For both polyimide membranes in aerospace and graphene membranes in nanoelectronics with surface accuracy requirements, wrinkles due to the extreme out-of-plane flexibility yield inverse influences on the properties and applications of membranes. In this study, on the basis of discrete topology optimization, we propose a prenecking strategy by adopting elliptical free edges to suppress the stretch-induced wrinkling. This prenecking strategy with the computer-aided-design (CAD)-ready format is versatile to eliminate wrinkles in stretched membranes with clamped ends and achieve wrinkle-free performances. The wrinkle-free capability of the prenecking strategy, capable of satisfying the shape accuracy requirements, indicates that by suffering insignificant area loss, concerning of wrinkling problems in membranes is no further required. As compared with the existing researches focusing on studying wrinkling behaviors, the prenecking strategy offers a promising solution to the stretch-induced wrinkling problem by eliminating wrinkles through design optimization.

Power equipment operates under high voltages, inducing space charge accumulation on the surface of key insulating structures, which increases the risk of discharge/breakdown and the possibility of maintenance workers experiencing electric shock accidents. Hence, a visualized non-equipment space charge detection method is of great demand in the power industry. Typical electrochromic phenomenon is based on redox of the material, triggered by a voltage smaller than 5 V with a continuous current in μA~mA level, which is not applicable to high electric fields above 106 V/m with pA~nA operation current in power equipment. Until now, no naked-eye observation technique has been realized for space charge detection to ensure the operation of power systems as well as the safety of maintenance workers. In this work, a viologen/poly(vinylidene fluoride-co-hexafluoropropylene)(P(VDF–HFP)) composite is investigated from gel to insulating bulk configurations to achieve high-voltage electrical-insulating electrochromism. The results show that viologen/P(VDF–HFP) composite bulk can withstand high electric fields at the 107 V/m level, and its electrochromism is triggered by space charges. This electrochromism phenomenon can be visually extended by increasing viologen content towards 5 wt.% and shows a positive response to voltage amplitude and application duration. As viologen/P(VDF–HFP) composite bulk exhibits a typical electrical insulating performance, it could be attached to the surface of insulating structures or clamped between metal and insulating materials as a space charge accumulation indicator in high-voltage power equipment.

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The substantial improvements in transmission voltage, which have been adopted to meet fast-growing energy demands, require more reliable power equipment and higher-quality insulating materials. The polytetrafluoroethylene (PTFE) nozzle, as the key part of a high-voltage circuit breaker, is often subjected to arc ablation and breakdown phenomena. Thus, it is very urgent to develop nozzles with better performance. In this study, PTFE/boron nitride (BN) composites were prepared. The relationships among the BN filler loading, thermal transition properties, spectral reflectance properties, arc ablation resistance, and AC dielectric breakdown performances, as well as their corresponding mechanisms, were studied. Experimental results show that the thermal conductivity and thermal diffusivity of PTFE/BN composites increased monotonously with BN loading, and that both parameters were improved by 41% and 44%, respectively, for 11 wt % composites compared with pure PTFE. Moreover, PTFE/BN composites had higher light reflectance in the wavelength range from 320 to 2500 nm. The PTFE/BN composites presented better arc ablation resistance performance with increased BN loading, which was improved by 88.5%. It is thought that the increased thermal conductivity, thermal diffusivity, the strong light reflectance, and surface sediment after arc ablation contribute to the improvement in arc ablation resistance performance. The AC breakdown strength of PTFE/BN composites was enhanced by 30.93%, attributed to the good heat dissipation properties introduced by the BN fillers. Thus, filling BN into the PTFE matrix would be helpful to solve the equipment issue that comes from the improvement in transmission voltage.

To study the dynamic charge characteristics of XLPE cables. In this paper, a Qt test system is built in the laboratory to test the Qt dynamic charge characteristics of different thermal aging samples, and the current characteristics of different aging degrees are obtained according to the charge test differentiation. The experimental results show that the charge value of unaged sample is about 1100 nC, and the charge value of aged sample is about 2000 nC. At the moment of pressurization, the XLPE cable sheet sample flows through a large instantaneous charging current, and the initial current is more than 10−9 orders of magnitude. For the unaged sample, the charge accumulation value and conduction current value of H1 and H2 are better than those of F sample. The analysis shows that due to the insufficient aging degree of the sample, the initial aging stage is in the recrystallizaon stage.