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.

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.

UHF method to detect partial discharge (PD) phenomenon has been proven to be an effective way. Many types of UHF antenna have been developed in order to achieve a better sensitivity and accuracy in certain bandwidth (300 MHz-3.0 GHz) for detecting the ultra-high frequencies generated by partial discharge. Bowtie antenna is proven to be sensitive, accurate and easily designed and fabricated. This paper focuses on the enhancement of bowtie antenna to achieve better performance in detecting partial discharge using UHF method. Characteristics of antenna both on the simulation result prior to the fabrication and measurement using a network analyzer show the good agreement. Experiment was carried out in a gas insulated switchgear (GIS) model with a protrusion on the conductor as PD source and antenna located at different positions with applied voltage range from 20-25 kV. EM wave intensity and frequency captured by antenna were observed. The relation between the distances of PD source to antenna, either from one spacer aperture to others, or distance from one spacer aperture were investigated. Antenna mounted 55 cm from the closest spacer aperture to the PD source can still detect EM wave intensity very well. The lowest EM wave peak envelope intensity measured at 30.03 mV from the same spacer aperture compared to 1.952 mV peak-peak EM wave intensity from internal GIS UHF sensor demonstrates a sufficient sensitivity performance.

This review is conducted following a systematic approach by adopting the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline and using reliable and trustworthy databases, namely, IEEE Xplore , Science Direct, and Scopus, with Google Scholar as an additional database. This review has divided into three subsections. The first subsection shows the major publications searching for palm oil (PO)-based as an alternative to biodegradable oil insulation. The second subsection discusses the research trends on PO replacing mineral oil. Finally, the third subsection discusses the development and progress of PO-based nanofluid (NF) as a future substitute for biodegradable oil insulation and the types of analyzes conducted in the studies. This part contains 11 subsubsections, namely: 1) types of PO used; 2) tests of PO as an insulating liquid; 3) properties of PO as an insulating liquid; 4) thermal aging; 5) water content; 6) dissolved gas analysis; 7) selection of nanoparticles; 8) preparation of PO-based NFs; 9) characterization and stability of PO-based NFs; 10) analysis of electrical, physical, and chemical properties; and 11) current status of PO-based insulating liquid in Malaysia. This article highlights PO’s development, trends, and status and its NF as a liquid insulating alternative in transformers. The properties and performance of the liquid are also reported in this article. The promising results, shortcomings, and imbalances between PO and other types of natural ester oils are discussed, and suggestions are made for future work worth exploring.