It has been widely established that gaseous helium (GHe) can be injected into a sub-cooled liquid nitrogen (LN2) cooling system to control the pressure of such a system because of its non-condensing characteristics. A sub-cooled LN2 cooling system is known as one of the most promising method to develop a large scale superconducting machine . Unfortunately, the electrical breakdown voltage of GHe is not good enough for developing a high voltage electric machine such as a superconducting fault current limiter (SFCL). To enhance the dielectric characteristics of current leads placed in GHe, the use of solid barriers is regarded as an efficient method. In this study, experiments are made on the dielectric characteristics of GHe and the barrier effects and results are analyzed in order to improve the dielectric performance of a high voltage SFCL using a sub-cooled LN2 cooling system. The dielectric experiments of the energized sphere and the grounded plane in GHe are examined according to various pressures with a solid insulating barrier. The dielectric experiments are performed by installing barriers made of glass fiber reinforced plastics (GFRP) between two electrodes and the electrical breakdown voltage according to the pressure of GHe and the position of a barrier is observed. As a result, it is found that the position of a solid barrier and the pressure of GHe are important in enhancing the dielectric characteristics of a sphere-to-plane electrode system with quasi-uniform field.
Bibliographical noteFunding Information:
Manuscript received August 03, 2010; accepted December 29, 2010. Date of publication February 10, 2011; date of current version May 27, 2011. This work was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2010-0003558). H. Kang is with the Department of Electrical Engineering, Chungju National University, Chungju, Korea (e-mail: email@example.com). J. B. Na and T. K. Ko are with the Electrical Engineering, Yonsei University, Seoul 120-749, Korea. Y. D. Chung is with the Industry Administration Institute, College of Engineering, The University of Suwon, Gyeonggido 445-743, Korea. Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TASC.2010.2104310
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering