Study on the thermal decomposition characteristics of C ₄ F ₇ N–CO ₂ mixture as eco‐friendly gas‐insulating medium

Abstract

The authors explored the thermal decomposition characteristics of perfluoroisobutyronitrile-carbon dioxide (C 4 F 7 N-CO 2) gas mixture as eco-friendly dielectric medium. The main by-products and decomposition mechanism of C 4 F 7 N-CO 2 gas mixture under different temperature and gas pressure conditions were revealed and analysed. It was found that the thermal decomposition of 6%C 4 F 7 N-94%CO 2 gas mixture starts at about 350°C (0.15 MPa), producing C 3 F 6 and CO first. Some other characteristic by-products such as CF 4 , C 2 F 6 , CF 3 CN, COF 2 and (CN) 2 could also be detected at higher temperature. The yield of C 3 F 6 , (CN) 2 increased with the temperature (lower than 450°C) first and then decreased when it reached to 500°C. While the yield of CO, C 3 F 8 , COF 2 and CF 3 CN increased with temperature (350-550°C). The generation of CF 4 and C 2 F 6 begins at temperatures higher than 500°C, which can be used as the feature component of severe overheating fault. The thermal decomposition amount and by-products yield of C 4 F 7 N-CO 2 gas mixture slowed down with the increase of gas pressure, indicating that C 4 F 7 N-CO 2 gas mixture is quite suitable used at high-pressure equipment, especially high-voltage devices such as gas insulated switchgear.

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

“…V Flashover (PTFE) > V Flashover (PE−UHMW) > V Flashover (Epoxy) > V Flashover (HDPE) (7) The comparison of inception voltage of the different insulators is as follows:…”

“…For a 4% Novec TM 4710/96% CO 2 , the equivalence with SF 6 at 5.5, 6.5, 7.5 bar abs are feasible for a minimum operating temperature of −30 • C, −25 • C, and −20 • C [1][2][3][4], respectively. Novec TM 4710 (C 4 F 7 N)/CO 2 mixtures consist of complex molecules, formed from several basic elements (5 Carbons,7 Fluorines, 2 Oxygens, and 1 Nitrogen), the energy absorption by the constituents of these mixtures causes their fragmentation into smaller radicals, that are more stable [5][6][7]. Once at rest, unlike SF 6 , the decomposition products do not recombine to the original chemical arrangement.…”

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

“…1 However, it is still used in large quantities because there is no reliable SF 6 replacement gas. [2][3][4] It is estimated that the current global SF 6 usage is above 10 000 tons, and more than 80% is used in the power industry. 5 Every year, the power industry is facing the problem of recycling and emission of huge amounts of SF 6 .…”

Synergistic Effects of Boron Nitride (BN) Nanosheets and Silver (Ag) Nanoparticles on Thermal Conductivity and Electrical Properties of Epoxy Nanocomposites

“…Miniaturization of power equipment and electronic devices, coupled with a high voltage electromagnetic environment, demands superior thermal conductivity and electrical insulation strength in insulating materials [1][2][3]. An ideal insulating material is expected to possess high thermal conductivity, high breakdown strength, low permittivity, and low dielectric loss, simultaneously [4].…”