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Flexible pressure sensors applied in wearable detection often face challenges, such as low sensitivity, large device size, poor flexibility, and long response time. This study aims to design and develop high-performance pressure-sensitive materials for wearable human detection applications. Using a sensitive layer composite and microstructural design, rGO/Fe nanowires (NWs) composites were proposed as the pressure-sensitive material. This approach yields a compact sensor with high flexibility, good mechanical properties, and excellent sensing performance. Firstly, rGO/Fe NWs composites were prepared by the Hummers method and an in situ reduction technique under a magnetic field. Secondly, the structural design, component construction, and sensing mechanism of the sensors were thoroughly investigated. Finally, the performance of the flexible pressure sensor was tested, and its application in the wearable field was explored. The results demonstrate that the sensor exhibits excellent performance with a good response to both large and small pressures within the range of 0–30 kPa, providing an effective method for wearable human health detection.

Moisture has been a crucial problem during the operation of cable systems. When we are faced with polypropylene (PP)-based insulation for the development of cable systems, there are few reports on the effects of water intrusion on the electrical performances of PP. In this study, the water absorption characteristics of isotactic PP (iPP) and atactic PP (aPP), as well as their effects on volume resistivity and relative permittivity, were investigated. The structure evolution during the water absorption process of the two PPs was also compared via infrared spectra and X-ray diffraction analyses. The results show that both of the two PPs show a saturation of water absorption at ~216 h, even though there are structural differences. And water intrusion into bulk could increase the interplanar spacing of iPP while decreasing the interplanar spacing of aPP. Moreover, with the increase in water absorption, the volume resistivity of the two PPs show a decreasing trend while the relative permittivity presents an increasing behavior, which shows an almost linear correlation.

The online monitoring of GIS equipment can be realized through detecting SF6 decomposition gasses. Metal oxide heterojunctions are widely used as gas-sensing materials. In this study, the structural and electrical properties of In2O3-ZnO and TiO2-ZnO heterojunctions were analyzed based on density functional theory calculations. After heterojunction structural optimization, the electrical conductivity of these two heterojunctions was enhanced compared to each intrinsic model, and the electrical conductivity is ranked as follows: In2O3-ZnO heterojunction > TiO2-ZnO heterojunction. The gas-sensing response of these two heterojunctions to four SF6 decomposition gasses, H2S, SO2, SOF2, and SO2F2, was investigated. For gas adsorption systems, the adsorption energy, charge transfer, density of states, charge difference density, and frontier molecular orbitals were calculated to analyze the adsorption and gas-sensing performance. For gas adsorption on the In2O3-ZnO heterojunction surface, the induced conductivity changes are in the following order: H2S > SO2F2 > SOF2 > SO2. For gas adsorption on the TiO2-ZnO heterojunction surface, H2S and SOF2 increase conductivity, and SO2 and SO2F2 decrease conductivity.

Abstract Online detection of insulation defects the decomposition products of SF6 plays a key role in ensuring the safe operation of the gas‐insulated switchgear (GIS) equipment. The pristine TiO2 (1 0 1) modified by Ni cluster (1–3 Ni atoms) is used as a new gas‐sensing material to study its gas‐sensing characteristics to the characteristic decomposition products of SF6: SO2, SOF2, and SO2F2. Through density functional theory (DFT) calculation, we found that the modification of Ni clusters significantly improved the conductivity of pristine TiO2 (1 0 1) and the gas sensitivity of SF6 decomposition products. More importantly, the change of conductivity after gas adsorption lays a theoretical foundation for identifying the type and concentration of SF6 characteristic decomposition products and further judging the type of defects in GIS.

A series of latent insulation failures, including insulation aging and the breakdown of insulating devices caused by the decomposition products of SF6, are quite a threat to the power system. In this study, the adsorption behavior of SO2F2 gas over TM (TM = Co, Rh, Pd) embedded g-C3N4 systems were studied in order to find a sensitive gas-sensing material for SO2F2 detection. The geometric structure, electronic properties, and molecular orbit were calculated based on DFT calculations. By comparing the gas adsorption properties before and after TM modification, the interaction mechanism and gas-sensing properties were theoretically analyzed. The results reveal that the TM embedded g-C3N4 monolayer can indeed improve the electrical conductivity of g-C3N4 and the stability of adsorption structure is in order of Co＞Pd＞Rh. In conclusion, TM-embedded g-C3N4 systems are expected to become a potential gas-sensing material as SO2F2 gas sensors.

The potential decoration structures of Pd atom, Pd2 cluster and Pd3 cluster on the AlN nanotubes (AlNNTs) surface were initially studied. As the structure of Pd2 decoration on AlNNTs is similar to that of two single Pd atom decoration, only Pd-AlNNTs and Pd3-AlNNTs were further analyzed. It is found that Pd atom and Pd3 cluster preferred to adsorb on the surface surrounding N atom. Pd atom and Pd3 cluster reduced the energy band gap, and increases the electrical conductivity of AlNNTs, especially Pd3 decoration. The adsorption behavior, charge transfer, densities of states, projected densities of states, and molecular orbital analysis of AlNNTs towards four oil-dissolved gases, including H2, CH4, C2H2, and C2H4, were analyzed. These analyses indicated that Pd-AlNNTs and Pd3-AlNNTs showed strong interaction to four gas molecules. Pd-AlNNTs and Pd3-AlNNTs acted as the electron donators by transmitting electrons to the gas molecules during the interaction. According to the analysis of gas-sensing response, gas molecules adsorption on Pd-AlNNTs and Pd3-AlNNTs decreases the conductivity of the whole adsorption system.

Detection and analysis of sulfur hexafluoride (SF6) decomposition components is one of the most used methods to realize online monitoring of gas insulated switchgear (GIS) faults. In this paper, Pd3-doped anatase TiO2(101) surface was constructed, and studied about its geometric and electronic properties to characteristic SF6 decomposition products: SOF2 and SO2F2 based on DFT calculations. Comparing with intrinsic TiO2(101), the conductivity of Pd3-TiO2(101) surface decreases dramatically. Studies on adsorption energy, charge transfer, and adsorption distance show that Pd3-TiO2(101) shows strong chemisorption to SOF2 and SO2F2 molecules. Based on density of states and molecular orbital theory analysis, it is found that the adsorption of SOF2 and SO2F2 can dramatically change the conductivity in different degrees. As a result, the Pd3-TiO2(101) surface exhibits high gas sensitivity and selectivity to SOF2 and SO2F2 molecules. Our calculations would be meaningful for the development of new sensing materials for SF6 decomposition components detection.

Detection of oil dissolved gases is of great significance to diagnose the diverse insulation faults in oil-immersed transformers. Therefore, the Metal oxides (CuO, NiO) doped SnS2 monolayer were exploited to reveal their gas-sensing properties to the typical oil dissolved gases (C2H4, CH4, H2) and H2O. Based on density functional theory calculations, the most stable modified substrate and adsorption structures were selected according to adsorption energy and geometry optimization. In addition, the gas-sensing mechanisms were obtained through the analysis of the adsorption structure, molecular orbit, charge transfer, total density of states and projected density of states. For gases adsorption on CuO-SnS2 the adsorption capacity is ranked as: C2H4 > H2O > H2 > CH4. For NiO-SnS2 the adsorption capacity is ranked as: H2O > C2H4 > H2 > CH4. By contrast, CuO-SnS2 shows higher superiority towards C2H4 adsorption, while the adsorption energy of CH4 ,H2 and H2O on NiO-SnS2 is more prominent than that of CuO-SnS2. Considering the ameliorative electronic properties and appropriate adsorption energy, NiO-SnS2 can be a potential candidate sensor for C2H4.

The adsorption mechanism of CO and CH4 on GeSe, modified with the most stable 1–4 Ag-atom clusters, is studied with the help of density functional theory. Adsorption distance, adsorption energy, total density of states (TDOS), projected density of states (PDOS), and molecular orbital theory were all used to analyze the results. CO was found to chemisorb exothermically on GeSe, independent of Ag cluster size, with Ag4-GeSe representing the optimum choice for CO gas sensors. CH4, in contrast, was found to chemisorb on Ag-GeSe and Ag2-GeSe and to physisorb on Ag3-GeSe and Ag4-GeSe. Here, Ag GeSe was found to be the optimum choice for CH4 gas sensors. Overall, our calculations suggest that GeSe modified by Ag clusters of different sizes could be used to advantage to detect CO and CH4 gas in ambient air.

To propose a novel type of sensing material applied in the field of sulfur hexafluoride (SF6) insulated gas, we investigated the adsorption performance of SF6 decomposed species (H2S, SO2, and SOF2) on Pt-doped graphyne (GD) monolayer. We initially studied the possible stable structure of Pt-GD monolayer and found that the Pt dopant preferred adsorption onto the $\text{C}\equiv \text{C}$ bond. We further investigated electronic differential density, band structure, and density of states to evaluate the chemical and physical interactions between Pt-GD and four typical gases, namely, H2S, SO2, SOF2, and SF6. The results indicated that only H2S, SO2, and SOF2 molecules were adsorbed onto the Pt-GD with strong chemical interactions due to the large adsorption energy, evident electronic differential density change, and orbital hybridization. These results showed that the strong interactions were caused by the Pt dopant. The conductivity of monolayer was enhanced by H2S but was weakened by SO2 and SOF2. The adsorption capacity occurred in the following order: SO2 > H2S > SOF2 > SF6. Our work determined the stable Pt doping structure on GD and provided theoretical support for a novel material realizing the operation state evaluation of SF6 insulated gas equipment.

The adsorption capacity of intrinsic SnS2 to NH3, Cl2 and C2H2 is very weak. However, non-metallic elements B and N have strong chemical activity, which can significantly improve the conductivity and gas sensitivity of SnS2. Based on density functional theory, SnS2 was modified with B and N atoms to analyze its adsorption mechanism and gas sensitivity for NH3, Cl2 and C2H2 gases. The optimal structure, adsorption energy, state density and frontier molecular orbital theory are analyzed, and the results are in good agreement with the experimental results. The results show that the adsorption of gas molecules is exothermic and spontaneous. Only the adsorption of NH3 and Cl2 on B-SnS2 belongs to chemical adsorption, whereas other gas adsorption systems belong to physical adsorption. Moderate adsorption distance, large adsorption energy, charge transfer and frontier molecular orbital analysis show that gas adsorption leads to the change of the conductivity of the modified SnS2 system. The adsorption capacity of B-SnS2 to these gases is Cl2 > NH3 > C2H2. The adsorption capacity of N-SnS2 is NH3 > C2H2 > Cl2. Therefore, according to different conductivity changes, B-SnS2 and N-SnS2 materials can be developed for greenhouse gas detection of gas sensors.

Detecting the characteristic decomposition products (SO2, SOF2, and HF) of SF6 is an effective way to diagnose the electric discharge in SF6-insulated equipment. Based on first-principles calculations, Au, Ag, and Cu were chosen as the surface modification transition metal to improve the adsorption and gas-sensing properties of MoTe2 monolayer towards SO2, SOF2, and HF gases. The results show that Au, Ag, and Cu atoms tend to be trapped by TH sites on the MoTe2 monolayer, and the binding strength increases in the order of Ag < Au < Cu. In gas adsorption, the moderate adsorption energy provides the basis that the TM-MoTe2 monolayer can be used as gas-sensing material for SO2, SOF2, and HF. The conductivity of the adsorption system changes significantly. The conductivity decreases upon gases adsorption on TM-MoTe2 monolayer, except the conductivity of Ag-MoTe2 monolayer increases after interacting with SOF2 gas.

Online impulse frequency response analysis (IFRA) has proven to be a promising method to detect and diagnose the transformer winding mechanical faults when the transformer is in service. However, the existing fast Fourier transform (FFT) is actually not suitable for processing the transient signals in online IFRA. The field test result also shows that the IFRA signature obtained by FFT is easily distorted by noise. An improved method to obtain the online IFRA signature based on multi-scale complex continuous wavelet transform is proposed. The electrical model simulation and online experiment indicate the superiority of the wavelet transform compared with FFT. This paper provides guidance on the actual application of the online IFRA method.

In the long-running of sulphur hexafluoride (SF(6))-insulated equipment, SF(6) inevitably decomposes to various decomposition products under electric discharge, including SOF(2) and SO(2)F(2). In this work, single Pt modified molybdenum disulphide (Pt-MoS(2)) monolayer, and double Pt modified molybdenum disulphide (Pt(2)-MoS(2)) monolayer are proposed to analyse its adsorption and sensing properties to SOF(2) and SO(2)F(2) with single and double gas molecules adsorption based on density functional theory. The adsorption energy, density of states, and molecular orbit theory are employed to analyse the adsorption and sensing mechanism. It turns out that the Pt-MoS(2) and Pt(2)-MoS(2) present outstanding adsorption capacity to gas molecules. Specifically, double SOF(2) adsorption on Pt(2)-MoS(2) shows the best adsorption performance, and the conductivity of the adsorption system changes the most in the adsorption process. Overall, both Pt-MoS(2) and Pt(2)-MoS(2) perform as an excellent gas sensor. This study provides a theoretical basis to develop Pt-MoS(2) and Pt(2)-MoS(2) based materials for SOF(2) and SO(2)F(2) detection in SF(6)-insulated equipment.

H2S and SOF2 gas are two typical decomposition products of SF6 gas under partial discharge condition. Based on the density functional theory (DFT), several doping structures of Si-MoS2 and adsorption structures of gas adsorbed Si-MoS2 were investigated. The electronic property, adsorption energy, charge transfer, and electron density difference were calculated to analyze the adsorption mechanism. Compared with the structure of pristine MoS2 monolayer, Si doping improves the surface activity of MoS2 monolayer. Moreover, the introduction of Si atom increases the effects of orbital hybridization between gas molecules and MoS2 monolayer, and promotes the charge transfer. Especially, SOF2 possesses a large adsorption energy with Si-MoS2 by crossing a small energy barrier. In addition, the good compatibility of Si-MoS2 with SF6 atmosphere, makes it a promising adsorbent for SF6 decomposition products removal. Keywords: H2S, SOF2, Si-MoS2 absorbent, DFT calculations

Hydrogen sulfide (H2S) is an important decomposition component of sulfur hexafluoride (SF6), which has been extensively used in gas-insulated switchgear (GIS) power equipment as insulating and arc-quenching medium. In this work, electrospun ZnO-SnO2 composite nanofibers as a promising sensing material for SF6 decomposition component H2S were proposed and prepared. The crystal structure and morphology of the electrospun ZnO-SnO2 samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. The composition of the sensitive materials was analyzed by energy dispersive X-ray spectrometers (EDS) and X-ray photoelectron spectroscopy (XPS). Side heated sensors were fabricated with the electrospun ZnO-SnO2 nanofibers and the gas sensing behaviors to H2S gas were systematically investigated. The proposed ZnO–SnO2 composite nanofibers sensor showed lower optimal operating temperature, enhanced sensing response, quick response/recovery time and good long-term stability against H2S. The measured optimal operating temperature of the ZnO–SnO2 nanofibers sensor to 50 ppm H2S gas was about 250°C with a response of 66.23, which was 6 times larger than pure SnO2 nanofibers sensor. The detection limit of the fabricated ZnO–SnO2 nanofibers sensor toward H2S gas can be as low as 0.5 ppm. Finally, a plausible sensing mechanism for the proposed ZnO–SnO2 composite nanofibers sensor to H2S was also discussed.

Tin oxide SnO2-based gas sensors have been widely used for detecting typical fault characteristic gases extracted from power transformer oil, namely, H2, CO, CO2, CH4, C2H2, C2H4, and C2H6, due to the remarkable advantages of high sensitivity, fast response, long-term stability, and so on. Herein, we present an overview of the recent significant improvement in fabrication and application of high performance SnO2-based sensors for detecting these fault characteristic gases. Promising materials for the sensitive and selective detection of each kind of fault characteristic gas have been identified. Meanwhile, the corresponding sensing mechanisms of SnO2-based gas sensors of these fault characteristic gases are comprehensively discussed. In the final section of this review, the major challenges and promising developments in this domain are also given.

Partial discharge has become a serious threat to the stable operation of gas-insulated switchgears. SOF2 is a characteristic decomposition component of SF6 decomposition components under partial discharge, which further deteriorate the severity of partial discharge. In order to find an excellent adsorbent for SOF2, Pd/Pt-Ni(111) composite surface is raised as an adsorbent to investigate its adsorption ability of the SOF2 molecule. The results of the study show that Pd or Pt composite layer on Ni(111) atoms can significantly enhance the adsorption capacity, the adsorption ability to SOF2 is in the sequence of Pt-Ni(111) > Pd-Ni(111) > Ni(111) > Ni-Pd-Ni(111) > Ni-Pt-Ni(111). However, the adsorption of SOF2 on Pt-Ni(111) and Pd-Ni(111) surfaces is strong chemisorption, which is an irreversible adsorption process. On the contrary, Ni-Pd-Ni(111) and Ni-Pt-Ni(111) show moderate physisorption of SOF2. In addition, the density of electronic states, and electron density difference are further calculated to analyze the adsorption mechanism of SOF2. This research provides important theoretical support for developing an ideal SOF2 adsorbent.

The effects of background gases (He, Ar, N2 and air) on SF6 removal in a dielectric barrier reactor were investigated at atmospheric pressure. A comparison among these background gases was performed in terms of discharge voltage, discharge power, mean electron energy, electron density, removal efficiency and energy yield for the destruction of SF6. Results showed that the discharge voltage of He and Ar was lower than that of N2 and air, but the difference of their discharge power was small. Compared with three other background gases, Ar had a relatively superior destruction and removal rate and energy yield since the mean electron energy and electron density in SF6/H2O/Ar plasma were both maintained at a high level. Complete removal of 2% SF6 could be achieved at a discharge power of 48.86 W with Ar and the corresponding energy yield can reach 4.8 g/kWh.

In this paper, a molecular dynamics simulation method was used to study the thermo-mechanical properties of cross-linked epoxy resins doped with nano silica particles that were grafted with 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and 3-[2-(2-aminoethylamino)ethylamino]-propyl-trimethoxysilane with different chain lengths. Firstly, a set of pure epoxy resin models, and four sets of SiO2/EP composite models were established. Then, a reasonable structure was obtained through a series of optimizations using molecular dynamics calculations. Next, the mechanical properties, hydrogen bond statistics, glass transition temperature, free volume fraction, and chain spacing of the five models were studied comparatively. The results show that doped nano silica particles of surfaces grafted with 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and 3-[2-(2-aminoethylamino)ethylamino]-propyl-trimethoxysilane with different chain lengths enhanced mechanical properties such as elastic modulus, shear modulus, and volume modulus obviously. The glass transition temperature increased by 15⁻16 K, 40⁻41 K, and 24⁻27 K, respectively. Finally, the data show that the cross-linked epoxy resin modified by nanoparticles grafted with N-(2-aminoethyl)-3-aminopropyl trimethoxysilane had better effects for improving thermo-mechanical properties by the comparatively studying the five groups of parameter models under the same conditions.

SF6 decomposition components detection is a key technology to evaluate and diagnose the insulation status of SF6-insulated equipment online, especially when insulation defects-induced discharge occurs in equipment. In order to detect the type and concentration of SF6 decomposition components, a Ni-modified carbon nanotube (Ni-CNT) gas sensor has been prepared to analyze its gas sensitivity and selectivity to SF6 decomposition components based on an experimental and density functional theory (DFT) theoretical study. Experimental results show that a Ni-CNT gas sensor presents an outstanding gas sensing property according to the significant change of conductivity during the gas molecule adsorption. The conductivity increases in the following order: H2S > SOF2 > SO2 > SO2F2. The limit of detection of the Ni-CNT gas sensor reaches 1 ppm. In addition, the excellent recovery property of the Ni-CNT gas sensor makes it easy to be widely used. A DFT theoretical study was applied to analyze the influence mechanism of Ni modification on SF6 decomposition components detection. In summary, the Ni-CNT gas sensor prepared in this study can be an effective way to evaluate and diagnose the insulation status of SF6-insulated equipment online.

In this paper, a Ni-doped MoS2 monolayer (Ni-MoS2) has been proposed as a novel gas adsorbent to be used in SF6-insulated equipment. Based on the first-principles calculation, the adsorption properties of Ni-MoS2 to SO2 and H2S molecules, the main decomposition components of SF6 under a partial discharge (PD) condition have been studied. The adsorption energy, charge transfer, and structural parameters have been analyzed to find the most stable gas-adsorbed Ni-MoS2. Furthermore, the density of states (DOS), projected density of states (PDOS), and electron density difference were employed to explore the interaction mechanism between SO2, H2S, and the Ni-MoS2 surface. It is found that the H2S molecule and SO2 molecule interact with the Ni-MoS2 surface by strong adsorption energy. Therefore, we conclude that the interaction between these two kinds of gases and the Ni-MoS2 monolayer belongs to chemisorption, and the Ni-MoS2 monolayer might be a promising gas adsorbent for the fault recovery of SF6-insulated equipment. Additionally, we have to point out that all of the conclusions only considered the final adsorption energy, the barrier in the transition state has not been analyzed in this paper.

In this paper, pure and Ag-doped SnO2 nanospheres were synthesized by hydrothermal method and characterized via X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectra (XPS), respectively. The gas sensing performance of the pure, 1 at.%, 3 at.%, and 5 at.% Ag-doped SnO2 sensing devices toward hydrogen (H2) were systematically evaluated. The results indicated that compared with pure SnO2 nanospheres, Ag-doped SnO2 nanospheres could not only decrease the optimum working temperature but also significantly improve H2 sensing such as higher gas response and faster response-recovery. Among all the samples, the 3 at.% Ag-doped SnO2 showed the highest response 39 to 100 μL/L H2 at 300 °C. Moreover, its gas sensing mechanism was discussed, and the results will provide reference and theoretical guidance for the development of high-performance SnO2-based H2 sensing devices.

A transformer is the most valuable and expensive property for power utility, thus ensuring its reliable operation is a major task for both operators and researchers. Online impulse frequency response analysis has proven to be a promising technique for detecting transformer internal winding mechanical deformation faults when a power transformer is in service. However, as so far, there is still no reliable standard code for frequency response signature interpretation and quantification. This paper tries to utilize a machine learning method, namely the support vector machine, to identify and classify the winding mechanical fault types, based on online impulse frequency response analysis. Actual transformer fault data from a specially manufactured model transformer are collected and analyzed. Two feature vectors are proposed and the diagnostic results are predicted. The diagnostic results indicate the satisfied classifying accuracy by the proposed method.

Graphene-based materials have aroused enormous focus on a wide range of engineering fields because of their unique structure. One of the most promising applications is gas adsorption and sensing. In electrical engineering, graphene-based sensors are also employed as detecting devices to estimate the operation status of gas insulated switchgear (GIS). This paper reviews the main synthesis methods of graphene, gas adsorption, and sensing mechanism of its based sensors, as well as their applications in detecting SF6 decomposing products, such as SO2, H2S, SO2F2, and SOF2, in GIS. Both theoretical and experimental researches on gas response of graphene-based sensors to these typical gases are summarized. Finally, the future research trend about graphene synthesis technique and relevant perspective are also given.

Detection of decomposition products of sulfur hexafluoride (SF6) is one of the best ways to diagnose early latent insulation faults in gas-insulated equipment, and the occurrence of sudden accidents can be avoided effectively by finding early latent faults. Recently, functionalized graphene, a kind of gas sensing material, has been reported to show good application prospects in the gas sensor field. Therefore, calculations were performed to analyze the gas sensing properties of intrinsic graphene (Int-graphene) and functionalized graphene-based material, Ag-decorated graphene (Ag-graphene), for decomposition products of SF6, including SO2F2, SOF2, and SO2, based on density functional theory (DFT). We thoroughly investigated a series of parameters presenting gas-sensing properties of adsorbing process about gas molecule (SO2F2, SOF2, SO2) and double gas molecules (2SO2F2, 2SOF2, 2SO2) on Ag-graphene, including adsorption energy, net charge transfer, electronic state density, and the highest and lowest unoccupied molecular orbital. The results showed that the Ag atom significantly enhances the electrochemical reactivity of graphene, reflected in the change of conductivity during the adsorption process. SO2F2 and SO2 gas molecules on Ag-graphene presented chemisorption, and the adsorption strength was SO2F2 > SO2, while SOF2 absorption on Ag-graphene was physical adsorption. Thus, we concluded that Ag-graphene showed good selectivity and high sensitivity to SO2F2. The results can provide a helpful guide in exploring Ag-graphene material in experiments for monitoring the insulation status of SF6-insulated equipment based on detecting decomposition products of SF6.

In this study a new built-in ultrahigh frequency (UHF) antenna sensor was designed and applied in a high-voltage switchgear for partial discharge (PD) detection. The casing of the switchgear was initially used as the ground plane of the antenna sensor, which integrated the sensor into the high-voltage switchgear. The Koch snowflake patch was adopted as the radiation patch of the antenna to overcome the disadvantages of common microstrip antennas, and the feed position and the dielectric layer thickness were simulated in detail. Simulation results show that the antenna sensor possessed four resonant points with good impedance matching from 300 MHz to 1000 MHz, and it also presented good multi-frequency performance in the entire working frequency band. PD detection experiments were conducted in the high-voltage switchgear, and the fabricated antenna sensor was effectively built into the high-voltage switchgear. In order to reflect the advantages of the built-in antenna sensor, another external UHF antenna sensor was used as a comparison to simultaneously detect PD. Experimental results demonstrated that the built-in antenna sensor possessed high detection sensitivity and strong anti-interference capacity, which ensured the practicability of the design. In addition, it had more high-voltage switchgear PD detection advantages than the external sensor.

In this paper, a Ni-doped MoS2 monolayer (Ni-MoS2) has been proposed as a novel gas adsorbent to be used in SF6-insulated equipment. Based on the first-principles calculation, the adsorption properties of Ni-MoS2 to SO2 and H2S molecules, the main decomposition components of SF6 under a partial discharge (PD) condition have been studied. The adsorption energy, charge transfer, and structural parameters have been analyzed to find the most stable gas-adsorbed Ni-MoS2. Furthermore, the density of states (DOS), projected density of states (PDOS), and electron density difference were employed to explore the interaction mechanism between SO2, H2S, and the Ni-MoS2 surface. It is found that the H2S molecule and SO2 molecule interact with the Ni-MoS2 surface by strong adsorption energy. Therefore, we conclude that the interaction between these two kinds of gases and the Ni-MoS2 monolayer belongs to chemisorption, and the Ni-MoS2 monolayer might be a promising gas adsorbent for the fault recovery of SF6-insulated equipment. Additionally, we have to point out that all of the conclusions only considered the final adsorption energy, the barrier in the transition state has not been analyzed in this paper. [ABSTRACT FROM AUTHOR]

Graphene-based materials have aroused enormous focus on a wide range of engineering fields because of their unique structure. One of the most promising applications is gas adsorption and sensing. In electrical engineering, graphene-based sensors are also employed as detecting devices to estimate the operation status of gas insulated switchgear (GIS). This paper reviews the main synthesis methods of graphene, gas adsorption, and sensing mechanism of its based sensors, as well as their applications in detecting SF6 decomposing products, such as SO2, H2S, SO2F2, and SOF2, in GIS. Both theoretical and experimental researches on gas response of graphene-based sensors to these typical gases are summarized. Finally, the future research trend about graphene synthesis technique and relevant perspective are also given. [ABSTRACT FROM AUTHOR]

Air-insulated switchgear cabinet plays a critical role in entire power transmission and distribution system. Its stability directly affects the operational reliability of the power system. And the on-line gas detection method, which evaluates the insulation status of insulation equipment by detecting the decomposition components of filled air in cabinet, becomes an innovative way to ensure the running stability of air-insulated switchgear cabinet. In order to study the characteristic gas types and production regularity of decomposition components under partial discharge, three insulation defects: needle-plate, air-gap and impurity defect are proposed to simulate the insulation defects under partial discharge in air-insulated switchgear cabinet. Firstly, the generation pathways and mechanism of composition components are discussed. Then CO and NO2 are selected as the characteristic decomposition components to characterize the partial discharge due to their high concentration and chemical stability. Based on the different change regularity of CO and NO2 concentration under different insulation defect, it provides an effective way to evaluate and predict the insulation defect type and severity in the field. [ABSTRACT FROM AUTHOR]

A three-layered structure comprising two layers of substrates with an adhesive layer at the center is introduced to improve heat dissipation of light-emitting diodes (LEDs). The adhesive layer is a type of treated composite composed of three components: hexagonal boron nitride (H-BN), epoxy resin (EP), and silane coupling agent. EP can be better positioned as a filler agent by using H-BN, thereby increasing adhesion. Introducing the silane coupling agent builds a heat conducting path from H-BN to EP, which effectively increases the thermal conductivity of the adhesive layer. In addition, the substrate surface treatment acts as an attraction agent and a catalyst that increases the interstitial between the composite and treated substrate surface. When the weight fraction of H-BN is 75%, the thermal conductivity of the treated composites at the center reaches 11.536 W·m-1 K-1, which is 38.57% higher than that of untreated H-BN/EP composites and 49 times that of EP. The thermal conductivity and adhesion strength of surface-treated three-layered structure are 9.571 W·m-1 K-1 and 56.60 MPa, respectively. Analysis of the thermal stability of the three-layered structure shows that surface-treated structures are more durable than surface-untreated structures. [ABSTRACT FROM AUTHOR]

In this study, molecular dynamics simulations were used to investigate the micro-scale effects of modification of nano-SiO2 with commonly used silane coupling agents (KH550, KH560, KH570, and KH792) on the cellulose/nano-SiO2 interface. The relative optimum silane coupling agent and grafting density for nano-SiO2 modification to improve the cellulose/nano-SiO2 interface were determined. The results showed that at the same grafting density, modification of nano-SiO2 with KH792 yielded the highest interfacial binding energy and binding energy density, the largest number of hydrogen bonds at the cellulose/nano-SiO2 interface, the strongest binding to the cellulose chains, and the largest overlapping area at the cellulose/nano-SiO2 interface. We found that the non-bonding interaction energy played a decisive role in the energy of the model system and the interfacial interaction force mainly consisted of van der Waals forces and the hydrogen-bonding energy. When silane coupling agents with amino groups (KH550 and KH792) were used to modify nano-SiO2, the number of hydrogen bonds at the cellulose/nano-SiO2 interface was larger than that for unmodified nano-SiO2. When silane coupling agents without amino groups (KH560 and KH570) were used to modify nano-SiO2, the number of hydrogen bonds at the cellulose/nano-SiO2 interface was lower than the case for unmodified nano-SiO2. Nano-SiO2 modification with various amounts of KH792 was investigated. The results showed that the interfacial bonding energy increased with grafting density. When the grafting density was 1.57 nm−2, the interfacial bonding energy and number of hydrogen bonds formed at the cellulose/nano-SiO2 interface was relatively stable, which indicates that the interface had reached a relatively stable state. Modification of nano-SiO2 with KH792 achieved the greatest improvement of the cellulose/nano-SiO2 interface; this interface reached a relatively stable state when the grafting density of KH792 was 1.57 nm−2. [ABSTRACT FROM AUTHOR]