Single Ni Atom-Dispersed WSe2 Monolayer for Sensing Typical Fault Gases in Dry-Type Transformers: A First-Principles Study.

This work, using the first-principles theory, uses the Ni-decorated WSe2 (Ni-WSe2) monolayer as a novel gas sensing material upon CO and HCHO in the dry-type transformers in order to evaluate their operation status. Results indicate that the Ni atom can be stably adsorbed on the TW site of the pristine WSe2 monolayer with the binding force of -4.33 eV. Via the gas adsorption analysis, it is found that the Ni-WSe2 monolayer performs chemisorption upon CO and HCHO molecules, with adsorption energies of -2.27 and -1.37 eV, respectively. The analyses of the band structure and Frontier molecular orbital manifest the potential of the Ni-WSe2 monolayer as a resistance-type gas sensor upon CO and HCHO, with sensing responses of 55.9 and 30.9% based on the band gap change and of 55.0 and 38.5% based on the energy gap change. The analysis of the density of state clearly shows the modified electronic property of the Ni-WSe2 monolayer in gas adsorptions. On the other hand, the analysis of the work function (WF) reveals the limited possibility to explore the Ni-WSe2 monolayer as a WF-based gas sensor for CO and HCHO detections. This work systemically studies the sensing potential of the Ni-WSe2 monolayer upon two typical gas species in the dry-type transformers, which is meaningful to explore novel nanomaterial-based gas sensors to monitor the operation condition of electrical equipment.

PD Flexible Built-In High-Sensitivity Elliptical Monopole Antenna Sensor.

In view of the insufficient signal detection sensitivity of Gas Insulated Switchgear (GIS), partial discharge (PD), ultra-high frequency (UHF), and failure to conform with GIS surface structure when the existing rigid stereo structure UHF sensor is built in, this paper, using rectangular patch antenna equivalent technique, trapezoidal ground plane technique, and coplanar waveguide (CPW) feed line index asymptotic linearization technique, conducts research on a flexible built-in high-sensitivity elliptic monopole antenna. The flexible antenna, with a thickness of only 0.28 mm, can be kept at a voltage standing wave ratio (VSWR) of less than three in the 300 MHz to 3 GHz band under the curvature radius of 0, 100, 300, and 500 mm, and at less than two in the 650 MHz to 3 GHz band. Through the true 220 kV-GIS partial discharge experimental platform built to analyze the high frequency electromagnetic wave detection performance of the built-in flexible antenna, it is shown that the flexible built-in high-sensitivity elliptical monopole antenna designed in this paper can effectively detect the characteristic signals of high-frequency electromagnetic waves emitted by partial discharges with an average discharge amount below 10 pC.

Flexible Planar Monopole Built-in GIS PD Sensor Based on Meandering Technology.

To address the problem of low space utilization of existing rigid Ultra-High Frequency (UHF) sensors for partial discharge (PD) in Gas-Insulated Switchgears (GIS) and the problem of disrupting the electric field distribution inside the GIS. This paper draws on the idea of flexible wearable antennas and introduces planar monopole antennas commonly used in the communication field as GIS PD detection sensors and carried out research on flexible planar monopole sensing technology built into GIS PD. The VSWR of monopole antenna in the UHF low band is optimized by the meandering technique. The size of the designed flexible antenna is 142 mm × 195 mm × 0.28 mm. The simulation and physical test results show that the improved monopole antenna with meandering technology has a VSWR of ≤2 in the frequency bands 570 MHz-830 MHz, 1.38 GHz-1.8 GHz, and 2.2 GHz-2.76 GHz when the bending radius is 0 mm, 200 mm, and 400 mm, respectively. The VSWR in the frequency band 450 MHz-3 GHz is ≤5. A 220 kV GIS PD detection platform was built to test the performance of the designed antenna, and the results showed that the antenna could detect the PD signal after bending deformation with a high Signal Noise Ratio (SNR).

Effect of Air Gap on Electrical Tree in Epoxy Resin Under High Frequency Bipolar Square-Wave Voltage.

Insulation fails quickly under high-frequency AC high voltage, especially bipolar square-wave voltage with a high dV/dt. It is of great significance to study the failure mechanism of epoxy casting insulation under such kind of voltage. In this paper, pin-plane epoxy casting insulation samples with air gaps were prepared, and the relation between the electrical trees under the high frequency bipolar square-wave voltage and the air gap conditions and voltage frequencies (1~20 kHz) were studied. Results indicated that, with the presence of air gaps, the electrical trees were bush-type and had a relatively slow growth rate, which was different from the fast-growing branch-type trees in the samples without air gap. The electrical tree characteristics related with the size of air gap and voltage frequency were also studied. The electrical tree grew faster under higher voltage frequency or with a smaller air gap. Results proved that discharge introduced a lot of defects for the surface layer of the epoxy resin samples and hence induced the possibility of multi-directional expansion of electrical trees. In addition, the resulting heat accumulation and unique charge transport synergistically affected the electrical tree characteristics under the high frequency bipolar square-wave voltage.

Recent Progress on Electromagnetic Field Measurement Based on Optical Sensors.

Electromagnetic field sensors are widely used in various areas. In recent years, great progress has been made in the optical sensing technique for electromagnetic field measurement, and varieties of corresponding sensors have been proposed. Types of magnetic field optical sensors were presented, including probes-based Faraday effect, magnetostrictive materials, and magnetic fluid. The sensing system-based Faraday effect is complex, and the sensors are mostly used in intensive magnetic field measurement. Magnetic field optical sensors based on magnetic fluid have high sensitivity compared to that based on magnetostrictive materials. Three types of electric field optical sensors are presented, including the sensor probes based on electric-optic crystal, piezoelectric materials, and electrostatic attraction. The majority of sensors are developed using the sensing scheme of combining the LiNbO3 crystal and optical fiber interferometer due to the good electro-optic properties of the crystal. The piezoelectric materials-based electric field sensors have simple structure and easy fabrication, but it is not suitable for weak electric field measurement. The sensing principle based on electrostatic attraction is less commonly-used sensing methods. This review aims at presenting the advances in optical sensing technology for electromagnetic field measurement, analyzing the principles of different types of sensors and discussing each advantage and disadvantage, as well as the future outlook on the performance improvement of sensors.

Bacillus hunanensis sp. nov., a slightly halophilic bacterium isolated from non-saline forest soil.

A novel Gram-stain-positive, slightly halophilic, catalase- and oxidase-positive, endospore-forming, motile, aerobic, rod-shaped bacterium, designated strain JSM 081003(T), was isolated from non-saline forest soil in Hunan Province, China. Growth occurred with 0.5-15% (w/v) NaCl (optimum 2-4%) at pH 6.5-10.5 (optimum pH 7.5-8.5) and at 5-40 °C (optimum 30 °C). meso-Diaminopimelic acid was present in the cell-wall peptidoglycan. The major cellular fatty acids were iso-C15:0, anteiso-C15:0 and iso-C14:0. Strain JSM 081003(T) contained MK-7 as the predominant respiratory quinone, and diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol as the major polar lipids. The genomic DNA G + C content of strain JSM 081003(T) was 40.9 mol%. A phylogenetic analysis based on 16S rRNA gene sequence comparisons revealed that strain JSM 081003(T) should be assigned to the genus Bacillus, and was related most closely to the type strains of Bacillus lehensis (sequence similarity 99.6%), Bacillus oshimensis (99.4%) and Bacillus patagoniensis (96.6%); lower than 96.0% sequence similarity was observed with other Bacillus species. The combination of phylogenetic analysis, DNA-DNA relatedness values, phenotypic characteristics and chemotaxonomic data supports the view that strain JSM 081003(T) represents a new species of the genus Bacillus, for which the name Bacillus hunanensis sp. nov. is proposed. The type strain is JSM 081003(T) (= DSM 23008(T) = KCTC 13711(T)).

Activated carbon supported TiO2-photocatalysis doped with Fe ions for continuous treatment of dye wastewater in a dynamic reactor.

Fe-doped TiO2 coated on activated carbon (Fe-TiO2/AC, FTA) composites were prepared by an improved sol-gel method and characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffractometry, inductively coupled plasma mass spectrometry and BET surface area analysis. Obtained FTA composites were applied to the continuous treatment of dye wastewater in a dynamic reactor. The effects of Fe ion content, catalyst content, UV-lamp power and flowrate of the continuous treatment of dye wastewater on degradation efficiency were analyzed to determine the optimum operating conditions of dye wastewater degradation. Continuous photocatalytic experiments provided interesting results that VIFTA had a high chemical oxygen demand (COD) removal rate compared with TiO2, Fe doped TiO2 (FT) and TiO2 coated on activated carbon (TA). In particular, when using the FTA catalyst with a Fe ion content of 0.33%, the kinetic content (k = 0.0376) of COD removal was more than the sum of both TA (0.0205) and 0.33% FT (0.0166). FTA showed a high photoactivity because of a synergistic effect between Fe ions and AC on TiO2, which is higher than the individual effects of AC or Fe ions on TiO2. Additionally, for the photocatalytic degradation of dye wastewater, the optimum Fe ion content, catalyst content, UV-lamp power and flowrate were 0.33%, 6 g/L, 60 W (two lamps) and 300 mL/hr, respectively. An investigation of catalyst reuse revealed that the 0.33% FTA showed almost no deactivation in photocatalytic degradation of naturally treated wastewater.