Suppressing carbon formation in dielectric fluid during discharge - using gas mixt. of sulphur hexafluoride and or carbon dioxide

摘要

Suppression of C formation in a dielectric fluid during electric discharge from a conductor is achieved by contacting the conductor with a gas dielectric mixt. during operation. This mixt. consists of (a) SF6 and 1-50 mole-% CO2; (b) 1-4C haloalkane(s) contg. F, Cl and/or Br, with max. 1 H atom, and SF6 and/or CO2; or (c) -6 C pefluoroether(s), with a vapour pressure of min. 100 torr at 20 degrees C and SF6 and/or CO2. Suitable haloalkanes are CHClF2, CCl2F2, CClF2CClF2, CClF3, CClF2CF3, CBrF3, CCl2FCClF2CHF, CCl3F, C2F6 and c-C4F8 and suitable ethers (CF3)2O and (C2F5)2O. E.g. it was found that the addn. of 40-60 mole-% CCl2F2 to SF6 caused an increase of ca. 1 kV in the breakdown voltage of 17.43 kV. Used in switches, circuit breakers, transformers etc.