Search Results (58)

Mine ventilation systems are critical for ensuring operational safety, yet air leakage remains a pervasive challenge, leading to energy inefficiency and heightened safety risks. Traditional tracer gas methods, while effective in simple networks, exhibit significant errors in complex multi-entry systems due to static empirical parameters and environmental interference. This study proposes an integrated methodology that combines multi-path airflow analysis with dynamic longitudinal dispersion coefficient correction to enhance the accuracy of air leakage detection. Utilizing sulfur hexafluoride (SF6) as the tracer gas, a phased release protocol with temporal isolation was implemented across five strategic points in a coal mine ventilation network. High-precision detectors (Bruel & Kiaer 1302) and the MIVENA system enabled synchronized data acquisition and 3D network modeling. Theoretical models were dynamically calibrated using field-measured airflow velocities and dispersion coefficients. The results revealed three deviation patterns between simulated and measured tracer peaks: Class A deviation showed 98.5% alignment in single-path scenarios, Class B deviation highlighted localized velocity anomalies from Venturi effects, and Class C deviation identified recirculation vortices due to abrupt cross-sectional changes. Simulation accuracy improved from 70% to over 95% after introducing wind speed and dispersion adjustment coefficients, resolving concealed leakage pathways between critical nodes and key nodes. The study demonstrates that the dynamic correction of dispersion coefficients and multi-path decomposition effectively mitigates errors caused by turbulence and geometric irregularities. This approach provides a robust framework for optimizing ventilation systems, reducing invalid airflow losses, and advancing intelligent ventilation management through real-time monitoring integration. Full article

To address the impact of insulation medium degradation in the arc quenching chambers of ultra-high-voltage SF₆ circuit breakers on phase-controlled switching accuracy caused by multiple operations throughout the service life, this paper proposes an adaptive switching algorithm. First, a modified formula for the breakdown voltage of mixed gases is derived based on the synergistic effect. Considering the influence of contact gap on electric field distortion, an adaptive switching strategy is designed to quantify the dynamic relationship among operation times, insulation strength degradation, and electric field distortion. Then, multi-round switching-on and switching-off tests are carried out under the condition of fixed single-arc ablation amount, and the laws of voltage–current, gas decomposition products, and pre-breakdown time are obtained. The test data are processed by the least squares method, adaptive switching algorithm, and machine learning method. The results show that the coincidence degree of the pre-breakdown time obtained by the adaptive switching algorithm and the test value reaches 90%. Compared with the least squares fitting, this algorithm achieves a reasonable balance between goodness of fit and complexity, with prediction deviations tending to be randomly distributed, no obvious systematic offset, and low dispersion degree. It can also explain the physical mechanism of the decay of insulation degradation rate with the number of operations. Compared with the machine learning method, this algorithm has stronger generalization ability, effectively overcoming the defects of difficult interpretation of physical causes and the poor engineering adaptability of the black box model. Full article

Monitoring SF₆ decomposition gases has emerged as a vital diagnostic technique for evaluating insulation conditions and identifying faults in SF₆-based electrical equipment. This study comprehensively explores the adsorption properties and sensing capabilities of a Pd-doped InSe (Pd-InSe) monolayer for SF₆ decomposition gases, including SO₂, SOF₂, and SO₂F₂, through density functional theory calculations. The Pd-InSe monolayer is constructed by substituting one Se atom with a Pd atom in the pristine InSe structure. Then, the Pd doping effect on the InSe monolayer and the adsorption behaviors of the Pd-InSe monolayer for three gases are thoroughly examined. The adsorption configurations, charge density differences, and electron localization functions are scrutinized to elucidate the gas adsorption mechanisms of the Pd-InSe monolayer; and the band structures, along with the density of states, are analyzed to gain insights into the resistive gas sensing mechanisms for detecting these three gases. Finally, the temperature-dependent recovery characteristics are evaluated to assess the reusability of the monolayer. These findings not only underscore the potential of the Pd-InSe monolayer for sensing SF₆ decomposition gases but also open new avenues for the development of next-generation 2D materials in gas sensing applications within the field of electrical engineering. Full article

With growing environmental concerns, the search for alternative gases to replace SF₆ has become a key focus in the power industry. Perfluoromethyl vinyl ether (PMVE), with its low global warming potential (GWP) and excellent insulation properties, is a promising candidate. When mixed with N₂, PMVE not only decreases the liquefaction temperature but also enhances insulation performance, making the gas mixture more suitable for engineering applications. In this study, reactive molecular dynamics (ReaxFF-MD) and density functional theory (DFT) calculations were combined to investigate the influence of temperature on the decomposition characteristics of a PMVE/N₂ mixture. The reaction pathways and reaction enthalpy of PMVE and its major decomposition products were analyzed in detail. The results showed that, as temperature increases, the decomposition intensity of PMVE is enhanced, leading to a higher reaction rate and accelerated formation of decomposition products. Moreover, the main decomposition products of the PMVE/N₂ mixture include C, C₂F₂, CF₂, CN, CO, CF₂O, F, O, and other small molecules and free radicals. The dynamic balance between the generated free radicals helps maintain the system’s insulation capacity. However, toxic decomposition byproducts such as CF₂O, C₂N₂, and CO were also detected. This study provides valuable insights into the engineering applications of PMVE/N₂ mixtures. Full article

A highly sensitive sulfur dioxide (SO₂) photoacoustic gas sensor was developed for the sulfur hexafluoride (SF₆) decomposition detection in electric power systems by using a novel 266 nm low-cost high-power solid-state pulse laser and a high Q-factor differential photoacoustic cell. The ultraviolet (UV) pulse laser is based on a passive Q-switching technology with a high output power of 28 mW. The photoacoustic signal was normalized to the laser power to solve the fluctuation of the photoacoustic signal due to the power instability of the UV laser. A differential photoacoustic cell can obtain a high Q-factor and reduce the gas flow noise in SF₆ buffer gas. The parameters of the SO₂ sensor system were optimized in terms of laser power and operating pressure. A 1σ detection limit (SNR = 1) of 2.34 ppb was achieved with a 1 s integration time, corresponding to a normalized noise equivalent absorption (NNEA) coefficient of 7.62 × 10⁻¹⁰ cm⁻¹WHz^−1/2. Full article

SF₆ is a strong greenhouse effect gas, which is widely used in high-voltage electrical equipment such as circuit breakers and high-voltage switchgear because of its excellent insulation performance and arc extinguishing ability. In recent years, the use and emission of SF₆ have been rising, and with the proposal of the dual carbon strategic goal, its harmless degradation has become an urgent problem to be solved. In this paper, SF₆ was degraded by pulsed DBD plasma technology and O₂. Studies have shown that the addition of O₂ can effectively promote the degradation of SF₆. With the increase in the added O₂ content, the DRE and EY of SF₆ first increased and then decreased. Under the conditions of the input power of 50 W, SF₆ concentration of 2%, and gas flow rate of 50 mL/min, the reaction system obtained the highest DRE and EY of 58.40% and 5.24 g/kWh when the O₂ content was 1%, respectively. In the SF₆/Ar/O₂/H₂O system, the addition of H₂O could improve the product selectivity of SO₂F₂, and when the O₂ concentration was 1%, the highest selectivity of SO₂F₂ was 48.96%, and the concentration was 8006.76 ppm. The addition of O₂ inhibited the production of SO₂, and with the addition of the O₂ system, SO₂F₂ and SOF₄ were the main components of degradation products; however, there were also SOF₂, SO₂, SiF_4, SF₄, etc. In this paper, the decomposition path of O₂ under SF₆ was analyzed in detail according to infrared spectroscopy and decomposition products. Full article

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. Full article

In this study, the synergetic action of nanopulsed plasma bubbles (PBs) and photocatalysts for the degradation/mineralization of trimethoprim (TMP) in water was investigated. The effects of ZnO or TiO₂ loading, plasma gas, and initial TMP concentration were evaluated. The physicochemical characterization of plasma-treated water, the quantification of plasma species, and the use of appropriate plasma species scavengers shed light on the plasma-catalytic mechanism. ZnO proved to be a superior catalyst compared to TiO₂ when combined with plasma bubbles, mainly due to the increased production of ⋅OH and oxygen species resulting from the decomposition of O₃. The air–PBs + ZnO system resulted in higher TMP degradation (i.e., 95% after 5 min of treatment) compared to the air–PBs + TiO₂ system (i.e., 87%) and the PBs-alone process (83%). The plasma gas strongly influenced the process, with O₂ resulting in the best performance and Ar being insufficient to drive the process. The synergy between air–PBs and ZnO was more profound (SF = 1.7), while ZnO also promoted the already high O₂–plasma bubbles’ performance, resulting in a high TOC removal rate (i.e., 71%). The electrical energy per order in the PBs + ZnO system was very low, ranging from 0.23 to 0.46 kWh/m³, depending on the plasma gas and initial TMP concentration. The study provides valuable insights into the rapid and cost-effective degradation of emerging contaminants like TMP and the plasma-catalytic mechanism of antibiotics. Full article

Sulfur hexafluoride (SF₆) is a typical fluorine gas with excellent insulation and arc extinguishing properties that has been widely used in large-scale power equipment. The detection of SF₆ gas in high-power electrical equipment is a necessary measure to ensure the reliability and safety of power grid operation. A failure of SF₆ insulated electrical equipment, such as discharging or overheating conditions, can cause SF₆ gas decomposition, resulting in various decomposition products. The decomposed gases inside the equipment decrease the insulating properties and are toxic. The leakage of SF₆ can also decrease the insulating properties. Therefore, it is crucial to monitor the leakage of SF₆ decomposed gases from electrical equipment. Quantitative testing of decomposition products allows us to assess the insulation state of the equipment, identify internal faults, and maintain the equipment. This review comprehensively introduces the decomposition formation mechanism of SF₆ gas and the current detection technology of decomposition products from the aspects of principle and structure, materials, test effect, and practicability. Finally, the development trends of SF₆ and decomposition gas detection technology for the reliability and safety of power grid operation are prospected. Full article

Internal discharge and overheating faults in sulfur hexafluoride (SF₆) gas-insulated electrical equipment will generate a series of characteristic gas products. Hydrogen fluoride (HF) is one of the main decomposition gases under discharge failure. Because of its extremely corrosive nature, it can react with other materials in gas-insulated switchgear (GIS), resulting in a short existence time, so it needs to be detected online. Resonant gas photoacoustic spectroscopy has the advantage of high sensitivity, fast response, and no sample gas consumption, and can be used for the online detection of flowing gas. In this paper, a simulated GIS corona discharge experimental platform was built, and the HF generated in the discharge was detected online by gas photoacoustic spectroscopy. The absorption peak of HF molecule near 1312.59 nm was selected as the absorption spectral line, and a resonant photoacoustic cell was designed. To improve the detection sensitivity of HF, wavelength modulation and second-harmonic detection technology were used. The online monitoring of HF in the simulated GIS corona discharge fault was successfully realized. The experimental results show that the sensitivity of the designed photoacoustic spectroscopy detection system for HF is 0.445 μV/(μL/L), and the limit of detection (LOD) is 0.611 μL/L. Full article

Perfluorinated compounds (PFCs) are used for manufacturing purposes in the semiconductor and display industries, resulting in an increased need for emission reduction due to the significant global warming potential of the associated greenhouse gases. The decomposition characteristics of etch-type and water film (WF)-type plasma-wet scrubbers were investigated. The PFCs used in the study were CF₄, SF₆, NF₃, CHF₃, C₂F₆, C₃F₈, and C₄F₈, and the destruction removal efficiency (DRE) and by-product gas generation rate were confirmed based on the changes in the parameters (total flow rate and power) of the plasma-wet scrubber. When the total flow rate reached 100 L/min and the measured maximum power (11 kW), the reduction efficiency of CF₄ in the etch type was 95.60% and the DRE of other PFCs was 99.99%. Moreover, for the WF type, the DRE of CF₄ was 90.06%, that of SF₆ was 96.44%, and that of other PFCs was 99.99%. When the total flow rate reached 300 L/min and 11 kW, the DRE of SF₆ in the etch type was 99%, and the DRE of NF₃, CHF₃, C₂F₆, C₃F₈, and C₄F₈ was 95.57%, 87.06%, 70.74%, 81.45%, and 95.59%, respectively. In addition, in the WF type, the DRE of SF₆ was 94.39%, and the DRE of NF₃, CHF₃, C₂F₆, C₃F₈, and C₄F₈ was 99.80%, 95.34%, 85.38%, 88.49%, and 98.22%, respectively. The decomposition efficiency was high for the etch type for gases with small flow rates or no by-product gas generation. The by-product gas generation rate was significantly lower for the WF type. Full article

The accurate and effective detection of SF₆ decomposition components inside a gas-insulated switchgear (GIS) is crucial for equipment fault diagnosis and condition assessment. The current method for detecting SF₆ decomposition components involves gas extraction at the GIS inlet, which only provides limited information on the decomposition component content. Therefore, there is a need to explore more effective ways to obtain internal gas component information within GIS. In this study, we propose a graphene-coated microfiber gas detection method for SO₂. We establish a physical simulation model of the microfiber and analyze the sensing mechanism of the microfiber diameter and cladding refractive index changes in its evanescent field. A graphene-coated microfiber gas sensor was prepared using a drop-coating method, and a fiber loop ring-down (FLRD) gas detection system was constructed for the experimental studies on SO₂ gas detection. The results demonstrated that the graphene-coated microfiber exhibits an excellent gas-sensitive response to SO₂ and achieves trace-level detection at room temperature. The concentration range of 0 to 200 ppm showed good linearity, with a maximum detection error of 4.76% and a sensitivity of 1.24 ns/ppm for SO₂. This study introduces an all-fiber method for detecting SF₆ decomposition components, offering a new approach for online monitoring of SF₆ decomposition components in GIS equipment using built-in fiber-optic sensors. Full article

Identifying the main byproducts of SF₆ decomposition proves to be an effective strategy for determining the nature and severity of internal discharge faults in gas-insulated switchgears (GISs). In this research, it was suggested to utilize the coordination polymer Zr-MOF-808 as a sensor for the main byproducts of SF₆ decomposition. This study examined the adsorption of SF₆ and its main decomposition products (CF₄, CS₂, SO₂, SO₂F₂, and SOF₂) on Zr-MOF-808, utilizing Gaussian16 simulation software through a method anchored on quantum chemistry. Adsorption parameters were calculated and analyzed, including binding energy, charge transfer, adsorption distance, along with variations in bond length, bond angle, density of states, and frontier orbital of gas molecules. Our research indicated that the Zr-MOF-808 cluster demonstrated varying degrees of chemical adsorption for the six gases, leading to differential conductivity changes in each system following adsorption. Consequently, the detection of resistance value alterations in the materials would allow for the identification of the gas products. Full article

SF₆ gas is an arc extinguishing medium that is widely used in gas insulated switchgear (GIS). When insulation failure occurs in GIS, it leads to the decomposition of SF₆ in partial discharge (PD) and other environments. The detection of the main decomposition components of SF₆ is an effective method to diagnose the type and degree of discharge fault. In this paper, Mg-MOF-74 is proposed as a gas sensing nanomaterial for detecting the main decomposition components of SF₆. The adsorption of SF₆, CF₄, CS₂, H₂S, SO₂, SO₂F₂ and SOF₂ on Mg-MOF-74 was calculated by Gaussian16 simulation software based on density functional theory. The analysis includes parameters of the adsorption process such as binding energy, charge transfer, and adsorption distance, as well as the change in bond length, bond angle, density of states, and frontier orbital of the gas molecules. The results show that Mg-MOF-74 has different degrees of adsorption for seven gases, and chemical adsorption will lead to changes in the conductivity of the system; therefore, it can be used as a gas sensing material for the preparation of SF6 decomposition component gas sensors. Full article

Hydrogen sulfide (H₂S) and sulfur dioxide (SO₂) are two typical decomposition byproducts of sulfur hexafluoride (SF₆), commonly used as an insulating medium in electrical equipment; for instance, in gas circuit breakers and gas insulated switchgears. In our work, fiber-like p-CuO/n-ZnO heterojunction gas sensing materials were successfully prepared via the electrospinning method to detect the SF₆ decomposition byproducts, H₂S and SO₂ gases. The sensing results demonstrated that p-CuO/n-ZnO nanofiber sensors have good sensing performance with respect to H₂S and SO₂. It is noteworthy that this fiber-like p-CuO/n-ZnO heterojunction sensor exhibits higher and faster response–recovery time to H₂S and SO₂. The enhanced sensor performances can probably be attributed to the sulfuration–desulfuration reaction between H₂S and the sensing materials. Moreover, the gas sensor exhibited a high response to the low exposure of H₂S and SO₂ gas (below 5 ppm). Towards the end of the paper, the gas sensing mechanism of the prepared p-CuO/n-ZnO heterojunction sensors to SO₂ and H₂S is discussed carefully. Calculations based on first principles were carried out for Cu/ZnO to construct adsorption models for the adsorption of SO₂ and H₂S gas molecules. Information on adsorption energy, density of states, energy gap values and charge density were calculated and compared to explain the gas-sensitive mechanism of ZnO on SO₂ and H₂S gases. Full article