This paper presents the influence of three different voltage stabilizers, 4-n-propylbenzoic acid, 2-methoxyphenylboronic acid, and 3-aminobenzoylmethylamide, on the insulation properties of cross-linked polyethylene (XLPE). The 1 wt % voltage stabilizers are blended with XLPE by a solution method, and then the samples are prepared via a hot pressing method. Electrical and physicochemical properties of the XLPE blends are analyzed by space charge, DC resistivity, DC breakdown strength, thermally stimulated depolarization current, Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry experiments. It is found that the addition of the voltage stabilizers enhances the DC resistivity and DC breakdown strength of the XLPE, which also inhibits the accumulation of space charges in the XLPE. The results show that the XLPE blend with the addition of 4-n-propylbenzoic acid has the lowest conduction current and a 23.3% increment in the DC breakdown strength compared to that of the reference XLPE among the used voltage stabilizers. Moreover, it is found that the melting properties and thermal stability of the XLPE are not affected by the addition of the voltage stabilizers. The XLPE blend with 4-n-propylbenzoic acid exhibits a uniform trap depth distribution, which facilitates the migration of the space charge to the anode and reduces the electric field inside the sample bulk. Quantum chemical calculations demonstrate that the matching ability of the electron-withdrawing and electron-donating groups of the three voltage stabilizers effectively enhances the electrical properties of the XLPE. In contrast, the 4-n-propylbenzoic acid has the lowest unoccupied molecular orbital energy level, which can effectively buffer the high-energy electrons and increase the DC breakdown strength. A charge carrier transport mechanism is also proposed to explain the effect of the voltage stabilizer on the space charge movement in the tested samples.

This paper presents the effects of the filler type and testing temperature on the charge dynamics and thermal properties of the epoxy resin. The micro‐nano hybrid composites with different content of the micro and nano aluminum nitride (AlN) fillers are fabricated. The morphology of micro‐nano hybrid composites is characterized. Electrical testing and thermal analysis methods are adopted to analyze its electrical and thermal performance. The results show that the space charge accumulation is suppressed and the charge decay process is facilitated in the hybrid composites. The electrical performances of the hybrid composites are enhanced by the nano‐fillers. The apparent mobility and activation energy are decreased with nano‐AlN fillers in the composites at the high temperature. The glass transition temperature and thermal stability of the materials is improved with the nano‐AlN. A hypothetical mechanism is proposed to explain the charge carrier injection and transport of the composites at different temperatures.

This research investigates the optimal region to achieve balanced thermal and electrical insulation properties of epoxy (EP) under high frequency (HF) and high temperature (HT) via integration of surface-modified hexagonal boron nitride (h-BN) nanoparticles. The effects of nanoparticle content and high temperature on various electrical (DC, AC, and high frequency) and thermal properties of EP are investigated. It is found that the nano h-BN addition enhances thermal performance and weakens electrical insulation properties. On the other side, under HF and HT stress, the presence of h-BN nanoparticles significantly improves the electrical performance of BN/EP nanocomposites. The EP has superior insulation properties at low temperature and low frequency, whereas the BN/EP nanocomposites exhibit better insulation performance than EP under HF and HT. The factors such as homogeneous nanoparticle dispersion in EP, enhanced thermal conductivity, nanoparticle surface modification, weight percent of nanoparticles, the mismatch between the relative permittivity of EP and nano h-BN, and the presence of voids in nanocomposites play the crucial role. The optimal nanoparticle content and homogenous dispersion can produce suitable EP composites for the high frequency and high temperature environment, particularly solid-state transformer applications.

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This paper investigates the electrical and thermal properties of pure epoxy resin (EP) and its micro–nano hybrid composites (20 wt% micro-AlN fillers with 1 wt% and 3 wt% nano-Al2O3 fillers; 50% micro-AlN with 3% nano-Al2O3 fillers) for power electronic packaging applications. Electrical properties such as space charge distribution, electrical conductivity and surface potential decay are measured. The thermal performance of the fabricated samples is estimated using thermal analysis devices. The hybrid composite consisting of 20 wt% micro-AlN and 1 wt% nano-Al2O3 fillers exhibits the least space charge accumulation, higher thermal conductivity and better thermal stability. However, the excessive addition adversely affects space charge and electrical conductivity properties. The micro–nano hybrid composites significantly exhibit higher electrical conductivity than pure EP. The microfiller addition from 20 wt% to 50 wt% significantly improves the thermal conductivity of the EP. The reduced space charge injection and accumulation in the hybrid micro–nano composites are attributed to the enhancement of the injection barrier and reduction of the charge carrier traps in these materials. A theoretical mechanism of the charge dynamics inside the samples under different test conditions is proposed to support the experimental results.

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Electrical insulation materials play a key role in stable and uninterrupted operation of electrical power system. Researchers working in the field of electrical insulation have turned their focus to nano composite insulation materials for better performance and reliability. A typical nano composite insulation material is a combination of nano particles and base materials. Since last 25 years silicon rubber and epoxy are two widely used electrical insulation materials for outdoor and indoor applications respectively. To further enhance the electrical insulation performance of these materials addition of nano particles has proven to be of practical value. This study presents an investigation on zepoxy (a military grade epoxy) incorporated with three different nano particles at varying percentages. The main aim was to find the nature of relationship between leakage current (LC) and partial discharge (PD). In addition to that optimum composition which results in lowest values of PD and LC was also investigated for each of three nano composites. The results of this study help to understand the interdependence between LC and PD for indoor electrical insulation based on zepoxy. LC and PD play a vital role in condition assessment of any insulation material.