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In this article, an experimental study was carried out on the switching impulse (SI) breakdown characteristics of C5F10O/CO2 mixture, and the effects of pressure and mixing ratio on its breakdown characteristics were analyzed. The results show that there is a polarity effect between positive and negative breakdown voltages, and the polarity effect becomes stronger with the pressure increased, and a polarity reversal occurred at 0.15 MPa. Increasing the gas pressure and the content of C5F10O can improve the SI breakdown voltage of C5F10O/CO2, but it can only reach 60%–70% of SF6 under the same conditions. The positive breakdown voltage has a “hump” phenomenon as the pressure increases. With the increase in C5F10O content, the “hump” tends to shift toward low pressure. The “hump” is explained from the improving effect of positive space charge on electric field, and the influence of the applied voltage, pressure, and C5F10O content on the positive charge layer is comprehensively considered. The results of this article can provide reference for the engineering application of C5F10O gas insulating medium. [ABSTRACT FROM AUTHOR]

Since the environmental-friendly insulating gas C5F10O not only has good environmental compatibility, but also has excellent insulating properties, it has the potential to replace SF6 in equipment such as medium and low voltage switchgear. When a partial over-thermal fault occurs on metal material surface inside the gas-insulated equipment, the C5F10O can be decomposed by overheating, and the presence of the gas–solid interface has a certain influence on C5F10O decomposition process. To this end, this article uses the Density Functional Theory to study on C5F10O over-thermal decomposition mechanism on metal materials surface in the equipment. The results show that when it does not involve Cu atoms in the reaction, the energy barrier of C5F10O decomposed into C2F4O and C3F6 is reduced by about 14.7 kcal/mol compared with that in free space; when C5F10O decomposition involves Cu atoms in the reaction and chemical adsorption occurs, the reaction energy barrier is further reduced by about 7.4 kcal/mol. In addition, the participation of Cu surface reduces the reaction energy barrier of 2 C2F4O → CF2O + C3F6O and C2F4O → CF4 + CO by 8.4 kcal/mol and 26.6 kcal/mol respectively, and increases the reaction energy barrier of C3F6 + CF2O → C3F8 + CO by 23.4 kcal/mol. It is believed that copper material has the effect of promoting the C5F10O decomposition to some degree. The research conclusions in this article can provide theoretical guidance for selections of internal metal materials or surface coating for the design of environmentally friendly gas-insulated switchgear in the future. [ABSTRACT FROM AUTHOR]

The perfluoroketone C5F10O, not only has good environmental compatibility, but also has excellent insulation properties and has the potential to replace SF6 in medium and low voltage switchgear. This paper focuses on the compatibility of C5F10O and its main decomposition products with the copper material inside the equipment and specifically constructs several adsorption models of C5F10O and its main decomposition products on a Cu (1 1 1) surface. The adsorption mechanism was studied from a system structure, electron density distribution and density of states perspective. The results showed that C5F10O mainly adsorbed chemically on the Cu surface through carbonyl oxygen atoms. Its maximum adsorption energy is −24.48 kcal mol−1, with electrons transferring from the copper surface to the adsorbed oxygen atom; and the adsorption energies of the main breakdown products CF4, C2F6, C3F8, C3F6, CF2O, C2F4O and CO2 with the surface are all less than −9.56 kcal mol−1. There is no obvious electron transfer between these decomposition gases and the copper surface, and thus, they belong to physical adsorption; while the adsorption energies of C3F6O, C2F4 and CO in the top, bridge and Hcc sites are respectively −9.661 kcal mol−1, −14.651 kcal mol−1 and −25.489 kcal mol−1, electrons on the copper surface transfer to the oxygen atom of C3F6O and carbon atoms of C2F4 and CO, forming stable chemical bonds, which belong to chemical adsorption. Through further analysis of the electron density of states, it is found that C5F10O and C3F6O bonded to the copper surface mainly by p orbitals on carbonyl oxygen atom and the pseudogaps are 3.2 eV and 2.5 eV. C2F4 and CO bonded to the copper surface by sp hybrid orbitals of carbon atoms, with a pseudogap of about 4 eV. Based on the above analysis, it can be seen that C5F10O and its main decomposition products C3F6O, C2F4 and CO have poor compatibility with metal copper. [ABSTRACT FROM AUTHOR]

It has been recognized that the gas insulating medium SF6 decomposes when the partial over-thermal fault (POF) occurs inside the equipment. The insulation condition monitoring and fault diagnosis of the equipment can be carried out by utilizing the decomposition characteristics of SF6 under POF. Similar to the discharge decomposition of SF6, trace H2O is an important factor affecting the decomposition of SF6 under POF while its mechanism is not clear yet. In order to investigate the characteristics and micro mechanism of decomposition, the paper combines isotope tracer by adding H218O as a tracer into SF6 gas and carries out experiments. Detecting the concentration and isotope abundance of products by gas chromatography–mass spectrometry, the paper studied the influence of H2O on the production of decomposition products and the specific formation process of CO2, SO2F2, SOF2 and SO2 under the influence of H2O. The research further verified the assumption on formation process of CO2 and SO2 and also brought up with new theory on the formation of SO2F2 and SOF2 based on experimental results. [ABSTRACT FROM AUTHOR]

The Junggar Basin is one of the main oil basins in Northwest China, and the north‐west part of the basin is a significant petroleum exploration target. Mesozoic structural activity had an important influence on the present structural characteristics of the north‐west Junggar Basin. In this paper, we discuss the tectonic evolution of the Junggar Basin by studying the structural characteristics of the Ke‐Bai Fault. Our results suggest that the Ke‐Bai Fault has obvious strike‐slip characteristics and that it is an important basin‐controlling fault that has controlled the tectonic evolution of the north‐west Junggar Basin. The Junggar Basin was a rift basin in the Early Permian, but it experienced a tectonic reversal during the Middle Permian to the Triassic. The Ke‐Bai Fault changed from a normal fault into a thrust fault from the Early Permian to the Triassic. During the Jurassic, dextral strike‐slip structures developed along the Ke‐Bai Fault, horsetail splay faults developed in its north segment, and there is evidence that it was under WNW–ESE compression. The dextral strike‐slip faulting of the Ke‐Bai Fault is consistent with tectonic movement along the Kelameili, Sangequan, Wu‐Xia, Hong‐Che, and North Tianshan fault systems in the Junggar Basin. We therefore infer that counterclockwise rotation occurred in the Junggar Basin in the Jurassic. [ABSTRACT FROM AUTHOR]

In this letter, the vertically‐stacked GaSe/MoS2 heterostructures with indium tin oxide (ITO) and Ni/Au as contact electrodes are successfully fabricated, respectively. The GaSe/MoS2 heterostructure exhibits a broadband photoresponse covering the range of visible to near‐infrared spectra at room temperature without external bias voltage. When ITO serves as contact electrodes, a high rectification ratio, i.e., 1.5 × 104 at VDS = ±1 V, and an excellent photoelectric performance, i.e., responsivity of ≈0.67 A W‐1, specific detectivity of ≈2.3 × 1011 cm Hz1/2 W‐1 and external quantum efficiency of ≈160% at the wavelength of 520 nm is achieved. Moreover, the GaSe/MoS2 heterostructure with Ohmic‐contact ITO electrodes demonstrates a faster response time of 155 µs, which is 4 times faster than the GaSe/MoS2 heterostructure with Ni/Au electrodes and about 300 times faster than previous reports. These results reveal the presence of an abrupt p–n junction between GaSe and MoS2 and significant role of electrode‐contact mode in determining the photoelectric properties of GaSe/MoS2 heterostructure. [ABSTRACT FROM AUTHOR]

It has been recognized that the gas insulating medium SF6 decomposes when the partial over-thermal fault (POF) occurs inside the equipment. The insulation condition monitoring and fault diagnosis of the equipment can be carried out by utilizing the decomposition characteristics of SF6 under POF. Similar to the discharge decomposition of SF6, trace H2O is an important factor affecting the decomposition of SF6 under POF while its mechanism is not clear yet. In order to investigate the characteristics and micro mechanism of decomposition, the paper combines isotope tracer by adding H218O as a tracer into SF6 gas and carries out experiments. Detecting the concentration and isotope abundance of products by gas chromatography–mass spectrometry, the paper studied the influence of H2O on the production of decomposition products and the specific formation process of CO2, SO2F2, SOF2 and SO2 under the influence of H2O. The research further verified the assumption on formation process of CO2 and SO2 and also brought up with new theory on the formation of SO2F2 and SOF2 based on experimental results. [ABSTRACT FROM AUTHOR]