Electrical breakdown characteristics of superconducting magnet system in sub-cooled liquid nitrogen

Hyoungku Kang, Chanjoo Lee, Tae Kuk Ko, Bok Yeol Seok

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Dielectric characteristics of gaseous helium (GHe) injected into the cooling system to make sub-cooled nitrogen condition with constant pressure is found to be extraordinarily weak in dielectric strength [1]. In high voltage superconducting machines using the sub-cooled nitrogen cooling system, the current lead part in GHe environment could be electrical weak points rather than the superconducting magnet part in liquid nitrogen (LN2). In order to enhance dielectric characteristics of current lead part, three methods are suggested in this paper. The first one is enclosing the current leads with solid dielectric material and the second is exposing the current leads to high vacuum, and the last is topping up the magnet system with dielectric materials such as Glass Bubbles (GB) which is usually used as heat insulator. In addition, the extinction time of bubbles caused by the electrical breakdown is measured to determine the suitable pressure of sub-cooled nitrogen system. It is found that the characteristics of bubble extinction in LN2 are drastically enhanced over 1 bar.

Original languageEnglish
Pages (from-to)1509-1512
Number of pages4
JournalIEEE Transactions on Applied Superconductivity
Volume17
Issue number2
DOIs
Publication statusPublished - 2007 Jun 1

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Superconducting magnets
superconducting magnets
Liquid nitrogen
electrical faults
liquid nitrogen
Helium
Nitrogen
bubbles
cooling systems
Cooling systems
nitrogen
extinction
Lead
helium
high vacuum
Magnets
high voltages
magnets
insulators
Vacuum

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Electrical and Electronic Engineering

Cite this

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abstract = "Dielectric characteristics of gaseous helium (GHe) injected into the cooling system to make sub-cooled nitrogen condition with constant pressure is found to be extraordinarily weak in dielectric strength [1]. In high voltage superconducting machines using the sub-cooled nitrogen cooling system, the current lead part in GHe environment could be electrical weak points rather than the superconducting magnet part in liquid nitrogen (LN2). In order to enhance dielectric characteristics of current lead part, three methods are suggested in this paper. The first one is enclosing the current leads with solid dielectric material and the second is exposing the current leads to high vacuum, and the last is topping up the magnet system with dielectric materials such as Glass Bubbles (GB) which is usually used as heat insulator. In addition, the extinction time of bubbles caused by the electrical breakdown is measured to determine the suitable pressure of sub-cooled nitrogen system. It is found that the characteristics of bubble extinction in LN2 are drastically enhanced over 1 bar.",
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Electrical breakdown characteristics of superconducting magnet system in sub-cooled liquid nitrogen. / Kang, Hyoungku; Lee, Chanjoo; Ko, Tae Kuk; Seok, Bok Yeol.

In: IEEE Transactions on Applied Superconductivity, Vol. 17, No. 2, 01.06.2007, p. 1509-1512.

Research output: Contribution to journalArticle

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