Search Results (7)

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

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

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

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

The optimized concentration of SF₆ gas is the key to maintaining a good insulation performance by GIS equipment. The precise measurements of the SF₆ concentration and decomposition byproducts could be used to indicate the remaining GIS insulation level during long-term operations. In this paper, a finite-element simulation model was created to investigate the SF₆ gas decomposition and diffusion dynamics. A theoretical analysis and simulation of the overheating fault, i.e., the contact between the GIS disconnect switches, were carried out, followed by an estimation of the SF₆ decomposition and diffusion characteristics caused by the local heating faults, based on the calculated flow velocity field and temperature field. Full article

The research on decomposition characteristics of SF₆ and its by-products have great significance to the operation, maintenance, condition assessment and fault diagnosis of power equipment. In this paper, the particle composition models of SF₆, SF₆/polytetrafluoroethylene (PTFE), SF₆/PTFE/O₂, SF₆/PTFE/H₂O, and SF₆/PTFE/O₂/H₂O were established by using Gibbs free energy minimization method, and the effects of trace H₂O and O₂ impurities and PTFE vapour on SF₆ by-products were studied by the models. In order to verify the correctness of the simulation results, a series of breaking experiments were carried out on a 40.5 kV SF₆ circuit breaker, and a gas chromatograph was used to detect and analyse the SF₆ by-products. It was found that when PTFE vapour is involved in the arc plasma, the main by-product after arc quenching is CF₄, and the molar fractions of C₂F₆ and C₃F₈ are very low. When O₂ is involved, the main by-products are SOF₂, SO₂ and SO₂F₂, and a small amount of CO and CO₂ was also produced. When H₂O is involved, the main by-products in simulation are SOF₂, SO₂ and HF, and a small amount of SO₂, CO₂, CO, SO₂F₂ and H₂ was also produced. The experimental results are in good agreement with the above results. Full article

The detection of partial discharge and analysis of the composition and content of sulfur hexafluoride SF₆ gas components are important to evaluate the operating state and insulation level of gas-insulated switchgear (GIS) equipment. This paper reported a novel sensing material made of pure ZnO and NiO-decorated ZnO nanoflowers which were synthesized by a facile and environment friendly hydrothermal process for the detection of SF₆ decomposition byproducts. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were used to characterize the structural and morphological properties of the prepared gas-sensitive materials. Planar-type chemical gas sensors were fabricated and their gas sensing performances toward the SF₆ decomposition byproducts SO₂, SO₂F₂, and SOF₂ were systemically investigated. Interestingly, the sensing behaviors of the fabricated ZnO nanoflowers-based sensor to SO₂, SO₂F₂, and SOF₂ gases can be obviously enhanced in terms of lower optimal operating temperature, higher gas response and shorter response-recovery time by introducing NiO. Finally, a possible gas sensing mechanism for the formation of the p–n junctions between NiO and ZnO is proposed to explain the enhanced gas response. All results demonstrate a promising approach to fabricate high-performance gas sensors to detect SF₆ decomposition byproducts. Full article