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Title: Dielectric breakdown properties of hot SF{sub 6}/He mixtures predicted from basic data

Sulfur hexafluoride (SF{sub 6}) gas has a quite high global warming potential and hence it is required that applying any substitute for SF{sub 6} gas. Much interest in the use of a mixture of helium and SF{sub 6} as arc quenching medium was investigated indicating a higher recovery performance of arc interruption than that of pure SF{sub 6}. It is known that the electrical breakdown in a circuit breaker after arc interruption occurs in a hot gas environment, with a complicated species composition because of the occurrence of dissociation and other reactions. The likelihood of breakdown relies on the electron interactions with all these species. The critical reduced electric field strength (the field at which breakdown can occur, relative to the number density) of hot SF{sub 6}/He mixtures related to the dielectric recovery phase of a high voltage circuit breaker is calculated in the temperature range from 300 K to 3500 K. The critically reduced electric field strength of these mixtures was obtained by balancing electron generation and loss mechanisms. These were evaluated using the electron energy distribution function derived from the Boltzmann transport equation under the two-term approximation. Good agreement was found between calculations for pure hot SF{sub 6}more » and pure hot He and experimental results and previous calculations. The addition of He to SF{sub 6} was found to decrease the critical reduced electric field strength in the whole temperature range due to a lack of electron impact attachment process for helium regardless its high ionization potential. This indicates that not the behaviour of dielectric strength but possibly the higher energy dissipation capability caused mainly by light mass and high specific heat as well as thermal conductivity of atomic helium contributes most to a higher dielectric recovery performance of arc interruption for SF{sub 6}/He mixtures.« less
Authors:
 [1] ;  [2] ; ;  [3] ;  [4]
  1. Qian Xuesen Laboratory of Space Technology, China Academy of Space Technology, Beijing 100094 (China)
  2. (China)
  3. Department of Electrical Engineering and Electronics, The University of Liverpool, Brownlow Hill, Liverpool L69 3GJ (United Kingdom)
  4. State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an Shaanxi 710049 (China)
Publication Date:
OSTI Identifier:
22218456
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 20; Journal Issue: 11; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; APPROXIMATIONS; BOLTZMANN EQUATION; DIELECTRIC MATERIALS; DISSOCIATION; ELECTRIC ARCS; ELECTRIC FIELDS; ELECTRIC POTENTIAL; ELECTRONS; ENERGY LOSSES; ENERGY SPECTRA; HELIUM; IONIZATION; MIXTURES; PLASMA DENSITY; SPECIFIC HEAT; SULFUR FLUORIDES; TEMPERATURE DEPENDENCE; THERMAL CONDUCTIVITY; THERMODYNAMICS