The detection of partial discharge (PD) activities in high-voltage equipment can be conducted according to several mechanisms of signal detection, including electromagnetic wave signal detection, acoustic signal detection, chemical reactions, electrical signal detection, and optical emission detection. Recently, multiple methods of detection and localization of partial discharge activities, which occurred in power transformers and gas-insulated switchgear (GIS), have been proposed to monitor the health condition of high-voltage equipment, especially when the awareness regarding preventive maintenance has been emphasized at the industrial level and among electrical providers. In aligning the needs of the industrial sector and the improvement of PD-detection methods, this manuscript focuses on reviewing the current practice methods for the detection and localization of PD signals in high-voltage equipment, comparing their efficacy, and summarizing the future direction of research work-related methods of PD detection. The comparative reviews are discussed in terms of the mechanism of PD signal detection, indication parameters, calibration techniques, and the advantages and limitations of each method of PD measurement in detail.

Polymer nanocomposites have gained much attention among researchers due to their excellent characteristics, such as high thermal resistivity and the ability to withstand higher electrical stress. Introducing nanoparticles into the polymer matrix can further improve the insulation characteristics. However, the effectiveness of polymer nanocomposite to suppress an electrical tree, enhancing the partial discharge, and increase the breakdown strength is still a question mark due to the agglomeration issue of nanoparticles, which causing the nanoparticle to be dispersed non-uniformly within the polymer matrix. Plasma treatment is one of the methods that potentially replace conventional modification techniques such as chemical functionalization and heat treatment to improve the dispersion of nanoparticles, nanocomposite bonding, and the compatibility between polymer-nanoparticle interfaces. By altering the surface of nanoparticles using cold plasma with a glow discharge mechanism, the surface morphology of nanoparticles can be modified in terms of chemical structure, which indirectly solves the nanoparticle agglomeration. This study presents a review on the application of cold plasma in surface modification to enhance insulation characteristics of polymers nanocomposite. Various polymer hosts combined with different untreated and plasma-treated nanofillers are also reviewed. The trends on nanomaterial surface modification using the cold plasma technique based on its operating pressure to improve the dielectric properties of polymers nanocomposite are also discussed accordingly.

Mineral oil has been chosen as an insulating liquid in power transformers due to its superior characteristics, such as being an effective insulation medium and a great cooling agent. Meanwhile, the performance of mineral oil as an insulation liquid can be further enhanced by dispersing nanoparticles into the mineral oil, and this composition is called nanofluids. However, the incorporation of nanoparticles into the mineral oil conventionally causes the nanoparticles to agglomerate and settle as sediment in the base fluid, thereby limiting the improvement of the insulation properties. In addition, limited studies have been reported for the transformer oil as a base fluid using Aluminum Oxide (Al₂O₃) as nanoparticles. Hence, this paper reported an experimental study to investigate the significant role of cold plasma treatment in modifying and treating the surface of nano-alumina to obtain a better interaction between the nano-alumina and the base fluid, consequently improving the insulation characteristics such as breakdown voltage, partial discharge characteristics, thermal conductivity, and viscosity of the nanofluids. The plasma treatment process was conducted on the surface of nano-alumina under atmospheric pressure plasma by using the dielectric barrier discharge concept. The breakdown strength and partial discharge characteristics of the nanofluids were measured according to IEC 60156 and IEC 60270 standards, respectively. In contrast, the viscosity and thermal conductivity of the nanofluids were determined using Brookfield DV-II + Pro Automated viscometer and Decagon KD2-Pro conductivity meter, respectively. The results indicate that the 0.1 wt% of plasma-treated alumina nanofluids has shown the most comprehensive improvements in electrical properties, dispersion stability, and thermal properties. Therefore, the plasma treatment has improved the nanoparticles dispersion and stability in nanofluids by providing stronger interactions between the mineral oil and the nanoparticles.

Detection of partial discharge (PD) activities in high-voltage equipment can be done according to the several mechanisms of signal detection, which are electromagnetic wave signal detection, acoustic signal detection, chemical reactions, electrical signal detection, or optical emission detection. Recently, multiple methods of detection and localization of partial discharge activities occurred in power transformers and gas-insulated switchgear (GIS) have been proposed to monitor the health condition of high-voltage equipment, especially when the awareness regarding preventive maintenance has been emphasized at the industrial level and electrical providers. In aligning the needs of industrial and the improvement of PD detection methods, this manuscript focused on reviewing the current practice methods for the detection and localization of PD signals in high-voltage equipment and comparing their efficacy, in summarizing the future direction of research work-related methods of PD detection. The comparative reviews are discussed in terms of the mechanism of PD signal detection, indication parameters, calibration technique, advantages, and limitations of each method of PD measurement in detail.

Cold plasma with a glow discharge mechanism is a homogeneous and effective mechanism of nonthermal plasma for industrial applications due to the continuous and stable discharge process compared with the filamentary discharge. The discharge mechanism is essentially dependent upon the input parameters of the plasma system, such as the voltage supply, excitation frequency, and the flow rate of the background gas. This article discusses the effects of input parameters on plasma discharge characteristics produced from the plasma jet reactor. The voltage and supply frequency are tuned to match the discharge gap and background gas flow rate in producing the homogeneous glow plasma discharge. The characteristics of the glow plasma discharge produced were analyzed based on the characteristics of the time–domain discharge current and charge-voltage Lissajous figure techniques. Results show that the most efficient and uniform plasma was disclosed by the configuration of input parameters such as 0.5 kV of the applied voltage, 20 kHz of operating frequency, and 0.8 L/min of purified helium gas flow rate. The single pulse of discharge current and parallelogram-like Lissajous figure obtained indicating the homogeneous plasma discharge with a constant value of discharge capacitance.

Polymeric insulating materials have been widely used in high voltage equipment, particularly in power cables, as insulating material, due to their excellent performances. This study investigates the significance of atmospheric pressure plasma (APP) treatment on silicon dioxide (SiO ₂ ) nanoparticles in enhancing the partial discharge (PD) resistance and breakdown strength of low-density polyethylene (LDPE) nanocomposites. The duration of plasma treatment was manipulated for 15 and 30 minutes to identify the effects of treatment duration on their dielectric properties. The loading of fillers was varied into 1, 3, and 5 wt% to identify the promising formulations. The results exhibited that the dielectric properties of LDPE nanocomposites have improved as the SiO ₂ nanoparticles were treated, anticipated due to the surface activation via functionalizing hydroxyl group on the fillers as ultimate oxidation agent, resulting in reduced size of agglomerated clusters. The PD resistance and breakdown strength have increased up to 47% and 70% of the unfilled samples, respectively, as the SiO ₂ nanoparticles were treated using plasma. Plasma treatment was found to be an alternative technique for improving the filler-polymer surface interaction, at once promising the better dielectric properties of LDPE nanocomposites, potentially prolonging the lifetime of the insulating materials.