Gas-insulated equipment (GIE) that utilizes the most potent greenhouse gas sulfur hexafluoride (SF 6 ) as insulation and arcquenching medium has been widely used in the power industry. Seeking eco-friendly insulating gas with advanced performance for next-generation SF 6 -free GIE is significant for the "net-zero" goal and sustainable development. In this paper, the utilization, emission, and reduction policies of SF 6 around the world were summarized first. Then, we systematically reviewed the latest progress in comprehensive performance evaluation of eco-friendly insulating gas in terms of molecular design, dielectric insulation, arcquenching, stability and decomposition, materials compatibility, biosafety, etc. Further, the representative applications of ecofriendly insulating gas in medium-voltage, high-voltage GIE as well as relevant maintenance-related technologies were highlighted. Accordingly, the existing challenges and future perspectives were proposed, presenting a roadmap to hopefully steer the development of eco-friendly insulating gas and GIE. KEYWORDSEco-friendly insulating gas, net-zero, dielectric insulation, arc-quenching, SF 6 -free gas-insulated equipment (GIE).
The streamer discharge is the inaugural stage of gas discharge, and the electron average energy directly determines the electron collision reaction rate, which is a key parameter for studying the streamer discharge. Therefore, taking into account the electron average energy, this work establishes a fluid chemical reaction model to simulate and study the streamer discharge’s evolution course in a 5 mm rod-plate gap, considering 12 particles and 27 chemical reactions. It introduces the electron energy drift diffusion equation into the control equation, and analyzes the temporal and spatial changes of electron average energy, electric field intensity and electron density with the change of rod radius and voltage, the effects of voltage and rod radius on the course of streamer discharge can be reflected more comprehensively by combining the average electron energy. Three different values of 0.3 mm, 0.4 mm and 0.5 mm are set for the rod radius, and three different values of 5 kV, 6 kV and 7 kV are set for the voltage. The influence of the excited reaction on the discharge of the streamer is studied. The findings indicate that as voltage raises, the streamer head’s electron density, electric field, and electron average energy all rise, and the streamer develops more quickly. When the rod radius increases, the streamer head’s electron density, electric field, and electron average energy all decrease, and the streamer’s evolution slows down. When the excitation reaction is added to the model, the electron average energy, the magnitude of the electric field and the density of electrons decrease, and the evolution of streamer slows down. The increase of electron average energy will lead to the increase of electric field strength and electron density, and the development of streamer will be faster.
Liquid rubber toughened epoxy resins are widely used in electrical equipment and electronic packaging. Previous studies have only investigated the relaxation process of epoxy resins through dielectric spectroscopy. The trap characteristics of the relaxation process by thermally stimulated depolarization current (TSDC) analysis are less studied. In this work, TSDC and broadband dielectric spectroscopy techniques were used to complementarily characterize the dielectric relaxation process of hydroxyl-terminated liquid nitrile-butadiene rubber (HTBN) toughened epoxy resin polymers. The experimental results show that HTBN introduces two new relaxation processes in the epoxy matrix, which are attributed to the α polarization of the rubber molecule and the interfacial polarization based on the correlation between the TSDC and the dielectric spectroscopy data, respectively. The trap parameters of each TSDC current peak were obtained using the multi-peak fitting method. The addition of rubber increases the trap density in epoxy composites significantly, especially for traps with energy levels in the range of 0.5–0.9 eV. The trap energy level of the DC conductivity process increases with increasing rubber concentration. The above results provide analytical ideas for rubber-toughened epoxy resins’ polarization and trap characteristics and theoretical guidance for formulation improvement.
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