Analysis of the energy transport processes in DC air and SF6 nozzle arcs

Quan Zhang, Fang Yang, Haiyang Qi, Jiudun Yan

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3 Citations (Scopus)


As a naturally existing gas of abundant supply, the insulation and interruption capability of air has been extensively investigated. Research has also recently been done to use air as a dilution gas of Fluoroketone for SF6 free interruption in medium voltage switchgear. Much evidence has shown that air gas-blast circuit breakers have far inferior interruption capability than SF6 breakers. However, no clear explanation has so far been given regarding why an air switching arc has much larger time constant than an SF6 arc, and thus exhibiting far inferior interruption capability than the latter. Based on reliable experimental measurements, the present work first calibrated the turbulence parameter in a two-dimensional axisymmetrical turbulent arc model which was then used for computational investigation of the air arc behaviour and analysis of the dominant energy transport processes. Through comparative study, it has been found that, for air nozzle arc at low current, the radial and axial cooling mechanisms play almost equal roles, while for SF6 arc the radial cooling mechanism is dominant. The difference in cooling mechanisms for air and SF6 arcs is directly related to the difference in radial temperature profiles which is controlled by the material property, ρCp, through turbulence enhanced thermal conduction. The present work therefore provides clear direction on the explanation of the differing interruption performance of different SF6 replacement gases under transient discharge conditions.

Original languageEnglish
Pages (from-to)41-47
Number of pages7
JournalGaoya Dianqi/High Voltage Apparatus
Issue number12
Publication statusPublished - 16 Dec 2016
Externally publishedYes


  • Air arc
  • SF replacement gases
  • Supersonic nozzle
  • Turbulence effects
  • U-I characteristics

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