The 2050 carbon‐neutral vision spawns a novel energy structure revolution, and the construction of the future energy structure is based on equipment innovation. Insulating material, as the core of electrical power equipment and electrified transportation asset, faces unprecedented challenges and opportunities. The goal of carbon neutral and the urgent need for innovation in electric power equipment and electrification assets are first discussed. The engineering challenges constrained by the insulation system in future electric power equipment/devices and electrified transportation assets are investigated. Insulating materials, including intelligent insulating material, high thermal conductivity insulating material, high energy storage density insulating material, extreme environment resistant insulating material, and environmental‐friendly insulating material, are categorised with their scientific issues, opportunities and challenges under the goal of carbon neutrality being discussed. In the context of carbon neutrality, not only improves the understanding of the insulation problems from a macro level, that is, electrical power equipment and electrified transportation asset, but also offers opportunities, remaining issues and challenges from the insulating material level. It is hoped that this paper envisions the challenges regarding design and reliability of insulations in electrical equipment and electric vehicles in the context of policies towards carbon neutrality rules. The authors also hope that this paper can be helpful in future development and research of novel insulating materials, which promote the realisation of the carbon‐neutral vision.

In this paper, we report on electrical and mechanical properties of isotactic polypropylene (PP) blended with polyolefin elastomer (POE) and propylene-based elastomer (PBE). Carrier trap distribution of the samples was estimated by isothermal surface potential decay measurement, while dc breakdown strength was measured through a pair of semicircle electrodes. Elongation at break and tensile strength were obtained to examine the variation in mechanical property of PP caused by the addition of elastomers. Furthermore, scanning electron microscope (SEM), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) have been employed to assist the understanding of morphology of the blends, thermal properties, and mechanical properties. Obtained results have indicated that with the increase of the elastomer content from 0 to 30 wt%, the trap depth appeared to be shallower and the dc breakdown strength tended to be reduced for both PP/PBE and PP/POE samples. Compared with PP/POE blend, PP/PBE blend had deeper trap depth, which should be responsible for its higher dc breakdown strength. In addition, PP/PBE blend has presented a better performance in elongation at break and tensile strength measurement. With the growth of the elastomer content, the crystallinity of the blends appeared to decrease, whereas the melting and the crystallization temperatures did not change remarkably. The SEM inspections and DMA results revealed better compatibility between PP and PBE compared with that between PP and POE, which should be the reason for the better electrical and mechanical properties of PP/PBE blend. The blend of PBE with low content could result in remarkably improved flexibility of PP with acceptable electrical strength for dc cable insulation.

Free metal particle can affect surface charge accumulation on epoxy insulator installed in gas-insulated transmission line (GIL) or gas-insulated switchgear (GIS), which results in reduction of surface flashover voltage thus threatening the safe operation of the power equipment. This article reports on the charge accumulation behavior on a real size epoxy insulator with bouncing metal particle under DC voltage. A coaxial electrode system was designed for the test under -30 kV, a metal particle-launching system was employed to inject the bouncing linear particle to the insulator surface. The charge distribution was measured by a Kelvin-type probe, and the influence of the particle on the charge accumulation was analyzed with the help of electric field simulation. The results showed that there were mainly two moving patterns of the bouncing particle: the charges were accumulated with speckle shape and the charged particle that hit the edge of electrode had more remarkable influence on the charge accumulation than other particles. It is suggested that the charge distribution feature is dependent upon the collision point and the trajectory of the bouncing particle.

This paper reports on the ageing phenomenon of the polypropylene (PP) /elastomer blends that are used as DC cable insulation. The elastomers employed are propylene-based elastomer (PBE) and ethylene-octene copolymer elastomer (EOC), which are blended into the PP to form the test samples. The samples go through thermal cycling treatment with temperatures from -30 to 150 °C, after which the trap distribution and the DC breakdown strength are measured. Structural changes in the samples are estimated through Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and differential scanning calorimetry (DSC) measurements. The test results indicate that, with the growth of the thermal cycling number, the trap center decreases whereas the trap density increases, and the DC breakdown strength tends to be reduced. The appearance of oxidation product, loose structure and decreased crystallinity with the thermal cycling ageing should be responsible for the encouragement in charge transport and the reduction in the breakdown strength. The degradation of PP/EOC is more obvious than that of PP/PBE due to its worse compatibility, the PP/PBE exhibits better resistance to the thermal cycling ageing.

In this work, effect of nano-sized SiO ₂ and micro-sized hexagon boron nitride (h-BN) on charge transport behavior of low-density polyethylene (LDPE) has been investigated. LDPE based micro-nanocomposites samples were prepared through hot-press method by adding 20 nm-SiO ₂ and 5 µ m-h-BN as the fillers. Isothermal surface potential decay measurement was carried out with sample temperature of 40 °C and relative humidity of 23%–29% to obtain trap depth, carrier mobility and field dependent conductivity, by which the effect of fillers on charge transport manners could be estimated. In addition, thermal conductivity test, scanning electron microscopy and differential scanning calorimetry had been employed to assist the analysis of the filler effect. Test results indicated that the crystal structure of LDPE was changed by the doping of the fillers. With the increase of the micro- and nano-filler content, the trap depth tended to be deeper firstly then became shallower. Both band and hopping transport of charge occurred in the composite, and the carrier mobility was dependent upon the filler content. It is suggested that the addition of the nano-sized SiO ₂ and the micro-sized h-BN particles has an effect to inhibit the charge transport, where a synergistic effect among the nano-sized and the micro-sized particles is expected to modify charge trapping and de-trapping behavior.