As one of the major concerns of climate change, identifying a proper eco-friendly insulation gas for replacing sulphur hexafluoride (SF 6 ) becomes a prominent research topic in recent years. c-C 4 F 8 , CF 3 I, C 5 F 10 O, C 6 F 12 O and C 4 F 7 N are some potential alternatives that are proved to have excellent characteristics, including high insulation strengths and low Global Warming Potentials (GWPs). Beyond these key factors, the decomposition products of these alternatives are closely related to the gases' insulation performance, as well as the safety of operators and the compatibility with other materials. In addition, the type and content of decomposition products can be used for fault diagnosis. Therefore, a number of studies were carried out to reveal the decomposition mechanism of these alternative gases, and then to explore the gases' application feasibility and strategy. The recent advances obtained in these studies, including theoretical calculation methods, detection of gas decomposition products, decomposition mechanism are reviewed, and some perspectives for future works are proposed. It is concluded that the phenomenon of solid matter precipitation in c-C 4 F 8 and CF 3 I gas decomposition cannot be ignored and that more research is needed to reveal the influence of buffer gases, microaerobic, micro-water and other impurities on the gas decomposition process.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
The application of eco‐friendly C4F7N/CO2 gas mixture has become a hot topic in the power industry. To obtain the influence law of micro‐water on the AC insulation characteristics of C4F7N/CO2 gas mixture, breakdown tests were carried out under different non‐uniform electric fields and micro‐water volume fractions. With the gap distance of 1 mm and the electric field non‐uniform coefficient less than 4.42, the breakdown voltage is positively correlated with gas pressure. With the gap distance of 6 mm and the electric field non‐uniform coefficient of 9.28, the breakdown voltage shows a typical N‐type change trend with the increase of gas pressure. With the gap distance of 9 mm and the electric field non‐uniform coefficient up to 16.45, the breakdown voltage shows a typical N‐type change trend with the increase of gas pressure. Micro‐water has a negative effect on breakdown voltage under different electric fields, meanwhile the breakdown voltage of slightly non‐uniform electric field is greatly affected by micro‐water, and the influence of micro‐water on breakdown voltage is different under different gas pressures. Therefore, the influence of operating gas pressure and slightly non‐uniform electric field should be considered when the micro‐water control index of C4F7N/CO2 gas mixture insulated equipment is formulated.
Cohesive soil containing calcareous nodule in Huaibei plain is a kind of regional special soil, which has a unique material composition and structure. The paper discusses the types and distribution of calcareous concretion in soil, and the influence on the strength of soil and the engineering property. Through a lot of the load test and the corresponding static cone penetration test, analyzing the correlation between them.Then linear regression equation between and is established. Finally, it is show that linear regression effect is remarkable, and the equation can be reference for the local practical engineering
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