Decomposition Mechanism of C5F10O: An Environmentally Friendly Insulation Medium

Mechanistic study of C5F10O-induced lung toxicity in rats: An eco-friendly insulating gas alternative to SF6

The global warming and other environmental problems caused by SF6 emissions can be reduced due to the widespread use of eco-friendly insulating gas, perfluoropentanone (C5F10O). However, there is an exposure risk to populations in areas near C5F10O equipment, so it is important to clarify its biosafety and pathogenesis before large-scale application. In this paper, histopathology, transcriptomics, 4D-DIA proteomics, and LC-MS metabolomics of rats exposed to 2000 ppm and 6000 ppm C5F10O are analyzed to reveal the mechanisms of toxicity and health risks. Histopathological shows that inflammatory cell infiltration, epithelial cell hyperplasia, and alveolar atrophy accompanied by alveolar wall thickening are present in both low-dose and high-dose groups. Analysis of transcriptomic and 4D-DIA proteomic show that Cell cycle and DNA replication can be activated by both 2000 ppm and 6000 ppm C5F10O to induce cell proliferation. In addition, it also leads to the activation of pathways such as Antigen processing and presentation, Cell adhesion molecules and Complement and coagulation cascades, T cell receptor signal path, Th1 and T cell receptor signal path, Th1 and Th2 cell differentiation, complement and coagulation cascades. Finally, LC-MS metabolomics analysis confirms that the metabolic pathways associated with glycerophospholipids, arachidonic acid, and linoleic acid are disrupted and become more severe with increasing doses. The mechanism of lung toxicity caused by C5F10O is systematically expounded based on the multi-omics analysis and provided biosafety references for further promotion and application of C5F10O.

Recent progresses, challenges and proposals on SF6 emission reduction approaches

The increasing utilization and emission of sulfur hexafluoride (SF6) pose severe threats to the climate and the environment, owing to its potent greenhouse gas properties. In this paper, we comprehensively review the recent progresses of SF6 emission reduction approaches. Currently, the use and emission of SF6 are still on the rise, and mainly concentrated in the power industry. Restrictive use and emission reduction policies are fundamental step in guiding SF6 emission, but they are poor promoted in developing economies. More specific policies and regulations are needed in conjunction with timely and accurate assessments of SF6 atmospheric properties and emissions. SF6 recovery is the direct emission reduction approach, but defects in recovery methods and equipment limit its applications. The development of SF6 purification technologies and optimizations in recovery devices and processes are needed for its treatment of different regions and SF6 volumes. SF6 degradation is the final step of waste gas treatment, and its development needs to better balance the degradation rate and product selectivity, as well as to improve their multi-scenario responsiveness. SF6 substitution is a necessity for future large-scale SF6 emission reduction. Improvements in SF6-free applications and its long-term stability are critical via new gas design, gas mixture optimization and equipment updates. Finally, all the emission reduction approaches are closely related, and promoting their synergistic development and complementarity is the ultimate way to realize SF6 lifecycle management.

High-Throughput Screening of Gas Sensor Materials for Decomposition Products of Eco-Friendly Insulation Medium by Machine Learning

Nowadays, trifluoromethyl sulfonyl fluoride (CF3SO2F) has shown great potential to replace SF6 as an eco-friendly insulation medium in the power industry. In this work, an effective and low-cost design strategy toward ideal gas sensors for the decomposed gas products of CF3SO2F was proposed. The strategy achieved high-throughput screening from a large candidate space based on first-principle calculation and machine learning (ML). The candidate space is made up of different transition metal-embedded graphic carbon nitrides (TM/g-C3N4) owing to their high surface area and subtle electronic structure. Four main noteworthy decomposition gases of CF3SO2F, namely, CF4, SO2, SO2F2, and HF, as well as their initial stable structure on TM/g-C3N4 were determined. The best-performing ML model was established and implemented to predict the interaction strength between gas products and TM/g-C3N4, thus determining the promising gas-sensing materials for target gases with the requirements of interaction strength, recovery time, sensitivity, and selectivity. Further analysis guarantees their stability and reveals the origin of excellent properties as a gas sensor. The high-throughput strategy opens a new avenue of rational and low-cost design principles of desirable gas-sensing materials in an interdisciplinary view.

Deep-learning-assisted theoretical insights into the compatibility of environment friendly insulation medium with metal surface of power equipment

Exploring a new generation of eco-friendly gas insulation medium to replace greenhouse gas sulphur hexafluoride (SF₆) in power industry is significant for reducing the greenhouse effect and building a low-carbon environment. The gas-solid compatibility of insulation gas with various electrical equipment is also of significance before practical applications. Herein, take a promising SF₆ replacing gas trifluoromethyl sulfonyl fluoride (CF₃SO₂F) for example, one strategy to theoretically evaluate the gas-solid compatibility between insulation gas and the typical solid surfaces of common equipment was raised. Firstly, the active site where the CF₃SO₂F molecule is prone to interact with other compounds was identified. Secondly, the interaction strength and charge transfer between CF₃SO₂F and four typical solid surfaces of equipment were studied by first-principles calculations and further analysis was conducted, with SF₆ as the control group. Then, the dynamic compatibility of CF₃SO₂F with solid surfaces was investigated by large-scale molecular dynamics simulations with the aid of deep learning. The results indicate that CF₃SO₂F has excellent compatibility similar to SF₆, especially in the equipment whose contact surface is Cu, CuO, and Al₂O₃ due to their similar outermost orbital electronic structures. Besides, the dynamic compatibility with pure Al surfaces is poor. Finally, preliminary experimental verifications indicate the validity of the strategy.

Degradation and dechlorination of trichloroacetic acid induced by an in situ 222 nm KrCl* excimer radiation

Since the coronavirus disease 2019 (COVID-19) pandemic epidemic, the excessive usage of chlorinated disinfectants raised the substantial risks of disinfection by-products (DBPs) exposure. While several technologies may remove the typical carcinogenic DBPs, trichloroacetic acid (TCAA), their application for continuous treatment is limited due to their complexity and expensive or hazardous inputs. In this study, degradation and dechlorination of TCAA induced by an in situ 222 nm KrCl* excimer radiation as well as role of oxygen in the reaction pathway were investigated. Quantum chemical calculation methods were used to help predict the reaction mechanism. Experimental results showed that UV irradiance increased with increasing input power and decreased when the input power exceeded 60 W. Decomposition and dechlorination were simultaneously achieved, where around 78% of TCAA (0.62 mM) can be eliminated and 78% dechlorination within 200 min. Dissolved oxygen showed little effect on the TCAA degradation but greatly boosted the dechlorination as it can additionally generate hydroxyl radical (•OH) in the reaction process. Computational results showed that under 222 nm irradiation, TCAA was excited from S₀ to S₁ state and then decayed by internal crossing process to T₁ state, and a reaction without potential energy barrier followed, resulting in the breaking of C-Cl bond and finally returning to S₀ state. Subsequent C-Cl bond cleavage occurred by a barrierless •OH insertion and HCl elimination (27.9 kcal/mol). Finally, the •OH attacked (14.6 kcal/mol) the intermediate byproducts, leading to complete dechlorination and decomposition. The KrCl* excimer radiation has obvious advantages in terms of energy efficiency compared to other competitive methods. These results provide insight into the mechanisms of TCAA dechlorination and decomposition under KrCl* excimer radiation, as well as important information for guiding research toward direct and indirect photolysis of halogenated DBPs.

Ab initio molecular dynamics calculations on electron ionization induced fragmentations of C4F7N and C5F10O for understanding their decompositions under discharge conditions

C₄F₇N and C₅F₁₀O are the most promising SF₆ alternatives as eco-friendly insulating gaseous mediums in electrical engineering. It is necessary to clarify their electrical stability and decomposition mechanisms. In this work, we first introduced our experimental results for decomposition products of C₄F₇N/CO₂ and C₅F₁₀O/synthetic air mixtures under partial discharge and spark discharge conditions. Then, we performed ab initio molecular dynamics (AIMD) simulations on the typical decomposition products. The simulations were performed under standard electron impact mass spectrometry (EI-MS); thus, the statistical results of the mass spectra were compared with those of the experimentally obtained standard mass spectra from the NIST database. The AIMD simulation method in simulating the electron-induced ionization process was verified and found to be reliable. Finally, the calculations were also performed for C₄F₇N and C₅F₁₀O with incident electron energies of 20 eV and 70 eV, respectively. The dominant pathway for both gases is the formation of CF₃⁺ with the fracture of the C-C bond. The AIMD simulation is able to predict the decomposition channels after electron-impact ionization without any preconceived knowledge of fragmentation pathways, which provides a novel insight into understanding the decomposition mechanisms of C₄F₇N and C₅F₁₀O under different discharge conditions with different energies.

Exploring the Decomposition Products of 1,3,3,3-Tetrafluoropropene and Perfluoro-(3-methylbutan-2-one) Gas Mixtures in Medium-Voltage Electrical Switchgear as Alternatives to SF6

In this work, binary and ternary gas mixtures of 1,3,3,3-tetrafluoropropene, HFO-1234ze(E), and perfluoro-(3-methylbutan-2-one), CF₃C(O)CF(CF₃)₂, with CO₂ and synthetic air, are presented as alternatives to SF6 in medium-voltage electrical equipment. They were used in four medium-voltage switchgear cubicles replacing SF6 gas, and after a period of time, under permanent 30 kV AC voltage, gas mixture samples were extracted and analyzed on the same day using a validated methodology based on gas chromatography (GC) coupled to mass spectrometry (MS) and thermal conductivity (TCD). CF₄ (tetrafluoromethane), C₂F₆ (hexafluoroethane), C₃F₆ (hexafluoropropylene), C₃HF7 (1,1,1,2,2,3,3-heptafluoropropane), CH₂F₂ (difluoromethane), and the cis and trans-C₃H₂F₄ (1,3,3,3-tetrafluoropropene) have been identified as decomposition products in these gas mixtures. In addition, a quantity of water has been observed, as well as CO in one of the cubicles. The most abundant decomposition products identified in gas mixture samples (C₃HF₇ and C₃F₆) together with water and CO content have been quantified using commercial gas mixture reference standards. The toxicity and global warming of the analyzed compounds are evaluated to determine the most adequate gas mixture among those studied as a candidate to substitute SF6.

A Comparison of Partial Discharge Sensors for Natural Gas Insulated High Voltage Equipment

The research in this paper consists of practical experimentation on a gas insulated section of high voltage equipment filled with carbon dioxide and technical air as a direct replacement to sulphur hexafluoride (SF₆) and analyses the results of PD measurement by way of internal UHF sensors and external HFCTs. The results contribute to ongoing efforts to replace the global warming gas SF₆ with an alternative such as pure carbon dioxide or technical air and are applicable to mixtures of electronegative gases that have a high content of buffer gas including carbon dioxide. The experiments undertaken involved filling a full-scale gas insulated line demonstrator with different pressures of CO₂ or technical air and applying voltages up to 242 kV in both clean conditions and particle contaminated conditions. The results show that carbon dioxide and technical air can insulate a gas section normally insulated with SF₆ at phase-to-earth voltage of 242 kV and that both HFCT and UHF sensors can be used to detect partial discharge with natural gases. The internal UHF sensors show the most accurate PD location results but external HFCTs offer a good compromise and very similar location accuracy.

Partial Discharge Measurements in a High Voltage Gas Insulated Transmission Line Insulated with CO2

This paper uses practical experimentation to analyse the effect of replacing SF6 with pure CO2 in conventional gas insulated transmission line sections by studying partial discharge measurements taken with applied voltages up to 242 kV (rms). The results can also help in understanding the properties of new alternative gas mixtures which can be utilised with a ratio of up to and over 95% CO2. The experiments undertaken involved filling a gas insulated line demonstrator with 3 bars of CO2 and applying voltages up to 242 kV in both clean conditions and particle-contaminated enclosure conditions. The results demonstrate that CO2 can be used to insulate gas equipment without breakdown at high voltage, however, a higher gas-filling pressure may be needed to reduce the partial discharge found in the tests presented in this paper. Another aspect of the work showed that partial discharge (PD) measurements from internal ultra-high frequency (UHF) sensors compared with a direct measurement from a capacitive divider both clearly showed the effect of contaminating particles in CO2. However, the PD divider measurements also showed considerable external PD on the outside of the gas compartment, leading to the conclusion that UHF sensors are still regarded as having the highest sensitivity and noise immunity for gas insulated switchgear (GIS) or gas insulated transmission line (GIL) systems including when the equipment is insulated with CO2.

Analysis of Gaseous By-Products of CF3I and CF3I-CO2 after High Voltage Arcing Using a GCMS

Increasing demand for an alternative insulation medium to sulphur hexafluoride (SF₆) has led to the investigation of new environmentally friendly insulation gases which could be used in high voltage equipment on the electrical power network. One such alternative, which is currently being explored by researchers, is Trifluoroiodomethane (CF₃I) which could potentially be used in a gas mixture with carbon dioxide (CO₂) as an insulation medium. In this paper an analysis of gaseous by-products detected as a result of high voltage breakdown through pure CF₃I and a CF₃I-CO₂ gas mixture across a sphere-sphere electrode arrangement is given. Gas chromatography and mass spectrometry (GCMS) is used to identify the gaseous by-products produced as a result of high voltage arcing which causes the gas between the electrodes to dissociate. Analysing these gas by-products helps to identify the long-term behaviour of the gas mixture in high voltage equipment.

Alternative Environmentally Friendly Insulating Gases for SF6

Sulfur hexafluoride (SF6) shows excellent insulation performance as an insulating gas. It is suitable for various climate conditions due to its low boiling point (−64 °C). Therefore, it has been widely used in power grid equipment. However, its global warming potential (GWP) is 23,500 times higher than that of CO2. Thus, it is imperative to find an environmentally friendly insulating gas with excellent insulation performance, lower GWP, and which is harmless to equipment and workers to replace SF6. In this review, four possible alternatives, including perfluorocarbons, trifluoroiodomethane, perfluorinated ketones, and fluoronitrile are reviewed in terms of basic physicochemical properties, insulation properties, decomposition properties, and compatibility with metals. The influences of trace H2O or O2 on their insulation performances are also discussed. The insulation strengths of these insulating gases were comparable to or higher than that of SF6. The GWPs of these insulating gases were lower than that of SF6. Due to their relatively high boiling point, they should be used as a mixture with buffering gases with low boiling points. Based on these four characteristics, perfluorinated ketones (C5F10O and C6F12O) and fluoronitrile (C4F7N) could partially substitute SF6 in some electrical equipment. Finally, some future needs and perspectives of environmentally friendly insulating gases are addressed for further studies.

Effect of oxygen on power frequency breakdown voltage and decomposition characteristics of the C5F10O/N2/O2 gas mixture

Sulfur hexafluoride (SF₆) is widely used in the power industry because of its excellent insulation and arc extinguishing performance; however, as the global environment is deteriorating, the need to replace SF₆ is becoming significantly critical. In recent years, C₅F₁₀O has received extensive attention as a potential alternative to SF₆. In this study, a part of N₂ in C₅F₁₀O/N₂ was replaced by O₂, and the breakdown voltages of C₅F₁₀O/N₂/O₂ at different oxygen concentrations under a slightly uneven electric field were tested. The dispersion of breakdown voltage and the discharge decomposition components of C₅F₁₀O/N₂/O₂ with different oxygen concentrations were analysed. It was found that as the oxygen concentration increased, the breakdown voltage of C₅F₁₀O/N₂/O₂ with 15 kPa C₅F₁₀O at 0.2 MPa increased, and the dispersion of the breakdown voltage became worse. When 0.5% O₂ or more O₂ was added to the C₅F₁₀O/N₂ gas mixture, the carbon precipitates on the electrode surface disappeared. As the oxygen concentration continued to increase, another characteristic component, CF₂O, could be detected, whereas C₂F₄ and C₃F₆ disappeared. It is believed that O₂ can inhibit the formation of C₂F₆, C₃F₈, C₄F₁₀, and C₃F₇H. Therefore, it is recommended to use oxygen as the second buffer gas for the engineering applications of C₅F₁₀O. Moreover, the ratio of C₅F₁₀O to O₂ is recommended to be 1 : 1.

C₅F₁₀O gas mixture is a SF₆ potential substitute with high insulation strength and is a new type of environmentally friendly insulating gas. By adding oxygen to C₅F₁₀O gas mixture, insulation strength can be improved and carbon deposition can be suppressed.

Insights on decomposition process of c-C4F8 and c-C4F8/N2 mixture as substitutes for SF6

In recent years, many scholars have carried out studies on c-C4F8 and its gas mixture and found it has potential to be used as an environment-friendly insulating medium to replace SF6 in medium-voltage equipment. In this paper, the c-C4F8 and c-C4F8/N2 gas mixture models were built to study its decomposition process by the combination of reactive molecular dynamics method and density functional theory. The yield of the main decomposition products, the reaction pathways and enthalpy under different temperatures were explored. It was found that the decomposition of c-C4F8/N2 mainly produces CF2, F, CF3, CF, C, CF4 and C2F4. c-C4F8 can decompose to C2F4 by absorbing 43.28 kcal/mol, which is the main decomposition path and this process easily occurs under high temperature. There is a dynamic equilibrium process among the various produced radicals, which ensures the insulation performance of system to a certain extent. The decomposition performance of c-C4F8/N2 mixture is better than that of pure c-C4F8 at the same temperature. Relevant results provide guidance for engineering application of the c-C4F8/N2 gas mixture.

Assessment of Eco-friendly Gases for Electrical Insulation to Replace the Most Potent Industrial Greenhouse Gas SF6

Gases for electrical insulation are essential for the operation of electric power equipment. This Review gives a brief history of gaseous insulation that involved the emergence of the most potent industrial greenhouse gas known today, namely sulfur hexafluoride. SF₆ paved the way to space-saving equipment for the transmission and distribution of electrical energy. Its ever-rising usage in the electrical grid also played a decisive role in the continuous increase of atmospheric SF₆ abundance over the last decades. This Review broadly covers the environmental concerns related to SF₆ emissions and assesses the latest generation of eco-friendly replacement gases. They offer great potential for reducing greenhouse gas emissions from electrical equipment but at the same time involve technical trade-offs. The rumors of one or the other being superior seem premature, in particular because of the lack of dielectric, environmental, and chemical information for these relatively novel compounds and their dissociation products during operation.

Reactive molecular dynamics study of the decomposition mechanism of the environmentally friendly insulating medium C3F7CN

The decomposition mechanism of an environmentally friendly insulating medium C₃F₇CN was explored.