Palm Fatty Acid Ester (PFAE)) at room temperature. Insulation oil is known to have the ability to sustain its good performance up to certain percentage moisture increase. In this paper, an empirical relationship between the palm based oil BDV and the percentage moisture added was developed to approximate oil BDV at various moisture increases. Fourier Transform Infrared (FTIR) Spectroscopy was employed to investigate changes in the oil samples' functional group to assess the physical changes. This equation has been tested and verified. This equation can be used to estimate the BDV of the palm based insulation oils as their percentage moisture increases.Index Terms -Palm oil, transformer, insulation, palm fatty acid ester, refined bleached deodorized palm oil, Fourier transform infrared spectroscopy, breakdown voltage.

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Weibull distribution has been used widely by many researches around the world especially in the analysis of high voltage experimental data. Unfortunately, the statistical techniques used to analyse the high voltage experimental data are not highly accurate. In view of the foregoing, this paper presents a new statistical approach to analyze the tree inception voltage of silicone rubber and epoxy resin. The tree inception voltage of silicone rubber and epoxy resin was measured via camera-equipped online monitoring system. The leaf-like specimen was used as test sample. AC ramp voltage was applied to obtain the tree inception voltage of silicone rubber and epoxy resin. It was observed that, the electroluminescence emission and ultraviolet (UV) radiation occurred indicating the early stage of tree occurrence. The obtained results were analysed statistically by using fitting method. Anderson-Darling goodness-of-fit test was performed in order to obtain the best fitting distribution. Comparison was made between the best-fitted distribution and Weibull distribution. Based on Anderson-Darling tests, the tree inception voltage of silicone rubber and epoxy resin was best fitted with Johnson S B distribution. Based on this fitted distribution, the value of tree inception voltage for silicone rubber and epoxy resin was calculated and equalled to 11.80 kV and 20.11 kV respectively. From this study, it was found out that the best-fitted distribution for the value of tree inception voltage for silicone rubber and epoxy resin is the Johnson S B distribution by means of Anderson-Darling goodness-of-fit test.