Surface flashover characteristics of epoxy insulator in C4F7N/CO2 mixtures in a uniform field under AC voltage

Li, Zhichuang; Ding, Weidong; Liu, Yishu; Li, Yue; Zhang, Zheng; Liu, Wei; Gao, Keli

doi:10.1109/tdei.2019.007847

Cited by 24 publications

(15 citation statements)

References 17 publications

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“…E average stands for average electric field. The breakdown characteristic of CO 2 and 4%Novec TM 4710/96%CO 2 shows a strong nonlinear behaviour with the gas pressure increasing under AC voltage as opposed to the uniform field configuration that exhibits a linear trend [19]. This effect can be attributed to the space charge created in the gas volume.…”

Section: Gas Breakdownmentioning

confidence: 94%

“…In uniform electric fields, the surface electrical strength (ES) of Novec TM 4710/CO 2 mixtures [19] relative to CO 2 is lower than the volume electrical insulation strength [2,4] (see Figure 1). The validity of the optimal gas mixture must be extended and verified at different electric field distributions, on the surface and in the volume, particularly in highly divergent fields that appear when a metal particle is stuck at the insulator surface or very close to it [20].…”

Section: Introductionmentioning

confidence: 99%

“…Electrical strength (ES) relative to CO 2 for different Novec TM 4710/CO 2 gas mixtures in uniform electric field (Volume discharge [2,4] vs. Surface discharge (epoxy insulator) [19]).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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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).

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Section: Gas Breakdownmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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“…The surface flashover along the solid insulation-gas interface should be avoided in the design of gas-insulated equipment. The insertion of spacers not only distorts the electric field because of the difference of permittivity, but also accumulates and stores charge [26]. For the 50-Hz AC voltage tests, the voltage was raised to 75% of the expected flashover voltage at a rate of 10 kV/s, and then raised until flashover at a rate of 5 kV/s.…”

Section: B Surface Fiashover Voltage Testsmentioning

confidence: 99%

Study of Compatibility Between Epoxy Resin and C₄F₇N/CO₂ Based on Thermal Ageing

Yuan

Zhou

et al. 2020

IEEE Access

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Fluorinated nitrile (C4F7N) is a potential SF6-alternative gas in Gas-Insulated Transmission Line (GIL) due to its lower impact to global warming and excellent dielectric strength. To ensure the longterm physical and chemical stability at the interface between C4F7N/CO2 gas and epoxy resin assembly in GIL, laboratory thermal ageing tests on the material compatibility were carried out. In order to evaluate the compatibility, the authors set up a gas-solid compatibility test platform in this paper. Thermal ageing tests of C4F7N/CO2 and epoxy resin were set up at different temperatures. Also, the groups of SF6 and He gas were adopted to evaluate the influence of temperature. The compatibility between the gas and solid insulating materials in contact was evaluated in terms of the changes of insulation performance after over long period of tests. The changes of gas compositions and solid contents were also assessed. Dielectric spectroscopy, surface flashover voltages, surface morphology, and chemical elements of epoxy resin and gas composition before and after the ageing tests were compared. The surface insulation of epoxy resin decreased only after ageing reached 160 ℃, when a small amount of C3F6 and trimer of C4F7N were found. Under the normal operation of GIL (below 90 ℃), the compatibility of epoxy resin with 9 % C4F7N/91 % CO2 is as good as epoxy resin with SF6.

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“…Due to its relatively high boiling point, the content of C 4 F 7 N used in the mixture gas is usually no more than 20% [22,23]. Therefore, the adsorbents or desiccants used to remove the moisture or acidic by-products from C 4 F 7 N should not be able to adsorb C 4 F 7 N. Some of the moisture adsorbents, including 3A, 4A, 5A and F-03 molecular sieves, the desiccants including Na 2 SO 4 , CaCl 2 , and the HF adsorbents, including NaF, MgF 2 , Al(OH) 3 and CaF 2 , were tested for their adsorption capacities on C 4 F 7 N gas.…”

Section: Compatibility Of Samples With C 4 F 7 Nmentioning

confidence: 99%

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

Huang¹,

Wang²,

Liu³

et al. 2019

Processes

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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.

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Surface flashover characteristics of epoxy insulator in C₄F₇N/CO₂ mixtures in a uniform field under AC voltage

Cited by 24 publications

References 17 publications

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

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

Study of Compatibility Between Epoxy Resin and C₄F₇N/CO₂ Based on Thermal Ageing

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

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Surface flashover characteristics of epoxy insulator in C4F7N/CO2 mixtures in a uniform field under AC voltage

Cited by 24 publications

References 17 publications

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

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

Study of Compatibility Between Epoxy Resin and C4F7N/CO2 Based on Thermal Ageing

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

Contact Info

Product

Resources

About

Surface flashover characteristics of epoxy insulator in C₄F₇N/CO₂ mixtures in a uniform field under AC voltage

Study of Compatibility Between Epoxy Resin and C₄F₇N/CO₂ Based on Thermal Ageing