High Voltage (Jun 2019)

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

  • Yi Li,
  • Xiaoxing Zhang,
  • Xiaoxing Zhang,
  • Ji Zhang,
  • Cheng Xie,
  • Xianjun Shao,
  • Ziling Wang,
  • Dachang Chen,
  • Song Xiao

DOI
https://doi.org/10.1049/hve.2019.0032

Abstract

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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.

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