Electronic devices are increasingly dense, underscoring the need for effective thermal management. A polyimide (PI) matrix nanocomposite film combining boron nitride (BN)-coated copper nanoparticles (CuNPs@BN) and nanowires (CuNWs@BN) was fabricated by a flexible and fast technique for enhanced thermal conductivity and the dielectric properties of nanocomposite films. The thermal conductivity of (CuNPs-CuNWs)@BN/PI composite comprising 10 wt % filler loading rose to 4.32 W/mK, indicating a nearly 24.1-fold increase relative to the value obtained for pure PI matrix. The relative permittivity and dielectric loss approximated 4.92 and 0.026 at 1 MHz, respectively. The results indicated that the surface modification of CuNPs and CuNWs by introducing a ceramic insulating layer BN effectively promoted the formation of thermal conductive networks of nanofillers in the PI matrix. This study enabled the identification of appropriate modifier fillers for polymer matrix nanocomposites to improve electronic applications.

Epoxy resin-based nanocomposites have been widely researched for being potential insulating materials in high voltage power equipment. In this paper, nano-TiO₂ particles were chosen and surface-modified by a silane coupling agent containing an epoxy group. The effect of functionalized nano-TiO₂ doping on the physical properties of epoxy resin was studied. The results of differential scanning calorimetry show that T_g increased significantly and can be increased by up to 35 °C. Therefore, it is believed that the suppression of molecular motion by the addition of nanofillers works effectively in the case of this functionalized nano-TiO₂ and a strong interaction between the epoxy resin and the nano-TiO₂ was formed after surface modification. Consequently, dynamic mechanical properties, thermal conductivity, electrical conductivity, and trap characteristics of epoxy resin are all adjusted after introducing functionalized nano-TiO₂. All of these physical properties were analyzed from the perspective of suppression of molecular motion, and it is of significance to establish the theory of a nanocomposite dielectric. Besides, the results show that the epoxy/TiO₂ nanocomposite is expected to be applied in the insulation system of electrical equipment.

Surface flashover is one of the main factors leading to insulation failure. For example, epoxy insulator in Gas Insulated Switchgear (GIS) is the most vulnerable insulation components; the failure endangers the reliability of GIS and even leads to accidents and economic losses. Thus, developing advanced materials to be much more safely used in GIS is significant. Here we report the study on surface flashover characteristics of a nanocomposite, nano-TiO ₂ /epoxy. The samples were prepared using molded method after uniformly dispersing nano-scale TiO ₂ particles in epoxy resin with different loadings (0.1%, 0.5%, 1%, 3%, and 5%). The flashover characteristic was studied under 1.2μs/50μs standard lightning impulse voltage and DC voltage. The flashover voltage of TiO ₂ /epoxy nanocomposites was increased compared with neat epoxy resin. However, the flashover voltage decreased slightly when the filler loading exceeded 1%. At the same time, surface charge accumulation and decay behaviors and volume resistivity were also investigated. Experimental results show the trap density and trap energy in samples related with the flashover characteristics in SF ₆ . It seems that surface flashover voltage is mainly affected by deep trap density of the samples. Low trap density may lead to better flashover performance. The volume resistivity results showed that the resistivity of Nano-TiO ₂ /epoxy decreased at lower filler content which was contributed to the increase of the flashover characteristics in SF ₆ .

In SF₆ gas-insulated equipment, solid dielectrics critically degrade insulation performance by reducing the electric field’s ability to withstand gas gaps. To investigate the critical role played by solid dielectric surfaces during the initial phase of gas–solid interface discharge phenomena, this paper experimentally measures the AC breakdown voltage (U_bd) of both dielectric surface-initiated breakdown (DIBD) and electrode surface-initiated breakdown (EIBD) across eight types of post insulator samples. Tests are conducted in 36 mm SF₆ gas gaps under pressures ranging from 0.1 to 0.4 MPa. Combined with electrostatic field simulations, the results reveal that DIBD requires substantially lower U_bd than EIBD under comparable maximum electric field (E_max) conditions. As gas pressure increases, this difference becomes more pronounced. This phenomenon can be explained by three key mechanisms: First, due to the regulatory effect of dielectric materials and shielding electrodes on the electric field distribution, the high-electric-field zone along the gas–solid interface exhibits a longer effective discharge path compared to that in a pure gas gap. This configuration creates more favorable conditions for discharge initiation and subsequent propagation toward the opposite electrode. Second, microscopic irregularities on the dielectric surface induce stronger local electric field enhancement than comparable features on metallic electrodes. Third, in high-electric-field regions adjacent to the dielectric surface, desorption processes significantly enhance electron multiplication during gas discharge, and this enhancement effect becomes more pronounced as gas pressure increases, further lowering the discharge inception threshold. As a result, discharge initiation at dielectric interfaces requires less stringent electric field conditions compared to breakdown in a gas gap, especially at high gas pressure. This conclusion not only accounts for the saturation behavior in the U_bd-p characteristic of SF₆ gas–solid interface discharges but also explains why surface contaminants/defects disproportionately degrade interfacial insulation performance relative to their impact on gas gaps.

As a critical insulation component in cable systems, the cable terminal is susceptible to defects caused by human and environmental factors during manufacturing, installation, and service. Such defects may lead to local electric-field distortion and insulation weaknesses at the cable terminal, posing a severe threat to the safe operation of the cable system. In this study, an electric-field simulation model of a 10 kV cable terminal was implemented to investigate the effects of various defects, such as insufficient stress-cone overlap, axial scratch, ring-cut defect, and moisture ingress on the cable terminal. The results show that insufficient stress-cone overlap produces a severe field distortion, and the distortion level is strongly correlated with the misalignment distance. For mechanical damage defects, axial scratches and ring-cut defects mainly distort the electric field inside the air gap, and defect position induces a stronger distortion level than that of defect depth. With increasing ring-cut depth, the maximum value of distorted electric field first decreases and then rises slightly. For moisture defects, the distorted field primarily occurs at the angle between the water-film tip and the stress cone, where the maximum value appears near the XLPE/SIR interface. These results provide a theoretical basis for defect diagnosis, structural optimization, and assembly process control of cable terminals.