Assessment on the toxicity and application risk of C4F7N: A new SF6 alternative gas

Trace Analysis of C4F7N Insulating Gas Mixtures by Spontaneous Raman Spectroscopy and Gas Chromatography

2,3,3,3-Tetrafluoro-2-(trifluoromethyl) propanenitrile (C4F7N) is being researched as an alternative to sulfur hexafluoride (SF6) for applications in gas-insulated switchgear. We independently assessed the effectiveness of gas chromatography-mass spectrometry (GC-MS) and a novel method of feedback-assisted multipass cavity spontaneous Raman spectroscopy (SRS) for the trace quantification of impurities in C4F7N and its related byproducts. A total of 14 gases were identified with estimated concentrations as low as 20 ppm (ppm) for C3F6 using GC-MS and 7.4 ppm for CH4 using SRS and as high as 500 ppm for CF4 using GC-MS and 1430 ppm for CO using SRS. While GC-MS is highly effective in selectively detecting and quantifying trace contaminants, it necessitates separate detectors for various gases, such as CH4 and H2. SRS succeeded in detecting CF4 and C2F6 at concentrations of 465 and 100 ppm, respectively, and in placing an upper bound of several hundred ppm for the other analytes. Crucially, SRS holds potential for portability-and thus for field applications-in gas-insulated switchgear equipment diagnostics.

Real-Time Monitoring of Air Discharge in a Switchgear by an Intelligent NO2 Sensor Module

An air-insulated power equipment adopts air as the insulating medium and is widely implemented in power systems. When discharge faults occur, the air produces decomposition products represented by NO2. The efficient NO2 sensor enables the identification of electrical equipment faults. However, single-sensor-dependent NO2 detection is vulnerable to interfering gases. Implementing the sensor array could reduce the interference and improve detection efficiency. In the field of NO2 detection, In2O3 sensors have exhibited tremendous advantages. In our work, four composites based on In2O3 are integrated into sensor arrays, which could detect 250 ppb of NO2 and exhibit excellent selectivity when simultaneously exposed to CO. To further reduce the impact of humidity on gas-sensing performance, a convolutional neural network and a long short-term memory model equipped with an attention mechanism are proposed to evaluate NO2 concentration within 1 ppm, and the detection error is 63.69 ppb. In addition, the NO2 concentration estimation platform based on a microgas sensor is established to detect air discharge faults. The average concentration of NO2 generated by 10 consecutive discharge faults at 15 kV is 726.58 ppb, which indicates severe discharge in the switchgear. Our NO2 estimation method has great potential for large-scale deployment in low- and medium-voltage switchgears.

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.

Room-Temperature Detection of Perfluoroisobutyronitrile with SnO2/Ti3C2Tx Gas Sensors

Ti₃C₂T_x MXene is an emerging two-dimensional transition-metal carbide/nitride with excellent properties of large specific surface and high carrier mobility for room-temperature gas sensing. However, achieving high sensitivity and long-term stability of pristine Ti₃C₂T_x-based gas sensors remains challenging. SnO₂ is a typical semiconductor metal oxide with high reaction activity and stable chemical properties ideal for a dopant that can comprehensively improve sensing performance. Ti₃C₂T_x and SnO₂ are investigated for the first time in this study as functional materials for hybridization and room-temperature detection of the gas insulating medium fluorinated nitrile (C₄F₇N) with microtoxicity. A Ti₃C₂T_x-SnO₂ nanocomposite sensor exhibits superior sensitivity, high selectivity, strong anti-interference ability, and excellent long-term stability. The enhanced sensing mechanism is ascribed to the synergistic effect between SnO₂ and Ti₃C₂T_x and the strong adsorption ability of SnO₂ to C₄F₇N similar to bait for fish. We also established an actual leakage scene and demonstrated the feasibility of the Ti₃C₂T_x-SnO₂ sensor to provide distribution rules with high sensing efficiency for actual engineering applications. The results of this work can expand the gas sensing application of Ti₃C₂T_x MXene and provide a reference for maintaining C₄F₇N-based eco-friendly gas-insulated equipment.

Heptafluoroisobutyronitrile (C4F7N), a gas used for insulating and arc quenching in electrical switchgear, is neurotoxic in the mouse brain

Fluoronitrile gas (C₄F₇N, CAS number 42532-60-5) is one of the most promising candidates as insulating and/or breaking medium in high and medium voltage electrical equipment. Besides its promising properties, C₄F₇N gas is however not devoid of acute toxicity when used pure or in gas mixtures. The toxicity was not extensively analyzed and reported. The aim of the present study was to analyze in mice the consequences of a single exposure to C₄F₇N gas, at different concentrations and different timepoints after exposure. Male and female Swiss mice were exposed to breathable air or C₄F₇N gas, at 800 ppmv or 1500 ppmv, for 4 h on day 0. Behavioral tests (spontaneous alternation in the Y-maze and object recognition) were performed on days 1, 7 and 14 to assess memory alterations. The animals were then sacrificed and their brains dissected for biochemical analyses or fixed with paraformaldehyde for histology and immunohistochemistry. Results showed behavioral impairments and memory deficits, with impairments of alternation at days 1 and 7 and object recognition at day 14. Histological alterations of pyramidal neuronal layer in the hippocampus, neuroinflammatory astroglial reaction, and microglial alterations were observed, more marked in female than male mice. Moreover, the biochemical analyses done in the brain of 1500 ppmv exposed female mice showed a reductive stress with decreased lipid peroxidation and release of cytochrome c, leading to apoptosis with increases in caspase-9 cleavage and γ-H2AX/H2AX ratio. Finally, electrophysiological analyses using a multi-electrode array allowed the measure of the extracellular activity of pyramidal neurons in the CA2 area and revealed that exposure to the gas not only prevented the induction of long-term potentiation but even provoked an epileptoid-like activity in some neurons suggesting major alterations of synaptic plasticity. This study therefore showed that an acute exposure of mice to C₄F₇N gas provoked, particularly in female animals, memory alterations and brain toxicity characterized by a reductive stress, microglial toxicity, loss of synaptic plasticity and apoptosis. Its use in industrial installations must be done with extreme caution.

Toxic Study on the New Eco-Friendly Insulating Gas Trifluoromethanesulfonyl Fluoride: A Substitute for SF6

It has been proven that the gas trifluoromethanesulfonyl fluoride (CF3SO2F) has good dielectric performance and the potential to replace the potent greenhouse gas sulfur hexafluoride (SF6), which is the most commonly used insulating gas in high-voltage electrical equipment. However, there are many key biochemical properties, such as toxicity, that the new eco-friendly insulating gas will need to obtain. It could protect the operator and equipment and help the chemical engineering development of this gas in the power grid industry. In this study, according to Horn’s method, an acute toxic gas inhalation test was carried out. The results showed that the lethal concentration of 50% (LC50) for female rats was 27.1 g/m3, and that for male rats was 23.3 g/m3. The behavioral and vital sign changes in the rats were recorded. Pathological sections of the main organs revealed that the heart, lungs, spleen, and eyes suffered the most damage from the gas. This research also provides scientific suggestions for the protection of electrical workers exposed to the insulating gas CF3SO2F.

SnO2 nanoparticles based highly sensitive gas sensor for detection of C4F7N: A new eco-friendly gas insulating medium

As a novel eco-friendly gas insulation medium, perfluoroisobutyronitrile (C₄F₇N) has been utilized in various gas insulated equipment. Considering the biological toxicity of C₄F₇N, it is of great engineering significance to develop highly sensitive sensors for leakage detection scenarios. Herein, we fabricated the first SnO₂ nanoparticles based highly sensitive C₄F₇N gas sensor that realized a superior response of 65.01% within 21 s for 50 ppm C₄F₇N exposure and a detection limit of 0.25 ppm. Meanwhile, successive response-recovery tests were performed to confirm its durability and stability. We also explored the sensing mechanism of SnO₂ nanoparticles towards C₄F₇N and explained the superior sensing performance compared with other gases based on the density functional theory. It was found that the O vacancy demonstrates strong interaction with the -CN group in C₄F₇N that promotes the detection response, which was also confirmed by sensing experiments for SnO₂ with different O vacancy density. We believe this paper provides convincing support for lowering the potential operation risk brought by C₄F₇N in electrical engineering and the application scenarios of SnO₂ based gas sensors.

Recent Development of Two Alternative Gases to SF6 for High Voltage Electrical Power Applications

For many years, SF6 has been the preferred dielectric medium in electrical power applications, particularly in high voltage gas-insulated equipment. However, with the recognition that SF6 has an extremely long atmospheric lifetime and very high global warming potential, governments have pursued emission reductions from gas-filled equipment. The electrical power industry has responded to this environmental challenge applying SF6-free technologies to an expanding range of applications which have traditionally used SF6, including gas-insulated switchgear, gas-insulated circuit breakers and gas-insulated lines or bus bars. Some of these SF6-free solutions include gas mixtures containing fluorinated compounds that have low climate impact, among them, a fluoronitrile and a fluoroketone developed as 3M™ Novec™ 4710 Insulating Gas and 3M™ Novec™ 5110 Insulating Gas, respectively. Both fluoronitrile and fluoroketone mixtures are successfully used in gas-insulated equipment currently operating on the grid where they reduce greenhouse gas emissions by more than 99% versus SF6. This paper reviews these leading components of alternative-gas mixtures with updates on the performance, safety and environmental profiles in electrical power applications.

A review of strategies for mitigating roadside air pollution in urban street canyons

Urban street canyons formed by high-rise buildings restrict the dispersion of vehicle emissions, which pose severe health risks to the public by aggravating roadside air quality. However, this issue is often overlooked in city planning. This paper reviews the mechanisms controlling vehicle emission dispersion in urban street canyons and the strategies for managing roadside air pollution. Studies have shown that air pollution hotspots are not all attributed to heavy traffic and proper urban design can mitigate air pollution. The key factors include traffic conditions, canyon geometry, weather conditions and chemical reactions. Two categories of mitigation strategies are identified, namely traffic interventions and city planning. Popular traffic interventions for street canyons include low emission zones and congestion charges which can moderately improve roadside air quality. In comparison, city planning in terms of building geometry can significantly promote pollutant dispersion in street canyons. General design guidelines, such as lower canyon aspect ratio, alignment between streets and prevailing winds, non-uniform building heights and ground-level building porosity, may be encompassed in new development. Concurrently, in-street barriers are widely applicable to rectify the poor roadside air quality in existing street canyons. They are broadly classified into porous (e.g. trees and hedges) and solid (e.g. kerbside parked cars, noise fences and viaducts) barriers that utilize their aerodynamic advantages to ease roadside air pollution. Post-evaluations are needed to review these strategies by real-world field experiments and more detailed modelling in the practical perspective.

Acute toxicity and health effect of perfluoroisobutyronitrile on mice: a promising substitute gas-insulating medium to SF6

Perfluoroisobutyronitrile (C₄F₇N) is a new eco-friendly gas insulation medium that has potential to replace the most greenhouse gas sulfur hexafluoride (SF₆) used in power industry. In order to ensure the engineering application safety, an in-depth assessment of the acute inhalation toxicity of C₄F₇N gas mixture is required. This article revealed gender differences in male and female mice after exposure to C₄F₇N and the physiological recovery characteristics of surviving mice by means of 4 h acute inhalation toxicity tests, hematological determinations and histopathological examination. Comparative analysis on the toxicity of C₄F₇N on mice and rats is also evaluated. We find that the LC₅₀ of C₄F₇N for male and female mice is 1175 ppm (4 h), 1380 ppm (4 h) and female ones are more tolerant to C₄F₇N. Mice that exposed to 1000 ppm C₄F₇N for 4 h could survive and return to their normal state after the 14-day observation period without irreversible damage. The toxic effect duration of C₄F₇N on rats is longer than that of mice. Relevant results revealed the acute inhalation toxicity of C₄F₇N systematically and provided fundamental reference for inhalation safety protection and engineering application.

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.

Autogenic single p/n-junction solar cells from black-Si nano-grass structures of p-to-n type self-converted electronic configuration

Photovoltaic performance of solar cells automatically improves when the absorber layer itself simultaneously acts as the anti-reflection nanostructure with an enhanced active absorber area on the front surface. Combined physical and chemical etching of p-c-Si wafers by (Ar + H2) plasma in inductively coupled low-pressure plasma CVD produces various nanostructures with subsequent minimization of reflectance. At a reduced temperature, the rate constant of thermal diffusion of atomic-H in the Si-network becomes smaller, leading to enhanced chemical etching reactions that further increase at an elevated RF power. Regrowth of the SiHn precursors produced by etching and subsequent hydrogenation in the plasma develops a high density of elongated nano-grass structures, which further align with sharp tips via Ar+ ion bombardment and elimination of loosely bound amorphous over-layers, on application of negative dc substrate bias during real-time etching and regrowth. A significantly reduced reflectance (∼0.5%) via coherent light trapping within the uniformly distributed vertically aligned nano-grass surfaces evolves truly black-silicon (b-Si) nanostructures, which further self-convert from the p-type to n-type electronic configuration via etching-mediated modification of B-H bonds from BH1 to BH2 and/or BH3 states, producing autogenic p/n junctions. Using (Ar + H2) plasma etched b-Si nano-grass structures at low temperature (∼200 °C), one-step fabrication of autogenic single p/n-junction proof-of-concept solar cells is accomplished. There is plenty of room for further progress in device performance.

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.

AC Volume Breakdown and Surface Flashover of a 4% NovecTM 4710/96% CO2 Gas Mixture Compared to CO2 in Highly Nonhomogeneous Fields

AC pre-discharge currents, breakdown, and flashover voltage measurements are reported in a 10 mm needle-plane arrangement in a 4% NovecTM 4710/96% CO2 gas mixture and compared with CO2 for pressures up to 8.8 bar abs. Flashover measurements were performed on different solid dielectrics (Al2O3_filled epoxy resins, PTFE (Polytetrafluoroethylene) and PE (polyethylene)) for different roughness surface finishes. The effect of fixed conducting needles at various positions on electrical strength is reported. A strong nonlinear behaviour as function of gas pressure was observed for all the studied parameters (gas, needle position, solid insulator, insulator roughness). The non-linear behaviour is attributed to the inception and quenching of glow corona, in the interval between inception and breakdown or flashover voltages. It is found that a 4% concentration of NovecTM 4710 in CO2 has a breakdown/flashover voltage ≈ 1.14 higher than CO2. The glow corona-induced stabilization effect is seen for pressures between 2 and 5 bar abs for all the studied parameters. The peak flashover voltage and its associated pressure of the different insulators are strongly dependent on surface roughness. At 8.8 bar abs, the flashover voltage level obtained with various materials was ordered as follows: PTFE > PE-UHMW > Epoxy > HDPE(High-density polyethylene).

Interaction Mechanism between the C4F7N-CO2 Gas Mixture and the EPDM Seal Ring

C₄F₇N (fluorinated nitrile) has been introduced as a remarkable substitute gas for the greenhouse gas SF₆ (sulfur hexafluoride) which is used in gas-insulated equipment (GIE). Intensive investigations about the compatibility between C₄F₇N and materials used in GIE are required to decide their long-term behavior. In this paper, the interaction mechanism between EPDM, used as a sealing ring in GIE, and C₄F₇N-CO₂ was explored. The composition and morphology properties of EPDM were first revealed based on scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that EPDM rubber is incompatible with the C₄F₇N-CO₂ gas mixture at temperatures higher than 70 °C. There exist chemical reactions between EPDM and C₄F₇N, resulting in the generation of gaseous byproducts including C₃F₆, CF₃H, and C₂F₅H and corrosion of EPDM. DFT calculation also shows that the interaction between C₄F₇N and EPDM could cause the dissociation of C₄F₇N. Relevant results provide important guidance for the engineering application of the C₄F₇N gas mixture.

Compatibility between C6F12O–N2 Gas Mixture and Metal Used in Medium-Voltage Switchgears

C6F12O has been introduced as the potential alternative gas to SF6 because of its excellent insulation properties and great eco-friendly performance. Considering that C6F12O may react with the internal materials of switchgears in practical applications, its compatibility with metal materials must be tested to evaluate its long-term application possibilities. In this work, the compatibility of C6F12O–N2 gas mixtures with aluminum and copper was tested at different temperatures by setting up a heat-aging reaction platform between the gas and each metal. The metal surface morphology and gas composition before and after the reaction were compared and analyzed. The results show that the surface color of the copper sheet changed considerably, and the corrosion degree of the surface deepened with the increase of temperature. The decomposition of C6F12O was also promoted. In contrast, aluminum did not react severely with the gas mixture. The compatibility of the gas mixture with aluminum was generally better than that of copper.

SF6 abatement in a packed bed plasma reactor: study towards the effect of O2 concentration

SF₆ is a greenhouse gas with extremely high global warming potential value (GWP). In this paper, oxygen and a packed bed plasma reactor (PBR) were applied to remove it. The synergistic effect between oxygen and PBRs was evaluated by the destruction and removal efficiency (DRE) and energy yield (EY) at different oxygen concentrations. The results show that excessive oxygen weakened the micro-discharge in a PBR to suppress SF₆ degradation while the addition of a proper amount of oxygen (1–4%) can improve the DRE and EY. 2% O₂ in the system had the best promoting effect on the destruction of 6–10% SF₆, which made the maximum energy yield (EY) increase by 50.99% to 37.99 g kW⁻¹ h⁻¹ (SF₆ concentration was 10%, flow rate was 150 mL min⁻¹). Moreover, in the flow rate range of 100 mL min⁻¹ to 250 mL min⁻¹, the DRE decreased and the EY increased with the flow rate. In addition, the selectivity of different products were affected by the oxygen concentration. For 6% SF₆, SO₂F₂ selectivity was always the highest while SO₂ was always the lowest; when the oxygen concentration did not exceed 2%, SOF₂ selectivity was higher than SOF₄, otherwise, SOF₄ selectivity was higher than SOF₂. This paper provided experimental support for better understanding of the effect of additional gas concentration on SF₆ decomposition in a PBR.

SF₆ is a greenhouse gas with extremely high global warming potential (GWP).

Study on the Compatibility of Gas Adsorbents Used in a New Insulating Gas Mixture C4F7N/CO2

An environment-friendly insulating gas, perfluoroisobutyronitrile (C4F7N), has been developed recent years. Due to its relatively high liquefaction temperature (around −4.7 °C), buffer gases, such as CO2 and N2, are usually mixed with C4F7N to increase the pressure of the filled insulating medium. During these processes, the insulating gases may be contaminated with micro-water, and the mixture of H2O with C4F7N could produce HF under breakdown voltage condition, which is harmful to the gas insulated electricity transfer equipment. Therefore, removal of H2O and HF in situ from the gas insulated electricity transfer equipment is significant to its operation security. The adsorbents with the ability to remove H2O but without obvious C4F7N/CO2 adsorption capacity are essential to be used in this system. In this work, a series of industrial adsorbents and desiccants were tested for their compatibility with C4F7N/CO2. Pulse adsorption tests were conducted to evaluate the adsorption performance of these adsorbents and desiccants on C4F7N and CO2. The 5A molecular sieve showed high adsorption of C4F7N (22.82 mL/g) and CO2 (43.86 mL/g); F-03 did not show adsorption capacity with C4F7N, however, it adsorbed CO2 (26.2 mL/g) clearly. Some other HF adsorbents, including NaF, CaF2, MgF2, Al(OH)3, and some desiccants including CaCl2, Na2SO4, MgSO4 were tested for their compatibility with C4F7N and CO2, and they showed negligible adsorption capacity on C4F7N and CO2. The results suggested that these adsorbents used in the gas insulated electricity transfer equipment filled with SF6 (mainly 5A and F-03 molecular sieves) are not suitable anymore. The results of this work suggest that it is a good strategy to use a mixture of desiccants and HF adsorbents as new adsorbents in the equipment filled with C4F7N/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.

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.