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Analysis on the dielectric characteristics of a composite insulation system composed of LN2 and GN2

  • Kim, Junil (Department of Electrical Engineering, Korea National University of Transportation) ;
  • Lee, Onyou (Department of Electrical Engineering, Korea National University of Transportation) ;
  • Mo, Young Kyu (Department of Electrical Engineering, Korea National University of Transportation) ;
  • Bang, Seungmin (Department of Electrical Engineering, Korea National University of Transportation) ;
  • Kang, Jong O (Department of Electrical Engineering, Korea National University of Transportation) ;
  • Lee, Hongseok (Department of Electrical Engineering, Korea National University of Transportation) ;
  • Nam, Seokho (Department of Electrical Engineering, Applied Superconductivity Lab, Yonsei University) ;
  • Kang, Hyoungku (Department of Electrical Engineering, Korea National University of Transportation)
  • Received : 2015.08.11
  • Accepted : 2015.09.24
  • Published : 2015.09.30

Abstract

A liquid nitrogen ($LN_2$) is usually used to be a coolant and insulant for a HTS coil system. HTS wires for a superconducting apparatus may be surrounded by gaseous nitrogen ($GN_2$) due to film boiling generated by a quench or voids occurred by electrical breakdown. The increased maximum electric field intensity at $GN_2$ may result in the degradation of dielectric strength of a HTS coil system. In this paper, a study on the dielectric characteristics of a composite insulation system composed of $LN_2$ and $GN_2$ is performed. A sphere-to-plane electrode system made with stainless steel is used to perform the experiments under AC and lightning impulse voltage condition. A sphere electrode is surrounded by $GN_2$ and a plane electrode is immersed into $LN_2$ to conduct dielectric experiments with a composite insulation system. The dielectric experiments are performed according to the level of $LN_2$ from the plane electrode to a sphere electrode. It is found that the dielectric characteristics of a composite insulation system are dependent on the level of $LN_2$ and the field utilization factor of an electrode system.

Keywords

References

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