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Polypropylene (PP) receives significant interests because of environmental friendship and excellent insulation. The development of PP cables depends heavily on the semi-conductive shielding layers that match the PP insulation layers. In this paper, propylene–ethylene copolymer (POP) is used to toughen the PP-based shielding layer. The effects of POP content (40 parts, 50 parts and 60 parts) on the electrical and mechanical characteristics are investigated. Further, the interface matching characteristics and toughening mechanism of the shielding layer are explored. According to the experimental findings, owing to the growth in POP content, the distribution of carbon black (CB) particles becomes more uniform, and the surface roughness decreases from 52.7 nm to 14.7 nm. When the POP content is 60 parts, the charge injected into the insulation layer is the least, which is 0.643 × 10−7 C, and the maximum electric field distortion decreases to 11.4 kV/mm. All three POP content shielding layers maintain a low resistivity at high temperatures (110 ℃, 80 Ω·cm). Besides, as the POP content increases, the toughness of PP-based shielding layer is improved and the elongation at break of POP-60 semi-conductive shielding layer reaches 420%. This research paves a new way for the development of semi-conductive shielding layer of PP cables. [ABSTRACT FROM AUTHOR]

With the concept of environmental protection is deeply popular, the power cables change from traditional thermosetting cross‐linked polyethylene (XLPE) cables to low‐carbon, environmentally friendly, recyclable polypropylene (PP) cables and the semi‐conductive shielding layer that matches the insulation layer for PP cables is highly valued. In this paper, LDPE is replaced with PP in the formulation of shielding layer of commercial XLPE cables. The physicochemical and electrical properties of PP/EVA/CB (PP‐based) and LDPE/EVA/CB (LDPE‐based) shielding layers were compared. The effect of interface matching characteristics on the electric field distortion was analyzed by finite element simulation software. The experimental results show that the volume resistivity of the shielding layers all tend to rise with the increasing temperature, but the resistivity of the PP‐based shielding layer has a smaller fluctuation. The PP‐based shielding layer has a smoother surface, while the space charge injected into the PP insulation layer is the lowest, about 0.433 × 10−7 C. Compared to the LDPE‐based shielding layer/insulation layer, the PP‐based shielding layer/insulation layer has a 50% reduction in interfacial electric field distortion rate. This work is an essential reference for the development for PP cables and their shielding layer selection. [ABSTRACT FROM AUTHOR]

Results from a 1D kinetic simulation, for the first time, reveal the important role of modified electron acoustic wave (MEAW) in auroral electron acceleration. Parallel electric fields, generated due to the mode coupling between kinetic Alfven waves (KAWs) and MEAWs in the transition region from the magnetosphere and the ionosphere, can be sustained by continuous energy input carried by Alfven waves from the magnetosphere. Under the incidence of long‐period Alfven waves carrying upward field‐aligned currents, a parallel potential drop can be formed in the transition region, leading to mono‐energetic electron acceleration. Such a mechanism provides a possible link between shear Alfven waves and the mesoscale mono‐energetic auroral electron acceleration. Plain Language Summary: Discrete aurora is supposed to be caused by precipitated electrons accelerated by parallel electric field. The mode coupling between modified electron acoustic waves (MEAWs), which received little attention, and kinetic Alfven waves is an effective mechanism of the generation of parallel electric field. The present simulation results show that the generation of parallel electric field, due to the mode coupling in the transition region, could be important or even dominant under certain circumstances. Our findings point out the importance of the MEAWs on the auroral electron acceleration. Key Points: Simulation results indicate that modified electron acoustic waves (MEAWs) strongly affect the auroral electron accelerationKinetic Alfven waves under certain circumstances lead to mono‐energetic acceleration through mode coupling to MEAWsSuch a mechanism provides a possible link between Alfven waves and mono‐energetic electron acceleration [ABSTRACT FROM AUTHOR]

Space charge accumulation in the cable insulation will cause local electric field distortion, and accelerate the aging of the material. The inner semi‐conductive layer as an important structure of cable will affect the charge injection characteristics in the insulation layer. This work intended to explore the method of modifying the semi‐conductive layer with the Nitrogen‐doped graphene (NG) to suppress the charge accumulation utilizing the super‐smoothness of graphene and electron adsorption of N element. First, the NG is prepared using N‐modified graphene, and the semi‐conductive layer with different NG content is fabricated. Second, the physical and chemical properties of the semi‐conductive composite are carried out, then the charge accumulation characteristics in the insulation layer under the effect of the semi‐conductive layer are characterized. The results showed that an appropriate amount of NG doping can significantly inhibit the charge accumulation in the insulation layer. The surface roughness decreased by about 32.13% when the doped NG content is 0.5 phr. With the increase of NG content from 0 to 1 phr, the accumulation charges inside the insulation layer decreased by about 36.84%. This research provided a new approach for suppressing space charge accumulation in the insulation material of high voltage cable. [ABSTRACT FROM AUTHOR]

To fully understand the distribution network cable accessories’ moisture fault, the variation in insulation parameters of the cable main insulation of cross-linked polyethylene (XLPE) and the cable accessory reinforced insulation of silicone rubber (SIR) under different moisture conditions are studied experimentally. Furthermore, the effects of typical moisture defect forms and moisture positions on electric field distributions are studied by establishing the interface defect model. The experimental results show that the insulation properties of XLPE after water immersion are more seriously reduced than SIR. The resistivity of XLPE and SIR specimens decreases significantly with the increase in moisture time, decreasing by 90.3% and 48.3% after 720 h, respectively. The relative dielectric constants of the two kinds of specimens increase with different degrees after moisture, increasing by 5.16% and 7.83%, respectively, and the breakdown strength decreases by 18.3% and 13.1% after 720 h, respectively. The simulated results show that the moisture form and position have a great influence on electric field distribution. The electric field distortion caused by water trees’ defect is the most serious, followed by water film defects and water droplet defects. Besides, for different types of moisture defects, the position of the maximum distortion electric field is different. [ABSTRACT FROM AUTHOR]